Resistance to Rhopalosiphum padi (Homoptera : Aphididae) in wheat germplasm accessions

Studies compared and characterized host giant resistance to Rhopalosiphum p adi (L.) (bird cherry-oat aphid) among promising accessions of hexaploid wh eat, Triticum aestivum L. Resistance was assessed for 7 wheat accessions. R . padi populations did not increase uniformly over time or by accession. Af ter 7 d, accessions did not differ in numbers of R. padi, but by 11 d, MV4: had fewer R. padi per plant than other accessions except MV8 and Jubilejna ja 50. At 14 d, MV4 had fewer R, padi than other accessions except MV8; Jub ilejnaja 50 had fewer aphids per plant than remaining accessions, but more than MV4 or MV8. R. padi nymphs developed more slowly on MV4 than other acc essions, but plant accession did not affect the number of progeny that R, p adi produced. The intrinsic rate of increase of R. padi was less on MV4 tha n on Ommid. R. padi produced a higher proportion of alatae on accession MV4 , whereas they produced a lower percentage of alates on the accession Vista . In choice tests, distribution of alatae or apterae did not differ among w heat accessions. Low levels of antibiosis in MV4: may limit infestations of R, padi on wheat, and this may indirectly slow the spread of barley yellow dwarf virus and reduce the need for aphicide applications in wheat fields.