Preliminary cytogenetic studies in Prunus salicina Lindl.

Male sterility in Japanese plum (Prunus salicina Lindl.) can be of genetic, biochemical or physiological origin. As a contribution to the microsporogenesis studies of six genotypes initiated between 2003 and 2004, we found two genotypes with few pollen mother cells without callose. In the meiotic reduction phase, normal and collapsed tetrads were observed, and lower amounts of monads, dyads, triads, pentads and hexads. Minimicrospores were found in S2 in all flower buds tested. Furthermore, joined pollen grains were found in S2, S5 and S6 genotypes, with maximum values of 47.57, 12.09 and 20.54%, respectively. Pollen fertility was very low in all genotypes, 0.2% for S1, 3.7% for S2, 5.7% for S3 and 0% for S5 and S6. Low amounts of pollen grains were found in anthers of some genotypes. Besides, S2 and S5 showed different size of pollen grains, supporting the idea of irregularities in the meiotic process. It is important to mention the observation of cytomixis, which could explain, partially, the male sterility observed in these genotypes.