An aphid resistant wheat variety reduces the transmission of Barley Yellow Dwarf Virus (BYDV) by Rhopalosiphum padi (L.)

INTRODUCTION: Rhopalosiphum padi (L.) is a major vector of Barley Yellow Dwarf Virus (BYDV), one of the most economically damaging viral diseases of cereals including wheat. While host resistance to BYDV or to aphids individually has been exploited, less is known about how aphid resistance performs against viruliferous vectors. We recently identified a winter genotype (G1) exhibiting strong aphid resistance through antixenosis and antibiosis. Here, we test whether this resistance remains effective against BYDV-vectoring aphids and how it compares with BYDV resistance. RESULTS: We evaluated G1 alongside four wheat cultivars with contrasting aphid and BYDV resistance traits, including the BYDV-resistant cultivar RGT Wolverine and the fully susceptible RGT Illustrious. Seedling settlement assays showed that antixenosis in G1 remained effective against R. padi carrying BYDV-PAV. Electrical penetration graph recordings revealed restricted phloem access and reduced salivation of viruliferous aphids on G1, consistent with lower virus transmission efficiency. Quantitative RT-PCR showed a three- fold reduction in BYDV gene expression in inoculated leaves of G1 compared with RGT Wolverine and RGT Illustrious. In contrast, RGT Wolverine exhibited high initial transmission but reduced systemic infection, consistent with resistance acting on suppression of viral replication and/or movement. Aphid rearing host genotype altered subsequent aphid host-selection behaviour, indicating vector conditioning with consequences for virus spread. CONCLUSION: Aphid resistance in G1 significantly reduced BYDV transmission, whereas Bdv2-mediated resistance in RGT Wolverine limited systemic infection. These complementary resistance mechanisms highlight the value of combining aphid- and virus- targeted traits to improve durable BYDV management in wheat.