Predicting Heterosis and F1 Performance based on Combing Ability and Molecular Genetic Distance of Parental Lines in Ethiopian Mustard

Abstract

Ethiopian mustard (Brassica carinata A. Braun) is one of the oldest oil crops cultivated and utilized by  farmers for many purposes. However, it is one of the most neglected and least genetically studied crops.  The improvement of the crop mainly depends on line breeding, but the crop is amenable to heterosis  breeding. However, information regarding heterosis is scanty and the identification of parental lines from  phenotypic observation is expensive and time-consuming. Therefore, this study was conducted to  determine the association of genetic distances of seven Brassica carinata A. Braun lines measured by  random amplified polymorphic DNA (RAPD) markers with heterosis, F1 performance, and general  combining ability (GCA). The study was aimed at comparing the effectiveness of parental GCA effects and  genetic distance in predicting heterosis and F1 performance. Seven Brassica carinata lines and their 21  F1s generated in a half diallel fashion were evaluated in a replicated field trial for two years (2009/10 and  2010/11) at G.B. Pant University, India. Per se performances and GCA effects of the parents, heterosis  and F1 performance were calculated based on mean values from the two years for 13 traits. Correlations  were computed among genetic distance, heterosis, GCA, and F1 performances. Genetic distances among the parents were calculated from 95 random amplified polymorphic DNA (RAPD) markers and  dendrogram  was constructed using Unweighted Pair Group Method with Arithmetic Means (UPGMA)  method, which effectively grouped the parental lines in to three major clusters. The measured genetic  distance was significantly correlated with parental GCA sum only for plant height (r = 0.6) and percent oil content (r = 0.55). However, the correlations with mid and better parent heterosis and F1 performance were non-significant for all traits except a negative and significant correlation observed between genetic distance and better parent heterosis for length of main shoot. The correlation between GCA and F1  performance was positive and significant for most of the traits. Mid and better parent heterosis had positive and significant correlations with GCA for days to 90% maturity, length of main shoot, and  number of secondary branches. In addition, better parent heterosis of number of seeds per pod was positive and significantly correlated with the GCA of the parents. Correlation of GCA effects and parental performance was positive for all traits and significant in most cases. It could be concluded that molecular marker based distances is not a reliable predictor of heterosis, combining ability, and F1 performance whereas GCA is better in predicting heterosis, parental line, and F1 performances for the crop species.

Keywords: Brassica carinata A. Braun; General Combing Ability; Genetic Distance; Heterosis; Random Amplified Polymorphic DNA (RAPD)