Patterns of Bee Visitation to Flowers of Almond Cultivars in an Orchard as Determined by Molecular Genetic Marker Analysis of Pollen in the “Pollen Basket”

Abstract

Self-incompatibility of almond cultivars used in commercial orchards (Kester and Griggs 1959; Baker and Gathercole 1977) means that gene flow by pollen between the different cultivars are essential to obtain nut set. A study made in a south Australian orchard showed that gene flow by pollen resulting in nut set is quite restricted, taking place essentially only between neighboring trees (Jackson and Clarke 1991). This is surprising, considering the comparatively large distances that the bees must travel within the orchard (at least twenty rows and more). To explain these results and the fact that only a small proportion of lowers gives rise to nuts, Jackson and Clarke (1991) suggest that the honeybee predominantly visits only one cultivar, either visiting single trees in times of pollen plenty or along rows of one cultivar when pollen is scarcer, and that cross-pollination results from accidental or rare visits involving two or more compatible cultivars. Here we examined the pollen brought back to the hive by individual honeybees, so as to trace patterns of flower visitations within the almond orchard.