Chapter VI Crop Improvement PDF

 Republic of the Philippines Mindanao State University at Naawan College of Agriculture and Forestry Naawan, Misamis Oriental CROP IMPROVEMENT CHAPTER VI Prepared by: Russel D. Bañoc, MSc. ...

 Republic of the Philippines Mindanao State University at Naawan College of Agriculture and Forestry Naawan, Misamis Oriental CROP IMPROVEMENT CHAPTER VI Prepared by: Russel D. Bañoc, MSc.  Gregor Mendel ▪ The first person to lay the mathematical foundation of the science of genetics. ▪ His findings were now known as Mendelism or Mendelian Laws of Inheritance.  What is Plant Breeding? Is the Art and Science of improving the heredity of plants for the benefit of humankind. “Yield is the ultimate objective of plant breeding”  Chromosome and Gene Chromosome – a structural unit in the nucleus, which carries the genes in a linear constant order; it preserves its individuality from one cell generation to the next and is typically constant in number in any species. Gene – the unit of inheritance, located on the chromosome. A segment of DNA that determines an amino acid sequence in a polypeptide. Some Known Plant Breeders Glen W. Burton Distinguished forage crop breeder for the U.S. Department of Agriculture. Improved pearl millet Development of turf grasses for golf courses and grazing Some Known Plant Breeders Edgar E. Hartwig Soybean breeder for the United States Department of Agriculture. “The Father of Soybeans in the South” Some Known Plant Breeders Norman E. Borlaug Recipient of the 1970 Nobel Peace Prize for his contribution to peace and humanity through the breeding of the “high yielding” wheat. “The Father of Green Revolution”  International Breeding Centers Asian Vegetable Research and Development Center (AVRDC) Shanhua, Taiwan (Chinese cabbage, mungbean, pepper, tomato, soybean) International Center for Agricultural Research in the Dry Areas (ICARDA), Aleppo Syria (barley, chickpea, faba beans, tropical forages, lentil, wheat) International Center for Maize and Wheat Improvement (CIMMYT), Mexico (Maize, Triticale, Wheat) International Center for Tropical Agricuture (CIAT), Cali, Columbia (Dry bean, Cassava, rice, tropical forages)  International Breeding Centers International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), Patancheru, Andhra Pradesh, India (Chickpea, millet, peanut, pigeonpea, sorghum) International Institute of Tropical Agriculture (IITA) Ibaban, Nigeria (Cassava, Cocoyam, Cowpea, lima bean, maize, pigeon pea, rice, soybean, sweet potato, winged bean yam) International Potato Center (CIP) Lima, Peru (Potato, sweet potato) International Rice Research Institute (IRRI) Los Banos, Laguna, Philippines Modern plant breeder must have knowledge and training on: ▪ Botany – to understand the taxonomy, morphology, reproduction of plants ▪ Genetics and Cytogenetics – to understand the mechanism of heredity ▪ Plant physiology - to understand variety adaptation t environment ▪ Plant pathology - to understand breeding for disease resistance Modern plant breeder must have knowledge and training on: ▪ Entomology – to understand breeding for insect resistance ▪ Plant biochemistry – suitability for industrial utilization which determines market demand for a particular variety of crop. ▪ Statistics – plant breeder measure the comparative performance of many strains. ▪ Agronomy – He should know crops and their respective productions. Goals of plant breeders in developing new hybrids/varieties: a. High yielding b. Adaptability c. Resistant to insect pest and diseases d. Early maturing e. Good storage f. Consumer’s g. Adapted to machine  Reproductive Processes of Plants What is reproduction? Reproduction – is the process by which plant produces its offspring  Reproductive Processes of Plants Classification of plants based on their mode of reproduction A. Asexually propagated plants B. Sexually propagated plants  A. Asexually Propagated Plants ▪ These are plants that undergo a type of reproduction which does not involve the union of male and female gametes (mature germ cells). ▪ This is known as vegetative propagation.  Importance of Asexual propagation It makes possible the propagation of some species of plants that produce very few seeds or none at all. It produces plant that mature earlier than those under sexual propagation. It produces true to type individuals.  Forms of Asexual Propagation Clones – these are group of plants which are propagated vegetatively through cutting, grafting, or division and which originated from a single individual. Root cuttings  Forms of Asexual Propagation Stem cuttings Leaf cuttings  Forms of Asexual Propagation Layering – formation of adventitious roots or buds occurs before the separation of the propagule from the parent plant.  Forms of Asexual Propagation Grafting – the scion of one good variety is grafted to another variety with good stock. Union of tissues occurs later  B. Sexually Propagated Plants ▪ Seeds are used to produce plants which are intermediate of the plant materials and is known as HYBRIDS. ▪ HETEROSIS or HYBRID VIGOR - increased vigor or growth of a hybrid progeny in relation to the average of the parent.  Groups of Sexually Produced Crops 1. Normally self-fertilized crops – where transfer of pollen from an anther to a stigma of another flower on the same plant.  Groups of Sexually Produced Crops 2. Normally cross pollinated crops – where transfer of pollen is from an anther to a stigma in a flower on a different plant.  