Dissimilar molecular defense responses are elicited in Triticum aestivum after infestation by different Diuraphis noxia biotypes

Abstract

For sustainable solutions to the problem of insect infestation, the study of molecular plant-insect interactions is integral to resistance breeding strategies. This also holds true in the case of wheat (Triticum aestivum), where the Russian wheat aphid (Diuraphis noxia, Kurdjumov, RWA) is responsible for significant crop losses in most major wheat producing countries around the world. Our study is focused on gaining a greater understanding of the resistance mechanisms activated by the RWA resistance gene Dn7 by comparing responses following infestation with three different aphid biotypes (RWA-SA, RWA-US1 and RWA-US2). This consisted of analyzing the resistant wheat line 94M370 (containing Dn7) and its susceptible counterpart (Gamtoos) on a transcriptional level with complementary DNA-amplified fragment length polymorphisms (cDNA-AFLPs) using 17 primer combinations, as well as quantitative reverse transcription polymerase chain reaction (qRT-PCR) of 10 differentially expressed transcripts. The results of this expression profile analysis suggest that Dn7 activates similar responses against the two US aphid biotypes, which differ noticeably from the response following infestation with a South African aphid biotype. This is consistent with recent research showing limited molecular variations between the two US aphid biotypes (approximately 0.12%), compared with a distinctly different South African biotype. We therefore conclude that Dn7 recognizes and interacts in a highly specific manner with different aphid's putative eliciting agents, which in turn activates specific defense pathways unique to that interaction.