Genetic variation in South African Diuraphis noxia biotypes

Abstract

Wheat (Triticum aestivum L.) is an important winter and spring crop in South Africa with average dryland yields of 2.5 t/ha, while irrigated wheat yields 5 t/ha. Diuraphis noxia (Kurdjumov) commonly referred to as the Russian wheat aphid was recorded in 1978 to South Africa and has become a major pest in the wheat industry. It can cause over 80% yield loss in the summer rainfall region if not controlled. There are five described RWA biotypes in SA, namely RWASA1 to RWASA5. We investigated the genetic variation of 24 specimens which are representative of four South African RWA biotypes using three molecular techniques, AFLP, cDNA-AFLP and microsatellites. With AFLP and cDNA-AFLP, we detected variation among specimens within a biotype. The cDNA-AFLP results increased the amount of the variation detected compared to the genomic AFLP results, but it was not sufficient to be linked to a specific biotype. With microsatellites, we were able to detect variation among biotypes and distinguish between them. We were unable to identify markers unique to a biotype. We found evidence that the genetic diversity may be linked to geographic location of the RWA, but further investigation is required to confirm this.