Lecture 6: Breeding and Selection Methods for Self-Pollinated Crops PDF

Breeding and Selection Methods for Self -Pollinated Crops EFREN E. MAGULAMA, PhD Professor VI Department of Crop Science College of Agriculture Breeding and Selection Methods for Self - Pollinated Crops End Product-homozygous lines A. Selection withi...

Breeding and Selection Methods for Self -Pollinated Crops EFREN E. MAGULAMA, PhD Professor VI Department of Crop Science College of Agriculture Breeding and Selection Methods for Self - Pollinated Crops End Product-homozygous lines A. Selection within Impure or Heterogenous Populations 1. Selection Methods i.Mass Selection Mass Selection 1. Procedures: Seasons 1: a. Grow impure populations as a plot or spaced planted. b. Select plants with similar phenotype. c. Harvest selected plants and bulk seeds. Season 2: d. Grow bulked materials in preliminary yield trials using local cultivars as well as original population as checks. e. Observe for desirable traits such as maturity, pest resistance, etc. Season 3-7: f. Continue yield tests with checks lines. Regional testing may be done. Season 8: g. If cultivar proves superior, start seed increase and release to farmers Mass Selection Advantages of Mass Selection 1. It is a rapid and inexpensive procedure for increasing the frequency of desirable genotypes of population. Disadvantages of Mass Selection 1. It can only be used in an environment where the desirable traits are expressed. 2. It is not effective in characters with low heritability. Pureline Selection ii. Pureline Selection- method based on Johannsen experiment. Johannsen- proposed the pureline theory. Pureline Seelction Procedures: Season 1. a. Grow impure population as a plot or spaced plants. b. Select 200-1000 individual plants and harvest seeds separately. Season 2: c. Grow seeds from each plant in separate progeny rows d. Harvest superior plants by bulking seeds from plant within each row Pureline Selection Season 3. e. Grow replicated observation plots or in preliminary yield trial including check plots of local cultivars. f. Harvest only superior selections Season 4-7. g. Continue yield testing using larger plots and more replications. Season 8. h. Choose the best lines and start seed increase. Pureline Selection Loss of Desirable features. 1. Mechanical mixing of some genotypes 2. Some amount of outcrossing 3. Mutations Do not create new genotypes but isolate the best genotype from the original populations. No gene recombination. It cannot be used in populations with no existing genetic variability. Development of New Pureline Cultivars Incorporation of several traits into one variety through hybridization. Phase 1. Hybridization phase Incorporate two or more traits into one variety. Phase 2. Stabilization phase Bases for Selecting Parents to be crossed. Example a. Presence of complementary traits Desirable Traits 1 2 3 4 5 6 7 8 Parent 1 x x x X Parent 2 x x x x b. Known superiority of variety as a parent Hybridization Phase 1. Based on observations/published reports In rice-peta In Wheat-Fiorillo 2. Combining ability test How many plants of the parent variety are needed to produce F1 Number of seeds that ca be produced per cross Number of F2 plants needed. Stabilization Phase a. Through continuous selfing with or without selection in early generations Ways of Handling Segregating Generations 1. Pedigree Methods 2. Bulked Methods 3. F2 Derived Lines Methods 4. Single Seed Descent Method Pedigree Method Procedures 1. F2 population is spaced planted. Desirable plants are selfed and seeds harvested separately. 2. F3 seeds of each F2 plant are grown in a row (F2 lines) leaving sufficient spaced between plants for single plant selection. Select best rows and then select and self-plants in selected rows. Pedigree Method 3. F3, F4, F6 seeds of each selected F3, F4, F5 plants, respectively are (grown in row) treated in the same way as the F3 progenies. Selection depends on the uniformity of the plants in a row. 4. The F2 seeds of each selected F6 plants (f6 lines) are grown in a row. The best rows are selected and selfed seeds of selected planted within a row are bulked. Pedigree Method 5. Selected F7 lines are entered in preliminary yield trials. 6. Continuation of yield tests within undesirable lines eliminated each season.  Pedigree Method AxB F1 Self the F1 At F2 F2 Start selection Select on the row basis first and then select the best plants in these rows F3 At F4 to F6 Several traits are scored/rated F4 Lines not homozygous in F6 are discarded At F6 or F7 F5 Line is stable or uniform Conduct yield trials --- observational YTs, replicated YTs, advanced YTs, national cooperative testings in multilocations F6 Release for seed multiplication (seed growers, and distribution to farmers --- upon approval of evaluating/approving body F7 EE Magulama DPBG-CA-USM 16 Pedigree Nursery EE Magulama DPBG-CA-USM 17  Modifications: yield testing in F3 and F4 as a guide or basis of selection. Why pedigree? The ancestry or parentage of the selected lines can be traced. It requires considerable record keeping. Pedigree Method Advantages 1. Inferior genotypes are discarded early if the selection is effective, and yield test involves only the superior lines. 