QTLs for Brown Spot Resistance in European Pear

Brown spot (Stemphylium vesicarium) is one of the most serious fungal disease that affects the pear tree orchards in the Po valley. In this region, which produces 90% of the pears in Italy, several antifungal treatments must be repeated along the period between flowering and harvest. In addition, many of the most widely grown varieties of pear (e.g., ‘Abbé Fétel’) are very susceptible to this fungus, while others, such as William and his mutated sports are substantially resistant. With the aim to develop molecular markers linked with brown spot resistance, plants derived from the cross ‘Abbé Fétel’ × ‘Max Red Bartlett’ were challenged for two consecutive years with a suspension of conidia both on leaves and fruits of each seedling. As a control, both the parents of the progeny and the varieties ‘Conference’ and ‘William’ were inoculated. On the genetic maps of the two parents QTL analysis revealed the presence of two QTLs, one for resistance to brown spot in ‘Max Red Bartlett’ and another for the susceptibility in ‘Abbé Fétel’. The availability of molecular markers in the regions of QTLs is an important step forward towards the selection of new pear genotypes resistant to brown spot by Marker-Assisted Selection (MAS).