Studies On The Relationship Between Flowering And Chilling Accumulation And Flowering Regulation In Litchi(Litchi Chinensis Sonn.)

Low temperature is required for litchi flowering.Previous studies have revealed the characteristics of flowering of litchi,but there are few studies on the chilling requirement of flowering.In this study,all collections of litchi intheorchardwere selected and the chillingrequirement for floral induction were calculated by data collected for three years.Also,'Huaizhi','Feizixiao','Sanyuehong','Nuomici','Guiwei'potted treesfor the studiesof terminal shoot maturity,temperatures,and plant growth regulators on chilling requirement and flowering conditions.The main results are as follows:1.The relationship between litchi flowering process and temperature change and chilling capacity of litchi from 2014 to 2017 year was analyzed.It was found that compared with thatofother two years,many litchi collections in the year of 2015-2016 have shorter panicles and pure inflorescences,due to the long and low temperature.In 2016-2017,winter temperature is high,early flowering cultivars flowered early,while the late flowering ones had poor flowering condition.According to the data collected,it was concluded that the chilling requirement was range from 137.9 to 12545.0 CDHs.In gene expression,LcFT1 and LcFPA tended to increase with the flowering of three early,middle and late litchi varieties?'kom','Ruanzhizaohong'and'Guiwei'?.LcEMF2 was no change trend in the varieties,but in the middle and late varieties of litchi varieties were in the"white spots"period showed a downward trend;LcFCA in the three litchi varieties are in the"white"period showed a downward trend;other genes have no obvious rules.2.ABA and different temperature treatments for'Sanyuehong'and'Huaizhi'potted plants suggested that'Sanyuehong'litchi trees were able to flower above 20?,but floral buds were easily reversed.'Huaizhi'litchi trees were not be able to flower above 20?.ABA treatment could reduce the demand for low temperature,and improve the flowering rate.The flowering rate in ABA-treated'Sanyuehong'trees was as high as 97.50%,and was significantly higher than that of the water control at the same temperature?37.14%?.The flowering rate of ABA-treated'Huaizhi'litchi trees was 43.38%,higher than that of the water control?19.80%?.ABA can inhibit the expression of FT1 and promote the expression of FLC and AP1.3.The results of different chemical treatment of litchi potted plants showed that in the late flowering induction,spraying ABA and PP₃₃₃33 could prolong the dormancy of litchi,increase the accumulation of chilling requirement,shorten the length of spikelets and promote flowering.Spraying GA₃ could promote flowering,increase the amount of flowers,but also improve the length of the spike and the overall range.In addition,ABA treatment of male and female ratio of 18.64%,PP₃₃₃33 treatment of male to female ratio of 9.13%,were significantly higher than GA₃ and H₂O treatment.