2. Maximization of the genetic variability to be kept. Genetic relationship of lines can be known. Avoidance of recommending closely related lines. Pedigree Method Limitations 1. The plants cannot be grown in the artificial or natural environment. 2. It involves a considerable amount of record keeping. 3. Needs experienced persons to do selection. 4. It requires more labor and land. Pedigree Selection Fig. 1 Flow chart of pedigree method of breeding. Bulked/Population Method Procedures: 1. Grow F2 seeds and harvest seeds. F3 seeds are harvested in bulk. 2. A sample of F3 seeds from season 1 is planted and F4 seeds of population are harvested in bulk. 3. A sample of F4 seeds from season 2 is planted and F5 seed populations are harvested in bulk. Bulked/Population Method 4. A sample of F5 seeds from season 3 is grown. Individual plant selection is practiced, and seeds of selected plants are harvested separately. 5. F6 seeds from each selected F5 plants are grown in a row and selection may be continued. Bulked/Population Method 6. Follow the same step as in season 5. 7. Selected lines are entered in preliminary yield trial. 8. Continue yield trials. Advantages 1. Easy way of handling segregants. 2. It can handle many crosses with the same. 3. It can increase the frequency of desirable genotypes under natural selection. Disadvantages 1. It is not suited to off-season nursery. 2. Natural selection may be undesirable to plant breeders. Bulk Method Fig 2 Flow chart of bulk method of breeding. F2 Derived Lines Method Procedures: 1. F2 plants are grown and selfed seeds of selected plants are harvested separately. 2. F3 seeds of each selected F2 plants are grown in a row (between row selection). The best rows are selected and selfed seeds are harvested separately. 3. Same as in Season 2. F2 Derived Lines Method 4. Selection within F2 derived lines (within row )is started. 5. Continue within row selection. 6. Start yield tests (could be earlier if lines are already look uniform enough. F2 Derived Lines Method Modifications. F3- derived line methods F4-derived line methods F5-derived line methods. F2 Derived Lines Method Advantages 1. It is less laborious than the pedigree analysis method. 2. More crosses can be handled. Disadvantages 1. It is effective only for traits with high heritability. 2. It is effective where trait of interest could be expressed. Single Seed Descent Method Procedures: 1. F2 plants of a population are grown one F3 seeds is harvested from each plant and the harvested seeds are bulked. 2. The bulk of F3 seeds from season one is planted. One F4 seed is harvested from each F3 plant, and the harvested seeds are bulked. Single Seed Descent Method 3. The bulk of F4/F5 from season two is planted. One F4/F5 seed is harvested from each F3 plant, and the harvested seeds are bulked. 4. The bulk of F5 seed is planted all seeds are harvested from each plant and kept as separate bulk. 5. Start yield tests. Single Seed Descent Method Advantages 1. It needs less space, labor, record keeping. 2. It is suited to greenhouse and off-season resulting to advance rapid use. Disadvantages 1. It can not be planted in the field for selection. 2. The identity of the superior F2 plants are lost. 3. It may have poor germination. Variability of SSD a. Single hill procedures Harvest a few seeds and maintain planting few seeds per hill. b. Multiple seed procedure Harvest more seeds rather than one Example: i. Want 200 F4 plants ii. Germination %=70% iii. 200/0.70=286 F4 seeds iv. 286/0.70=409 F3Seeds v. 409/0.70=584 F2 seeds c. Rapid generation advance Used for spaced type of materials Planting more than one plant. Two-more methods can be combined Single seed descent The number of seeds planted are not constant per season. Multiple seed descent The number of seeds planted can be constant each season. 3 seeds per plant. Stabilization Phase a. Through continuous selfing Determining number of F2 plants to grow Depends on the number of genes controlling the traits Single locus trait: F1 Aa F2 = ¼ AA : ½ Aa : ¼ aa F2 populations size (n) P (desirable types) 1 1/4 (3/4+ ¼)^1 2 7/16 (3/4 + ¼)^2 3 37/64 (3/4+ ¼)^3 (a+b)2 =a^2 + 2ab + b^2 Where: a= freq of undesirable type b= freq of desirable type (3/4+1/4)^2 =(3/4)^2 + 2[3/4)*(1/4)] + (1/4)^2 = 9/16 + 2(3/16)+ 1/16 = 9/16+6/16+ 1/16 =7/16-desirable (b)  Two or More Genes n=number of gene pairs No. of Gene Kinds of Kinds of possible phenotypes in F2 pairs Possible controlling Genotypes Traits in F2 Complete No No. of Dominance Dominance Epistasis 1 3 2 3 2 9 4 9 3 27 8 27 4 81 16 81 10 59,049 1,024 59,049 n 3n 2n 3n  The more distantly related the parents are, the more F2 plants will be needed. The F1 are more heterozygous in many loci. In general, 2000 F2 plants are needed. It takes 10-15 seasons before a variety is released. Purification takes more seasons. Double Haploid Double Haploid Techniques-offers quickest possible approach to homozygosity. Steps: 1. Produce haploid gametes or plants by some means from a heterozygous source. 