Molecular screening of squash and patisson squash collection samples using markers of the Pm-0 gene, which controls resistance to powdery mildew

Powdery mildew (PM) is one of the most harmful diseases of cucurbits. Modern commercial varieties of squash Cucurbita pepo L. var. giraumonas Duch and patisson C. pepo var. melopepo L. received powdery mildew resistance genes from wild species. The Pm-0 resistance gene belongs to the linkage group 10; two CAPS markers were developed for its mapping [15]. The main intragenic marker NBS_S9_1495924/HaeIII is localized in the NBS-LRR region, the additional marker S9_1539675/MspI shows complete co-segregation with resistance to PM [15]. In the present study, these markers were used for molecular screening of an experimental set of squash and patisson samples (differ in resistance to powdery mildew) from the VIR gene bank collection and perspective breeding lines of the Krymsk Experiment Breeding Station branch of VIR. In total, 80 samples were investigated. Samples, carrying fragments of both CAPS markers (17) and fragments of only one marker (31) were found. Presence of two markers of the Pm-0 gene (NBS_S9_1495924/HaeIII и S9_1539675/MspI) has the strong correlation with resistance to PM (r = 0.837). For three powdery mildew-resistant samples, which has demonstrated presence of both markers of the Pm-0 gene, additional analysis of individual plants was done. Resistant plants with Pm-0 gene markers were self-pollinated to create resistant lines. Thus, molecular screening allowed to preserve the valuable trait of resistance during maintaining of the squash collection samples.