Study On The Mechanism Of Arsenite Affecting Citrus Fruit Quality

As one of the most important economic fruit trees in China,citrus has made a huge economic contribution to our country.In the background of huge industry scale,citrus fruit quality has been a bottleneck for its development.There are several ways to improve citrus fruit quality including excellent citrus varieties and proper cultivation techniques.Citrus‘Bingtangcheng’is an outstanding variety in China,with over 70%of it planting in Hunan province.Its quality affects development of‘Bingtangcheng’industry mainly.Although fruit quality regulator’arsenite’is highly toxic,use of that can not been prohibited completely because of its positive effects on fruit quality.It is worthy to think how arsenite regulates citrus fruit quality.This study analyzed the fruit quality of‘Bingtangcheng’collecting from diverse producing areas of Hunan province,and discussed the impacts of environmental factors on fruit quality formation.Using sweet orange and satsuma mandarin,the effects of arsenite treatment on citrus fruit quality and the genes working in that were studied.Finally,this study will clarify the mechanism of arsenite regulating citrus fruit quality and provide a theoretical basis for innovating a safe and effective quality regulator.The main results in this study are as follows:1.Fruit quality of‘Bingtangcheng’in Yongxing county,Mayang county,and Hongjiang city differed in two consecutive years,which might be caused by changes of meteorological condition and cultivation managements in different years.A regression model between fruit juice pH and total acid content was constructed.The regression equation was Y_{（total acid content）}=5.1975×10^{-0.527X（pH）},R²=0.4646.Fruit juice pH was negatively correlated with total acid and soluble solid content,while soluble solid content correlated with total acid content positively.2.Spraying sodium arsenite could decline accumulations of citrate,fructose,glucose and soluble solid in‘山下红’（C.unsniv Marc.）.Citrate reduction was found in ‘Dahongtiancheng’（C.sinensis Osbeck cv.Dahong）with sodium arsenite treatment,while the soluble sugar content increased at fruit ripening stage.Also,sodium arsenite treatment reduced total acid and soluble solid in‘Juxiangzao’（C.unsniv Marc.）,but it effected seldom on solid-acid ratio.3.Gene espressions of AN1（bHLH）,PH3（WRKY）,PH4（MYB）and PH8(P_3A-ATPase)were inhibited by arsenite in‘Juxiangzao’fruit and calli of‘Bingtangcheng’and‘Guoqing No.1’（拉丁名）.Inhibition of vacuole acidification by arsenite could be the main cause of acid reduction in citrus fruit.