2. Double the chromosome complements of haploids obtained usually using colchicine. Double Haploid Double Haploid Some Methods of Obtaining/Producing Haploids 2. Use of naturally occurring material haploid a. Genetic markers are used to detect haploid Example in corn-purple plant color, purple aleurone a. Female parent should have a recessive marker b. Male parent should have a dominant marker  Harvest the purple seeds and grow and select for green plants Look for green plants-selfed and haploid with purple endosperm.  3. Use of naturally occurring paternal haploid Look for green F1 plants, Problem: The frequency is very low haploid green plants with purple endosperm 4. Indeterminate gametophytes It stimulates the development of male gametes if presence. Look for green F1 plants with purple endosperm with higher frequency. 5. Haploid from Interspecific crosses Example: barley The chromosomes of the H. bulbosome are eliminated. Thereby only chromosome of H. vulgare b. Anther Culture Process: 1. Development of embryoids or calli from the pollen cells 2. Differentiation into plants (regeneration) Factors to be considered in Producing anther culture 1.Source plants (genotype- F1=(AaBbCcDdFf) Disadvantages of Anther Culture Limited genetic recombination Breaking the linkage Crops vary in their response to anther culture 2. Stages of anther development Tetrad stage to intermediate after 1st pollen anthesis is the most critical stage 3.Culture media Proper culture medium determine the right medium that give desired results haploid are short, uniform and sterile Use of multiple crosses-as base population many of these are undesirable and needs large populations to obtain desirable results To reduce the number of recombination, select related plant Forming broad base population Improvement of Existing/Established Purelines Backcross methods- change of one or two traits without changing the other traits. It needs two parents 1. Adapted/established variety 2. Donor parent used in simply inherited trait Backcross Method Case I-character controlled by dominant gene and can be evaluated before pollination Number of backcrossing depend on the degree of genetic background to be recovered of recurrent parent Case II- character controlled by dominant gene and cannot be evaluated until after flowering Case III- character is controlled by a recessive gene Breeding Methods: Self-Pollinated Crops Backcross Method Crossing a hybrid (progeny of two parents) to one of its parents Repeated backcrossing at different generations → to get good quality of the parent (recurrent parent) Usually done to improve 1 or 2 specific defects of a high- yielding variety EE Magulama DPBG-CA-USM 59 Breeding Methods: Self-Pollinated Crops Backcross Method The hybrid and the progenies in the subsequent generations are repeatedly backcrossed to one of the original parents used in the cross The objective of backcrosses method is to improve one or two specific defects of a high yielding variety Recently, tungro resistance has been transferred from O. rufipogon by recurrent backcrossing to IR64 EE Magulama DPBG-CA-USM 60 Backcross Method Backcross Derived Line IR64 IR73885-1-4-3-2-1-6 (IR64*2/O. Rufipogon) EE Magulama DPBG-CA-USM 61 Backcross Method Advantages of Backcross Method 1. It is predictable method 2. It can be conducted in the greenhouse offseason nursery (two generation/cycle) 3. Very little testing is necessary 4. It requires few plants to recover the donor parent. Backcross Method Disadvantages of Backcross Method 1. It is affected only for highly heritable traits. 2. The performance of the product is limited by the donor parent. 3. Improved varieties could be obsolete before the variety can be released. 4. Undesirable gene of the donor parent is difficult if remove if it is closely linked. Multilines or Blends Development of Multiline or Blends Extensive use of pure lines could result to genetic vulnerability. Use of mixture of lines that are genetically different is called multilines oMultilines-mixture of isoline lines oBlends-lines of different traits Commercially accepted multilines Mixture-phenotypically the same lines Same in appearance but genetically different Example: mixture of all green seed coat varieties of mungbean To replace and alternative of crop rotation The yield of multilines exceeded the average yield of the components of multilines ❖Observations: 3.2% if components are unselected 7.45 if components are selected Advantages: 1.It minimizes genotype and environmental interaction effect 2.It is more stable. 3.It is resistant to diseases. 