Abstract
We investigated the cause of poor fruit set in Japanese plum ‘Kiyo’ (Prunus salicina Lindl.). Early fruit drop of ‘Kiyo’ was heavier than that of ‘Taiyo’. Fruit drop of ‘Taiyo’ and ‘Kiyo’ in 56 days after full bloom was 80.4 and 95.5%, respectively. There was little difference between ‘Kiyo’ and ‘Taiyo’ in the incidence of imperfect flower and ‘Holly wood’ pollen tube elongation on the style. However, ‘Kiyo’ demonstrated pollen grains that were nonuniform in size and shape. ‘Taiyo’ showed 91.6% stainability and 47.6% pollen germination rate, respectively, whereas those of ‘Kiyo’ were 70.4 and 3.2%, respectively. Furtheremore, developed seeds obtained from ‘Kiyo’ varied in weight from 0.02 to 0.59 g, and the percentage of developed seed of ‘Kiyo’ (71.3%) was less than that from ‘Taiyo’ (93.0%). Chromosome observation of immature leaflets demonstrated that ‘Kiyo’ was triploid with 24 chromosomes.
