Transfer of the Dominant Virus Resistance Gene AV-1pro From Asparagus prostratus to Chromosome 2 of Garden Asparagus A. officinalis L.

An introgression breeding programme was carried out to transfer the virus resistance gene <i>AV-1</i> ^<i>pro</i> from the wild species <i>Asparagus prostratus</i> to the garden asparagus <i>Asparagus officinalis</i>. Serious crossing barriers caused by genetic distance and different ploidy levels of the crossing parents have been overcome using embryo rescue for the F₁, BC₁, and BC₂ generations. The male and female fertility was widely restored in BC₂ and was shown to be comparable to the cultivated asparagus. Five AV-1 resistant diploid (2n = 2x = 20) BC₂ plants were selected and reciprocally backcrossed with asparagus cultivars. Segregation analyses of fourteen seedborne BC₃ progenies suggested a monogenic dominant inheritance of the AV-1 resistance. Genotyping by sequencing analysis gave a strong hint for location of the resistance gene on asparagus Chromosome 2. Using an Axiom single nucleotide polymorphism (SNP) genotyping array for the analysis of three BC₃ families with 10 AV-1 resistant and 10 AV-1 susceptible plants each, as well as 25 asparagus cultivars, the <i>AV-1</i> ^<i>pro</i> locus on Chromosome 2 was further narrowed down. The SNP with the highest LOD score was converted to a kompetitive allele specific PCR (KASP) marker, shown to be useful for the further backcross programme and serving as the starting point for the development of a diagnostic marker.