Parthenocarpy and self-and cross-incompatibility in ten European pear [Pyrus communis] cultivars

Self- and cross-incompatibility in European pear (Pyrus communis L.), which is estimated by the fruit set and seed formation, is yet unclear. We carried out self-, cross- and non-pollinations with one flower per cluster on 10 European pear cultivars, and estimated their parthenocarpic potential, and self- and cross-incompatibility. Most cultivars exhibited parthenocarpy, which suggests that the fruit set is not a suitable criterion for distinguishing incompatibility from compatibility. However, clear judgment could be provided by using the self-incompatibility (SI) index, (the number of viable seeds per flower obtained from test pollination / the number of viable seeds per flower resulting from compatible cross - pollination) x 100, as a new criterion. Based on this index, 'Grand Champion' has proven to be partially self-compatible, whereas others were classified as self-incompatible. Traits of the seeded fruits, such as weight, size, and soluble solids content, were superior to those of the parthenocarpic fruits. Thus, cross-compatible pollination is necessary for a stable fruit set and production of large, good quality fruits in cultivars with a high parthenocarpic potential. Two cross-incompatible combinations were found between 'Flemish beauty' and 'Starkrimson', and 'Bartlett' and 'Seigneur d'Esperen', respectively.