Using DArT Markers to Monitor Genetic Diversity throughout Selection In Structured Wheat Populations.

Assessing the genetic relationship among wheat (Triticum aestivum L.) lines in the middle generations of a breeding program has important consequences on conserving the genetic variability in later generations. The objectives of this study were to i) determine the breadth of the genetic base of two F3:6 nurseries that we currently use in our selection process and ii) to monitor the effect of selection on the genetic diversity. The first nursery contained 276 lines and two local checks genotyped using 1925 polymorphic DArT markers, while the second nursery consisted of 278 lines plus the same local checks and genotyped using 2236 polymorphic DArT markers. In both years, the F3:6 nurseries were grouped into three main clusters. Two approaches were employed to investigate the magnitude of the difference among clusters: first, using statistical tests such as nonparametric multivariate analysis of variance (NPMANOVA) and analysis of similarity (ANSIM); second, comparing the known genetic diversity between the check cultivars with that in the experimental lines. Overall, the results suggested that, in both years, the difference among clusters was significant, and the genetic diversity in the F3:6 nurseries exceeded that between the check cultivars. In addition to, using DArT markers to explore genetic diversity in F3:6 nurseries, DArT markers were also used to monitor the genetic diversity from the F3:6 nurseries to later generations by assuring that each cluster in the F3:6 were represented at least with one line in the F7 and F8 nurseries. In the current study we successfully explored and monitored the genetic diversity before and throughout the selection process using DNA molecular markers, which might have important consequences in producing improved and genetically different wheat cultivars.