Breeding Self-polinated crops

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Breeding Methods

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Submitted by Mr. J. M. Patil Reg.No.12/018 SEMINAR ON Breeding Methods for Self Pollinated Crops Submitted to Dr. N. S. Kute Course Teacher & Associate Professor of Botany

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2 Breeding Methods for Self Pollinated Crops

Cultivars:

3 Cultivar Is a group of genetically similar plants, which may be identified (by some means) from other groups of genetically similar plants Essential Characteristics: Identity: cultivar must be distinguishable from other cultivars Reproducibility: the distinguishing characteristic(s) need to be reproduced in the progeny faithfully Cultivars

Types of Cultivars:

4 Types of Cultivars Open-Pollinated cultivars O.P. seeds are a result of either natural or human selection for specific traits which are then reselected in every crop. The seed is kept true to type through selection and isolation; the flowers of open-pollinated or O.P. seed varieties are pollinated by bees or wind.

Types of Cultivars:

5 Types of Cultivars Synthetic cultivars A population developed by inter-crossing a set of good combiner inbred lines with subsequent maintenance through open-pollination. The components of synthetics are inbreds or clones so the cultivar can be periodically reconstituted.

Types of Cultivars:

6 Multi-line cultivars A mixture of isolines each of which is different for a single gene controlling different forms of the same character (e.g., for different races of pathogens) F1 cultivars The first generation of offspring from a cross of genetically different plants Pure-line cultivars The progeny of a single homozygous individual produced through self-pollination Types of Cultivars

Cultivars and Self-pollinated Crops:

7 Cultivars and Self-pollinated Crops In self-pollinated species: Homozygous loci will remain homozygous following self-pollination Heterozygous loci will segregate producing half homozygous progeny and half heterozygous progeny Plants selected from mixed populations after 5-8 self generations will normally have reached a practical level of homozygosity

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8 In general, a mixed population of self-pollinated plants is composed of plants with different homozygous genotypes (i.e., a heterogeneous population of homozygotes If single plants are selected from this population and seed increased, each plant will produce a ‘pure’ population, but each population will be different, based on the parental selection Cultivars and Self-pollinated Crops

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9 Selection involves the ID and propagation of individual genotypes from a land race population, or following designed hybridizations Genetic variation must be identified and distinguished from environment-based variation Selection procedures practiced in mixed populations of self-pollinated crops can be divided into two selection procedures Breeding Self-pollinated Crops

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10 Breeding Methods of Self Pollinated Crops Plant Introduction Pure line Mass Selection Bulk Method Pedigree Method Single Seed Descent ( modified pedigree) Backcross Multiline Method Mutation Breeding

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11 Definition: Transposition of crop plants from the place of their cultivation to such areas where they never grown earlier. Types : I. Based on adaptation: Primary introduction B. Secondary introduction II. Based on utilization: Direct introduction Indirect introduction 1. Plant Introduction

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12 A. Primary introduction: Introduction that can be used for commercial cultivation as variety without any change in the original genotype. Eg . Rice- Taichung Native1, IR8, IR20 and IR36 Wheat- Sonora 64 and Lerma Rojo B. Secondary introduction: Introduction that can be used as a variety after selection from the original genotype or used for transfer of some desirable gene to the cultivated variety . Eg . Wheat- Kalyan Sona and Sonalika

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13 A. Direct Introduction : As a variety : Semi-dwarf varieties Sonora 64 and Lerma Rojo in wheat Taichung Native, IR8, IR20 and IR36 in Paddy Bragg and Lee in Soybean B. Indirect Introduction: In Egyptian cotton, variety Sujata from Egyptian variety Karnak As a parent in hybridization : Pioneer cotton hybrid H 4 – Gujrat 67 x American nectariless

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14 Pure Line

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15 Pure Line: (Recount Johannsen. 1903) usually no hybridization Initial parents (IPs) selected from a heterogenous population (i.e. genetically variable) procedure continues until homogeneity is achieved last phase is field testing

Pure-line Selection:

16 A pure line consists of progeny descended solely by self-pollination from a single homozygous plant Pure line selection is therefore a procedure for isolating pure line(s) from a mixed population Pure-line Selection

Pure-line Selection:

17 Pure line cultivars are more uniform than cultivars developed through mass selection (by definition, a pure line cultivar will be composed of plants with a single genotype) Progeny testing is an essential component of pure line selection Improvement using pure line breeding is limited to the isolation of the ‘best’ genotypes present in the mixed population Pure-line Selection

