Identification of quantitative trait loci (QTLs) linked to Apple chlorotic leaf spot virus (ACLSV) resistance in apricot

Apple chlorotic leaf spot virus (ACLSV), also known as apricot pseudo pox, "viruela" (in Spain) and "butteratura" (in Italy), has had a significant impact on the production of Prunus species, including apricot (P. armeniaca L.). Two apricot cultivars have recently been described as resistant to this virus: the traditional Spanish cultivar 'Mauricio' and the French cultivar 'Bergeron'. However, as far as we know, no work on the genetic control of the resistance to ACLSV has been published in any Prunus species. In this study, the transmission of resistance to ACLSV and the related quantitative trait loci (QTLs) were analysed for 3 years in an F1 apricot progeny of 130 descendants derived from the cross 'Bergeron' (resistant to ACLSV) x 'Currot' (susceptible). The apricot descendants evaluated were classified as susceptible or resistant depending on the presence or absence of ACLSV evaluated through ELISA and RT-PCR. A non-parametric mapping method based on the Kruskal-Wallis (KW) test was used to score and identify linked QTLs. The 'Bergeron' cultivar showed a high capacity to transmit resistance to ACLSV, generating around 57% of the resistant descendants. Additionally, the results indicated an oligogenic control of ACLSV resistance in apricot, with significant QTLs in alternative years in linkage groups (LGs) 5 and 7 and in all years in LG2 and LG4.