Development of AFLP and CAPS markers linked to the scab resistance gene,Rvn2, in an inter-specific hybrid pear (Pyrusspp.)

SummaryScab, caused by Venturia nashicola, is one of the most damaging diseases in pear. The development of varieties resistant to scab has long been an aim of Asian pear breeding programmes. The application of molecular markers to select scab-resistant plants will increase the efficiency of breeding programmes. To identify DNA markers linked to the scab-resistance gene named Rvn2 in PS2-93-3-98, the progeny of a cross between PS2-93-3-98 and ‘Yali’ pear was studied. As scab-resistance clearly segregated 1:1 in the F1 progeny, Rvn2 is a single dominant gene. Bulked segregant analysis and amplified fragment length polymorphism (AFLP) analysis were then applied to identify markers associated with Rvn2. Three AFLP markers linked to Rvn2 were identified. Mapping of the markers indicated that the three selected markers, E-AGT/M-CCA234, E-ATT/M-CCG328, and E-GGT/M-TCT217, were located 4.9, 3.2, and 0.8 cM from the Rvn2 locus, respectively. Rvn2 was found to be located in a different linkage group from previously identified scab-resistance gene loci. For marker-assisted selection of scab resistance, two of the AFLP markers (E-AGT/M-CCA234 and E-GGT/M-TCT217) were converted into cleaved amplified polymorphic sequence (CAPS) markers. These CAPS markers, designated PSC217-Xho I and PSC234-Hae III could distinguish between resistant and susceptible individuals.These CAPS markers therefore have the potential to increase the efficiency of selection for scab-resistance in pear breeding programmes.