Deciphering defense strategies that are elucidated in wheat containing different Dn resistance genes

Russian wheat aphid (Diuraphis noxia, RWA, Homoptera: Aphididae) is a major pest problem in many wheat growing areas in the world. In the U.S. alone, the economic impact of RWA has been estimated at approximately $900M from 1987-1993. However, this estimate may be conservative, since several new biotypes were recently reported, presenting a difficult challenge for breeders. A lack of understanding of the interaction between the RWA and its host plant is a limitation in developing effective strategies for controlling the aphid. Wheat lines containing different resistance genes to the RWA exhibit different resistance or tolerance responses. We investigated these responses at transcriptome level in near-isogenic wheat lines (NILs) containing the Dn1, Dn2 and Dn5 resistance genes, respectively. Affymetrix gene technology (i.e. Affymetrix GeneChip Wheat Genome Array) and cDNA-amplified fragment length polymorphism (cDNA-AFLP) transcript profiling were utilized. Following these approaches, we have identified genes and pathways associated with different resistance phenotypes afforded by the Dn genes. Detailed expression analyses using qRT-PCR and Northern blots provided further supporting evidence that regulation of specific pathways is critical for the development of a specific mode of resistance.