Abstract: [Objective] The flowering phenology, flowering synchronism, seed setting and impacting climate factors of clones of the second-generation clonal seed orchard of Pinus massoniana were studied to evaluate the synchronization rule of clones, guide seed orchard management and production as well as improve seed genetic quality and yield.[Method] For two consecutive years, we investigated 22 clones in dwarfed second-generation clonal seed orchard of Pinus massoniana into the normal flowering and fruiting period in Laoshan Forest Farm in Chun'an County of Zhejiang province, including flowering phase, flower number and fruit characteristics, to analyze the flowering phenology and flowering synchrony index.[Result] The flowering period of both female and male flowers of all clones was 8-17 days. The initial flowering in 2014 was 6 days later than in 2013, and the lasting period was shortened by about 6 days relative to 2013. Overall, there were small differences in flowering period between female and male flowers in the same year, bigger differences were found among years in the initial time and peak time of flowering, and the flowering of female and male flowers of the same clone were more synchronized in 2014. The flowering phenology of clones was different greatly between the two years, related to climate during the flowering phase, which caused decrease of flowering synchronicity and increase of variation of flowering synchrony index, ranging from 0.041 to 0.556 and 0.284 to 0.802 respectively in 2013 and 2014. The average coefficient of variation of clones was 32.3% and 16.8%, respectively. When a clone was used respectively as male and female parent, the difference level of flowering synchronization was small within the same year. The level of flowering synchronization in male parent was higher than that as female parent. There was a significant difference between the two years in synchronism index when respectively used as male, female parent and for selfing. Compared with 2013, the flowering synchronization index in 2014 was significantly increased, but there was no significant difference in self-compatibility index between the two years. Correlation analysis showed that the clones with more female flowers had more fruits; and the clones with longer flowering period of female flowers had higher fruit-setting rate. There was significant positive correlation between the peaking time and flowering duration of female flowers and the weight of thousand seeds.[Conclusion] The second-generation clonal seed orchard of Pinus massoniana in Laoshan Forest Farm of Zhejiang Province had good flowering synchrony between female and male flowers, no asynchrony was found among the clones. The pollinating period of female flowers and the pollen dispersing period of male flowers of the mating pairs affected the quality of seeds and fruit setting rate. The synchronism of clone was influenced by meteorological factors. Observations in two consecutive years indicated that there were differences among clones in flowering synchronization level, which was made by the differences in flowering phenology of clone, and the differences were related to the genetic background of the parental clones in the second generation clonal seed orchard. The synchronicity of pollen dispersion period was higher when used as male parent than the synchronicity of the pollinating period when used as female parent. The flowering synchronization index showed a negative correlation when a clone uses respectively as male and female parent. The possibility of self-crossing of 1/3 of the clones in the seed orchard was higher than the average level of out-crossing, which was the factor that should be taken into account in the management of seed orchard and the selection of clones.

Key words: Pinus massoniana, second-generation seed orchard, clones, flowering synchronism