Genetic mapping and molecular characterization of AV1 resistances in asparagus

Asparagus (Asparagus officinalis L.) is an important vegetable crop, but its yields are increasingly compromised by asparagus decline syndrome (ADS). Asparagus virus 1 (AV1), a potyvirus transmitted non-persistently by aphids, is a major component of ADS. In Germany, more than 90% of production fields are infected, and although infected cultivars typically remain asymptomatic, yield losses are considerable. The aim of this project is to develop precise molecular markers tightly linked to AV1 resistance loci and to elucidate the underlying resistance mechanisms. The project builds on previous interspecific hybridization efforts using the wild species A. amarus and A. prostratus as resistance donors. For A. prostratus, a monogenic dominant resistance on chromosome 2 has already been identified, with KASP markers at 2.8 cM showing 96% co-segregation; these markers will be refined to achieve tighter linkage and support identification of the causal gene. Resistance from A. amarus maps to chromosome 10, but its genetic basis remains unclear. For both resistance sources, whole genome sequencing of resistant and susceptible individuals from segregating backcross populations will identify SNPs within the delimited regions. Long-read sequencing will be used to detect structural variants and assess whether a novel sequence element has been introduced. As a complementary approach, the physiological basis of resistance will be characterized by detecting hydrogen peroxide accumulation as an indicator of ROS production and by assessing callose deposition after inoculation, to test for a hypersensitive response. EPG recordings will pinpoint the onset of infection for precise sampling. Transcriptomic analyses will further characterize the response and support candidate gene selection.