GPB-301 Crop Improvement-I Kharif Crops PDF

1 UNIVERSITY OF AGRICULTURAL SCIENCES, DHARWAD e - Notes: Crop Improvement I (Kharif Crops) GPB 301(1+1) Prepared by Dr Shobha Immadi, Dr Bangaramma Wadeyar Dr Nandini...

1 UNIVERSITY OF AGRICULTURAL SCIENCES, DHARWAD e - Notes: Crop Improvement I (Kharif Crops) GPB 301(1+1) Prepared by Dr Shobha Immadi, Dr Bangaramma Wadeyar Dr Nandini Dr. S. A. Desai Dr. G. K. Naidu Dr. Shanthakumar DEPARTMENT OF GENETICS AND PLANT BREEDING COLLEGE OF AGRICULTURE, DHARWAD 2020  2 RICE Introduction: Rice is an important food for many across the world. More so in Asian continent where in it is a staple food. It ranks third in the world after wheat and maize in its importance considering the importance of rice to the food security, social security, nutritional &economic security of rice to the large part of the world community. it is warm season crop grown extensively in the humid tropical & sub tropical reigns of the world. China ,India, Japan, Korea, southeast Asia & adjacent high lands of the pacific account for about 90% of world rice production. India is currently producing about 8.8 million tons of rice annually from 43 million hectare area Genus oryza has 24 species out of which two species are cultivated &others are used as donors of traits. That two species are orysa sativa,& orysa glaberrima. the genome( total of all genes in the cell of an organism) of the different species & related generas is present in table 1(different species of oryza genus) Table1: different species of oryza genus Sl.no Species Genome Chromosome origin number 01 orysa sativa AA 24 World wide 02 orysa glaberrima Ag Ag 24 Africa 03 O australiensis EE 24 Australia 04 O minuta BBCC 48 Philipincs,papua,newgunia 05 O officinalis CC 24 India, Bangladesh, burma 06 O alta CCDD 48 Hondurus,Brazil,peraguae. 07 O granulata FF 24 South east asia 08 O nivara AA 24 India 09 O rufipogon AA 24 India 10 O banthii Ag Ag 24 Africa 11 O brachyantha FFFF 48 africa Cultivated rice has 24 chromosomes. the basic number is said to have 5 based on study of haploid meiosis. Several tetrapliods(from cpies of the genome ex:CCDD, FFFF) rices exist among the wild species. Paddy is said to be segmental allopolyploid. Importance of crop: 1. Among the food crops it occupies large area &contribute staple food for large population. 2. Among cereals it survives better under saline & alkaline conditions. 3. The crop is best suited to grow in low land & water logged conditions. 4. Short duration & photo insensitive variety availability makes it more suitable under multiple cropping system. 5. Rice contains about 20% husk & 80% grain (hulling-10%loss in the form of bran) 80% grain in fine polishing process. 6. Nutrient composition of rice is better than other crops: Water content: 11-13%  3 Protein: 7.5% Fat: 1.5% CHO: 77% Ca: 8gms/100gm Fe: 1mg/100gm Total calorific value: 352 National and international status of rice: Rice is the worlds most important food crop after wheat &maize,but in India it stand first in area & production. Out of 220 million tons of food production rice alone occupies 85 millon tons. Table 2: Sl.no Character Area(m.ha) Production(m.t) Productivity(t/h) 1 World 150 550 3.2 2 India 44 128.2 1.85 3 Karnataka Guntur has the higest productivity & south arcot has also said to have maximum productivity of about 3t/ha. In2003 four million tons of rice exported from India which is second largest exporer after Thailand. By 2030 we need to produce 70% more rice than the present production(i.e.145m.t) The food & agricultural organization has declared 2004 as the inter national year of rice the theme of year was “rice is life” Center of origin: a) Geographical origin: (as described by Vavilov as the geographical place where the crop evolved for the first time where even now considerable diversity is likely to be found) it is belived that Asia &Africa were together 10000 years ago which was called “Gondwanaland continent” due to splitting/drifting of continents the O glaberrima was moved to Africa and O sativa to the Asia. 1)O sativa: PCO is south & south east Asia imp centers are NE India ,china, Thailand Burma, Vietnam, Bangladesh, triangular area where we can find high genetic diversity. 2)O glabarima: PCO is upper valley of river Niger. Rice belongs to the family: Graminae Tribe: oryzeae Genus: oryza Genus oryza has 25 sps the two imp cultivated sps are O sativa& O glabarima Further O. sativa is divided into 3 sub sps, or strains or types, they are 1. Indica. 2. Japonica. 3. Javanica. 1) India Type:  4 It is tropical type rice. It is extensively grown in India, Srilankha, Thailand, Malaysia and adjacent countries. These are tall plants, weak stem, photoperiod sensitivity, easy shattering, and broad droopy leaves and having grain dormancy. 2) Japonica Type: These are temperate type extensively grown Yangtze river valley of china, Korea, and Japan, these are tolerant low temperature, have more leaves, few tillers, relatively resistant to shattering. The grains are short, broad low in amylase content. Rice becomes sticky on cooking. 3) Javanica Type: These are intermediate type. These are cultivated in Indonesia, Phillippines , Taiwan and Japan. These are tall, thick stemmed, low to tillering and resistant to shattering. These varieties have broad stiff leaves, long awns and large bold grains. Sl character japonica javanica indica no 01 Grain size short large Large 02 Co lour of plant & Deep green Pale green Pale green, rigidity Rigid rigid rigid 03 Flag leaf Narrow& Broad& long Narrow& long short 04 No of tillers& Many Few Many erectness upright upright spreading 05 Hairs on leaf Many many few 06 Awns & shedding Many Many Less Non Non shedding shedding shedding 07 Culm length short long long 08 Ear length short long medium 09 Branching of ear Few Many Medium & rachis density dense Medium medium 10 Geographical Sub tropical equatorial Tropical distribution climate 11 No of ears &its Many Few Many weight heavy heavy light 12 Sensitivity to varying low varying photoperiod 13 Amylose & Amylose is intermediate Amylose is high & amylopectin low& amyl amyl pectin is low pectin is high b)Botanical origin:  5 according to Sharma etal O. rufipogon(griff) perennial wild 2n=2x=24 AA & O. nivara annual wild are the two progenitors of cultivated Asian rices which are widely distributed in India. O. rufipogan X O. nivara O sativa O longistromiae &O breviligate having chromosome no 2n=2x=24 gg and 2n=2x=24 AA respectively are believed to be the progenitors of African cultivated rice i.e. O glabarima. O longiglumis X O breviligulata O glabarima The views regarding the origin of rice can be grouped in to two classes a) Polyphyletic origin b) Monophyletic origin Most of the modern rice workers believe that origin of cultivated rice monophyletic. From oryza perennis rose the Asian rice in South East tropical Asia and African rice in the upper valley of Niger River in West Africa. Eco-geographic races hydro-edaphic-cultural-seasonal regime  6 Upland (dryland) Indica aus (summer) Boro (winter) T-aman (autumn) Cereh, others low land (wet land) Deep water, B-aman Floating Javanica Bulu (awned) Gundil (awnless) Sinica/japonica Upland Lowland Genetics of certain important traits: 1)seedling vigor: early seedling vigor in upland rices help the plant to establish quickly. cover the ground & smother weeds.it also helps the roots to spread inside the soil so that seedlings survive even during the drought stress, it is a quantitative trait but combines easily with other desirable characters. 2)habit: semi erect habit of the rice plant is preferable to erect or spreading habit. erect habit retards sun light interception due to inter shading. in case of spreading habit the leaves of nibouring plant shade one another & do not allow the efficient utilization of solar energy. erect or spreading habit of rice is a wild trait or dominant trait controlled by single gene so it segregate in the ratio of 3:1 &spreading type is completely dominant over erect type. 3)culm: in larger areas of India and other countries rice is grown in deep water many traditional varieties grow in varying depth of water(1-5cm)in these varieties the culm elongates with the rise in water level & roots at the node. The genes for semi dwarf ness & floating habit are are non allelic& can be combined. Such hybrids remain dwarf under normal conditions but the stem elongates if flooding occurs. Flooding habit of rice is controlled by recessive gene at both the loci & dominent gene controls the normal habit, it folloes duplicate dominent gene interaction segregating in the ratio of 15:1. Dwarfing genes----dw1 dw1 dw2 dw2 (deep water) Elongation genes----ef1ef1 ef2ef2 eui---elongation of upper inter node. er---- erect growth habit. 4)flag leaf: semi erect flag leaf is considered to enhance photosynthetic efficiency of rice plant particularly at the grain filling stage, and hence this character is considered desirable. It is also believed that it saves panicle from bird damage, similarly slow senescence of leaves & panicle is considered to be a desirable character to promote greater photosynthetic activity & better grain filling.  7 5)Hairs : presence of trichomes on the leaves will resist the insect to lay eggs there by the pest resistance of the plant is accomplished. Two loci are governing the hairey ness(non glabrous) of the leaf H1H1H2H2 the character is governed by duplicate genes which can be easily incorporated through breeding. Cooking quality: The amylose content and gelatinsation temperature of starch determine the cooking quality of rice. The proportion of Amylose pectin is associated with stickiness of cooked rice. The variety with high Amylose type cook dry and pluffy. become hard on cooking. This trait is important in case of hybrids production. i.e, in case of KRH1 and KRH2 having high Amylose content. Aroma: Presence of fragrance in rice kernels is liked is India and hence scented rice fetch a premium price irrespective of size and shape of kernels and the inheritance of this character has not been fully understood. Efforts have been made to breed scented types with partial success. Floral biology and floral structure: The inflorescence of rice is a panicle. It consists a main axis with primary branches the secondary branches are toward basal regions of primary branches only rarely tertiary branches could be seen at the base of secondary branches. Spikelets are born these branches. Their no varies from 80 -300 in panicle. A spikelet of rice ( 0. sativa) consist of two short ( rarely long ) sterile lemmas, a fertile lemma and a palea – all structured on a rachilla. The fertile lemma some time bear a short or a long awn. Inside the fertile lemma and palea, are 6 stamens and an ovary with a feathery, bifid stigma. At the time of anthesis the lemma and palea seprate out. The filaments of stamens elongate and protude out