Analysis of Ploidy and S-alleles of 'Kiyo' a Japanese Plum

'Kiyo' was newly planted in many plum orchards in Korea and Japan. However, farmers who planted 'Kiyo' have suffered from little fruit set. To elucidate the cause for bad fruit set of 'Kiyo', we investigated S-alleles of S-RNase which is based on self-incompatibility of Japanese plum (Prunus salicina Lindl.). The compared eight cultivars of Japanese plum had 2 alleles while 'Kiyo' had 3 alleles, Sc, Sd and Sf. Most of Japanese plums are diploids (2n=2x=16) but 'Kiyo' was found to be a triploid (2n=3x=24) by cytometric analysis. A triploid 'Kiyo' produced more poor and abnormal pollens than 'Simka', a diploid Japanese plum. 'Kiyo' could set the fruits with pollens of 'Biocherry', 'Hollywood', and 'Simka' by artificial pollination.