Effects Of Plant Growth Regulators On Fruit Setting And Quality Of Huazhou Pomelo

Huajuhong is highly praised by consumers for its efficacy in relieving cough and reducing phlegm.Huazhou pomelo(Citrus grandis ‘Tomentosa’)is the original plant of Huajuhong,an authentic medicinal material.Due to the lagging cultivation technology,the yield is low,which is an important factor restricting the high-quality development of Huajuhong industry.It is an urgent problem to be solved in the industry to development a simple and efficient Huazhou pomelo fruit preservation technology.Aiming at the problems of Huazhou pomelo industry,this study screened and optimized exogenous plant growth regulators and their application methods for Huazhou pomelo preservation,systematically evaluated the safety after fruit preservation,and the impact on the fruit quality of Huazhou pomelo.Transcriptomics analysis was used to preliminarily explore the molecular mechanism of plant growth regulator-induced changes in the functional components of Pomelo fruit.1.The first fruit preservation was carried out when about 75% of the flowers dropped,and the second fruit preservation was carried out 15 days later.All treatments could increase the fruit setting rate.The effects of different concentrations of brassinosterol(BR),gibberellin(GA),and 2,4-dichlorophenoxyacetic acid(2,4-D)on flower and fruit preservation were compared and analyzed: 10 mg/L 2,4-D has the best effect of preserving fruit,with a fruit setting rate of 14.28%,which is 5.19 times that of the clean water control;the fruit setting rate after 20 mg/L GA treatment is 7.27%,and the fruit setting rate of 0.05 mg/L BR is 12.05%,both of which are significantly higher than the control of 2.75%.2.LC-MS/MS was used to detect residues after spraying 10 mg/l of 2,4-D until harvest time.The result shows that 2,4-D components were undetected in the fruit,which did not affect the safety of the fruit.3.After 2,4-D sprayed,the main functional components of the Huazhou pomelo fruit were effected.By the time of normal harvest,the content of naringin increased significantly by 13.62%,the content of rhoifolin decreased significantly by 54.76%,the content of bergapten decreased significantly by 44.07%,and the content of isoimperatorin decreased significantly by 18.09%;The total volatile components increased by 15.42%,and several volatile components such as D-limonene,β-myrcene,and γ-terpinene increased significantly by 78.13%,48.46%,and 45.54% respectively,and the overall compliance,it meets the requirement of no less than 3.5% naringin content specified in the Chinese Pharmacopoeia.4.2,4-D changed the expression of key enzyme genes of Cg PAL,Cg4 CL,Cg7Glc T,and Cg12 Rha T in the naringin synthesis pathway,which may be the reason for the changes in related functional components,and further verification is needed in the future.