and anther’s dehisce releasing the pollen in the air often the pollen grains fall on the same plant causing self pollination and fertilization. The ovary develops into a caryopsis. The lemma and palea become tough ad protect the caryopsis as husks. Floral biology: For entire panicle to bloom takes 2 – 8 days. Blooming is basipetal, blooming occurs between 10 AM – 2 PM stigma receptivity is seen for 2 – 7 days (maximum on 1st day and gradually decreases) pollen remain viable for 5 minutes only.the extent of natural crossing varying 0 to 3% with an average of about 5% depending upon varitey season and environment. Its chasmogamous nature is exploited by many breeders in breeding programme. Anthesis and Pollination Spikelet in a panicle bloom in nearly fixed order. Spikelets on the top branches open first and the spikelets on the lower branches open last. It takes 4 to 7 days for complete opening of all the spikelets in a panicle. The anthesis of rice inflorescence normally  8 occurs between 10 a.m. and 2.0 p.m., although weather conditions influence floret opening to a great extent and also with the type of cultivars. Anther dehiscence may coincide with opening of lemmas to shed pollen on the stigma. The lemma and palea close after the pollen grains are shed from the anther sacs. From anthesis, the panicle takes around 30-35 days to grain maturity. The fruit is known as caryopsis enclosed by lemma and palea that forms the husk. New Plant type concept The new plant type stresses the need for increasing the harvest index of rice crop which is aimed to be increased to 0.55. The strategy envisages increasing the biomass per unit area and hence grain yield by plating less profuse tillering but high panicle weight genotypes at high density by manipulating crop geometry. The model genotype combines advantageous features of both indica and japonica and with most japonica characters. The characteristics of NPT 1. Semidwarf habit, 5-6 productive tillers, sturdy stem and dark green upright foliage 2. Heavy panicles with high grain number (200 - 250) and high test grain weight (around 25 gm / 1000 grains) 3. More foliar growth during crop establishment 4. Less foliar growth and enhanced translocation of assimilates from leaf to stem during late vegetative and reproductive phases 5. High and descending concentration of tissues N from top to the base of plant canopy 6. Increased capacity of stems to store assimilates 7. Improved reproductive sink capacity with prolonged period of ripening 8. Increased harvest index The concept was initiated at IRRI, Philippines and was subsequently efforts are being taken at IARI New Delhi. Collection , conservation and use of germplasm The systematic collection being made mainly by IRRI since 1972 , had led to the ex situ conservation of over 1,00,000 accessions in gene banks. Of these about 50,000 were collected from Asia and Africa through the joint efforts of NARs and internatioanl institutes including IRRI, IIRA, WARDA, IBPGR, FAO, IRAT, OSTROM, Japanese Agencies etc. Nearly the entire global collection is being conserved under long and medium term storage at IRRI and partly duplicated in china, India, Japan and USA. Indian germplasm exceeding 30,000 is being conserved at the National Bureau of Plant Genetic Resources (NBPGR) under the ICAR at Delhi. Single seed descent (SSD) method coupled with rapid generation advance (RGA) Instead of taking one crop a year of a long duration photosensitive variety under field condition three crops can be taken by SSD - RGA strategy. This method reduces the time taken for breeding cycle. The F2 - F5 bulks derived from SSD grown in green houses without selection. Shuttle breeding  9 Shuttle breeding involves raising of breeding populations alternatively at two agroclimatically and diverse environments in order to make use of favourable environments available environments. INNOVATIVE BREEDING in RICE 1. Anther culture(100 new varieties in China and 42 new varieties in Korea) Eg. Hua Yu 1 and 2 For the production of doubled haploids; japonica are more responsive than indica types n 2. Wide hybridisation 3. Genetic engineering 4. DNA marker technology Rice Genomics The entire rice genome of Oryza sativa has been mapped Development of Monosomic Alien Addition Lines (MAALS) In wide hybridisation F1 hybrids between species belonging to different genomes of the genus are completely sterile and are good source for production of Monosomic Alien Addition Lines (MAALS). Progenies advanced through embryo rescue technique and backcrossing to recurrent parent have led to recovery of plants with normal chromosome complement plus addition of one chromosome of 5 wild sp viz. 12 chromosomes of O.officinalis, 11 chromosomes of O.latifolia, 8 of O. australiensis, 6 of O.minuta and 7 of O.brachyantha. MAALS are useful in RFLP mapping to detect introgression of useful genes from wild sp and are additional sources of genetic variation. Wide hybridisation A number of useful genes have been introgressed into cultivated rice from the wild germplasm. Transfer of resistance to grassy stunt virus from O.nivara (eg. IR 28, 29, 30, 32, 34, 36), brown plant hopper from O.officinalis (MTL 98, MTL 105 in Vietnam) and bacterial leaf blight from O.longistaminata (IR 24) are some of the successful transfer of resistance genes through wide hybridisation. Diversification of sources of cytoplasmic male sterility is another important objective of wide hybridisation. New cytosterile stocks alternative to the widely used WA have been developed using male sterility inducing cytoplasm from O.rufipogon and O.nivara (V20A, Zhenshan 97A, IR 58025A), Oryza glumaepetula through backcrossing. Porterisia coarctata is the donor salinity/alkalinity tolerance and O.rufipogan and O.glaberrima are donors for acidity tolerance. Genetic transformation Transgenic rice carrying insecticidal protein gene from Bacillus thuringiensis , chitinase gene from bacterial and other sources and bacterial leaf blight resistance gene, Xa 21 from O.longistaminata have been developed. Engineered rice with better nutritional quality (Golden rice with more Vit A and iron) submergence tolerance and male sterility are expected to be available soon.  10 Pedigree breeding procedure for rice Pedigree method of plant breeding is the most common method in rice. P1 X P2 (crossing and collection of crossed seeds) F1 hybrid (wider spacing of F1s along with parents) (collection of F2 seeds ) F2 (minimum of 5000 plants, space planted (30 x 15 cm), agronomically poor F2 crosses are discarded, individual plant selection, for screening for biotic stress no use of pesticide and fungicide and growing of spreader rows, screening for abiotic stress growing the F2 in hot spot, maintenance of pedigree record, seeds from individual plants are collected separately) F3 - F5 (pedigree nursery, seeds from single plant selections are planted in three rows of 5 mt length, 20 x 10 spacing, both family and single plant seletion) F6 bulk (tested for uniformity, grain quality, resistance for biotic and abiotic stresses) Observational yield nursery, prelimenary yield trial, comparative yield trial, multi location trial, adaptive researach trial, vareity release. National Research Institutes on rice a. Central Rice Research Institute , Cuttack b. Directorate of Rice Research, Hyderabad c. Indian Agrl Res Inst., New Delhi Objectives of Breeding Increasing production is achievable by capturing the yield potential of the existing varieties, stabilizing and increasing yield through developing varieties with resistance to biotic and abiotic stresses are the main breeding objectives for rice. 1. Enhancing Yield: Rice yields ranged from as little as 1 t/ha in many countries of Africa to more than 6 t/ha in China, Japan and South Korea. Genetic improvements in rice and the development of modern rice varieties, along with improved cultivation practices, account for the impressive growth in the production. To meet the increasing demand for rice, development of varieties with high yield potential by combining morphological characteristics like semi-dwarf high tillering, thick culms, compact panicles, erect leaves to reduce shading and utilize solar radiation efficiently and physiological characteristics like early maturity, photo-insensitivity and fertilizer responsiveness. The broadening the genetic base of the present day high yielding varieties necessitates the initiation to identify tall landraces with diverse and still  11 unexploited yield genes and pool the harmonious ones by convergent recombination breeding for evolving varieties with higher yield potential. 2. Stability and Adaptability: Stability particularly in yield refers to the ability of the plant genotype to express yield potential over a wide range of environments. The rice crop is grown over a wide range of climatic conditions and soil types including drought prone areas between 450N and 400S and over land from sea-level up to 3000 meters above the sea level. Hence we need to develop varieties for different agro-ecological situations. Constraints to productivity of rice crop due to seasonal fluctuations, such as low light intensity, floods, submergence, drought and others factors need to be taken into account to develop varieties that are suited to a specific location. Characterization and demarcation of areas on the basis of their relative vulnerability to weather aberration help in develop varieties to utilize still unexploited and under exploited seasonal variations to maximize the productivity potential. 3. Disease and Pest Resistance: The rapid development of dwarf high yielding rice varieties and their spread together with high management and intensive cultivation resulted in the outbreak of pests and diseases. Yield losses due to pests and diseases were estimated to be around 10-51% (Kalode and Krishnaiah, 1991). Rice harbours about hundred pests of which atleast twenty are important. Besides age old problem of blast and brown spot, rice crop today suffers from viral, bacterial and other fungal diseases as well as from many insect-pest damage. Development of virulent strains of pathogen and rapid emergence of insect biotypes emphasizes the need to pyramid different resistant genes into an elite genetic background. Identification of suitable novel donor sources as well as understanding their genetic control of inheritance is necessary for the development of varieties with resistance/tolerance to the specific pests/diseases and deployment in target areas. Crop management following the Integrated Pest Management as well as Integrated Disease Management also plays an important role in resistance breeding strategies. Name of Disease Donor Bacterial blight Xa-4, B-J-1 and TKM-6 Blast Ram-tulsi, Tetep and M-302. Ambemohor-157, IR-20 and Tungro Kamod Grassy Stunt IR-28, IR-29, IR-30,and IR-34. Name of Pest Donor Brown plant hopper Babawee, Rathu Henati Gall midge PTB-10, PTB-18, PTB-21 TKM-6, MTU-15, TKM-3, and Stem Borer Ratna 4. Quality: Rice grain quality is a combination of many characteristics that affect its market value and utilization as food. Breeding objectives for quality in rice may be grouped into four classes: Market quality, Milling quality, Cooking and processing quality, and Nutritional quality.  