Evaluation of Russian wheat resistance sources with the spectrum of South African Diuraphis noxia biotypes

Russian wheat aphid (RWA) Diuraphis noxia is a global pest of small grains, such as wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oat (Avena L.), and rye (Secale L.). Though laborious and time-consuming in terms of efforts required to eliminate the unwanted traits, wheat landraces have been widely used in breeding programs to deliver resistance sources and genes responsive to RWA among other stresses. Continuous exploitation of resistance traits/alleles in the landraces should be prioritized as a RWA intervention strategy to minimize its devastating impacts on wheat. Eighty donor lines were evaluated for their resistance to four South African RWA biotypes, namely RWASA1, RWASA2, RWASA3, and RWASA4. The collection was composed of 74 donor lines and six breeding lines collected from Afghanistan (38), Iran (22), Pakistan (11), United States (4), South Africa (2), Turkey (1), Georgia (1), and Egypt (1). Majority of the accessions were susceptible to RWASA3. Of the 80 accessions evaluated, 14 were uniformly resistant to moderately resistant to RWASA1, 9 to RWASA2, 7 to RWASA3, and 9 to RWASA4. A heterogeneous resistance (resistant-moderately resistant: >= 50%) was recorded in 18 accessions for RWASA1, 28 for RWASA2, 13 for RWASA3, and 17 for RWASA4. In addition, 25 genotypes performed comparably to the check genotype CItr 2401, with resistance to all four RWA biotypes. Selection of resistant lines for genetic improvement of RWA resistance is of paramount importance. The use of genotypes conferring both high levels and moderate resistance could offer scope for effective resistance to RWA in wheat. The merits of their exclusive resistance should be emphasized in prebreeding programs.