Genetic diversity based on SSR markers in maize (Zea mays L.)andraces from Wuling mountain region in China

摘要

Genetic diversity of maize (Zea mays L.) plays a key role in maize breeding (William and Michael 2002). Knowledge of the amount and the distribution of genetic variation within and among maize landraces will provide a guide for predicting the degree of inheritance, variation, and level of heterosis,that are essential for maize breeding (Duan et al. 2006). For several decades, maize breeders have focused on short-term breeding. This has resulted in the development of a narrow genetic base for commercial maize hybrids (Darrah and Zuber 1986). A survey that was conducted in late 1970s and mid 1980s on inbred lines showed that some of the inbreds continued to contribute substantially to hybrids marketed in the United States. And the pedigrees of most hybrids are derivatives of 6C8 inbred lines (Darrah and Zuber 1986; James et al. 2002). In China, the parenthood of 91.6% hybrids consists of about 20 elite inbred lines (Li et al. 2002). With such a restrictive base, maize may not contain all the desirable and favourable alleles to maintain selection progress.