Page 1 : ide BIOMETRICAL TECHNIQUES IN PLANT BREE by, waa, , Ail) Additive x dominance epistasis refers to interaction between two or mor ", exhibiting lack of dominance and other dominance individually. It is dont, and is non-fixable. It comes under non-additive gene action., , Adii) Dominance x dominance epistasis refers to interaction between two of mote {, each exhibiting dominance individually. It is denoted as DD and is hontfixaly i, comes under non-additive gene action. "a, , log} Oy, Gd fy Aj, , , , , , «5. Effect of Selection. The additive x additive type of epistasis is fixable, Henyy, selection is effective for traits governed by this type of epistasis. !, , —6. Uses. Heterosis breeding would be rewarding with additive x dominance and Cotnltiangy, x dominance types of epistasis, because these are non-fixable. :, , _7. Estimation. Epistatic variance can be measured by various biometrical techiiqucy, such as generation mean analysis, triallel analysis, quadriallel analysis, etc., , TABLE 7.2. Comparison of three types of Epistasis,, , , , , , , , , , , , , , , , , , , AxD, , , , , Denoted as AXA, Fixation Fixable Non-fixable Non-fixable, Type of gene Additive Non-additive Non-additive, , action, , , , , , , , , , , , , , , , , , , , , Selection Effective Not effective Not effective, Breeding Mass or progeny | Heterosis breeding Heterosis breeding, methodology selection, , , , GENE ACTION e, {Gene action, refers to the behavior or mode of expression_of genes in a genetic population, , The gene action is measured in terms of genetic variances and combining ability vatiariots, and effects. The gene action is studied with the help of various biometrical techniques such, as diallel cross, partial diallel cross, line x tester cross, triallel cross, quadriallel cross, triple, test_cross, biparental cross and generation mean analysis. The gene action is of two types, , viz., additive gene action and non-additive gene action. These are explained as follows:, “As Additive Gene Action : It includes additive genetic variance and additive “ additive, type of epistasis. Additive gene action is associated with homozygosity and, therefore, It Is, expected to be maximum in self pollinated or autogamous species. In self pollinated, species, pure line varieties, mass selected varieties, varietal blends and multiline varieties, , have additive gene action. Additive gene action can be exploited by pure line selection, miss, selection and progeny selection., , , , , , , , , , , , -2.Non-additive Gene Action: It includes dominance variance and additive x dominit, and dominance dominance types of epistasis. Non-additive gene action is associated a, heterozygosity and, therefore, it is expected to be maximum in cross pollinated of allogam™, , 4