GENETIC ANALYSIS FOR MORPHO-YIELD AND SEED QUALITY TRAITS IN RAPESEED (Brassica napus L.)

Abstract

Edible oil is main import of Pakistan and its bill costs 2 billion US$ annually. To overcome this problem, emphasis needs to be focused on developing of new high yielding oilseed cultivars. To achieve this goal, information regarding genetic diversity, underlying gene action, development and assessment of hybrids are pre-requisite of breeding program. Keeping in view the edible oil situation in the country this study was conducted to determine genetic analysis for important traits in rapeseed (Brassica napus L.) using 8 × 8 diallel design at the University of Agriculture-Peshawar during 2011-2014. Parental lines and their F1 and F2 progenies were evaluated in two separate experiments to do F1 and F2 diallel analysis. Analysis of variance revealed highly significant differences for all studied parameters in parents and F1 generation. Based on mean performance best parents were AUP-7, AUP-2, AUP-14 and AUP-18 for important traits. Among F1 hybrids, AUP-7 × AUP-14, AUP-2 × AUP-7, AUP-7 × AUP-2, AUP-9 × AUP-17, AUP-9 × AUP-2, AUP-17 × AUP-8, AUP-14 × AUP-7 and AUP-18 × AUP-7 performed better. Mean squares due to general combining ability (GCA), specific combining ability (SCA) and reciprocal combining ability (RCA) were found highly significant for all the parameters indicating the importance of both additive and non additive gene action. On the basis of GCA, parental lines, AUP-7, AUP-2, AUP-18 and AUP-17 were found best combiners. Among F1s, desirable SCA effects were shown by AUP- 7 × AUP-14, AUP-8 × AUP-9, AUP-17 × AUP-18, AUP-14 × AUP-20, AUP-2 × AUP-9, AUP-2 × AUP-18, AUP-2 × AUP-18, AUP-2 × AUP-14, AUP-2 × AUP-17 and AUP-2 × AUP-9. Desirable negative mid and better parent heterosis were exhibited by AUP-18× AUP- 8 for flowering and AUP-8 × AUP-9 for maturity. Maximum positive heterosis was recorded by AUP-8 × AUP-17, AUP-9× AUP-2, AUP-20 × AUP-2, AUP-2 × AUP-8, AUP-14 × AUP- 2, AUP-14 × AUP-8 and AUP-14 × AUP-17 for morphological traits. However for oil quality traits best crosses were AUP-9× AUP-20, AUP-20 × AUP-17, AUP-7 × AUP-14 and AUP-18 × AUP-2, AUP-9 × AUP-2, AUP-7 × AUP-18and AUP-2 × AUP-7. Best performing parents and crosses could be an asset for future breeding programs. The data of F2 generation revealed significant genotypic difference for all traits. Among F2 populations, best performer were AUP-7 × AUP-17, AUP-17 × AUP-18, AUP-9 × AUP-17, AUP-18 × AUP-9, AUP-2 × AUP-14 and AUP-20 × AUP-14 for morpho-yield traits. F2 populations AUP-8 × AUP-7, AUP-2 × AUP-18, AUP-7 × AUP-8, AUP-9 × AUP-18 and AUP-14 × AUP-20 were superior for oil quality traits. Mode of gene action in F2 generation vi vii 17 for seed per pod, pod length, pods plant-1, 1000 seed weight seed yield plant-1 and quality parameters (oil, protein, oleic and linolenic acid) revealed that additive dominance was adequate (partially). The model was fully adequate for rest of the traits. Hayman analysis revealed both additive and non additive gene actions for all the traits. Estimates of genetic components showed significant and higher magnitude of additive variances for flowering, maturity and plant height, whereas for rest of the traits dominance was significant and higher in magnitude. Inequality of H1 and H2 revealed asymmetrical (uneven) distribution of genes among the parental lines (H2/4H1<0.25). From Vr/Wr graph, negative intercept of the regression line and average degree of dominance values and H1> D revealed that over dominance was responsible for all traits except flowering, maturity and Plant height for which partial dominance (D>H1) was observed. The scatter of array point on the regression lines for studied traits suggested that parental lines were diverse and could be used in future rapeseed quality breeding programs. From the estimation of genetic components of variation and low narrow sense heritability except for days to flowering, maturity and Plant height it is clear that non additive type of gene actions were more important in effecting the variation for all the traits. To exploit both additive and non-additive gene actions as observed under the present investigation, bi-parental mating and inter se crossing between suitable lines following reciprocal recurrent selection may be useful to develop high yielding and early maturing lines. Keywords: Rapeseed, Brassica napus, diallel analysis, genetic analysis, combining ability, gene action, heterosis, heritability,