SELECTION OF SELF-COMPATIBLE TREES BY S₄^sm-HAPLOTYPE SPECIFIC MARKER IN JAPANESE PEAR

An S₄^sm-haplotype derived from a self-compatible cultivar ‘Osa Nijisseiki’ (S₂S₄^sm; sm = stylar-part mutant) is extensively used to breed self-compatible cultivars in Japanese pear.
To aid the early selection of self-compatible trees from a cross-progeny, S-RNase based CAPS marker systems have been used, but yield no products from the S₄^sm-haplotype.
We developed an S₄^sm-haplotype specific DNA marker based on the recent result that the S₄^sm-haplotype lacks approximately 236 kb around the S₄-RNase. A primer pair ‘SM-F’ and ‘SM-R’ was designed from the deletion junction sequences in the S₄^sm-haplotype.
Genomic PCR with ‘SM-F’ and ‘SM-R’ yielded a product of 666 bp from S₄^sm-haplotype but did not from S₁– to S₉-haplotypes.
This indicates that the product of 666 bp can be used as a DNA marker specific for the S₄^sm-haplotype.
Using the S₄^sm-haplotype specific marker and a CAPS marker system for discriminating S₁– to S₉-RNase alleles, a cross-progeny of ‘Osa Nijisseiki’ (S₂S₄^sm) × ‘Nansui’ (S₄S₉) was genotyped.
Based on the S-genotype, four S₄^smS₉ trees were selected as self-compatible trees.
These four selections were confirmed to be self-compatible by self-pollination tests.
Therefore, the combination of the S₄^sm-haplotype specific marker and the CAPS marker system provides an early and reliable selection system of SC trees in Japanese pear and is useful for the breeding of self-compatible cultivars in Japanese pear using the S₄^sm-haplotype.

X International Pear Symposium

K. Okada, N. Tonaka, T. Takasaki, T. Matsumoto, Y. Sawamura

self-incompatibility, self-compatibility, DNA marker, S-RNase, S-genotype

https://doi.org/10.17660/ActaHortic.2008.800.50