Pure-line Selection:

18 Pure-line Selection More effective than MS in development of self-pollinated cultivars However, leads to rapid depletion of genetic variation Genetic variability can be managed through directed cross hybridizations Essential to progeny test selections

Pure-line Selection-Steps:

19 Pure-line Selection-Steps Select desirable plants Number depends on variation of original population, space and resources for following year progeny tests Selecting too few plants may risk losing superior genetic variation A genotype missed early is lost forever Seed from each selection is harvested individually

Pure-line Selection-Steps:

20 Pure-line Selection-Steps Single plant progeny rows grown out Evaluate for desirable traits and uniformity Should use severe selection criteria (rogue out all poor, unpromising and variable progenies) Selected progenies are harvested individually In subsequent years, run replicated yield trials with selection of highest yielding plants After 4-6 rounds, highest yielding plant is put forward as a new cultivar

Flow chart for Pure line selection:

21 Flow chart for Pure line selection

Advantages:

22 Advantages ID of best pure line reflects maximum genetic advance from a variable population; no ‘poor’ plants maintained Higher degree of uniformity Selection based on progeny performance is effective for characters with relatively low h 2

Disadvantages:

23 Requires relatively more time, space, and resources for progeny testing than MS to develop new cultivar High degree of genetic uniformity; more genetically vulnerable and less adaptable to fluctuating environments ID and multiplication of one outstanding pure-line depletes available genetic variation; leads to fast genetic erosion Disadvantages

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24 How long will a cultivar remain pure? As long as the commercial life of the cultivar, unless: Seed becomes contaminated with seed from other sources (e.g. from harvesting and seed cleaning equipment) Natural out-crossing occurs (amount varies by species but seldom exceeds 1-2% in self-pollinated crops) Mutations occur To maintain purity, off-types arising from mutation or out-crossing must be rogued out

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25 Mass Selection

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26 Objectives of Mass Selection: To increase the frequency of superior genotypes from a genetically variable population Purify a mixed population with differing phenotypes Develop a new cultivar by improving the average performance of the population

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27 May or may not include hybridization Make IP selections based on single, ideal or desirable phenotype and BULK seed May repeat or go directly to performance testing Mass Selection has 2 important functions: Rapid improvement in land-race or mixed cultivars Maintenance of existing cultivars (sometimes purification) * Many pb’ers of self pollinated crops believe that combining closely related pure lines imparts “genetic flexibility” or buffering capacity and so are careful to eliminate only obvious off types Mass Selection

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28 Success depends on extent of variation and h 2 of the traits of interest Land races make an ideal starting source High genetic variability accumulated over generations of mutation and natural hybridization

Mass Selection:

29 Mass Selection Initial selection Can be either a positive or a negative selection Negative screening: A screening technique designed to identify and eliminate the non desirable plants. P ositive screening: which involves identifying and preserving the most desirable plants.

Mass Selection - 1st Year:

30 Mass Selection - 1 st Year Select plants with respect to height, maturity, grain size, and any other traits that have ‘production’ or ‘acceptability’ issues Bulk seed (may ‘block’ these bulks if wide variation is present for certain traits; e.g. height) May be able to use machines to select Harvest only tall plants, or save only large seed passed through a sieve

Mass Selection - 2nd Year:

31 Mass Selection - 2 nd Year MS really only takes 1 yr because selected seed represents a mixture of only the superior pure lines that existed in the original population However, additional rounds of selection and bulking will allow for evaluation under different environments, disease and pest pressures. Also, multiple years will allow you to compare performance with established cultivars over years and environments.

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32 1. Good method of improvement of old varieties and land races 2. Provide good protection against diseases 3. Variety developed by this method is more stable than pure lines due to heterogeneity 4. Easy and simple method of crop improvement , applicable to SP and CP species Advantages

Disadvantages:

33 Selection based on phenotypic performance; not effective with low h 2 traits Without progeny testing, heterozygote's can be inadvertently selected Population cannot realize maximum potential displayed by the ‘best’ pure line, due to bulking Final population is not as uniform as those developed through pure-line selection Disadvantages

Mass selection vs Pure line selection:

