Identification of candidate genes by sequencing the resistant and susceptible haplotypes at the main Sharka resistance QTL on ‘Lito’ chromosomes 1 of apricot

Sharka, a common disease among most stone fruit crops, is caused by the Plum Pox Virus (PPV). Resistant genotypes have been found in apricot (Prunus armeniaca L.), one of which (‘Lito’, heterozygous for resistance) has been used to map a major quantitative trait locus (QTL) on linkage group 1, following a pseudo-test-cross mating design. A ‘Lito’ bacterial artificial chromosome (BAC) library was produced, screened with markers of the region, and positive BAC clones were sequenced. Resistant (R) and susceptible (S) haplotypes were assembled independently. Although the results are not conclusive, the accurate and independent assembly of R and S haplotypes is a valuable resource to predict and test alternative transcription and regulation mechanisms underpinning PPV resistance.