Groups of Sexually Produced Crops 3. Both self and cross pollinated crops – plants that are normally self-fertilized may sometimes be cross pollinated; and plants that are normally cross pollinated may be at times, self-pollinated. Terminologies important in breeding crops Monoecious crop – both staminate and pistillate flowers are borne on the same plant. Terminologies important in breeding crops Dioecious crop – staminate and pistillate flowers are borne on different plants. Terminologies important in breeding crops Complete flowers – contain all the floral organs (sepals, petals, stamen, and pistil). Terminologies important in breeding crops Incomplete flowers – lack of one or more of the floral organs. Terminologies important in breeding crops Perfect flowers – bear stamens and pistil in the same flower structure. Most crop plants have perfect flowers. Terminologies important in breeding crops Imperfect flowers – one of the essential organs is absent. A plant may be staminate or pistillate. A pistillate plant has pistil but lacks stamen, whereas a staminate plant has stamen but lacks pistil. Terminologies important in breeding crops Apomixes – this is the condition wherein the seeds are formed without undergoing fertilization. Seeds are develop in the ovary but the embryo is formed without the union of male and female gametes (mature germ cells). METHODS OF CROP IMPROVEMENT 1. Plant introduction 2. Selection 3. Hybridization  PLANT INTRODUCTION Done to obtain superior variety from other localities. The collection of diverse genotypes is the initial stage in the breeding program. Some of the introduced crops and their respective places of origin: Corn – tropical Central America (Carribean) Cotton – tropical North America (Mexico, Trinidad-Tobago, Dominican Rep., etc) Tobacco – tropical America Soybeans – China Potatoes – South America Some of the introduced crops and their respective places of origin: Sorghum – Africa Tomatoes – tropical America Coconut – South Pacific Banana – Southeast Asia; South America Gabi (taro) – Southeast Asia  Once a plant is introduced or has been received, it should undergo the following: 1. Inspection for insect pests and diseases 2. Identification before it is prepared for propagation, testing and distribution 3. The original introduction, be it seed or clonal material, is usually limited in quantity and must be increased before it can be tested or distributed to plant breeders.  SELECTION refers to any processes, natural or artificial, which permits an increase in the proportion of certain genotypes or groups of genotypes in succeeding generations.  KINDS OF SELECTION A. MASS SELECTION ❑A system of breeding in which seeds from individuals selected on the basis of phenotype (outside appearance) are composited/bulked and used to grow the next generation.  A. MASS SELECTION Features: ❑ Selection of the best individuals. ❑ Selection is based on the physical features which are readily seen and are used as the basis for purification. ❑Selection is done to improve the general level of the populations. Steps in Mass Selection: First year – select a few hundred plants with similar phenotype and then harvest and composite the seeds. Second year – grow in preliminary yield test, comparing with standard varieties as checks. Observe comparative height, maturity, lodging and disease resistance, and eating quality. Steps in Mass Selection: Third to sixth year – continue the yield test to determine performance and adaptation in comparison with standard check. Seventh year – start seed increase for distribution Advantages of Mass Selection: Less record keeping than pedigree which saves time and labor. Very simple, convenient and less expensive. Natural selection increases the frequency of superior genotypes in the population. Most suitable for improvement of small grains.  Drawbacks in Mass Selection: Not possible to know whether the plants being grouped together are homozygous or heterozygous in genetic characteristics. It is difficult to know whether the selected phenotype is superior in appearance due to hereditary characteristics or due to the effects of environment.  B. PEDIGREE SELECTION ❑Sometimes called “individual selection”. ❑Plants with the desired combination of characteristics are selected in the F2 generation and the progenies of each selected plant are reselected in the succeeding generations until the genetic purity is reached.  Advantages of Pedigree Selection Performance of each individual selected is known Poorer individuals are eliminated right away and the better ones are carried on the further trials. Rapid separation/segregation of the pure lines from a mixed population.  Disadvantages of Pedigree Selection Record keeping is slow, tedious, time consuming, and expensive. The method is not suitable for species in which individual plants are difficult to isolate and characterize. Pedigree selection is a long procedure, requiring about 10-12 years or more to complete. Since large numbers of progenies are rejected in this method, there are chances of elimination of some valuable material. C. CLONAL SELECTION ❑“A clone is a group of plants produced by vegetative propagation of a single plant” ❑This is applied to plants propagated asexually. ❑Selection of clones is done from a mixed population. Characteristics of plants in a clone: ✓All the members of a clone are identical or there is no variation within a clone. ✓All the members of a clone are homozygous. ✓Clones are stable as pureline. ✓The phenotypic variation within a clone is due to environment only. Merits of clonal selection: Varieties are stable and easy to maintain clonally are as stable as purelines. Hybrid vigor is easily utilized. Only method to improve the clonal crops. Demerits of clonal selection: It is only applicable to vegetatively propagated crops. It does not create new variation. The progress of clonal selection is limited to the isolation of best genotypes already present in the population.  HYBRIDIZATION What is Hybrid Rice? The offspring that is obtained by crossing two genetically dissimilar homozygous parents is called hybrid and the process of producing hybrid is called hybridization.  HYBRIDIZATION The crossing of individuals of unlike genetic constitution. With this method, the best characteristics of the parent varieties may be combined into a single true breeding strain and made possible the selection of plants from a progeny of a cross that will be superior to the parents.  Basic Types of Hybrid Crosses ▪ Single Cross – involves two individual parents or inbreds. Inbreds are plants developed by self-pollination and selection until homozygous plants are obtained.  Basic Types of Hybrid Crosses ▪ Double Cross – is the hybrid progeny from a cross between two single crosses.  Basic Types of Hybrid Crosses ▪ Three-way Cross – is the hybrid progeny between a single cross and an inbred.  Basic Types of Hybrid Crosses ▪ Top cross – is an inbred variety cross; a cross between an inbred and an open pollinated variety. ▪ Multiple Cross – is a combination of more than four inbred lines. ▪ Back Cross – is the crossing of a hybrid with one of its parents to improve lines or cultivars that excel in most desirable characteristics but lack one or a few. THANK YOU!