34 Mass selection vs Pure line selection Line mixture Bulk of phenotypically similar plants Cultivar register and marketing Single plant offsprings L1 L2 L3……. LN Register and market the best pure lines Mass selection Pure line selection Heterogenous cultivars Homogenous cultivars Line mixture Bulk of phenotypically similar plants Cultivar register and marketing Single plant offsprings L1 L2 L3……. LN Register and market the best pure lines Mass selection Pure line selection Heterogenous cultivars Homogenous cultivars Line mixture Bulk of phenotypically similar plants Cultivar register and marketing Single plant offsprings L1 L2 L3……. LN Register and market the best pure lines Mass selection Pure line selection Heterogenous cultivars Homogenous cultivars

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35 Bulk Method

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36 Generalized steps in breeding by bulk selection

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37 Bulk Inbreed in bulk to have homozygous lines Select superior lines after F6 Crosses with no high heritability traits segregating

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38 Natural selection changes gene freq. via natural survival Breeder may assist nature and discard obviously poor types Relieves breeder of most record keeping Most of us treat bulks with extremely low inputs and low expectations. Points to consider in Bulk Method

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39 The bulk method is a procedure for inbreeding a segregating population until a desired level of homozygosity is reached. Seed used to grow each selfed generation is a sample of the seed harvested in bulk from the previous generation. In the bulk method, seeds harvested in the F 1 through F 4 generations are bulked without selection; selection is delayed until advanced generations (F 5 -F 8 ). By this time, most segregation has stopped.

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40 Advantages Less record keeping than pedigree Inexpensive Easy to handle more crosses Natural selection is primarily for competitive ability More useful than pedigree method with lower h 2 traits Large numbers of genotypes can be maintained Works well with unadapted germplasm Can be carried on for many years with little effort by the breeder

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41 Environmental changes from season to season so adaptive advantages shift Most grow bulk seed lots in area of adaptation Less efficient than pedigree method on highly heritable traits (because can purge non-selections in early generations) Not useful in selecting plant types at a competitive disadvantage (dwarf types) Final genotypes may be able to withstand environmental stress, but may not be highest yielding If used with a cross pollinated species, inbreeding depression may be a problem Disadvantages

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42 Pedigree Method

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43 Most popular Essentially a plant to row system to develop near pure lines Followed by performance testing of resulting strains This method and its variants require a lot of record keeping Pedigree Method

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44 Generalized steps in breeding by pedigree selection

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45 Pedigree Selection during inbreeding Early generations: High heritability traits Late generations: low heritability traits

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46 Genetic Considerations: Additive genetic variability decreases within lines and increases among lines, assuming no selection recall the movement toward homozygosity following the hybridization of unlike and homozygous parents Dominant genetic variability complicates pedigree selection homozygous and heterozygous individuals look alike and therefore you may continually select the heterozygote THUS, selection can be discontinued with phenotypic uniformity within a line is obtained

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47 Advantages Eliminates unpromising material at early stages; Multi-year records allow good overview of inheritance, and more effective selection through trials in different environments Multiple families (from different F 2 individuals) are maintained yielding different gene combinations with common phenotype Allows for comparison to other breeding strategies

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48 Disadvantages Most labor, time and resource intensive method; usually compromise between # crosses and population sizes; Very dependent on skill of breeder in recognizing promising material Not very effective with low h 2 traits Slow; can usually put through only one generation per year, and the right environmental conditions must be at hand for accurate selection. Upper ceiling set by allelic contents of F 2 ; can not purge selections of undesirable alleles once ‘fixed’.

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49 Single Seed Descent

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50 Single Seed Descent Inbreed with one seed from each plant in each generation Select superior line after F6 Crosses with no high heritability traits segregating

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51 Advantages Rapid generation advance; 2-4 generations/yr Requires less space,time and resources in early stages, therefore accommodates higher # crosses; Superior to bulk/mass selection if the desired genotype is at a competitive disadvantage; natural selection usually has little impact on population. Delayed selection eliminated confusing effects of heterozygosity ; more effective than pedigree breeding when dealing with low h 2 traits; Highly amenable to modifications and can be combined with any method of selection.

