Phenological Expression in Prunus salicina Lindl. Genotypes and Its Relationship with Insect Attraction and Pollination

In many areas of Japanese plum cultivation, productivity is limited by low flower fertility and a relevant factor in this is gametophytic incompatibility. For this reason, cross pollination has a strongly positive effect on fruit production. In this work the authors present results preliminary on the interaction between flower phenology and its effect on attractiveness to pollinator insects. A population of 1,500 trees of Japanese plums (Pranus salicinsa Lindl.) obtained by cross-pollination within a breeding program carried on at Florence (Firenze) and grown in San Casciano (Tuscany, It aly), has been studied during flowering time and fruit set time during the years 2004-2007. Some genotypes presented different anomalies during microsporogenesis, with inconsistent amounts of low viability pollen. Hence, cross-pollination and fruit set depended stronglly on the insect activity. Different Hymenoptera and Diptera were observed during the anthesis and post anthesis stages. Attraction appeared to be correlated with the pollen amount, anther color, flavor and nectar production. Furthermore, the attractiveness to insects was conditioned by the genetic origin of the seedling.