Masami Yamaguchi

Diversity of S-RNase genes and-s-haplotypes in Japanese plum (Prunus salicina Lindl.)

Summary This report demonstrates the diversity of S-haplotypes in Japanese plum by molecular cloning of genomic DNAs and cDNAs that encode S-RNases. Nine different DNA fragments, designated as Sa–Si, were obtained from 17 Japanese plum cultivars by PCR with an S-RNase gene-specific primer set, Pru-C2 and PCE-R. Eleven different S-haplotypes were found in these cultivars. The banding patterns obtained with another S-RNase gene-specific primer set, Pru-T2 and PCE-R, corresponded to the S-haplotypes predicted from the Pru-C2 and PCE-R primer set. Several cultivars had the same S-haplotypes. Partial genomic DNAs for eight S-RNase genes and cDNAs for two S-RNases were cloned and sequenced. Deduced amino acid sequences contained conserved regions among the rosaceous S-RNases. Comparisons of the sequences from cDNAs and genomic DNAs revealed the presence of two introns in the S-RNase genes of Japanese plum as in other Prunus S-RNase genes. Pollination incompatibility groups and self-compatibility in Japanese plum were discussed with reference to the S-haplotypes.

Determination of S-haplotypes of Japanese plum (Prunus salicina Lindl.) cultivars by PCR and cross-pollination tests

Summary S-haplotypes of Japanese plums were determined by PCR and cross-pollination tests. Five novel S-RNase genes corresponding to Sj- to Sn- haplotypes were identified by PCR with an S-RNase gene-specific primer set, Pru-C2 and PCE-R. Thirteen new S-genotypes (S-haplotype combinations) were found in the 19 cultivars used. Several cultivars had the same S-genotypes. Partial genomic DNAs for six S-RNase genes were cloned and sequenced. Deduced amino acid sequences contained conserved regions among the rosaceous S-RNases. Cross-pollination and pollen-tube growth tests revealed that pollen-tube growth was arrested in the upper middle part of stylar tissue in the crosses between the self-incompatible cultivars with the same S-genotypes. These results showed the first evidence for the existence of S-RNase-based cross-incompatibility in Japanese plum.

Se-haplotype confers self-compatibility in Japanese plum (Prunus salicina Lindl.)

Summary Involvement of the Se-haplotype in self-compatibility in the Japanese plum cultivars ‘Santa Rosa’ (ScSe) and ‘Beauty’ (ScSe), was investigated. Self-pollination and pollen-tube growth tests confirmed that cv. ‘Rio’, which also has a Se-haplotype (SaSe), is self-compatible. In self- and cross-pollination experiments between cultivars with the ScSe haplotype, the resultant progenies segregated into two S-haplotypes, ScSe and SeSe, suggesting that only the Se-haplotype was inherited in progeny from the male parent. These results indicated that the Se-haplotype is responsible for self-compatibility. Expression analyses of S-RNase showed that the Se-RNase gene was transcribed in the style. Therefore, it appeared that inhibition of transcription of the S-RNase gene is not responsible for the self-compatibility in the Se-haplotype of Japanese plum.

Study on Interspecific Hybridization among the Subgenera Amygdalus, Prunophora , and Cerasus

Interspecific crossing among the subgenera Amygdalus (Prunus persica, P. mira, P. dulcis, P. ferganensis, P. kansuensis, P. davidiana), Prunophora (P. salicina, P. cerasifera, P. mume, P. armeniaca), and Cerasus (P. tomentosa, P. japonica) was performed to determine their cross-compatibilities. In the combinations of species belonging to the subgenus Amygdalus, high fruit set averages were demonstrated, excluding the results when P. kansuensis was used as a seed parent. The pollination of species belonging to Prunophora and Cerasus by those of Amygdalus resulted in very few seeds. In contrast, fruit sets of Prunuphora species pollinated by Amygdalus fluctuated by cross combinations. P. cerasifera and P. salicina, when used as seed parents, bore a few seeds, but P. armeniaca and P. mume bore no seeds when pollinated by Amygdalus species. The cross using P. tomentosa as a seed or pollen parent resulted in very few fruit sets. On the other hand, several seeds were obtained from the cross between P. cerasifera and P. japonica. The pollination of P. japonica by P. cerasifera, P. dulcis, and P. mume also led to a relatively high rate of fruit sets.