Study of pollen-pistil interactions on crosses between 'Rocha' pear and potential pollinators

Abstract

Currently, ‘Rocha’ pear production relies mainly mi spraying with growth regulators, as this cultivar can set fruit parthenocarpically. The identification of suitable pollinators and cross pollination is of the most important for the devclopment of alternatives, which are safer to consuniers and to the environment. Observations of pollen-pistil interactions between the cv. Rocha and potential pollinators were carried out through fluorescence microscopy. Crosses with ‘Aurora’ and ‘Limonera’ and selected ‘Rocha’ clones, Clone 1, Clone 2, Clone 4c, Clone Z and Clone T behaved as incompatible. But, ‘Beurré Precoce Morettini’, ‘Doyenné du Comice’, ‘Passe Crassane’, ‘Clapp’s Favourite’, ‘General Leclerc’, ‘Beurré d’Avril’, ‘Coscia’, ‘Tosca’, ‘Carapinheira’, ‘Anindoa’ and ‘Agua’ showed themselves to be compatible with ‘Rocha’. The percentage of styles with pollen tubes at the base of the styie varied between 0 and 4% in the incompatible crosses and between 61 and 96% in the compatible crosses. The number of pollen tubes registered per flower varied between 0-0.04, in thc first case, and 4.1-8.9 in the Iatter. These results analysed in combination with the S genotypes for these cultivars showed thai crosses between cultivars either sharing a common allele or with two different alleles were indistinguishable in terms of pollen tuibe growth in the style and presumably this can explain why other authors have not found differences in fruit set. These results also confirm previous work conducted by other groups on the molecular identilication of the S-alleles coding for (he S-RNases iuivolved in the self incompatibility mechanism.