Studies on Genetic Variability and Path Analysis for Quality Characters in Rapeseed-Mustard (Brassica species)

Abstract

A two-year study was carried out during rabi 2003-04 and 2004-05 with 40 varieties of rapeseed-mustard to assess
the nature of variability and association for fatty acid profile, oil, protein and glucosinolate content. Analysis of
variance indicated significant differences for all the quality characters investigated. The environmental effects were
significant for erucic, oleic acid, glucosinolate and protein content and the influence of environmental factors appeared
to be less on other characters. The genotype x environment interactions were non-significant for all the characters,
hence the data were pooled over the years and discussed on the basis of mean of two years. The coefficients of
variation at phenotypic level varied from 4% for protein content to 50.9% for oleic acid. The genotypic coefficients
of variability were high for oleic, palmitic + stearic, erucic and linolenic acid. Protein and oil content had the
least genotypic variation (GCV: 2.6-2.7%). The heritability in broad-sense was relatively high for oleic (61.5%)
and erucic acid (56.3%). The high heritability was associated with high genetic advance only for oleic acid suggesting
the role of additive gene action in the inheritance of this character. Erucic acid was negatively and significantly
correlated with the rest of the fatty acids except linolenic acid. It had positive association with glucosinolate content
(r =0.331). Glucosinolate content had negative and significant correlations with oleic (r =-0.536) and eicosenoic
acid (r =-0.260). The negative association of palmitic + stearic, oleic, linoleic, linolenic and eicosenoic with erucic
acid was the result of their high to moderate negative direct effects. Although glucosinolate content had very low
direct effect (-0.051) on erucic acid but its positive association was the result of its strong positive indirect effect
via oleic acid (0.435), which was partially neutralized by negative indirect effects (-0.112) via linolenic acid. The
implications of these results in the quality-breeding programme were discussed in this paper.