ISHS Acta Horticulturae 587: International Symposium on Asian Pears, Commemorating the 100th Anniversary of Nijisseiki Pear
CULTIVAR DIFFERENCES IN THE EXPRESSION OF SELF-INCOMPATIBILITY IN JAPANESE PEARS |
| Authors: | S. Hiratsuka, S-L. Zhang |
| Keywords: | Pyrus pyrifolia Nakai, fruit set, pollen-tube growth, S-RNase, self-thinning cultivar |
| Abstract:
Data on cultivar differences in fruit set after self-pollination reported by many researchers were summarized. They varied from 0.6 to 15.2%, and our result on the growth rate of self pollen-tubes in the styles also varied from 0 to 47% among the cultivars. Cultivar differences in fruit set matched the differences in the tube growth (r=0.852**), indicating that each Japanese pear cultivar expresses different degrees of self-incmpatibility (SI). S-RNase (RNase associated with SI allele) concentrations in the style, which were quantified by scanning the protein bands on electrophoresed gel, were cultivar-dependent. They showed negative relations to fruit set (r=-0.764*) and the growth rate of self pollen-tubes (r=-0.888**), respectively. Purified S-RNases caused selective inhibition in vitro on the growth of self pollen-tubes (pollen-tubes from the same cultivar from which the S-RNases were prepared), and the inhibition was dose-dependent. S-RNases prepared from the cultivars with different degrees of SI expression exhibited almost the same inhibitory action at the same concentration. From these results, we conclude that cultivar differences in the expression of SI exist, and they may be regulated by the concentration of S-RNase differentially produced in the style of each cultivar of the Japanese pear. | |
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