Heterosis and gene effect studies for seed yield and related traits in Indian-mustard (Brassica juncea L. Czern & Coss)
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Date
2016-07
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G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand)
Abstract
Indian mustard (Brassica juncea (L.) Czern and Coss) is a largely self-pollinating major oilseed crop with upto 15 % out crossing under natural field conditions. Due to its wide cultivation it is essential to identify high yielding genotypes and formulate effective breeding programmes on the basis of genetic parameters. Devising a suitable improvement programme for desired improvement would depend on the knowledge of gene effects operating in the breeding population. Therefore, the present investigation was under taken to (1) test the adequacy of different models, (2) detect additive, dominance and epistatic gene effects (3) generate information about the genetics of heterosis in different crosses. The present investigation was carried out during rabi 2013-14, 2014-15 and 2015-16 in Indian mustard (Brassica juncea L.) comprising four families viz; PR-2009-6 × Albeli (Family A), PR-2009-6 × RGN-73 (Family B), PR-2009-6 × NDYR-8 (Family C) and KMR-13-3 × PR-20 (Family D). The study was based on six generations of these crosses which were sown in Compact Family Block design with 3 replications. The data were subjected to generation mean analysis following joint scaling test (Cavalli, 1952) for obtaining the necessary information. Analysis of variance showed presence of significant variability among families and also within families (among progenies) for various traits under study except for days to maturity, seeds per siliquae and siliquae length. Fixable effects [d] and [i] were found important in the inheritance of plant height, seed yield per plant and glucosinolate content. Among non fixable effects, dominance [h] gene action was significantly important for determining length of main raceme, number of siliquae on main raceme, siliquae length, oil content, seed yield per plant and glucosinolate content. Interaction gene effects were found significant in controlling plant height, length of main raceme, number of secondary branches per plant, siliquae on main raceme, siliqua length,1000seed weight, oil content, seed yield per plant and glucosinolate content. Thus both main effects and epistatic effects were found important in controlling the various traits under study. Family A showed considerable interaction effects for siliquae on main raceme, number of seeds per siliquae and oil content. Family B displayed epistatic interactions for characters such as plant height, length of main raceme, siliquae on main raceme, siliquae length, oil content seed yield per plant and glucosinolate content. Both main and interaction effects were found significant in Family C for characters namely, plant height, siliquae on main raceme, seed yield per plant and glucosinolate content. Family D had significant interaction effects important for the improvement of characters such as plant height seed yield per plant and glucosinolate content. The estimates of genetic parameters under adequate model were employed to calculate the value of expected heterosis. Close agreement between observed and expected heterosis implies that non-allelic interaction is important for heterosis. The heterosis manifested in different crosses studied was of high magnitude, significant in all the four families for seed yield per plant and number of primary branches per plant. For secondary branches pre plant significant positive heterosis was realized in Family B and D. The estimate of observed heterosis for seed yield per plant ranged from 15.67% in Family D to 11.97% in Family A. For primary branches per plant observed heterosis was highest for Family A and lowest in Family B. Observed heterosis for secondary branches per plant was significantly high for Family B and D. Considering the overall results, it is apparent that most of the characters in all the four families were found under the control of both fixable (additive, additive x additive) and non fixable (dominance and epistatic) gene effects coupled with duplicate type of epistasis. In such situations hybridization system such as multiple or reciprocal recurrent crossing which exploit both additive and non additive gene action simultaneously are important for genetic crop improvement. The duplicate epistatsis was found to be associated most of the traits which slows down the progress of breeding programme and hinders the isolation of desired type in the early segregating generations therefore, selection must be practiced in the advanced generations
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