12 4.1. Market quality: Market quality refers to the general appearance and physical properties of rice grain such as size, shape, uniformity of grain, hull pubescence, translucency, colour, freedom from chalkiness of kernel, etc. Depending on the geographical region, the preference of various quality traits also varies. Rice is classified in the market as long grain, medium grain or short grain as well as length/width ratio, thickness and grain weight. Each grain type possesses specific milling, cooking and eating qualities. 4.2. Milling quality: The unhusked rice grain is called rough rice or paddy. It is converted to brown rice by shelling the hulls and converted to milled rice by removing off the outer bran layers. The milling quality is determined by the yield and head rice (whole and broken grains of three quarter size or larger) to total rice, short and medium grain cultivars normally give larger mill yields than long grain cultivars. The milling output or recovery of head rice of advanced breeding lines need to be evaluated rigidly to ensure that newly released cultivars will produce high yields of head rice and total milled rice. 4.3. Cooking and processing quality: Cooking quality of rice is determined by physico- chemical properties of starch. Among them, amylose content determines the relative stickiness or dryness of cooked rice. Varieties with high amylose (> 25%) content cook dry and flaky, while those low amylose content cook sticky. Gelatinization temperature (GT), determines resistance to cooking. In India, moderate GT as well as intermediate amylose content is preferred. Water uptake, amylose content and alkali reaction which measures gelatinization temperature are rated as predictors of cooking and processing characteristics. High amylose content, medium GT and low water absorption characterize long grain cultivars whereas low amylose, low GT and high water absorption characterize medium and short grain cultivars. 4.4. Nutritional quality: Breeding for improved nutritional quality would be beneficial if it could be accomplished without any yield loss. Protein averages about 8% in brown and 7% in milled rice. Although relatively low in protein compared to other cereals, the nutritional value rice protein is high due to its favourable balance of amino acids. Milled rice is relatively poor in fat, protein and a number of vitamins and micronutrients, particularly deficient in lysine, vitamin A, iron and zinc. Biofortification for enrichment of vitamin A as well as micronutrients into elite genetic background is also an important objective of breeding for quality. Gene sources for high iron (Nilagrosa, Jalmagna, Tong Lan, Mo Mi, Azucina) and zinc (Conjay Roozay, Zuchem, Xua Bue Nuo) are an important resources for the improvement of quality in rice. Aromatic rices: Among the best quality rices which are grown in India, the aromatic rices, Basmati rice are important fetching highest premium in the International market for its unique quality. The Basmati rices are characterized by long slender superfine grains with pleasant aroma, extra elongation of kernel and soft texture, palatability, easy digestibility of cooked rice which is unmatched by any other rice variety. Besides Basmati, India also owns a large number of non-Basmati aromatic rice varieties grown and adapted to the specific agro-ecological conditions of the different rice growing regions of the country. The traditional Basmati cultivars are tall, prone to lodging, photoperiod and temperature sensitive and very low yielding. Therefore, to combine the quality attributes of basmati rice in the high yielding background, a systematic programme on genetic improvement of Basmati rice was initiated at Indian Agricultural Research Institute, New Delhi and other state Agricultural Universities. This resulted in the development of varieties like Basmati- 217, Type-3, Basmati370, Taraori Basmati, Basmati-386 and Ranbir Basmati, Sabarmati,  13 Impoved Sabarmati, Pusa 33 etc. which laid foundation for the Basmati breeding programme. Pusa Basmati-1, the first semidwarf photoperiod insensitive and high yielding Basmati rice variety has revolutionized the Basmati rice production. This variety contributes nearly 50 percent of the total Basmati rice export in value terms approximately Rs.1000 crores per annum. Intensive breeding efforts and rigorous screening for grain and cooking quality characters resulted in the development varieties like Punjab Basmati-1, Kasturi, Mahi Sugandha were released. Recently several varieties namely, Pus Sugandh-2, 3, 4, (Pusa 1121) and 5, Yamini (CSR30), Vasumati and Pant Sugandh Dhan-15 have been released. Pusa RH-10, is the World’s first superfine grain aromatic rice hybrid, with 40 percent higher yield was developed at Indian Agricultural Research Institute, New Delhi. Molecular analysis has revealed chromosome 8 (aroma), chromosome 1,2,3,6 and 11 (kernel elongation), chromosome 1, 2, and 7 (amylose content) chromosome 3, 4, 6 and 7 (grain length) and chromosome 10 (grain breadth) important for quality traits. 5. Breeding for resistance/ tolerance to drought/ water deficit Stress due to water deficit frequently occurs in all type of rice cultures even in irrigated areas. The rainfed cultures are more prone to drought. Varietal difference for drought resistance is one of the most complex dynamic responses to ecological races. Drought stress has location and growth stage specificity. 4 types of physiological mechanism involved in plant reaction to drought. 1) Escape - mainly by early maturity 2) Avoidance - mainly by deep and extensive root system and some water conservation reaction such as leaf rolling. 3) Tolerance - it is attributable to less understood physiological adjustment in plant tissue. 4) Recovery ability after rehydration - It is related to vegetative vigour. Escape and Avoidance - are important in dryland culture. Tolerance and Recovery - operate under rainfed wet-land culture. At IRRI, >5000 rice cultivars and lines have been screened for drought resistance in field. Resistant sources at vegetative phase are numerous, while few cultivars can withstand prolonged drought at the reproductive phase. Some deep water rices can tolerate drought at the juvenile plant stage. 6. Breeding for resistance/ tolerance to submergence Excess water affects deep water and floating rice. Stress due to excess water occurs as plant submerges during flash floods or prolonged rice in water depth, which necessitates rapid elongation of stems. Cultivars adapted to such condition generally have tall plant stature, internode elongation ability, submergence tolerance, kneeing ability following water withdrawal and photoperiod sensitivity (to synchronized grain ripening with receiving water depth). The most interesting variety group is Rayada rice of Bangladesh which have 11 months growth duration, ability to withstand 5 m water depth, a lack of grain dormancy and unusual long periods in both vegetative and photoperiod sensitive growth phases.  14 Zn deficiency and Salinity are additional problems frequently associated with deep water rice. Prospects of increasing grain yield in stress prone condition is limited, but yield stability can be insured with inbuilt tolerance mechanism. 7. Breeding for tolerance to high temperature Extremely high temp (>45C) at flowering time can reduce spikelet fertility. Extremely hot and dry weather at the time of anthesis may lead to failure in pollination and seed set. Such adverse conditions are found in Pakistan and sub-saharan area of west Africa. 8. Breeding for tolerance to low temperature Low temperatures at the two ends of growing season affect even larger areas at high latitudes or altitudes. It is the major constraint in south & south east Asia. Tolerance to cool temperature may enable farmers in sub-tropical & temperate area to grow two rice crops in a year. Low temp tolerance is more crucial in introducing modern varieties to marginal areas. Plant reaction to cool temperature is also specific to site and growth stages. Recovery during vegetative phase is more promising than at reproductive phase. 9. Breeding for tolerance to adverse soil factors Among the soil stresses, salinity and alkalinity are the most wide spread factors. Arable areas with adverse factors (salt, alkali, acid or organic matter) is observed among >100 million ha in Asia. Mineral toxicity and deficiencies are associated with acid, acid sulphate and peat soil. The elements are A1, Fe, Mn and Zn. Associated mineral deficiencies are N and P. Plant reactions to soil stresses vary with planting method i.e., seedling stage and developmental stage of plant. Many traditional cultivars have sown high level of tolerance to most of the soil stresses. A high level of salinity tolerance is present in a wild relative Porteresia coarctatum of the Bengal Bay areas. 10. Breeding for early maturity This character is desired to have multiple cropping. It also helps to overcome terminal drought and to escape from pests and diseases. The optimum early maturity is around 105 days in rice. Ideal plant type i) Short stature ii) Thick, stiff culm iii) Compact panicle that hold plant erect iv) Short, narrow, erect leaves to effectively utilize solar radiation v) High tillering vi) Non/low photosensitivity vii) Nitrogen responsiveness viii) Flag leaf angle – not more than 400  15 11. Breeding for resistance to lodging and shattering Non-lodging lines will have short stature, thick strong culm, short internode and leaf sheath tightly encircling the culm. Methods of Breeding Rice breeding in India was initiated at the beginning at 20th century. In 1952, FAO started a japonica-indica hybridization project aimed at transferring genes for fertilizer responsiveness from japonicas to indicas for increasing yields in South and South East Asian countries while retaining the quality and adaptability of indicas suited to these countries. A parallel scheme was taken up by the Indian Council of Agricultural Research (ICAR) for Indian states. The japonicaindica hybridization project could achieve limited success because the japonica parents selected from temperate regions were thermo-and photo-sensitive and also the hybrid combinations resulted in highly sterility due to restricted recombination. Only four varieties namely, Malinja and Mahsuri in Malaysia, ADT 27 in Tamil Nadu (India) and Circna in Australia could be released through this programme. To boost production and productivity in all the rice growing states and to have a coordinated approach to rice research at National level, an All India Coordinated Rice Improvement Project (AICRIP) was established by ICAR, in 1965 with headquarters at Hyderabad. The various breeding approaches for increasing rice production representing diverse ecological zones can be grouped into conventional approaches and molecular approaches. 