Effects Of SM,GA₃,CPPU And TDZ On Seedlessness And Fruit Quality Of ’Sunshine Muscat’ Grapes In Xichang

Xichang City has unique ecological conditions for producing high-quality’Sunshine Muscat’grapes.However,production issues such as unstable seedless rates,difficulty in fruit retention,low uniformity of berries,and small berries were present.Grape growers,in an attempt to solve these problems,used plant growth regulators indiscriminately,leading to a decrease in fruit quality and hindering the healthy development of the industry.In this experiment,3-year-old’Sunshine Muscat’（Vitis labruscana Bailey×V.Vinifera L.）grapes were used as the research subject.Four chemical agents SM,GA₃,CPPU,and TDZ were applied during the stages of floret separation,full bloom,and post-flowering.The effects of these on seedlessness and fruit quality of’Sunshine Muscat’grapes were studied.The results show:1.SM and TDZ alone,different concentrations of SM+TDZ,and different concentrations of SM+TDZ+GA₃all induce seedlessness in’Sunshine Muscat’grapes during the floret separation stage（7 days before flowering）.Seedless rates can reach up to 99%,with 200mg/L SM+1 mg/L TDZ showing the best overall effect,achieving a seedless rate of 96%and effectively improving berry uniformity,making it suitable for use during the floret separation period.2.During the full bloom stage of’Sunshine Muscat’grapes,treated with 20 mg/L GA₃+2mg/L TDZ can achieve a seedless rate of up to 88%,and it performed well under low-temperature conditions for flower retention.GA₃+CPPU treatment was less effective for flower retention than GA₃+TDZ,and high concentrations of TDZ can lead to uneven fruit sizes.The best overall treatment during full bloom was 20 mg/L GA₃+2 mg/L TDZ.3.The effect of inducing seedlessness during the floret separation stage in’Sunshine Muscat’grapes was better than that during the full bloom stage.In cases of sudden drops in temperature before and after flowering,seedless treatment can be selected during the floret separation period,and re-application during full bloom can have a flower-retention effect.4.Treated with a GA₃+CPPU+TDZ mixture 10 days after flowering can significantly improve fruit quality.GA₃+CPPU+TDZ treatment significantly alters fruit quality:various treatments thicken the peduncle and pedicel,decreased stress tolerance of fruit;increased fruit soluble solids content,decreased fruit titratable acidity,and increased fruit VC content.Compared the effects of various treatments on external and internal fruit quality,using 30mg/L GA₃+2 mg/L CPPU+4 mg/L TDZ for fruit enlargement results in a single fruit grain weight of 14.96 g,soluble solids content of 19.22%,titratable acidity of 0.7%,a sugar-acid ratio of 27.45,and VC content of 9.63 mg/100g,which significantly enhanced fruit quality.5.Enlarged fruit once and twice significantly affected the external and internal quality of the fruit.While enlarging fruit twice increased single fruit weight,horizontal and vertical diameters,and VC content,it also increased fruit skin thickness,fruit acidity,and hollow rate of fruit,reducing fruit aroma and the sugar-acid ratio,and decreasing fruit flavor.It was recommended to enlarge the fruit only once in production.In conclusion,using 200 mg/L SM+1 mg/L TDZ during the floret separation stage,20 mg/L GA₃+2 mg/L TDZ during full bloom,and 30 mg/L GA₃+2 mg/L CPPU+4 mg/L TDZ 10days post-flowering had beneficial effects on seedlessness and fruit quality of’Sunshine Muscat’grapes.