Linkage and mapping of resistance genes to Xanthomonas axonopodis pv. passiflorae in yellow passion fruit.

The cultivated passion fruit (Passiflora edulis f. flavicarpa) is a cross-pollinated species native to South America. In the current study, a segregating F1 population derived from a single cross between the clones IAPAR-06 and IAPAR-123 was used to construct AFLP-based linkage maps and to map resistance genes to bacterial spot caused by Xanthomonas axonopodis pv. passiflorae. Linkage analysis was performed by the 2-way pseudo-testcross mapping method using markers that segregated in a 1:1 ratio. The IAPAR-06 linkage map was constructed using 115 markers, 112 of which were allocated to 9 linkage groups (LG) covering 790.2 cM. The map of IAPAR-123 was constructed using 140 markers, 138 of which were allocated to 9 LG covering 488.9 cM. In both maps, clusters of markers were detected, indicating that the AFLP markers were not distributed at random. Bacterial resistance was assessed by measuring the diseased leaf area after wound-inoculating the leaves of F1 plants. Quantitative resistance loci (QRLs) mapping was carried out by composite interval mapping and 1 QRL was detected, which explained 15.8% of the total phenotypic variation. The possibility of considering these data for marker-assisted selection in passion fruit breeding programs is discussed.