Association of genetic distance and combining ability with heterosis in Indian mustard (Brassica juncea L)

Abstract

Heterosis and combining ability were carried out by evaluation of thirty-two F1s of Indian mustard (Brassica juncea L)
generated in Line × Tester mating design involving eight lines and four testers, in randomized complete block design for
thirteen quantitative traits. ANOVA showed significant differences among parents as well as among hybrids for almost
all the traits studied. The coefficient of variation for different traits was found higher in parents in comparison to hybrids.
The mean performance of hybrids was found higher than parents for all the traits except for days to 50% flowering, days
to maturity and oil content. ANOVA for combining ability exhibited significant variance for most of the traits for both
general and specific combining ability. The PCA analysis using quantitative traits explained that PC-I contributed
maximum of 90.24% with Eigen value of 977.94, and positively correlated with number of primary branches, total number
of siliquae on main shoot, total number of siliquae per plant, seed yield per plant, days to 50 % flowering, plant height,
point to first siliqua and main shoot length. Thirteen F1 combinations showed significant and positive heterosis over the
mid parent. The cross NRCHB 101 × JN032 showed 109.45 percent better parent heterosis for seed yield per plant. The
genetic distance among genotypes (parents and F1s) was calculated by using 13 quantitate traits and SSR markers. The
association of morphological genetic distance and molecular genetic distance with SCA and heterosis revealed that
molecular genetic distance has significant positive correlation (0.43*), while, morphological genetic distance has significant
negative correlation (-0.53**) with mid parent heterosis of seed yield per plant. Moreover, SCA for seed yield per plant
showed significant positive association and regression with mid parent heterosis for seed yield per plant (0.57**) and
better parent heterosis of seed yield per plant (0.67**). The study shows that SCA and molecular genetic distance are
important determinant of heterosis in Indian mustard.