Quantitative genetic analysis of total glucosinolate, oil and protein contents in Ethiopian mustard (Brassica carinata A. Braun)

Abstract

Cultivars of Ethiopian mustard are agronomically robust, but have very high levels of total glucosinolates, which impair feed value of the meal though it is rich in protein of balanced amino acids. This experiment was undertaken to assess the level of natural variation in total glucosinolate, and study its inheritance together with that of oil and protein from a diallel cross of six inbred lines which were field-tested in a randomized block design at two locations in Ethiopia. Seeds were analyzed using HPLC (glucosinolates), NMR (oil) and NIRS (protein). Analyses of variance, Hayman's method of diallel analysis and a mixed linear model of genetic analysis were employed to estimate and predict genetic parameters and interactions. There were significant differences among the parental lines as well as their hybrids. The additive, dominance and cytoplasmic effects were highly significant for all the traits. The additive component of variance, accounting for about 40% of the total variations in all the traits, was twice as much as the dominance, which in turn was also about twice as much as the variation accounted by the cytoplasm. A clear-cut case of inbreeding depression was evident with oil content. Partial dominance was most prevalent in governing total glucosinolate although some levels of over-dominance were also noticed. It appeared that in addition to nuclear genes, cytoplasmic components, which could be persistent or transient maternal effects, are also of significance in the inheritances of these quantitative traits in B. carinata. There were at least two dominant genes with decreasing effect on total glucosinolate for every single recessive gene of counter actions. The predominant additive component of variation coupled with the high narrow-sense heritability may allow fixation of low levels of total glucosinolate in recombinant inbred lines by selection.

Keywords: Brassica carinata, diallel cross, glucosinolates, oil, protein

SINET: Ethiopian Journal of Science Vol. 28(2) 2005: 141-150