Genetic Diversity Among Wheat Accessions Relative to Russian Wheat Aphid (RWA) Resistance.

Information on genetic relationships provides crucial information for breeding programs and germplasm enhancement. Russian Wheat Aphid (RWA), Diuraphis noxia (Mordvilko), is a major insect pest of cereals, which causes severe economic losses in wheat. Among the various RWA biotypes detected, biotype 1 and biotype 2 are the most prevalent and most virulent on many cultivated genotypes. Although many RWA resistant sources for these biotypes are available as landraces, genetic diversity among such resistant sources has not been well characterized. In this study, 38 accessions resistant to biotype 1 and/or biotype 2 were evaluated for molecular marker diversity based on amplified fragment length polymorphisms (AFLP). Fifteen AFLP selective primer combinations were used to genotype these accessions, resulting in 893 amplicons. Of those, 274 (30.6%) informative polymorphic bands were used for genetic diversity analysis. Genetic similarity coefficients ranged from 0.47 to 0.87 among the resistant accessions, indicating high genetic diversity between them. Cluster analysis grouped the 38 accessions into two major clusters consisting of resistant lines for biotype 1 and/or biotype 2. The cophenetic correlation coefficient value (r-value) between the data matrix and the co-phenetic matrix of AFLP data was 0.926, suggesting a good fit between the dendrogram clusters and the similarity matrixes. The study indicated that there are many resistant genes available for both of these RWA biotypes. Furthermore, our results suggest that a high level of genetic diversity in the resistance sources may offer the potential to improve RWA resistance in wheat.