Evaluation on the germplasm of maize (Zea mays L.) landraces from southwest China

Because of their local adaptation and economic factors that limit the adoption of commercial hybrids, farmer-saved maize landraces are still grown over a considerable area concentrated in southwest China. To evaluate the potential of using maize landraces, the germplasm characteristics of 96 landraces from southwest China were evaluated at phenotypic, cellular, and molecular levels. The existence of high phenotypic variation and elite germplasm tolerant to low-N, low-P, as well as drought stress was observed. Of the total landraces, 81.25, 7.29, 5.21, and 2.08% were found with 0, 1, 2, 3, and 4 B chromosomes. Using 42 microsatellite (simple sequence repeat) loci, 246 alleles were detected among the landraces. The number of alleles per SSR locus varied from 2 to 10, averaging 5.67 allele per locus, which revealed a high level of genetic diversity of maize landraces in southwest China. Cluster analysis showed that 96 landraces could distinctly be clustered into four groups, which tended to associate with their geographic origins. We propose that the genetic diversity center of maize landraces in southwest China might be in Sichuan. A sharp genetic deviation from Hardy-Weinberg equilibrium was observed from heterozygosity deficiency and a considerable genetic variation was revealed within, rather than among, the landraces. Based on their germplasm characteristics, the innovation and utilization of maize landraces in southwestern China for theoretical and applied research could be achieved by constructing heterosis groups, developing inbred lines with high combining ability, and maintaining the landraces with elite germplasm and B chromosomes using bulked pollen.