1. Conventional Approach (i). Varietal improvement: The major break through in rice breeding as achieved with semidwarf, fertilizer responsive non-lodging plant type with greater capacity to trap solar energy for increased photosynthesis through efficient foliar architecture with the development of TN-1an indica rice from the cross between tall indica Tsai-Yuan-Chung and Dee-geo-wu-gen (DGWG) dwarf mutant. Introductions played an important role in varietal improvement so as to enlarge and enrich genetic variability. The International Rice Research Institute (IRRI) located at Los Banos, Philippines through extensive breeding programmes has been distributing improved cultivars and breeding lines throughout the world. Mahsuri from Malaysia; Taichung (Native) 1, Taichung 65 and Tainan 3 from Taiwan; IR8, IR20, IR36, IR50, IR64 etc. from IRRI have become very popular and opened the gateway to green revolution. Similar Indian varieties like Jaya, Rasi, Sona, Swarna etc. being adopted in several countries. International Network for Genetic Enhancement of Rice (INGER) has proved an excellent vehicle to take advantage of exotic varieties / breeding lines. a. Pure line breeding: This simple breeding / selection approach had its strength in the early years of breeding in the existing rich variability to isolate improved strains or varieties which have been widely cultivated. The process of purification starts either at farmer’s field or farmer’s strains raised at experimental station. Seed harvested from promising plants are raised in successive generations till they become uniform and stable. Following seed increase, the  16 chosen best line(s) is intensively evaluated in replicated yield trial before it is released for commercial cultivation. Several hundred varieties have been developed by pure line selection. Some of the varieties develop through pure line selection that became very popular are with quality characteristics like GEB24, Mozhgolukulu, Basmati370, Taraori Basmati, etc., saline tolerant varieties like SR26B, Ptb33, Co44, Latisail etc. and deepwater rices FR13. b. Pedigree method: Pedigree method of breeding is the most common method of rice breeding. Rice being a self pollinated, recombination breeding consisting of controlled crosses between parents of choice followed by selection for superior recombinants in the segregating generations for targeted traits is the widely employed approach in rice improvement. To combine a set of trait that make a variety unique, convergent improvement approach which involves stepwise addition of constituent traits is the best approach. Pedigree method is followed for improvement of both qualitative and quantitative traits where land / laboratory facilities and manpower are adequate while modified-pedigree or mass-pedigree method of selection is followed when selection environment is not appropriate to discriminate desirable genotypes from undesirable ones. In mass pedigree method, the segregating generations are bulked up to five generations from F2 followed by pedigree selection. The selection methodology employed also varies depending on the genetic control of target trait as well as conducive environment for effective selection. Shuttle breeding which involves raising of breeding populations alternatively at two agro-climatically diverse environments by practicing selection at one center and advancing generation at the other to take advantage of its favourable weather or selection and generation advance at both the centers. c. Back cross method: Back cross method of breeding is used for transferring simply inheretted specific trait (s) to an improved variety that is deficent in that trait. In this method invariably an improved variety (A) is one of the parents of the cross & other parent (B) is one with the trait to be transferred to parent (A).Parent A is called take recipient or recurrent parent while B is called donor or non recurrent parent. The varieties developed by this backcross method are peta, Sabarmathi & Jamuna by back crossing (Taichung native 1x basmathi 370) B – 2655 (Mandya released – highly resistant to blast and stem borer) d. Bulk population method: Bulk population breeding is essentially involves handling of seggregating generation in bulk. With out any artificial selection. Early breeding work at the IRRI. The bulk method prove to be in effective for breeding high yielding dwarf types. Because of the deleterious effect of plant competation in seggregating generation The bulk population breeding is modified such as to 1. Reduce the effect of plant competation in seggregating population using parents of similar morphology in crosses.  17 2. Fixation of population with minimum bio-potential variability adopting single seed decent method of advancing the generations. 3. To shift the population in desried direction by exposing the bulk population to serve selection pressure. Bulk population method is extremely slow. Modified bulk population in combination with pedigree method at later generations may speed up the process. (ii). Breeding for Biotic Stresses: Resistance of host plant has been at greater importance in controlling spread of disease and pests. Several concerted efforts were made to evaluate rice germplasm against various pests and diseases and to identify sources of resistance. Utilizing these donors, resistance was incorporated into rice varieties developed for different rice ecosystems. However, of the sources available only a few donors were utilized for the development of various resistant varieties thereby leading to narrow genetic base of the present day. Hence, we need to utilize these sources to broaden the genetic base of the cultivars. Through conventional methods like selection, hybridization many varieties which are resistant to various biotic stresses have been developed. Wide hybridization between rice and related wild spreads has played an important role in the utilization of useful genes from wild species for resistance against brown plant hopper, white backed plant hopper, bacterial blight, blast and tungro. Various strategies to effectively manage the disease/pest either by sequential release of varieties with matching resistance gene or varietal mosaic consisting of planting varieties carrying different resistance gene is yet another approach in the endemic areas. (iii). Breeding for resistance to abiotic stresses: Abiotic stresses are caused by several factors such as high temperature, stress, low temperature or cold stress, excess of water causing submergence stress, water-logging stress or flooding stress or water deficit stress like drought, increased salts chemicals etc. that the plant development at various stages. Varietal tolerance is the most reliable and cost effective strategy, although the nature of their genetics as well as stress environment is complex in nature. Of the various breeding strategies, pure line selection in the native well adapted varieties to a given stress environment as short term approach is given emphasis. In order to develop high yielding varieties combining tolerance to abiotic stresses there is need to identify donors possessing different mechanisms of tolerance to abiotic stresses. (iv). Mutation breeding: Mutation breeding is very useful in situations where only one or two simple changes in well adapted local cultivars are needed so as to include gene complexes for tolerance to biotic and abiotic stresses, grain quality etc. A wide array of physical and chemical mutagens has been evaluated on rice and a wide array of economically useful point mutations affecting plant height, leaf, panicle, grain type has been recovered. Some of them have been either released directly as mutant varieties used as donor sources for improving specific characters. Among the notable mutants were early maturing Reimei of Japan, RD 15 of Thailand, dwarf statured fertilizer responsive Jagannath of India, Calrose 76 of the USA. Jaganath , Satteri – state varitey releasing committee. Hybrid mutant 25 – Punjab Purbani – maharastra AU-1----Tamilnadu 1 Au – 1 ---Pondichery  18 Indira – orissa Biraj – west Bengal (v). Heterosis breeding: Heterosis in rice was reported first by Jones (1926) followed by many researchers {Ramaiah (1933)} to an exploitable level for grain yield. The first commercially usable CMS (Cytoplasmic Male Sterility) line Wild Abortive (WA) type as a spontaneous male sterile plant in a population of wild rice O. sativa f spontanea was developed by Chinese scientists. This effort led to the successful development of hybrid rice technology where China released the first hybrid for commercial cultivation in 1976. Hybrid rice has a yield advantage of 15-20% over the best inbred varieties. Following the success of hybrid rice in China, IRRI initiated research to evolve hybrids ideally suited to tropical environment. Similarly countries like India, the Philippines, Vietnam launched hybrid rice breeding programme. Rice, with its wide variability, shows both nuclear and cytoplasmic male sterility system, many of these systems have been commercially utilized for hybrid seed production. There are three types of hybrid development system based on the number of parental lines involved: Three line hybrid system, Two line hybrid development system, One line hybrid development system. CMS source - Wild abortive (WA) Other CMS sources - GA (Gambica), Di (Disi), DA (Dwarf wild rice), BTC (Chinsurah Boro II), IP (Indo Paddy 6) a. Three line hybrid development system: It is based on cytoplasmic genetic male sterility stem, involving a CMS line, maintainer line and fertility restorer line designated as A, B and R lines respectively. This male sterility system is the result of interactions between male sterility inducing cytoplasm and nuclear fertility restorer genes. The genetic constitution A, B and R lines are rf rf / S, rf rf / N and Rf Rf / S/N, respectively. A CMS line is maintained by crossing it with its B line (maintainer line). The A and B lines are similar in all respects except the former is male sterile and the later is male fertile. The restorer gene possesses dominant fertility restoring gene. The hybrid seed is produced by crossing A and R lines and is fully fertile. The seed harvested from A-line after pollination with ‘R’ line is the hybrid seed. This three line system has been widely used in India particularly the WA source for the development of hybrids. Cytoplasmic genetic male sterility system in hybrid seed production is depicted as follows: Several strategies are adopted to entrance and production on the female plants some of the strategies adopted are 1. Planting across the wind direction to increase pollen dispersal on female plants. 2. Clipping of flag leaves of male sterile and restores lines at booting to facilitate pollen circulation. 3. Applying 20-30 ppm GA3 to male sterile and Restore lines at heading to promote emergence of panicle from sheath. 4. 4. Supplying pollination by rope pulling during flowering. Chinese now getting hybrid seed yield more than 1000 kg/ha. The seed rate used is only 25% of the conventional varieties and the country has sufficient manpower for hybrid seed production so the hybrid rice is popular in china.  19 The countries where manpower is expensive and higher seedling rate is necessary. This production technique is not economically acceptable. Generally the hybrids must yield 25% higher than the commercial varieties to become technology commercially reliable. E.g. Karats Hy.1-(Saihydri). Note:
