False brome grass, Brachypodium distachyon (L.) Beauv, has been proposedas 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, sixdiploid B. distachyon(2n = 2x = 10)accessions (Bd1-1, Bd2-3, Bd3-1, Bd18-1, Bd21 and BD29) were evaluated for their responseto infestation by two cereal aphid pests of common wheat (Triticumaestivum L.): the greenbug, Schizaphis graminum Rondani, and theRussian wheat aphid (RWA), Diuraphis noxia Mordvilko. Through databasemining of B. distachyon expressed sequence tag (EST) and genomic DNAsequences, 160 EST- and 21 genomic microsatellite markers were developed and used toevaluate genetic diversity among the B. distachyon accessions. All sixaccessions were resistant to RWA biotype RWA1 but showed distinct responses to feeding bygreenbug biotypes C and E, as well as RWA2 RWAs. Although microsatellite-based geneticdiversity among different accessions was generally low, Bd1-1 and BD29 were the mostdiverged from the other four lines. The genetic divergence was correlated withgeographical distances between the Brachypodium accessions. Comparison ofsimple sequence repeat polymorphisms in three inbred lines (Bd2-3, Bd3-1 and Bd18-1) withtheir respective original parental lines revealed no effect of inbreeding on geneticdiversity. Phylogenetic analysis suggested that Aegilops tauschii (Coss.)Schmal., the D genome donor of common wheat, was closer to B. distachyonthan to rice. The greenbug - B. distachyon system seemsto be a model of choice for plant–aphid interaction studies in the grassgenome.

Field studies were conducted to characterise the effects of infestations by adult and nymphal stages of cowpea aphid, Aphis craccivora Koch, on the growth and yield of cowpea, Vigna unguiculata (L.) Walp. Seedling, flowering, and podding stage plants of aphid-resistant (cv. ICV-12) and aphid-susceptible (cv. ICV-1) cowpea cultivars were used in the studies. Four treatments (consisting of infestations with adult and nymphal aphids, caged controls and uncaged controls) were administered on plants for 22 days post-treatment. Eight parameters of crop success were measured: extended leaf heights (ELH); plant mortality; incidence of sooty mould; incidence and abundance of natural enemy species; crop growth parameters (net assimilation rate, [NAR] in g/ dm2/day, and crop growth rate [CGR] in g/dm2 land surface/day); and plant yields (seeds per pod, weight per seed). Data were analysed using analysis of variance (ANOVA), orthogonal contrasts and 95% confidence intervals (C.I.). There were no significant (P > 0.05) differences between adult and nymphal infestations or between caged and uncaged controls, so the respective sets of data were combined for comparisons of aphid infestations with control treatments. Infestations caused severe plant stunting and other growth deformities, drastic yield reductions, higher plant mortality, greater incidence of natural enemies and abundance of Cheilomenes spp. on cv. ICV-1 than on cv. ICV-12, and on infested and uninfested plants. Aphid infestations did not significantly affect the incidence of sooty mould on plants of cv. ICV-12 or cv. ICV-1.