Valuable Russian wheat aphid-resistant bread wheat accessions identified using four South African Diuraphis noxia biotypes

Abstract

Resistance-breaking biotypes of Diuraphis noxia have been reported in both the USA and South Africa where commercial cultivars with genetic resistance to this pest have been deployed. The need to identify novel Russian wheat aphid (RWA) resistance for deployment against new biotypes of RWA has driven the recent re-evaluation and characterisation of resistance in landraces of bread wheat from germplasm collections worldwide. Twenty-three genotypes already in use in a South African pre-breeding programme were evaluated with the extended spectrum of South African RWA biotypes, while four genotypes not yet tested with South African RWA were screened with RWASA1, RWASA2, RWASA3 and RWASA4 for the first time. Five accessions, namely PI 94355, PI 243781, PI 361836, PI 626580 and the check CItr 2401, were resistant to all four South African RWA biotypes. The previously unused accessions PI 094355 and PI 243781 will be incorporated into the programme. The sixth accession resistant to RWASA4, namely PI 366518, is susceptible to RWASA2 and RWASA3 and may possibly be unique, meriting emphasis in pre-breeding activities. The use of multiple, distinct resistance genes, including those with a moderate resistance reaction, is seen as the most responsible strategy for the stewardship of genetic resistance to RWA in bread wheat.