The first CGMS was developed by Shinjyo and omora is 1966 by substituting Taichung – 65 nucleus with chinsura boro cytoplasm.
In 1973 Yoan her field a spontaneously occurring male sterile plant is oryza sativa spentura and called it wild abortive (WA cytoplasm) Steps involved in Hybrid breeding: 1. Development of CMS line 2. Maintenance of CMS line 3. Production of F1 hybrids. i) Development of CMS line Wild abortive x Mangala (CMS source) Maintainer line Donar parent Recurrent parent 5-6 back crosses to develop Mangala A line ii) Maintenance of B & R line by selfing Chemically induced male sterility - Gametocides - male gametocides like Zinc methyl arsenate (4000 ppm), Sodium methyl arsenate (2000 ppm), Ethrel etc. These are applied to female parent at boot leaf stage Transgenic male sterility – barnase-barstar iii) Techniques in hybrid seed production 1. Maintenance of CMS line : A line x B line 2. Hybrid seed production: A line x R line Planting is done across wind direction to facilitate pollen Isolation distance 40-100m Isolation period 21 days Supplementary pollen like rope pulling 3-4 times on an thesis day. GA-3 (20ppm) is applied to make sterile line & restore line to ensure panicle exertion (Panicle opening)  20 b. Two line hybrid development system: It can be obtained in two ways. One is the use of chemical hybridizing agents (CHA) or gametocides, which when sprayed on the panicle kills the pollen and makes the plant sterile. This male sterile plant can be crossed with other parental line to obtain hybrid seed. Another method of obtaining two line rice hybrid is the use of Environmental Sensitive Genic Male Sterility (EGMS) where male sterility is induced by environmental conditions like Temperature (TGMS) and photoperiod (PGMS) and has been reported to be under genetic control. In this system, only a male sterile line and pollinator are required. Hence seed production is easy and economical. Temperature sensitive genetic male sterility (TGMS) system: The first TGMS line of rice, Annong-IS was isolated as a spontaneous mutant in China and the sterility is controlled by a recessive gene. In rice, temperate of more than 280C, the TGMS lines are male sterile, while at lower temperature (below 240C), these lines transform into fertile. Some other TGMS lines are Annong S, Hennong S, Novin PL 12, IR 68945, Pei Ai 64S etc. In tropics, where consistent temperature differences are found at different altitudes or during different seasons in the same location, TGMS system is ideal for developing two line hybrids. Photoperiod sensitive Genetic male sterility (PGMS) system: Rice is a short day plant, as the onset of short days is accompanied by panicle initiation, heading and flowering. The PGMS system, which is under the control of recessive gene, induces male sterility in response to day length of more than 18 hours, while these male sterile plants transform into male fertile when grown in day length less than 10 hours. The first PGMS source was reported in the japonica cultivar Nongken 58S. Some other PGMS lines are Zennongs, X 88 and 700 IS. Using this system, the hybrid seed production can be undertaken in the longer day length seasons, while the seed of PGMS line can be multiplied in the shorter day length areas / seasons. Ex: pci ai 6us X Tequing - Hunan ( 1994)  21 7001s X Xiushuiu - Ahhui (1994) pci ai 6 us X Shaugingil - Guangdong ( 1996) 5088 s X R187 - Hubei ( 1995) Advantages of two line system over three line system: There is no need for a maintainer line; hence development of hybrids is easy and simple. Any genotype can be utilized as pollinator parent thus ensuring greater flexibility in the choice of parents in hybrid combination. Negative side effects of male sterility inducing cytoplasm on the F1 plants can be avoided. The seed production programme is simple and more efficient. The field area ratio between the female parent’s seed multiplication, hybrid seed production, and commercial cultivation of an F1 hybrid is 1:100:10000 as against 1:50:5000 in three line systems in rice. In case of CHA induced male sterility system the female line multiplication and hybrid seed production can be undertaken at a common location. c. One line system of hybrid development: It is based on utilization of apomixis for hybrid seed production. In this system hybrid plant is produced by crossing two parental lines and it can be maintained indefinitely by apomixes without losing the genotypic constitution of the hybrid. This system is still in a preliminary state and has not generated any stable hybrid till now. Eg: One line method of breeding - Vegetative propagation - Micropropagation - Anther culture - Apomictic lines 6. Biotechnological applications i) Anther culture: Rice pollens and anthers are amenable to tissue culture and regeneration into whole plant. Culture of anther or pollen grains taken from F1 generation can yield rapid fixation of genetic homozygosis of new haploid genotypes following spontaneous diploidization and regeneration into whole plant. ii) Somaclonal/ Gametoclonal variant - can be obtained through tissue culture. Somaclonal variant with improved tolerance to salt & Al have been obtained. iii) Recovery of distant crosses: Tissue culture helps hybrid embryos of distant incompatible crosses to grow into F1 plants. This is the first essential step in alien character addition or substitution. Reduction of amphidiploid individual of homologous character parent, which will facilitate alien gene transfer. An example of successful interspecific cross across unrelated genome via embryo rescue was demonstrated by hybrids and derivatives of the cross O. sativa (AA) X O. australiensis (EE). iv) Protoplast fusion: It allows production of cybrids (hybrids from same cytoplasm & formation of mitochondrial recombination). v) Transgenic rice: Transgenics can be developed either by Agrobacterium mediated transformation or by direct gene transfer using microprojectile/gene gun method.  22 Transgenics for insect resistance, herbicide tolerance, virus resistance are being developed. Eg. Yellow stem borer resistant variety – Bt rice Golden rice - rich in β-carotene GOLDEN RICE: Rice is the most important food crop in the world and is eaten by some 3.8 million people. In some regions of the world where rice forms a stable component of diet, Vitamin A deficiency is major problem. Deficiency of this vitamin can cause symptoms ranging from light blindness to total blindness, xeroopthalmia & keratomalacia. It is estimated that around 124 million children are Vit. A deficient causing about 5 lakh children to go blind each year. Vitamin A deficiency also causes other health problems like diagram resouratert….. diseases & childhood diseases such as measles. Vitamin A nutrition to prevent 1-2 million childhood death per year. One of the cause of Vit.A deficiency in regions where the majority of calories consumed comes from rice is that milled rice contain no β-carotene (Provitamin A). One of the solutions of this problem is to engineer rice to produce proVit.A in the rice endosperm. β-carotene synthesis in rice grain gives them a characteristics yellow/ orange colour. Rice which is genetically enriched in pro Vit A is described as ‘golden rice’. Biosynthesis pathway of Pro Vit A is continuation of the lycopene pathway. a) Golden Rice - Three genes introduced: 1) Phytoene synthase (Psy) - obtained from daffodils 2) Carotene desaturase (crt 1) - from Erwinia uredovora 3) Lycopene β-cyclase (lyc) - from daffodils 4) Selectable marker- hygromycin resistance gene  23 Gene constructs of Golden Rice and Golden Rice 2: b) Golden rice 2 – Bacterial carotene desaturase gene (Crt 1) Maize Phytoene synthatase gene (ZmPSY) and Phospodhomannomutatase (pmi) – Selection gene, to avoid antibiotic marker Golden rice trait was genetically engineered into Indica rice cultivars (Golden rice 2). Indica rice is consumed by 90% of the Asian population, original golden rice was produced using Japonica var. Taipei 309. Golden rice 2 showed 23 fold increase in (up to 37 µg /g) in carotenoids compared with the original golden rice. MAJOR BREEDING ACHIEVEMENTS : 1. The Rice Green Revolution In the 1960s, scientists quickly realized that most tall traditional rice varieties lodged easily when nitrogen fertilization was applied, which was the major limitation to grain yield. The semi-dwarf (sd1) ‘IR8’ was the first high yielding rice variety developed from a combination between the Indonesian variety ‘Peta’ and ‘Dee Geo Woo Gen’ from Taiwan. The key factor responsible for the increase in yield potential was the improvement of the harvest index. However, even though IR8 had a major drawback regarding its poor grain quality, it still became the symbol of the green revolution in rice. Within a few years, many countries around the world were replacing their traditional cultivars with the modern high-yielding varieties.  