Effects Of Compound Potassium Nitrophenolate And Potassium Phosphite On The Vegetative Growth,Endogenous Hormones And Expression Of Flowering-related Genes In ‘Fuji’ Apple (Malus Domestica Borkh.)

China is one of the countries with the highest yield and area of apple in the world,and‘Fuji’is the main variety of apple production in China,which has a large cultivation area and a wide range of suitable planting.But‘Fuji’shoot growth is vigorous,flower bud formation is more difficult,and the alternate bearing problem is also more serious.The balance between vegetative and reproductive growth is broken by the vigorous shoots of‘Fuji’,and the flower buds cannot be formed.To promote the spring shoot growth stop timely,prevent autumun shoot vigorous growth,promote flower bud formation,explore the use of functional chemical fertilizers and growth regulating substances in high concentrations spraying to inhibit the shoot growth,adjust the relationship of vegetative growth and reproductive growth,reduce the bad results caused by the single plant growth regulating substances,to promote flower bud differentiation and quality fruit production.Very few research have been reported whether compound potassium nitrophenolate and potassium phosphite affect the expression of genes related to flower formation in apples,and the mechanism of how to regulate flower formation remains unclear.In this experiment,the 8-year-old‘Nagafu No.2’was used as experimental material.Based on the preliminary test in 2020,four treatments were set up for the 2021growing season,including CK,T1(compound potassium nitrophenolate 1 mg.L^-1),T2(potassium phosphate 3340 mg.L^-1),T3(potassium phosphite 1mg.L^-1+potassium phosphate3340 mg.L^-1),The growth of apple shoots,endogenous hormone content,and fruit quality were measured,flowering rate of the next year were investigated,and the expression levels of flowering-related genes in apple short shoot terminal buds were verified by quantitative PCR.This study provided a new method for alleviating the growth of‘Fuji’apple shoots and provided a theoretical basis for exploring the regulation of‘Fuji’apple growth and development and promoting flower formation.The main results are as follows:1.In terms of the control of shoot growth,compared with the control,from the treatment to the end of the growing season,spraying compound potassium nitrophenolate and potassium phosphite can significantly control the growth of shoots in the late stage.After the first spraying treatment,compared with the control,the length of shoots decreased by 23.1%and19.8%under spraying T2（potassium phosphate）and T3（compound potassium nitrophenolate+potassium phosphite）,respectively,with significant differences.After July 20,the average growth of‘Fuji’apple shoots after spraying treatment was significantly lower than that of the control.The results showed that with the increase in spraying times,the growth of shoots was inhibited better after spraying compound potassium nitrophenolate and potassium phosphite.2.At the hormone level,compared with the control,the overall trend of GA₃ and IAA content was consistent throughout the determination period,IAA and GA₃content decreased gradually with the increase of spraying times,and the difference was significant compared with the control.The content of ZR and ABA increased first and then decreased,and the difference was significant after the third spraying.3.In terms of the expression of flowering genes,at the critical stage of flowering,the expression levels of flowering promoting genes Md SOC1,Md FD,Md LFY,Md CO and Md FT in short shoot apical buds were up-regulated,and the expression levels of Md SVP,Md GA20ox and Md TFL-1 were significantly down-regulated.The expression level of Md SOC1 increased and the difference was significant at 60～75 days after full bloom.The trends of Md FT and Md SOC1 were basically the same.The expression level of FT in flower buds increased significantly at 45～60 days after full bloom.The expression levels of Md LFY were significantly affected at 45 and 60 days after full bloom,and the difference was significant.At60～75 days after full bloom,the expression of Md FD gradually increased and the expression level of Md FD was significantly up-regulated.The expression of Md CO only increased at 45days after full bloom,and the other periods had little effect on flower bud.The expression level of Md TFL-1 was significantly down-regulated from 45 days after full bloom,and the expression level was lower than that of the control.The expression of Md GA20ox decreased at first and then increased.The expression of Md GA20ox was significantly down-regulated at45～60 days.At 45 days after flowering,the expression of Md SVP was down-regulated,and the difference was significant under T1.4.In the production,it was found that spraying compound potassium nitrophenolate and potassium phosphite had no significant effect on the fruit quality of‘Fuji’apple,but it could improve the flowering rate of‘Fuji’apple in the next year.Compared with the control,the number of inflorescences under T3 treatment was significantly different,indicating that T3treatment had a significant effect on promoting flowering.5.In the study of spraying compound potassium nitrophenolate and potassium phosphite to promote flowering experiment at the same time,it was observed that spraying potassium phosphite 3～4 times had a certain prevention and control effect on the occurrence of apple scab.Compared with the control,potassium phosphite played a good role in preventing the occurrence of apple scab,which could reduce the occurrence of apple scab by 25%～35%.Potassium phosphite can be recommended as a supplementary fertilizer for the prevention of scab,and it is recommended to be used in combination with or alternatively with systemic fungicide.In summary,the vigorous growth of shoots was controlled after the spraying of compound potassium nitrophenolate and potassium phosphate,the relationship between nutritional and reproductive growth was balanced,and the changes in the contents of ZR,ABA,IAA and GA₃ in endogenous hormones were significantly changed,and the flowering-promoting genes were expressed up-regulated and the flowering-inhibiting genes were expressed down-regulated during the critical period of flowering,and the flowering of‘Fuji’apple was promoted.Therefore,it is recommended that compound potassium nitrophenolate and potassium phosphite are used for 3～4 times in‘Fuji’orchards with suitable fruit load,the flowering bud differentiation of the following year can be effectively promoted and the phenomenon of alternate bearing of fruit trees can be alleviated.In addition,the spraying of potassium phosphite also has a certain effect on the prevention of apple scab.