4.It improves the yield performance. How to form Multilines? Components of multilines 1. Development of isolines Multilines 2. Make of closely related lines Lines with a common parent 3. Use of distinctly different lines Complement each line Multilines Predicting Performance of a Multiline Variety Performance of Multiline= ∑ [Perf. Of component i in pure stand] [Freq. or proportion of component i in mixture] L=lines Example: components are Var A and B with 100 and 110 units in purestand 25% and 75% proportion in mixture, respectively (100*0.25)+ (110*0.75) 107.5 units Multilines Factors to be considered in producing Multilines 1. Number of components and their relative frequency in mixture 2. Performance of the component lines in pure stand Reasons for deviation of multilines- intergenotypic competition Multilines Types of Intergenotypic competition 1. Undercompensation- actual performance is lesser than expected performance 2. Complementary compensation- no competition, actual performance is equal to expected performance. 3. Overcompensation- actual performance is greater than the expected performance. In mixing the components, seed viability is necessary to determine. Advantages of Multilines 1. It offers greater pest resistance 2. It offers greater standability and long-life span Disadvantages of Multilines 1. It requires longtime to develop multilines. 2. Reconstruction of mixture to prevent varietal shift. 3. It creates a problem for seed certification. Production of F1 hybrids 1. No need to produce inbred lines 2. Test for combining ability 3. It needs emasculation/sterile lines Composite Crosses Producing of different lines and allow natural selection The product is genetically diverse Subject to natural selection Systems of Pollination Control in Plants Mechanisms of pollination control 1.Diocy- male and female flowers are separated in different plants Examples: asparagus, rambutan, papaya 2. Self-compatibility- gametes are functional 1. Heteromorphic difference in the flower morphology Thrum type-short style and higher anthers Pin type-long style and shorter anthers o Thrum x pin cross-compatible o Pin x pin cross-incompatible o Thrum x thrum-incompatible  MATING PROGENY Phenotype Genotype Genotype Phenotype Pin x Pin ss x ss Incompatible Mating Pin x Thrum ss x Ss Ss: ss Thrum: pin Thrum x Pin Ss x ss Ss: ss Thum : pin Thrum x Thrum Ss x Ss Incompatible Mating 2. Homomorphic- no difference in flower morphology Gametophytic system-dependent on the genotype of the gametophyte (pollen) Known also as haplo-diplo system Controlled by a single locus with several alleles Pollen tube growth is very slow in the style containing the same S allele Alleles have individual actions (no interaction, no dominance relationship) Gametophytic system Female X Male Female X Male Female X Male (S1S2) (S1S2) (S1S2) (S1S3) (S1S2) (S3S4) No compatibility Half compatible Compatible 2. Sporophytic system-known as diplo-diplo systems Incompatibility reaction in imparted to the pollen by the plant (sporophyte) upon which pollen is borne Alleles may show individual action, dominance, competitive, etc. S1>S2>S3 Gametophytic system Female X Male Female X Male Female X Male (S1S2) (S1S2) (S1S2) (S1S3) (S1S2) (S2S3) No compatible No compatible Compatible (S1S2-behave as S1) 3. Male Sterility-gametes are nonfunctional 1. Genetically controlled- due to simple gene or chromosomal aberration oExample: sorghum, cotton, lima bean o MsMs and Msms-fertile, msms-sterile  Production of Male Sterile Line Male Male Sterility System Sterile X Fertile (msms) (MsMs) Maintaining the male sterile line Male X Male Male Male Male X Sterile Fertile Sterile Fertile Fertile (msms) (MsMs) (msms) (Msms) (Msms) ⮾ 50% Msms : 50%msms Male Fertile (Msms) 75% Ms_ : 25%msms Backcross to MsMs No compatible 2. Cytoplasmically controlled-used in corn- sterility is determined by cytoplasm Cytoplasmic male sterility 3. Cyto-genetically controlled- used in sorghum, onion and rice Cytoplasmic-genic male sterility 4. Chemically controlled-render inviable pollen without impairing female –use of chemical hybridizing agents (CHA) Maleic hydrazide, ethrel, FW 450 5. Apomixis-seed formation without fertilization Hybrid Varieties Hybrid varieties exploit the phenomenon of hybrid vigor for increasing the yield potential of rice beyond the level of inbred modern rice varieties Hybrid varieties are grown from the F1 seeds F1 seed is obtained from a cross between two inbred parents Farmers must obtain new hybrid seed for each planting from an accredited source EE Magulama DPBG-CA-USM 91 Hybrid Varieties (continued) Hybrids have been released in: China (e.g. Zhen Shan 97 A/Min-Hui 63 and V20 A/Ce 64) India (e.g. DRRH-1 and PA6201) Philippines (e.g. PSBRc26H–Magat andPSBRc72H- Mestizo). EE Magulama DPBG-CA-USM 92  Hybrid Varieties Three-line system Two-line system (A, B and R) (EGMS and Pollen Parent) Seed Parent Pollen Parent Seed Parent Pollen Parent (CMS line) (Maintainer line) Step 1 A B EGMS P x Pollen Parent Selfing (Restorer line) Step 2 A x R EGMS x P F1 hybrid seed F1 hybrid seed EE Magulama DPBG-CA-USM 93