24 The icon of the rice green revolution, when compared to traditional varieties, exhibits certain distinct characteristics; it has shorter stature, a shorter growth cycle, higher tillering ability, higher photosynthetic capacity, responsiveness to fertilizers (mainly nitrogen), and consequently much higher yield potential to high-input environments. In the following decades, IRRI developed IR36, which became the most widely planted variety in the 1980s and IR64 was the most used in the 1990s. In addition to these varieties, IRRI released a large series of IR coded varieties. However, while these newer materials were characterized by their resistance to disease and insects, they did not contribute significantly to genetic gains for grain yield. Scientists then believed that a new breakthrough in yield potential had to come through a new plant type. 2. The New Plant Type Donald (1968) was one the pioneers in the discussion of breeding for ideotype plants. Yang et al. (1996) suggested that in order to develop super high-yielding rice varieties it was essential to increase the biological yield. Searching for a second green revolution IRRI had been working on a new rice ideotype or new plant type (NPT) with a harvest index of 0.6 (60% grain, 40% straw weight) and with an increased ability for photosynthesis to increase total biological yield. Peng et al. (2005) considered the following components on this NPT: low tillering capacity, few unproductive tillers, from 200 to 250 grains per panicle, from 90 to 100 cm of plant height, thick and strong stems, vigorous root system, and from 100 to 130 days of growth cycle. These traits would allow the rice plant to transform more energy into grain production, increasing the yield potential by about 20% but with more input and cost. Even before IRRI, Japan was the first country to pursue research on the NPT idea. In 1981, Japan launched a project aiming at combining varieties from indica and japonica groups to develop a super high-yielding rice cultivar. Dingkuhn et al. (1991) carried out physiological studies to understand the yield potential limitations of the indica varieties. They observed that under direct seeded systems rice plants produced an excessive leaf area, which caused mutual shading and reduction in the canopy photosynthesis and sink size. In addition, they developed a large number of unproductive tillers. The development of this NPT was based on tropical japonica germplasm derived from Indonesia, being the source of low tillering, large panicles, thick stems, vigorous root system, and short stature. 3. Hybrid Rice The hybrid rice technology concept dates back to 1964 in China. However, only in 1970, when a wild abortive pollen plant was identified in Southern China, did the idea begin to materialize. In 1980, Shih-Cheng and Loung Ping (1980) published one of the first articles indicating the potential of hybrid rice. The proposed strategy then relied on the male sterility produced by the abortive pollen system identified in the wild species O. sativa L. f. spontanea.  25 Hybrid rice would then be produced through a so-called three-line system, where one line would have the genetic–cytoplasmic male sterility; the second line would be responsible for maintaining the sterility, and a third one would be used as the matching parent for the hybrid with the responsibility of restoring the fertility. The first set of genetic–cytoplasmic male sterile lines was produced in 1970, while the first hybrid rice was released in 1974, with the hybrids out-yielding, on average, the conventional rice varieties by 20%. In 1999, the area planted to hybrids was about 15.5 million ha, representing 50% of the total rice area and 60% of the total Chinese rice production. Since 1994, hybrids have been released in India, Philippines, Vietnam, Bangladesh and Indonesia. The yield gains of the released hybrids in relation to the conventional varieties vary from 20% in Philippines to 30.2% in Vietnam. India has released six hybrids since 1989, however, the pace of adoption by farmers has been slower than expected and only in 200,000 ha hybrids are cultivated. To simplify the hybrid rice production system, the concept of environmental genetic male sterility (EGMS) was introduced. The two environmental factors considered were the photoperiod (PGMS) and the temperature (TGMS) sensitivities, which are controlled by recessive nuclear genes. This technology allows the use of any genotype with good traits as male parent, to obtain japonica hybrids (eg. it is difficult to identify restorers for this group), and to develop inter-group hybrids such as indica/ japonica (eg. there is no restriction regarding the restorer–maintainer relationship). The first two-line hybrid was released in China. It represented 17.2% of the total hybrid rice area in the country in 2001, some 2.67 million ha. 4. NERICA Rice Upland and lowland dry land environments are the two most important rice production ecosystems in Africa, where it is staple food for the sub-Saharan population. Certain challenging problems and environmental conditions as well as production practices common to these ecosystems limit rice production, such as weeds, diseases, and insect pressure, soil fertility decline, soil acidity, and drought stress. WARDA began a program to combine the two cultivated rice species O.sativa and O.glaberrima in 1991. Their genetic dissimilarity needed the use of a different breeding approach. ‘Embryo rescue’ technique was employed to obtain viable segregating populations. The newly developed materials were called ‘NEw RIce for Africa’ and were popularized as NERICA varieties. The main features of these new varieties, when compared to the traditional O.glaberrima cultivated by farmers, are their improved ability to compete with weeds, their larger panicles with around 400 grains and a higher yield potential. In addition, shattering is reduced, stems are stronger thus preventing lodging, maturity occurs around 30 days earlier than other conventional cultivars, and they have greater resistance to the most common biotic and abiotic stresses, as well as improved adaptability to the poor African rice growing soils. The success story of the NERICA varieties includes a strong participation of the farmers in the process of evaluation of the breeding lines as well as in the development of the materials (eg. farmer–breeder initiatives, participatory plant breeding).  26 Major Rice breeders : International - Yuan long ping, G.S.Khush, S.S.Veeramani - IRRI India - K. Ramaiah, R.H. Richarria, S.K. Sen, M. Mahadevappa Research Institutes : International – International Rice Research Institute (IRRI), Los-Banos, Phillippines Important varieties: IR8, IR20, IR64 India – Central Rice Research Institute (CRRI), Cuttack, Orissa Directorate of Rice Research (DRR), Hyderabad Basmati Varieties: Basmati – 370, Pusa 150, Pusa-523, Kasturi , DRR-Hyderabd, Pusa basmati. Important varities of rice: 1. Varieties for disease resistance a. Bacterial blight JR– 28, JR 30. b. Blast - IR– 28, IR 29. c. Ricetungro Greenhouse Field Intan Intan IR – 20 IR 20 d. Grassy stunt IR – 20 IR – 29 IR – 34 , 32. II. Variety resistant to indirect pest BPH - IR 28, IR 30, IR 34. List vas and hybrids released in India Name Parentage Distinct chacters Basmathi 370 Basmathi aromatic IR – 20 IR – 64 IR – 22 IR – 8 Peta X DGWG Jaganath mutant of T141 Jaya Karikagga Kasthuri Basmathi 370 X CR88 – 17.-1-5 aromatic Mahusri myangehos 80 X taichung 65 fine grain Mandya vijaya N22 (N22) Drought tolerant CTH3 (Bili mukti) improved aromatic TET144 Rani X Suraj Ratna persitent to sten borer  27 Sonamasuri TN– 1 DWGW / Tsai yaun chung MR – 136 (Mahu) Inportant varities for Karnataka Jaya, IR – 8 , IR – 20 sona , Pankaj, pragathi, KRH 1, KRH 2, Anna purna, Triveni, pusa 33, shakthi ,rasi, mandya vani. Hybrids ;KRH1, KRH-2, KRH-4 Imp hybrid: 1. KRH1, KRH2, APRH2, CoRH1, MGR1, CNRH3, PHB71. Famous international rice varieties Jasmine rice: A traditional rice variety of Thailand, it is known for its good quality. Texmathi : Imitation of basmathi by a firm in USA and downed by a company in UK. Golden rice: Rice transformed with genes that can produce provitamin is the grain which will be converted to vitamin A when eaten by humans Important research stations on rice: National level: 1. All India co – ordinate rice improvement project (AICRCP) 2. Central rice research insistute -cuttak (CRRI) International level :International rice research institute (Philippines) (IRRI) Future prospect Rice enriched with modern varieties and know how originating to great extent from IRRI will play an important role in the fight against hunger and unemployment. The evolution of semi dwarf rice varieties has changed the image of rice crop from that of a third world crop grown by poor farmers into that of a crop that has become a model for yield improvement in other crops. The next significant breeding step should be in term of combining the high yield potential of modern day semi dwarf varieties resistance to disease and insect pests and the cooking quality ,aroma of traditional basmathi rice biotechnological approaches will need refinement and efficiency for routine application in a rice breeding programmer. Further the potential of hybrid will have to be exploited on wide scale in other countries as in china.  28 SEED PRODUCTION PRACTISES FOR KARNATAKA RICE HYBRID – 1 1. Keep 100M isolation distance. 2. Plant rows across the wind direction. 3. Sow A line on first day and R line on 13 and 16th day after sowing of A line. 4. Follow 8A : 2R row ratio. 5. Plant A lines single seedlings/hill and R lines at 2-3 seedlings/hill. 6. Keep 10 cm distance between plants within rows for both A & R lines. 7. Keep 15 cm between A line rows, 25 cm between R line rows and 20 cm between A & R line rows. 8. Clip the leaves at full boot leaf stage. 9. Spray GA3, 60 ppm at 5 per cent flowering. 10. Pull the rope across the rows during anthesis (2-3 times in a day) 10. Rogue the off type plants during tillering and flowering. 11. Harvest the R lines first and then the A lines. 12. Seed produced on A line is the Hybrid seeds.  29 MAIZE Maize (Zea mays L., 2n=2x=20) is the world’s leading cereal crop with 604 million tonnes of production in 2001-02. United States produce nearly half of the total world production. The present world acreage is 138 million he ctares. From average grain yields view-point, maize occupies first rank among cereals (more than 3000 kg/ha). In India, the area and production of maize during 2001-02 has been about 6.5 million ha and 12.06 million tons respectively, with productivity averaging about 1841 kg/ha. The states growing maize on substantial scale are Uttar Pradesh, Bihar, Rajasthan, Madhya Pradesh, Punjab and Himachal Pradesh. Corn is queen of cereals as it has C4 photosynthetic pathway which is more efficient than C3 pathway under high temperature and dryland conditions. C4 plant are the most productive in terms of food nutrients produced per unit land area, per unit of water transpired, and unit of time under the conditions for C4 plants. it has a wider adaptability and is grown as far north as 15oN latitude in Canada and over most of the United States, throughout Mexico and Central America to as far south as Central Argentina and Chile in South America. It is adapted to Africa, Central Europe, and Asia. Morphologically, corns show a greater diversity of phenotypes than perhaps any other grain crop. Architecturally, the plant has many desirable features like sparse leaf arrangement allowing maximum light interception and minimum of mutual shading. The multiplication ration is very high whereby one seed is capable of producing a plant which in turn bears 400-1000 kernels and only 60,000 seeds are required to plant one hectare. Thus, corn is ideally suited for hybrid seed production in view of the above and practical feasibility of hybrid seed production based on mechanical detasselling/cytoplasmic genetic male sterility (Stockopf, 1985). ORIGIN The maize is indigenous to the Americas. It was domesticated about 8,000 years ago and does not survive in its wild form. The early American farmers evolved high yielding dent cultivars adapted to the central Corn Belt and the eastern and southern regions of the USA, and early maturing flint cultivars for northern USA. It is now generally accepted that the teosinte, the nearest known relative of corn, has been its progenitor. Opinion is still divided as to whether corn originated by a single domestication from the basal branching teosinte subsp. Zea mays L. spp. parviglumis or from the lateral branching subspecies, Zea mays L. spp. mexicana, or by a dual domestication from two subspecies Teosinte is native to Mexico and Guatemala and may be found growing wild in its native habitat. Teosinte differs from corn in that the pistillate spikes bear 6-12 kernels in hard triangular, shell like structures. Further, teosinte is prone to shattering (Peohlam and Sleper, 1995).  