Effect Of Topical Application Of Tea Residues And (-)-Epigallocatechin Gallate On Apple Seedlings And Fruit Quality

The production and consumption of apples in China ranks first in the world,and apples have become an important pillar industry in promoting poverty alleviation and increasing farmers’incomes in the main production areas.Quality determines the flavour and texture of apple fruit,which in turn has a direct impact on farmers’economic income,so how to improve fruit quality while saving costs is a constant theme in the fruit tree industry.Research on the use of exogenous substances to promote plant growth and improve fruit quality is now common.（-）-Epigallocatechin gallate（EGCG）is the main pharmacologically active ingredient in tea and is very friendly to humans;EGCG can also help plants to withstand abiotic stresses.While the EGCG content of tea residues is still high after the tea has been steeped,the usual way to dispose of tea residues is mainly to simply discard it,but this would result in a waste of the beneficial components in tea residues,so we explored the tea residues and the main active ingredient in tea residues,EGCG,in the hope of providing a reference for the recycling of tea waste on fruit trees.This study investigated the effect of tea residues and EGCG,the main ingredient in tea residues,on the growth and fruit quality of apple seedlings.By comparing the prices of Common Lophanther,Xihu Longjing and Anji white tea and determining the EGCG content in the tea residues produced after brewing,Common Lophanther was finally chosen as the test material and configured into a 1 g/L tea residues suspension for treatment.Seedlings,fruit trees and apples were treated with EGCG and the main findings are as follows:（1）Spraying and pouring with tea residues significantly increased the net photosynthesis of seedlings,and the spraying treatment was more effective.Pouring with tea residues significantly increased the height of seedlings,but had no significant effect on stem thickness.The rate of ethylene release from stored apples after tea residues treatment was reduced by50%,and the wax fraction of esters was reduced by 56.57%and alkanes increased by 87.34%.（2）Different concentrations of EGCG significantly increased net photosynthesis,stomatal conductance,transpiration rate and intercellular CO₂concentration of seedlings,and also promoted the accumulation of wax on the leaf surface,and the optimum concentration range was 5-10μmol/L.（3）The content of H₂O₂in leaves was reduced by 23.52%after 5μmol/L EGCG treatment on fruit trees.EGCG treatment increased fruit transverse diameter,fruit longitudinal length and fruit weight per fruit by 4.66%,4.08%and 13.23%,respectively,compared with the control,increased surface gloss by 12.15%,reduced soluble solids by 6.67%and had no significant effect on titratable acid content.EGCG increased the content of esters in leaf waxes by 35.87%.It increased the content of primary alcohols and esters in the fruit surface waxes by 179.36%and 41.79%respectively.（4）EGCG at 5μmol/L not only inhibits surface greasing of apples,but also facilitates fruit storage.The rate of ethylene release from stored apples after EGCG treatment decreased by 30.75%,while the respiratory intensity and surface temperature of the fruit were suppressed.Transcriptomic data suggest that EGCG affects fruit storage by inhibiting the ethylene synthesis pathway and the fruit respiration pathway.Before harvest,tea residues and EGCG treatment could improve the photosynthetic efficiency of seedlings,affect the accumulation of wax components and promote seedling growth,while EGCG could also reduce the H₂O₂content in fruit leaves and affect the accumulation of wax components,thus promoting fruit growth.EGCG also improves the cosmetic quality of the fruit.After harvesting,both tea residues and EGCG treatments inhibited the release rate of ethylene and slowed down fruit spoilage during storage,and EGCG also inhibited respiration by suppressing the expression of genes involved in glycolysis,further extending the shelf life of the fruit.This study not only reveals the effect of EGCG,the main component of tea residues,on the quality and storage resistance of apples,but also supports the improvement of fruit quality at low cost.