Introgression of Russian Wheat Aphid Biotype 2 Resistance from Tetraploid Wheat Germplasm.
Ben Beyer, Scott Haley, Junhua Peng, Frank Peairs, and Nora Lapitan. Colorado State University, Colorado State University, Fort Collins, CO 80523
The Russian Wheat Aphid (RWA), Diuraphis noxia (Mordvilko), has been a serious problem in winter wheat (Triticum aestivum L.) production areas of the west central Great Plains since its introduction in 1986. Primary control first came from the use of systemic insecticides and was followed by cultural practices and the use of host plant resistance to prevent damage to infested fields. However, in 2003, a new biotype that was even more virulent than the original isolate was reported in eastern Colorado. Of the many resistance genes located on chromosomes 1D and 7D in wheat, the only effective one was Dn7, which is the product of a rye chromosome translocation and is associated with poor baking quality. The objective of this research was to develop new sources of resistance by transfer of gene(s) from four tetraploid wheat accessions into hexaploid wheat. Initial crosses were made between three Emmer (Triticum dicoccoides) and one durum (Triticum turgidum) wheat accessions to the hexaploid spring wheats 'Len' and 'Coteau'. Micrsatellite marker tests were done to confirm the ploidy level of the resistant parents. Pentaploid F1 seed was obtained and was increased to the F2:3 and backcrossed to the susceptible parents to produce BC1F2 and BC2F2 lines. Due to the differences in ploidy level between the parents, very little seed was obtained in the F1 crosses. Observed segregation ratios suggested that resistance from each of the tetraploid sources was dominant. Seed set increased with more advanced selfing or backcrossing as more progeny underwent spontaneous doubling of the chromosomes in the D genome. This germplasm will be useful to broaden the array of RWA resistance sources available for wheat breeding.