Discovery of candidate genes for heterosis breeding in Brassica oleracea L.

Heterosis is very important for hybrid breeding and productivity of various crop plants can be increased easily by exploitation of it. However, the molecular basis of heterosis has yet to be elucidated. In this study, 51 heterosis-associated genes of different families of Arabidopsis were selected based on their high differential expression in a hybrid relative to its mid-parent value and their orthologues were identified in Brassica oleracea. The selected B. oleracea genes were then characterized based on their predicted functions and expression patterns in four parent-hybrid combinations of cabbage. Many of these genes were found to be more highly expressed in the hybrid than the mid-parent value, and some were better in the parent. Moreover, these highly expressed genes were mostly related to the yield contributing characteristics. Cotyledon and young leaf sizes of these three genotypes were also well correlated with responsive expression of genes analyzed in the parent–hybrid combinations. Thus, the identified genes might be associated with the mechanism of heterosis of B. oleracea hybrid and provide a foundation to reveal the complexity of regulatory gene networks associated with genetic mechanism of heterosis in the plant life cycle. Subsequently, these genes would be useful resources for molecular breeding of hybrid Brassica crops, as well.