Abstract: Jinzhuili (Z) is a naturally occurred self-compatible (SC) mutant from Yali (Y) , a China native leading cultivar displaying typical gametophytic self-incompatibility ( GSI). How Z mutated to SC is unclear to date. In the p resent study, field pollination tests were carried out under four crosses ( Z selfed,
Yselfed, Z ×Y and Y ×Z) , and fruit setting percentage determined and pollen tube growth inspected under fluorescentmicroscope. It was observed that more than 76% flowers set fruits and many pollen tubes grewdown to the base of style in crosses of Z and YXZ, whereas fruit setting did not occurred and most pollen tubes were arrested at the upper part of style in the cross Y and ZXY. These results indicated that both Y and Z functioned normally in SI response on the stylar part and could reject competent Y pollen, but accep ted Z pollen。Furthermolecular analyses revealed that both Y and Z harbored S₂₁-and S₃₄-RNase, transcribed normally and were identical to one another in mRNA sequences of two S-RNase. All these data suggested that Zmost
likely lost pollen SI function, and its style behave normally in SI response as that of itswild type Y did. How pollen of Zmutated needs to be further investigated.

Key words: Pyrus bretschneideri, Self compatibility, Self-incempatibility, S-RNase gene, Mutation, Pollination