Abstract:Eight crosses were designed for Primula forbesii ‘Red Star’,‘Purple Cloud’ and ‘Fragrant Luolan’,separately,to investigate the fruiting rate and seed-set per capsule.Meanwhile,the pollen germination and pollen tube elongation of several crosses in P.forbesii ‘Red Star’ were observed by fluorescent microscopy.The results showed that:(1)For all three cultivars,the fruiting rate and seed-set per capsule were significantly different among different crosses,and in a descending order were legitimate crosses (T×P and P×T)＞within-pin cross and pin selfing＞within-thrum cross and thrum selfing.The fruit-setting rates of all legitimate crosses reached 100% and the mean number of seeds per capsule obtained ranged from 44 to 181,which were significantly higher than that of illegitimate crosses.By using intermorph pollens without vitality as mentor in intramorph pollinations,fruiting rate and seeds per capsule of T×T crosses were improved.However,mentor pollination had no unambiguous effect on P×P crosses.Among the three cultivars,fruiting rate and seeds per capsule of different crosses in P.forbesii ‘Red Star’ were the highest.(2)The results of fluorescent microscope observation suggested that pollens germinated easily and pollen tubes penetrated directly into the stigma surface in intermorph crosses (T×P and P×T),and pollen tubes grew nearly to the style base and began to insert into the ovary after pollination for 144 h.In P×P and T×T crosses,pollens began to germinate after pollination for 12 h.However,pollen tubes were blocked and did not penetrate the stigma surface after pollination for 144 h,and the pollen tubes were distorted.In pin and thrum selfings,pollens did not germinate on the stigma surface after pollination for 144 h.It was concluded that P.forbesii was self-incompatible,and the thrum form was more self-incompatible than the pin form.