30 TAXONOMY The genus Zea characterized by male terminal inflorescences with paired staminate spikelets and lateral female inflorescences with single or paired pistillate spikelets, contains four species namely. (i) Zea mays (2n= 2x=20)-corn (ii) Zea mexicana (2n= 2x=20)- annual teosinte (iii) Zea perennis (2n= 4x=40)- perennial tetraploid teosinte (iv) Zea diploperennis (2n= 2x=20)- perennial diploid teosinte Teosinte is native to Mexico and Guatemala and may be found growing wild. It crosses readily with corn and produces fertile hybrids. Like corn, it is monoecious but produces dispersible seeds (6-12 only) in hard triangular shell like structures. The genus Tripsacum is a close relative of Zea. It is characterized by bisexual terminal and lateral inflorescences. The lower section of each inflorescence branch is female and the upper part is male. This genus includes 11 species (de Wet and Harlan, 1978). 1. T. andersonii, 2n =64 2. T. australe, 2n =36 3. T. bravum, 2n = 36 4. T. dactyloides, 2n = 36, 54, 72 5. T. floridanum, 2n =36 6. T. lanceolatum, 2n = 72 7. T. latifolium, 2n = 72 8. T. laxum, 2n = 36 9. T. maizar, 2n = 36 10. T. pilosum, 2n = 72 11. T. zopilotense, 2n = 36 All these species are perennial and may be found growing in Mexico, Central America and the South-eastern USA. CYTOLOGY Corn has 2n = 2x= 20. The 10 chromosomes of corn were first characterized by McClintock (1929) in the cells from the first pollen mitosis. Later on she found much better morphological details in the pachytene state of meiosis. The pachytene chromosomes are distinguishable from each other on the basis of overall length, centromere position (arm ratio), appearance of the centromeric heterochromation, characteristic chromomere and possession of knobs at specific chromosomal sites (knobs are blocks of heterochromatin that are not associated with the centromere). The length of different chromosomes and arm rations are as follows (Neuffer and Coe, 1974). Chromosome Unit length Arm ratio  31 1 229 1.23 2 196 1.42, 1.14 3 179 2.0 4 175 1.63,2.0 5 175 1.07 6 142 3.1 7 140 2.6 8 140 3.0 9 122 2.0 10 100 2.6 Carlson (1988) has described in detail the cytogenetics of cron. For cytogenetic work of corn, the most useful meiotic stage is pachynema. Variant positions of centromere have been found for chromosome 2 and 4. Mitotic chromosomes are easily counted in root tip squashes. C banding of metaphase cells with Giemsa produce differential staining of metaphase chromosomes, with specific regions (bands) staining brightly. In mitotic metaphase cells, the chromosomes assume a densely staining appearance in which euchromatin and heterochromatin are indistinguishable. Each chromosome has a band of light staining material referred to as the primary constriction (centromere). In addition, some chromosomes may contain a secondary constriction that usually corresponds to a site for nucleolus formation. In corn, the NOR is located on chromosome 6 (6 S) and is marked by a secondary constriction. The NOR is responsible for reforming the nucleolus after cell division. Regions of the chromosome that are condensed and dark staining are referred to as heterochromatin. March of heterochromatin in corn is unnecessary as knobs are highly polymorphic and their frequency varies considerable. Their presence/absence seems unimportant. Haploids are produced roughly 1 in 1000 kernels spontaneously. Now they are also produced by anther culture. Haploids are useful in production of inbreds quickly and in breeding using hybrid sorting technique. Trisomics and monosomics have been reported in corn. Reciprocal translocations, inversions, etc. are also reported. For details, Carlson (1988) is suggested. PGR’s: More than 13000 accessions have been maintained at CIMMYT, Mexico with duplicate storage in Columbia, Peru & National seed storage laboratory, Fort Collins, Colorado, USA. TYPES/ VARIETIES OF MAIZE BASED ON KERNEL STRUCTURE & SIZE – by Sturt 1. Dent maize - Z. mays indentas Dent maize has softer endosperm than flint types. It has characteristic depression or dent in the crown caused by shrinkage during ripening in the deposit of soft starch. The  32 deposit of soft starch at the crown is surrounded on the sides by hard starch and grains are hallow. Dent maize is widely grown in America. 2. Flint maize - Z. mays indurata Endosperm is hard, soft starchy at the centre; kernels are round on the top, cultivated in Europe, Asia, central and south America. 3. Flour maize – Z. mays amylaea Kernels are composed of entirely soft starch, kernels show variation in pigmentation, cultivated in dryer parts of USA and some parts of south America and South Africa. Flour maize resembles flint maize. 4. Pop maize – Z. mays evertas It is an extreme form of flint, kernels with hard and corneous endosperm, cultivated in Europe, USA and Australia. 5. Sweet maize/ Baby corns: Z. mays saccharata The kernels are wrinkled at maturiy, endosperm contains sugar and starch and unripe kernels are sweet in taste. 6. Waxy maize - Z. mays ceratina kulogh Kernels gummy and contains greater amount of amylopectin, cultivated for starch in Burma Phillipines, Eastern China and USA. 7. Pod maize - Z. mays tunicata identified by Sturt Kernels enclosed in a husk, ear is also enclosed in husk, not cultivated commercially. Maize is genetically the most extensively characterized crop among the higher plants for qualitative as well as quantitative inheritance. Compared to any other crop species more intensive genetic and cytogenetic studies have been carried out in maize. Genetic studies have contributed to understanding of gene mutation and quantitative genetic theory. Genetic mapping using molecular and morphological marker is more complete than most other plant species. More than 6100 genes have been identified and established on linkage maps of 10 chromosomes. Jumping genes / Mobile genetic elements / Transposons: Barbara McClintock(1950) & Creighton. She was involved in characterization of all 10 members of haploid set of chromosomes of maize. The mobile nature of jumping genes/ transposon/ mutation controlling factor was discovered and analyzed as Ac (activator) and Ds (dissociator) elements and their abilities to control and affect many number of genes was explained. They contain autonomous and no-autonomous elements. Transposable elements express distinct non-Mendelian properties by transposing from site to site of the chromosomes by regulating other factors. Xenia effect: It is the sudden effect of the pollen on the developing endosperm/ kernel. Yellow x White White x Yellow YY yy yy YY Endosperm YYy - medium yellow Yyy - light yellow  33 ♀ ♂ Endosperm genotype (secondary nucleus) (Pollen) & Color YY (Yellow) Y (Yellow) YYY (Yellow) YY (Yellow) y (white) YYy (medium yellow) yy (white) Y (Yellow) Yyy (light yellow) yy (white) y (white) yyy (white) Examples of xenia effect : Waxy/Non-waxy, Shrunken/Non shrunken, Starchy/sugary endosperm FLORAL BIOLOGY AND CROSSING Maize is monoecious plant under natural conditions it is cross-pollinated as about 95% of the pistillate flowers on a cob receive pollen from nearby other plants and about 50% of the kernels are a result of self-pollination. Maize is protandrous in which pollen shedding normally begins 1-3 days before the emergence of silk and continues 3-4 days after the silks are ready to be pollinated. It has been estimated that a single tassel may produce as many as 25,000,000 pollen grains or an average of over 25,000 pollen grains for each kernel on an ear with 800-1000 kernels. Pollen grains remain viable for 12-18 h and may be killed in few hours by heat or desiccation. In hot, dry windy condition, the pollen shedding may be terminated early or the tassel may be injured or the silk may loss the moisture and the cumulative effect of all these may lead to barren cobs (Poehman, 1987). For crossing purposes, the top of an car before the emergence of the silk is cut by a sharp razor and covered with butter paper bag. On the same day, the tassel of the desired male parent is covered with tassel bag. The anthesis (dehiscence of anthers) start from the central shoot of the tassel from top and proceeds downwards. This is done on those plants in which one-fourth of the tassel has dehisced. Pollination is carried out when a uniform growth of silk is visible. The tassel bag containing freshly shed pollen grains is transferred over the cobs after removing the silk bags. Before tassel bags or put on the tassel, all details like date of pollination and breeding programme to be carried out are clearly written by water proof pencil. To avoid contamination and to get enough pollen for pollination, tassel bags are put one day earlier. The date of pollination will be one day later than the date of tasselling. The tassel bags are held in position with the help of U clips. If there are two (plot 1 and 2) used in making crosses, and if plot 1 is used as male, than × 1 should be written on the tassel bag. Female plot numbers are generally not written. For self- pollination pollen of the same plant is used for pollination of the same plant. The sign used on the tassel bag for selfing is (X). For sibbing, pollen from one plant is applied to the silks of the adjacent plants within the same plot. For bulk-sibbing, pollen from one half the rows are bulked and used to pollinate the other half in the same  34 plot. The sign used for sib-pollination is #, and for bulk sibbing (#). Following precautions are observed (Kishan Narayan and Singh, 1980). (i) Bagging of the tassels should be done in the previous evening to avoid contamination from foreign pollen. (ii) Programme and date of pollination must be written on the tassel bags. (iii) The date of pollinations is one day later than the date of tasselling. (iv) Pollination must be completed