Heterosis in root development and differential gene expression between hybrids and their parental inbreds in wheat (Triticum aestivum L.)

In spite of commercial use of heterosis in agriculture, the molecular basis of heterosis is poorly understood. In this study, heterosis was estimated for eight root traits in 20 wheat hybrids derived from a NC Design II mating scheme. Positive mid-parent heterosis was detected in 96 of 160 hybrid-trait combinations, and positive high-parent heterosis was detected in 79 of 160 hybrid-trait combinations. Improved differential display was used to analyze alterations in gene expression between hybrids and their parents in roots at the jointing stage. More than 990 fragments were repeatedly displayed, among which 27.52% were differentially expressed between hybrids and their parents. Four differential expression patterns were observed. Thirty differentially expressed cDNA fragments and three genes with open reading frames were cloned, and their expression patterns were confirmed by reverse-northern blot and semi-quantitative RT-PCR analysis, respectively. We concluded that these differentially expressed genes, though mostly with unknown function, could play important roles for hybrids to demonstrate heterosis in root system traits.