Allozyme polymorphisms of maize populations from southwestern China

Maize (Zea mays L.) is one of the most-important food crops in southwestern China. The diversity of maize populations from southwestern China has been evaluated on the basis of agronomic and morphological data, but not on marker data. Our objectives were to evaluate the allozyme polymorphism of these populations, and group the populations on the basis of allozyme data. We analyzed 27 maize populations from southwestern China and two populations [BS13(S)C2 and Lancaster] from the USA for genetic variation at 18 allozyme loci. We found a total of 69 alleles at 18 allozyme loci with an average of 3.8 alleles per locus. Compared with inbreds, hybrids, and populations from the U.S. Corn Belt, the 27 Chinese populations had a significantly higher (p<0.01) number of allozyme alleles per locus. Maize populations from southwestern China have accumulated abundant genetic diversity, and might be valuable germplasm for broadening the genetic base of U.S. Corn Belt breeding germplasm. The analyses of allele-frequency distributions and the expected heterozygosity also reflected the differences between the Chinese and the U.S. germplasm. The Chinese populations might be valuable germplasm for complementing U.S. Corn Belt breeding germplasm. The analysis of gene diversity showed that 77% of the allozyme variation resided within populations and 23% between populations. This result suggested that breeders should identify one or a few Chinese populations with the best agronomic performance, and exploit the genetic variation within these selected populations. Cluster analysis classified the 29 populations into four main groups. Groupings based on allozyme data could be useful for classifying the populations into different heterotic groups and, consequently, exploiting them in hybrid breeding.