DNA-based S-genotyping of Japanese Plum and Pluot Cultivars to Clarify Incompatibility Relationships

Diploid japanese plum ( Prunus salicina Lindl.) cultivars are commonly self-incompatible. To date, 14 incompatibility alleles ( S -alleles) have been identified and labeled with alphabetical ( S a - S n ) and 5 with numeric codes ( S 1 , S 3 - S 6 ). We applied polymerase chain reaction amplification of the S -RNase alleles with degenerate and allele-specific primers in 10 japanese plum cultivars and two pluots of unknown incompatibility alleles. Besides DNA sequencing, an additional method for the exact length determination of the first intron region was used for the first time for S -genotype japanese plums. The S 3 -allele was shown to correspond to S k in the alphabetic nomenclature, S 4 to S c , S 5 to S e , and S 6 to S f . The S 5 -allele-specific primer can be used as a reliable marker for self-compatibility in japanese plum. ‘Black Amber’, ‘October Sun’, ‘TC Sun’, and ‘Super Giant’ share the S b S c genotype, which was confirmed by test crosses. These cultivars belong to the widest incompatibility group currently known in japanese plum. An additional incompatibility group ( S c S h ) was established, including ‘Green Sun’ and ‘Queen Rosa’, a cultivar formerly known as a universal donor. By incorporating all previous and recent results, a table was assembled including 49 cultivars assigned to I–VII incompatibility groups, to the self-compatible group and to the group O of unique genotypes. These data may considerably contribute to further growing and breeding activities.