Fluorescence microscopy as a tool for determining self-incompatibility in apricot cultivars

Fluorescence microscopy is a relatively rapid and reliable method to determine self-incompatibility in fruit-tree species. It is based on observation of pollen-tube growth in the pistils. Pollen tubes stained with fluorochromes show fluorescence when exposed to ultraviolet light. Testing of the self-compatibility trait was carried out in 123 apricot cultivars using fluorescence microscopy. In self-compatible cultivars, in the majority of pistils (60-100%), the pollen tubes reached the ovary. In contrast, in self-incompatible cultivars, pollen tubes growth ceased in the style, with plugs forming at their tips. In these cultivars, pollen tubes rarely (0-30%) reached the base of the style. Although apricot cultivars of the European eco-geographical group are traditionally considered self-compatible, we identified many self-incompatible cultivars, especially among those originating from new North American and West European breeding programs. About half ( 62) of the studied cultivars were self-incompatible. Given that self-incompatibility occurs frequently among new apricot cultivars, special care should be taken when considering cultivar composition in new orchard plantings