POLLEN TUBE GROWTH AND FRUIT CHARACTERISTICS IN SELF-COMPATIBLE ALMOND CULTIVARS DEPENDING ON SELF- OR CROSS-POLLINATION

Abstract

Most traditional almond cultivars are self-incompatible, which implies that fruit cannot be obtained through self-pollination. However, there have been reports of obtaining some selfed fruits after bagging the branches of several self-incompatible cultivars, although the real origin of these fruits was not confirmed. Theoretically, this is not possible, since a pollen grain with a self-incompatible allele is not able to grow in the pistil of its parent cultivar. To verify whether this process was possible, ten self-incompatible almond cultivars were bagged before their flowers opened to allow passive self-pollination. Simultaneously, in the laboratory pistils were self-pollinated and the growth of pollen tubes observed. Among the 5,349 flowers bagged in 2006, 2007, and 2008, only 17 fruits were obtained. These fruits were germinated and analysis of S-RNase alleles of the seedlings showed that none of these fruits came from self-pollination, but were the result of pollination with foreign pollen. Under natural conditions, self-pollination of self-incompatible cultivars does not occur, and most likely the fruits obtained in previous reports were also accidental pollinations with foreign pollen.