Aphid feeding response and microsatellite-based genetic diversity among diploidBrachypodium distachyon(L.) Beauv accessions

Abstract

False brome grass,Brachypodium distachyon(L.) Beauv, has been proposed as a new model species to bridge rice and temperate cereal crops for genomics research. However, much basic information for this species is still lacking. In this study, six diploidB. distachyon(2n = 2x = 10) accessions (Bd1-1, Bd2-3, Bd3-1, Bd18-1, Bd21 and BD29) were evaluated for their response to infestation by two cereal aphid pests of common wheat (Triticum aestivumL.): the greenbug,Schizaphis graminumRondani, and the Russian wheat aphid (RWA),Diuraphis noxiaMordvilko. Through database mining ofB. distachyonexpressed sequence tag (EST) and genomic DNA sequences, 160 EST- and 21 genomic microsatellite markers were developed and used to evaluate genetic diversity among theB. distachyonaccessions. All six accessions were resistant to RWA biotype RWA1 but showed distinct responses to feeding by greenbug biotypes C and E, as well as RWA2 RWAs. Although microsatellite-based genetic diversity among different accessions was generally low, Bd1-1 and BD29 were the most diverged from the other four lines. The genetic divergence was correlated with geographical distances between theBrachypodiumaccessions. Comparison of simple sequence repeat polymorphisms in three inbred lines (Bd2-3, Bd3-1 and Bd18-1) with their respective original parental lines revealed no effect of inbreeding on genetic diversity. Phylogenetic analysis suggested thatAegilops tauschii(Coss.) Schmal., the D genome donor of common wheat, was closer toB. distachyonthan to rice. The greenbug - B. distachyonsystem seems to be a model of choice for plant–aphid interaction studies in the grass genome.