heritability, genetic advance ,G*E interaction

plant breeding

1. MAHATMA PHULE KRISHI VIDYAPEET RAHURI R.C.S.M COLLEGE OF AGRICULTURE KOLHAPUR Subject : Principles of plant breeding (GP-503) Topic :Heritability, genetic advance, G×E interaction To , Dr. M.S.Mote Asst . Professor From , R.C.S.M college of agriculture Sunil .L Msc 1 st yr(GPB)

2. HERITABILITY Definition: the ratio of genotypic variance to total or phenotypic variance is known as heritability. It is generally expressed in percent . The heritability is the heritable portion of phenotypic variation. Estimates of heritability are helpful to the plant breeder in the selection of elite genotypes from diverse genetic population

3. Types of heritability There are two types of heritability that are Broad sense heritability Narrow sense heritability

4. Broad sense heritability : The ratio of genotypic variance to total or phenotypic variance is known as broad sense heritability. It is calculated with the help of following formula, Where, Vg= genotypic variance Vp = phenotypic variance Ve = environmental variance Heritability ( bs ) = Vg / Vp x 100 = Vg / Vg+Ve x100

5. Application : It is more useful in animal breeding than plant breeding It is useful in selection of elite genotypes from homozygous line Calculation: It can be calculated from both parental as well as segregating populations

6. Narrow sense heritability  It is the ratio of additive genetic variance to the total or phenotypic variance. it is calculated with the help of following formula where, VA or D = additive genetic variance VP or VP = phenotypic variance Application: It is useful for plant breeding in selection of elite types from segregating populations Heritability (ns) = VA /VP x 100 or ½ D/VP x100

7. Difference b/w broad sense heritability and narrow sense heritability particulars bsH nsH Variance used for estimation Total genetic variance Additive variance Population used Both parental and segregating Specific population Useful in selection of elite types from Homozygous line Segregating material application Animal breeding Both animal and plant breeding

8. Factors influencing heritability Type of genetic material : the magnitude of heritability is largely governed by the amount of genetic variance present in a population for the character under study .greater the genotypic variance higher the heritability Sample size : Large sample give necessary for accurate estimates while small sample may mislead the information Sampling methods : two types of sampling methods , 1.Random: The random sampling methods provide true estimates of genetic variance 2.biased: the biased sampling method will not provide true estimates of gv

9. Conduct of experiments : Heritability estimates are influenced by the environmental error. By Increasing the plot size and no. of replications we can reduce experimental error and get reliable estimates Method of calculation : the estimates of bs Heritability are always higher than ns heritability

10. Advantages : ‘H’ are useful in predicting the transmission of characters from parents to their offspring. It is free from genetic assumption ‘H’ estimates are useful in selection of elite genotypes from homozygous material as well as from segregating populations. Limitations : It is based on second order statistics and therefore are not statistically very robust and reliable Components of variance sometimes turn out to be negative resulting in negative estimates of heritability

11. GENETIC ADVANCE  Improvement in the mean genotypic value of selected plants over the parental population is known as genetic advance It is the measure of genetic gain under selection The success of genetic advance under selection depends upon three factors (Allard , 1960) Genetic variability : greater the amount of genetic variability in base populations higher the genetic advance Heritability : the G.A. is high with characters having high heritability Selection intensity : the proportion of individuals selected for the study is called selection intensity . high selection intensity gives better results

12. The genetic advance is calculated by the following formula GS = K × H × SDP where , GS =genetic advance K = standardize selection differential H = heritability of the character under selection SDP = phenotypic standard deviation

13. Genetic gain:  The difference between the mean phenotypic value of the progeny of selected plants and the base population is known as genetic gain It is denoted by R R = Xp – Xo Where, Xp = mean phenotypic value of progeny of selected plants Xo = base population

14. Selection differential: It is the difference between the mean phenotypic value of selected population and the parental population it is denoted by K K = Xs - Xo where , Xs = mean of phenotypic value of selected plants Xo = parental population

15. Genotype ×environment interaction Differences in performance of genotypes in different environments is referred to as Genotype X Environment Interactions Types G×E interaction Quantitative G x E interaction or Non crossover interaction : In case of this interaction performance of the varieties does not change over the environments. the differential response of genotypes is only a matter of scale. Qualitative or Cross over G x E interaction : In case of this interaction performance of varieties changes with the environment and a given environment favors some genotype or detrimental to some genotype . (promotion or inhibition)