Transfer of the Dominant Virus Resistance Gene AV-1(pro) 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 AV-1(pro) from the wild species Asparagus prostratus to the garden asparagus Asparagus officinalis. Serious crossing barriers caused by genetic distance and different ploidy levels of the crossing parents have been overcome using embryo rescue for the F(1), BC(1), and BC(2) generations. The male and female fertility was widely restored in BC(2) and was shown to be comparable to the cultivated asparagus. Five AV-1 resistant diploid (2n = 2x = 20) BC(2) plants were selected and reciprocally backcrossed with asparagus cultivars. Segregation analyses of fourteen seedborne BC(3) 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 BC(3) families with 10 AV-1 resistant and 10 AV-1 susceptible plants each, as well as 25 asparagus cultivars, the AV-1(pro) 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.