Abstract:

To reveal the cross-compatibility of Michelia crassipes and that of other three species（M. figo，M. maudiae and M. platypetala），M. crassipes was used as female parent and M. figo，M. maudiae and M. platypetala as male parent respectively for artificial hybridization. The pollen viability of the species was determined via culture in vitro，and the pollen tube germination after pollination was observed by fluorescence microscope. The fruit setting rate and seed quality of interspecific hybridization were investigated. The results indicated that the pollen viabilities of M. crassipes，M. figo and M. maudiae were above 65%，whereas the pollen viability of M. platypetala was only 29.07%. By fluorescence microscope，pollen germination rate and the pollen tube growth rate of M. crassipes × M. figo and M. crassipes × M. maudiae were higher than those of M. crassipes selfing. Pollen tubes could normally elongate to complete fertilization. The pollen grains of M. crassipes × M. platypetala germinated on the stigma，but the pollen germination and the growth rate of pollen tube were slower than that of the self-pollination，and inflated pollen tube，growth stop，and deposition of callose on stigma and in stylet were observed. The fruit setting rate and seed germination rate in the cross of M. crassipes × M. figo and M. crassipes × M. maudiae were above 80%，indicating that cross-compatibilities of M. crassipes with M. figo and M. maudiae were better. However，the fruit setting rate of M. crassipes × M. platypetala was only 11.1%，and hybrid embryo was abortive. The pre-fertilization barriers caused by the pollen tubes stopping growth could be one of the main barriers of interspecific hybridization between M. crassipes and M. platypetala.

Key words: Michelia crassipes, interspecific hybridization, cross-compatibility, fruiting rate, pollen tube