Molecular Characterization of the S-alleles and Compatibility among Hybrid Pear Tree Cultivars for Subtropical Regions

Abstract

Pear (Pyrus spp.) is a temperate-climate fruit species that has gametophytic self-incompatibility. Cross-pollination among intercompatible cultivars can be useful in selecting for breeding programs. The objective of the present study was to evaluate effective fruiting from cross-pollination between hybrid pear cultivars and to characterize pear tree S-alleles. Seven cultivars were evaluated: Cascatense, Centenária, D’água, Primorosa, Seleta, Tenra, and Triunfo. Controlled crosses were carried out in two seasons and consisted of spontaneous self-pollination, parthenocarpy, and cross-pollination between cultivars. During the 2 years of research, the overlap of the entire flowering periods of all cultivars was higher than 50%. Phenology was evaluated from the beginning of pruning, and the time elapsed from pruning to the flowering phenophase was computed. Finally, the flowering-period overlap of the cultivars was analyzed. S-alleles were characterized by polymerase chain reaction (PCR) using primers specific to previously known alleles. Under field conditions, the Primorosa cultivar has high potential as a pollinizer for D’água, Seleta, Tenra, and Triunfo. Pear tree hybrid cultivars have a high frequency of the S1 and S5 alleles. The S5S8 and S1S4 alleles are amplified in the D’água and Seleta cultivars, respectively, conferring compatibility between these cultivars. The S1 and S5 alleles are amplified in ‘Primorosa’, ‘Cascatense’, and ‘Triunfo’, conferring interincompatibility.