Effects of Exogenous Hormones on Female Ginkgo biloba’s Flowering and Expression of Flowering Related Genes

In April 2018, 15 female bearing trees of Ginkgo biloba with 10-year age were selected for experiment. They were applied organic fertilizer once respectively during period of dormancy and flowering each year. Meantime, bearing branches were cut for flower and leaf bud number. In June 2018, these trees were sprayed 3 times of 200 mg/L GA3, 100 mg/L PP333 and water for control with interval of 10 days. In April 2019, bearing branches were obtained for extraction of RNA and test of RT-qPCR. The results showed that repeated application of 200 mg·L-1 GA3 during the differentiation induction period of G. biloba could inhibit the flowering. GA3 and PP333 treatments had no induction effect on the expression of GinNdly gene in the female mixed bud, but they had significant induction effect on the expression of GinLFY and GBM5 genes. Among them, the GinLFY gene expression after GA3 and PP333 treatment increased by 7.6 and 5.4 time, and the GBM5 increased by 904 and 551 time, respectively. Correlation analysis showed that the expression of GinNdly gene was negatively correlated with average number of flower buds per meter (ANFB), while the GinLFY and GBM5 genes was positively correlated with ANFB. Therefore, GinLFY gene was closely related to flowering and sensitive to the response of exogenous hormones, which was likely to be the peripheral factor regulating the flowering and fruiting of G. biloba. The expression of GinLFY, an upstream flowering related gene, regulated the relative expression of GBM5 gene, thus affecting the flowering and fruiting of G. biloba.