within 3-4 h after the removal of tassels. (v) Pollination mush be completed within one week of silk emergence. QUALITATIVE GENETICS The genetic stock for qualitative genes of corn is maintained at the university of Illinois, urbana-Champaing. A Maize Genetics Cooperative Newsletter (MNL) is published by the USDA and the Department of Agronomy, University of Missouri, Columbia. This publication provides informal route through which qualitative genetical and related information are shared among corn geneticists. Exhaustive gene list of maize has been provided by Coe and colleagues (1988). A few important genes are listed in Table 4.1, (Neuffer and Coe, 1979; Coe et al., 1988). Table1.1 List of important genes of maize (Adopted from neuffer and Coe, 1974; Coe et al., 1988) Symbol Name Phenotype 1 2 3 Ac Activator Transposable factor, regulates Ds activity Adh 1 Alcohol dehydrogenase Electrophoretic mobility of enzyme, dimeric Adh 2 Alcohol dehydrogenase Electrophoretic mobility, of enzyme, dimeric Amy 1 Alpha Amylase Electrophoretic mobility monomeric Amy 2 Beta amylase Electrophoretic mobility monomeric Ba 1 Barren stalk Ear shoot, tassel florets missing Ba 2 Barren stalk Like ba, but tassel more normal br 1 Barren stalk Short internone, stiff erect leaves br 2 Brachytic short plant, like br1 br 3 Braqchytic Like br1 Cms-S Cytoplasmc male sterility Female-transmitted male sterility, S type, restored by Rf 3 Cms-T Cytoplasmic male sterility Female-transmitted male sterility, texas type, restored by Rf 1 and 2. Cms-C Cytoplasmic male sterility Female transmitted, male sterility C type, restored by Rf4 d1 Dwarf Andromonoecious dwarf, plant short, compact; responds to gibberellins d2 Dwarf Like d I d3 Dwarf Like d 1 d5 Dwarf Like d 1  35 D8 Dwarf Dominant dwarf; resembles d 1 not responsive to gibberellins Ds Dissociation Transposable factor, associated with chromosome breakage and/or control of expression of adjacent genes, regulated by Ac Dt Dotted Regulates controlling element at a locus, coloured dots on colourless a kernels, purple sectors on brown a plants Du Dull endosperm Dull endosperm, with wx, endosperm is shrunken fl 1 Floury endosperm Endosperm opaque, soft dosage effect fl 2 Floury endosperm Life fl 1 fl 3 Floury endosperm Like fl 1 Hm 1 Susceptibility to Disease lesions on leaves, block masses of Helminthosporium carbonum fruiting bodies on ears Hm 2 Susceptibility to Like hm 1 Helminthosporium carbornum ln 1 Linoleic acid Lower ratio of oleate to linoleate in kernel Mp Modulator of pericarp Transposable factor affecting P locus, parallel to Ac-Ds Ms Male sterile Anthers shriveled, not usually exserted nl Narrow leaf Leaf blade narrow, some white streaks O2 Opaque endosperm High lysine content Rf 1 Restorer of fertility Restores fertility to cms-T, complementary to Rf 2 see Rf 2 Restorer of fertility See Rf 1 Rf 3 Restorer of fertility Restorers to cms-S Rf 4 Restorer of fertility Restorers fertility to cms-C Rp 1 Rust resistant Resistant to Puccinia sorghi Rp 3 Rust resistant Resistant Puccinia sorghi Rp 4 Rust resistant Resistant to Puccinia sorghi rt 1 Rootless Secondary roots few or absent sh 1 Shrunken endosperm Endosperm collapses, smoothly indented kernels sh 2 Shrunken endosperm Large, transparent, sweet kernels that collapse on drying sh 4 Shrunken endosperm Chalky endosperm sk 1 Silkless Pistils abort, no silks spm Suppressor-mutator Transposable factor, regulates responsive element at a-m-1, c 2-m, pg 14-m, etc. su 1 Sugary endosperm Endosperm translucent, sometimes wrinkled Ts Tassel seed Tassel pistillate, if removed, small ear with irregular kernel placement develops wxl Waxy endosperm Amytopectin replaces amylase in endosperm and pollen, stained red by iodine BREEDING OBJECTIVES:  36 1. Breeding for high yield: Grain yield is the most important and complex economic trait. It is quantitatively inherited and its expression is influenced by yield components and physiological and other traits. Main yield components are, - No.of ears/ plant - Ear size (length, girth) - No. of kernels rows/ ear - No. of kernels/ row - Size of kernels (test weight) - Harvest index - Rate of filling of kernels - Shelling % Important physiological traits having bearing on grain yield are nutrient uptake, photosynthesis, translocation, sink size, transpiration and respiration. Grain yield also depends on maturity, standability and resistance to biotic and abiotic stresses. In addition to high yield potential, the cultivar must have desired adaptation. Multi-environmental evaluation is very important to properly assess genotypes for their yield potential and adaptation. Higher grain yield of recently developed hybrids was accompanied by longer grain filling period (earlier flowering and delayed senescence), rapid grain filling, increased sink size (more kernels per unit area, larger kernels and reduced bareness), higher harvest index and shelling percentage, shorter plant and tassel, upright leaves, shorter anthesis-silking interval, better standablity, better disease and insect pest resistance and better tolerance to abiotic stresses. Two important features of present day hybrids are their ability to exploit high nitrogen and suitability for cultivation under high plant density. Yield can also be improved through indirect selection for yield components. Prolificacy, the ability of a plant to produce more than one ear, is closely correlated with grain yield. I is useful in imparting stability under stresses. Ideal plant type in Maize: - Plant with upright leaves - Extended grain filling period - Cob with increased no.of kernel rows (>15) - Multi-cob plant - High harvest index - High shelling/ milling % - Shorter anthesis to silking interval (ASI) In India, many high-yielding hybrids and composites have been developed and released for cultivation. Composites – Vijay, Kisan, Partap, Parbhat and Ageti 76 Hybrids – Ganga safed 2, Histarch, Ganga 5, Deccan 103 and Sartaj 2. Breeding for wider adaptability: - Genotypes have to be developed which can adapt to wide range of environmental conditions.  37 3. Breeding for maturity: - Maize is a short-day plant. The time of flowering is influenced by temperature and photoperiod. - Various maturity traits are days to silk, tassel, and brown husk, kernel moisture at harvest, and black layer formation. - Days to silk is widely used as an index of maturity. - Kernel moisture is another trait used for assessing the crop duration. - Maturity is quantitatively inherited. - Negative correlation is observed between grain yield and early maturity. - Early maturing cultivars are preferred under rainfed conditions, where they escape drought. - Multiple cropping patterns or delayed planting also demand shorted duration cultivars. - Long duration cultivars are useful when the cropping system permit them and management is good. 4. Breeding for standability - Good standability is an important trait. Poor standability may be due to root lodging or stem breakage, which are primarily due to weak root system and poor stalk strength, often aided by root and stem rots and borers. - To have good standability, there should be a well developed root system, strong stem, short plant height, low ear placement, ability to stay green and resistance to diseases and pests. - Quantitative variation has been observed for root volume, root weight and pulling strength of root system and for rind thickness and crushing strength in case of stem. - The kick test is also used for quick assessment of standability. - Tall genotypes with highear placement are prone to lodging. - Composites Partap and Parbhat and hybrids Sartaj, Deccan 103 and Deccan 105 have better standability. 5. Breeding for better quality: Kernel color, protein content (lysine & tryptophan content) Illinois high protein strain having 26.6% protein. QPM (Quality Protein Maize): - Opaque 2 (o2) gene doubled the concentration of lysine and tryptophan in maize endosperm. - Incorporation of o2 gene resulted in low grain yield, dull and soft grain, delayed maturity, susceptibility to some diseases and pests and processing problems due to soft endosperm. - Extensive breeding efforts using o2 gene resulted in QPM at CIMMYT, Mexico by Surendra Kumar Vasal and Villegas using modifier genes. - Endosperm protein ‘Zein’ shows inadequacy of lysine and tryptophan. - QPM Maize Contain ‘opaque 2’ gene. As a result, richer is lysine and tryptophan but yield and kernel weight is poor, sugar content is increased. All kernels in QPM contain soft and starchy endosperm with introduction of opaque 2.  38 - Modified opaque maize populations at CIMMYT have high quality, and their grain yield, vireousness, appearance and resistance to disease and pests are comparable to normal maize. - Composites having QPM properties are Shakti, Ratan and Protina. - Commercial cultivation of opaque maize is limited to small acreage in US, South America and China. Higher oil maize is useful for food and feed purposes because of high energy. Germ (embryo) contains 3-5% oil. Illinois high oil strain has 21.3% oil. Higher milling % - 100kg of cob is shelled, 40kg of kernels = 40% 100 kg of cobs 6. Breeding for disease resistance - Maize suffers from about 110 diseases on a global basis, caused by fungi, bacteria and viruses. The disease spectra vary in different climatic zones, but more serious diseases are leaf blights, downy mildews, stalk rots and rusts. - Oligogenes for resistance to some diseases have been reported, though quantitative variation has been reported for most diseases. - Pedigree and backcross methods have been used to transfer oligogenes into inbred lines. - Emphasis should be on multiple disease resistance. - Most serious diseases in India are Tursicum leaf blight, maydis leaf blight, sorghum downy mildew (Scleropthora sorghi), post-flowering stalk rot complex (Macrophomina phaseoli, Fusarium spp., Cephalosporium spp.) and common rust. - Composite Parbhat and Navjot possess multiple disease resistance. - Inbred lines CM 105 and OH545 are sources of general resistance to common rust. - Three populations developed at CIMMYT, Population 22, 28 & 31 have resistance to diverse races of downy mildew pathogen. - DMR1 and DMR5 have resistance to downy mildew. 7. Breeding for insect resistance - Of the 130 insect-pests that affect maize crop, stem borers, shootfly, armyworm, jassids, thrips, white ants, pyrilla, grasshopper, grey weevil, hairy caterpillars, root worms, earworms and leaf miner are more serious, though spectrum varies in different agroecological regions. - Most research efforts has been on breeding for resistance to European corn borer, a pest in United States and Europe. A chemical found in the maize plant, DIMBOA (2,4-dihydroxy-7-methoxy-1,4-benzoxazine-3-one). - Fall armyworm is the most important pest in tropical and subtropical areas. - Quantitative inheritance has been reported for these pests