LAUSR

Abstract ‘Zizhenzhu’ is a spontaneous, self-compatible hawthorn (Crataegus pinnatifida Bge.) mutant of unknown parentage. Although ‘Zinzhenzhu’ possesses typical S-RNase-based gametophytic self-incompatibility, the molecular mechanism underlying its self-compatible phenotype is still unclear. In this study, two full-length RNase T2 gene family S-RNases were cloned from ‘Zizhenzhu’, and their deduced amino acid sequences were found to have a conserved structure similar to S-RNases from Pyrus and Malus. In a phylogenetic tree, the two S-RNases clustered with Malus and Pyrus, thereby suggesting that the self-incompatibility recognition system in hawthorn is the same as in Malus and Pyrus. Genetic analysis of selfed and crossed progeny revealed that the switch to self-compatibility in ‘Zizhenzhu’ is due to the mutation of a non-S factor in the style. In addition, evidence for apomixis, an interesting phenomenon, was detected in the crossed progeny of ‘Zizhenzhu’ for the first time.