Effects Of SM,GA₃ And CPPU On Seedless Induction And Fruit Quality Of ’Shine Muscat’ Grape（Vitis Labrusca L.）

Seedless grapes are favored by the market because of their convenient consumption and better processing.At present,there are two sources of seedless grapes:one is the natural seedless varieties;the other is the seedless treatment on seeded varieties.However,there are a few seedless varieties planted currently,which cannot meet the growing demand of the market,so seedless induction of normal grape varieties is still a research hotspot.‘Shine Muscat’grape which was introduced from Japan in 2009,has been popular in recent years because of its unique rose fragrance and high soluble solids to acidity ratio.However,under the natural environment,the fruit of this variety has seeds,small berries,and easy to produce fruit rust,which seriously decreases the commerciality.Therefore,the use of plant growth regulators for seedless introduction and expansion treatment meets market demand.This study was conducted from 2018 to 2019.The‘Shine Muscat’grape was used as the test material in Zhengzhou and Xinxiang,Henan Province.In 2018,we used 200 mg/L streptomycin（SM）to treat‘Shine Muscat’grape at different periods,and selected the appropriate treatment period.At different concentrations of gibberellin acid 3（GA₃）and N-（2-Chloro-4-pyridyl）-N’-phenylurea（CPPU）,the treatments were performed at 2 to 3 days after full bloom,and the effect of different concentrations on the seedless berry rate was observed.In 2019,we studied the effect of different treatments on the fruit quality of‘Shine Muscat’with different concentration ratios of GA₃ and CPPU and whether or not SM treatment was performed.After comprehensive comparison,we selected the most suitable seedless treatment scheme for‘Shine Muscat’grapes.In addition,based on the results of previous experiments,we selected the treatment with the best comprehensive effect 2.5 mg/L CPPU+25 mg/L GA₃+200 mg/L SM to treat‘Shine Muscat’at 2 days after full bloom,to study effects of seedless induction treatment on endogenous hormones during fruit development.This research provides theoretical basis for the seedless production of‘Shine Muscat’grape.The main research findings are as below.（1）We selected the SM trearment period that was suitable for‘Shine Muscat’grape.The results showed that the seedless rate of fruits treated with 200 mg/L SM at one week after inflorescence separation in 2018 was the highest,reaching 90%,the average of 1 seed per 10 berries.In 2019,the seedless rate of fruit was the highest when treated at inflorescence separation,reaching 90%,and per 9 berries had one seed.Therefore,the best time for SM to induce seedless for‘Shine Muscat’was inflorescence separation and a week later.（2）We studied the effects of different concentrations of GA₃ and CPPU on the seedless rate of‘Shine Muscat’grape.The seedless rate of all treatments was significantly improved compared with the control,and the seedless rate of low concentration GA₃+CPPU treatment was lower than that of medium and high concentration treatments,and there was no significant difference in the effect of medium and high concentration seedless induction.However,none of these treatments could meet the production needs,because the highest seedless rate was only 56.67%.（3）We also studied the effects of different treatments on the fruit quality of‘Shine Muscat’grape.After treatment with different concentrations of GA₃+CPPU added the SM,the seedless rate of berry increased significantly,and all the fruits treated with medium and high concentrations were seedless.All treatments significantly increased the cluster weight,single berry weight,and fruit longitudinal and transverse diameter.The content of soluble solids and the total acid content of most treatments increased.The spikes and stems of all fruits became thicker after treatment.At high concentrations of GA₃+CPPU and SM,the length of fruit stalks in other treatments increased;except for low concentration GA₃+CPPU treatment,the stress tolerance of other treatments increased;after treatment,the fruit flavonoids,vitamin C and soluble protein content were reduced compared with the control.Treating with 200 mg/L SM when inflorescences were separated,and treating with 5 mg/L CPPU+50 mg/L GA₃ at 2 days after flowering was the best combination according to comprehensive evaluation of all treatments.（4）The effects of seedless induction on endogenous plant hormones during fruit development of‘Shine Muscat’grape were studied.After seedless treatment with 2.5 mg/L CPPU+25 mg/L GA₃+200mg/L SM,the contents of GA₃,t-ZT and IAA decreased during the fruit development compared with the control.The ABA content of the control dropped sharply after flowering,and it was not detected at 8 days after treatment,while the ABA content in the treated fruits showed another peak at 12 days after treatment.Generally speaking,the ABA appearance time was prolonged after treatment.It may be due to the lack of growth-promoting hormones and the increase in growth-suppressing hormones that lead to abortion of embryos.