Evaluating Uniformity and Stability of Wheat Cultivars Based on Ratio of Homozygous DNA Locus

Abstract

Evaluation of the uniformity and stability is of great importance before the release determination of crop cultivars. The ratio of homozygous DNA locus is one of the main factors affecting the uniformity and stability of wheat ( Triticum aestivum L.) cultivars. The objective of this study was to figure out the feasibility and effectiveness of molecular markers in evaluating the uniformity and stability of wheat cultivars based on the ratio of homozygous DNA loci. A total of 172 pairs of simple sequence repeat (SSR) primers, 99 pairs of expressed sequence tag-derived SSR (EST-SSR) primers, and 76 pairs of amplified fragment length polymorphism-derive sequence characterized amplified region (AFLP-SCAR) primers were screened with the plants from 511 wheat cultivars (136 released and 375 under the evaluation of the National Regional Trials from 2006 to 2009) and each 10 breeding lines (50 plants per line) in F 4 and F 5 generations. The ratios of homozygous DNA loci were 82.1–94.5% in F 4 generation and 95.7–99.4% in F 5 generation. The ratios of homozygous DNA loci in F 6 generation was predicted to a range from 98% to 100% based on the homozygous DNA locus ratio of 500 F 5 individuals. In the 511 cultivars, 10% had the ratio of homozygous DNA loci smaller than 95%. Cultivars with higher ratios of homozygous DNA locus possessed better uniformity and stability. In the 375 cultivars from the National Regional Trials, most cultivars with the ratio of homozygous DNA loci higher than 95% and a few cultivars with the ratios ranging from 90% to 95% showed good performance on uniformity and stability, whereas, cultivars with the ratio of homozygous DNA loci smaller than 90% had obviously phenotypic segregation. Therefore, the ratio of homozygous DNA locus can serve as a supplementary criterion in evaluating uniformity and stability of wheat cultivars. The proposed evaluation system is based 20 individuals and 50 loci.