Rapid phenotypic assessment of bird cherry-oat aphid resistance in winter wheat

Rhopalosiphum padi L. causes significant damage to winter wheat (Triticum aestivum L.), even without obvious aboveground symptoms of injury. Our objectives were to develop a juvenile-plant bioassay for bird cherry-oat aphid (BCOA) resistance that allows rapid phenotypic differentiation. Central features of the bioassay include root and shoot weight measurements of 3-week-old seedlings produced in seed germination pouches, a 14-day aphid exposure period, and a non-infested control treatment to establish a baseline for expected biomass per genotype. Cultivars used in bioassay development were Illinois Rustproof and Skala , which showed smaller BCOA-induced reductions in biomass than the more susceptible genotypes, Patrick and Scout 66 . Mean reductions in root biomass were 48% for Patrick and Scout 66 , compared with 29% for Illinois Rustproof and Skala . This rapid and repeatable bioassay is extendable to large wheat collections and inbred line populations.