Asparagus virus 1 (AV-1) resistant garden asparagus generated by transfer of the AV-1^pro gene from A. prostratus Dumort.

Asparagus virus 1 (AV-1) is the economically most important virus attacking garden asparagus (A. officinalis L.) worldwide. Various studies reported yield losses between 30 and 70%. Whereas no AV-1 resistant cultivars are available, genetic resistance was confirmed for various wild relatives. The virus resistance gene AV-1pro was transferred from A. prostratus Dumort. to A. officinalis by interspecific crosses. Embryo rescue was necessary in the first two backcross generations to overcome severe crossing barriers caused by the great genetic distance and different ploidy level of the crossing partners. Already in the BC2 generation, male and female fertility has been shown to be comparable to the cultivated asparagus. At the diploid level (2n=2x=20), a monogenic dominant inheritance mode for AV-1 resistance was confirmed. The AV-1pro locus was mapped on chromosome 2 using an Axiom SNP genotyping array for the analysis of three BC3 families and 52 asparagus cultivars. The SNP with the highest LOD score was converted into a KASP marker. In progenies from crosses between male and female, AV-1 resistant BC2 and BC3 individual plants homozygous for this marker were identified. Half of these plants suffered from severe chlorosis and died already in seedling stage. But two male and three female homozygous plants were classified as green, vigorous and AV-1 resistant. These putative homozygous resistant plants could serve as basic material for asparagus breeding.