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52 Disadvantages May carry inferior material forward Fewer field evaluations, so you lose the advantage of natural selection Need appropriate facilities to allow controlled environment manipulation of plants for rapid seed production cycles (day length, moisture and nutrient control)

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53 Backcross Method

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54 Same form whether self or cross pollinated species Only difference is pollination control With backcross we approach homozygosity at the same rate as with selfing Goal is to move 1 to a few traits from a donor parent (deficient in other traits) to a recurrent parent (deficient in the trait of interest) Backcross Method

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55

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56 Limited use of BC to create a population for selection that fosters wider genetic variance and modest introgression is a separate issue than a repeated BC to derive a new cultivar Jensen suggested that a 3-way (a backcross to another recurrent or superior parent following he single cross of a desirable and an undesirable parent) was superior to single cross followed by pedigree or other selection methodology Backcross

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57 BC must be used with other, more exploratory procedures Must have a suitable recurrent parent # of BCs to make? usually 4 Use several RP plants! WHY? To incorporate > 1 trait, use parallel programs and then converge Evaluation phase can be less stringent because you should already know the utility of the recurrent parent! Backcross

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58 Backcross Breeding Recovery of the recurrent parent genotype follows this pattern: % recurrent % donor F 1 50 50 BC 1 75 25 BC 2 87.5 12.5 BC 3 93.7 6.3 BC 4 96.9 3.1 BC m 1-(1/2) m+1 (1/2) m+1

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59 1. Retain all desirable characters of a popular adapted variety. 2. Useful method for transfer of oligogenic characters like disease resistance. 3. Male sterility and fertility restorer genes are transferred to various agronomic bases by this method. 4. Used for inter-specific gene transfer. 5. Does not require multilocation testing. Advantages

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60 1. Time consuming, it involves lot of crossing work (6-8 ) . 2. Sometimes, undesirable character is tightly linked with desirable one, which is also transferred to the new variety . Disadvantages

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61 First suggested in oats by Jensen (1952) Method for developing multiline in wheat : Borlaug and Gibler (1953) Seed mixture of isolines , closely related lines or unrelated lines are referred to as multiline and a variety which is developed for commercial cultivation from any of these mixtures is known as multiline variety. Isogenic lines: lines that are genetically identical except for the allele at one locus Multiline Breeding

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62 Features of multiline varieties SP only Genetic constitution: Homozygous and Heterogeneous Adaptation: Wide adaptation than pureline Disease control: less prone to attack of new race of a disease Quality of produce: Less uniform than pureline Yield: Lesser than pureline under normal condition, but higher yield under adverse condition

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63 Procedure of developing multiline Selection of recurrent parents Selection of donor parents Transfer of resistant gene into recurrent parent Mixing of seed of the isogenic lines

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64 Multiline are more adaptable to environmental changes than pureline cultivar due to genetic diversity They provide better protection form the infection of new race of a disease Merits

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65 Multiline varieties is less attractive and less uniform due to mixture of several purelines . Development of multiline cultivars involves several backcrosses, hence is costlier than conventional breeding methods. Disadvantages

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66 Mutation Breeding Genetic improvement of crop plants for various economic characters through the use of induced mutations. Commonly used in self pollinated and asexually propagated species. Mutation refers to sudden heritable change in the phenotype of an individual. Types : 1. Spontaneous mutation 2. Induced mutation: Macro-mutations & Micro-mutations

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67

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68 Mutagens Procedure: M1 Plants obtained from treated seeds/cuttings or from seeds obtained after pollination with treated pollens are called M1 plants . M1 Plants Large no. of plants are grown Grown in wider spacing. Dominant mutations are recorded if any (generally mutations are recessive and do not express in M1) Chlorophyll sectors and fertility is recorded. M1 plants are selfed and their seed is harvested separately.

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69 M2---- Seed obtained from M1 is sown in wide spacing Selected mutants are selfed . Oligogenic mutations are detected in M2 and are harvested separately. M3---- M3 progeny is raised from selected M2 and evaluated for homozygosity . Selected homozygous M3 progenies are bulked together to conduct yield trials in M4. M4---- M4 progeny are raised in replicated trials using local check for comparison. M5-M9--- Selected lines are tested in multiplication coordinated trials

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70 Applications of mutation breeding in crop improvement: Development of improved varieties. Induction of male sterility. Production of haploids creation of genetic variability. Improvement in adaptation. Overcoming self incompatibility.

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71 List of some varieties developed in India through mutation breeding Crop Mutant Parent Mutagen Wheat Sharbati Sonara Sonara 64 Ƴ rays Rice Jagnnath T-141 - Tobacco Jayshri - Chemical Cotton MCU 5 1143 EE - S’cane Co-8152 Co-527 Ƴ rays Chickpea BGM-417 BG-203 -

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72 T H A N K Y O U A L L

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