QTL ANALYSIS FOR RESISTANCE TO SHARKA DISEASE (PPV-DIDERON STRAIN) IN APRICOT USING AN F1 PROGENY DERIVED FROM ´STARK EARLY ORANGE´

Since the late 1980s, sharka disease has become a serious threat for apricot (Prunus armeniaca). It is caused by an aphid-borne virus, Plum pox virus (PPV), which is included in the genus Potyvirus. Two major types of PPV occur: Dideron (PPV-D) and Marcus (PPV-M) strains for which the only known sources of resistance in apricot have been identified in North-American cultivars. As traditional breeding methods are time-consuming, the identification of the regions of the genome involved in resistance to PPV is a promising solution for the selection of new resistant cultivars. For this purpose, phenotypic evaluations were carried out in Spain, in a greenhouse, during 4 vegetative cycles, using PPV-Dideron RB 3.30 isolate, on a progeny derived from a cross between the susceptible cv. ‘Polonais’ and ‘Stark Early Orange’, a resistant cultivar. Quantitative trait loci (QTL) analyses were then performed with QTL Cartographer software, using different statistical procedures. Three genomic regions involved in PPV resistance were detected. One of these mapped to the upper distal region of linkage group 1 of ‘Stark Early Orange’ and accounted for 56% of the phenotypic variation. Two additional regions accounting for minor effects were detected on 2 homologous linkage groups of the maps of both cultivars. PPV resistance seems to be controlled by one major dominant factor and putative additional recessive factors are suspected.