Effects Of Potassium Chlorate On The Flowering And Fruiting And The Expression Of Genes Related To Oxidative Stress In Longan Cv. Shixia

In this experiment,Dimocarpus longan Lour.cv.Shixia was used as the test material to be treated with potassium chlorate at different time to study the effects of potassium chlorate on tree nutrients,flowering period of male and female flower,rate of male to femal flowers,yields,leaf photosynthetic pigment content and endogenous hormone content and the expression of oxidative stress-related genes in leaves.The differences between different treatments were analyzed and compared.The best period for applying potassium chlorate in longan was screened,and preliminary analysis and identification were performed based on the expression levels of related genes.The experiment consists of 5 treatments,treatment A:potassium chlorate applied on December 1,2018,treatment B:potassium chlorate applied on December 15,2018,treatment C:potassium chlorate applied on January 10,2019,treatment D:January 2019on the 23th,potassium chlorate was applied.Treatment E:contrast（without any treatment）,the results of the study indicate:1.The time of flower primordium appearing in four treatments of A,B,C,and D was obviously earlier than that of contrast.Treatment A was the earliest among all treatments,followed by treatment of B,C,and D.The end of four treatments was significantly later than the contrast,D treatment was the latest,C treatment was the second,heading rate,female and male flower ratio and yield of A treatment and B treatment were significantly higher than other treatments.2.The content of chlorophyll a,chlorophyll b,total chlorophyll and carotenoid in longan leaves decreased slightly after the application of potassium chlorate,and it increased rapidly in the later period.The total chlorophyll and carotenoid content of leaf A treament in the whole flower bud differentiation period was the highest in all treatments,the highest and significantly higher than the contrast.3.The content of mineral elements P,Ca and Mg in the leaves gradually increased with time,and the content of K decreased significantly.The content of P,Ca and Mg in leaves of A and B treatments was significantly higher than that of contrast,the content of K in leaves of A treatment was significantly lower than that of contrast,and there was no significant difference between C and D treatments and contrast.4.The content of endogenous hormones IAA and ABA in leaves increased gradually during the physiological differentiation period of longan flower buds,and the content of GA₃and ZT gradually decreased after the physiological differentiation period of flower buds.The contents of IAA and ABA in leaves treated with A and B treatments were higher than those of other treatments and significantly different from the contrast.The contents of GA₃and ZT in leaves treated with A,B and D treatments were lower than those of contrast.5.The fruit weight and soluble solid content of the four treatments A,B,C and D are higher than the contrast.The edible rate of the B and D treatments is higher than the other treatments during the early stage of fruit ripening,and the soluble sugar content of the A and B treatments is high than that of the contrast,the titrated acid content of the four treatments A,B,C,and D was lower than that of the contrast.6.After potassium chlorate treatment,the expressions of Dl ZAT10 and Dl PR1 genes related to oxidation were down-regulated,and the expressions of Dl YY1 and Dl WIP2 genes were up-regulated.Dl ZAT10 and Dl PR1 could be preliminarily determined as genes related to oxidative stress and Dl YY1 and Dl WIP2 were related genes for oxidative defense.In summary,the application of potassium chlorate in the early or middle of December for longan cv.Shixia in this experiment can significantly delay and prolong the flowering period of longan,form more high-quality flower buds,increase tree nutrition,improve fruit quality and increase the yield.