Effects of Compound Potassium Nitrophenolate and Potassium Phosphite on Hormone Content and Expression of Related Flowering Genes in ‘Fuji’ Apple (Malus domestica Borkh)

SONG Yaofeng;ZHANG Linsen;ZHAO Ziyan;CHEN Fengnan;LIU Yu;ZHAO Xianfei;YU Guokang;WANG Linlin;College of Horticulture, Northwest A&F University;

Compound potassium nitrophenolate;;Potassium phosphite;;Fuji;;Endogenous hormones;;Flowering gene

In apple production, shoot growth of ‘Fuji' apple is vigorous, the overgrowth of shoots decrease the coordination between vegetative growth and reproductive growth, which is harmful to the flowering of ‘Fuji' apple, so the problem in biennial bearing of fruits is serious.In order to prevent vigorous growth of shoots, alleviate the problem in biennial bearing of fruits, and promote flower bud formation, in this experiment, the 8-year-old ‘Nagafu No. 2' was used as experimental material, and the clear water was used as CK,T1(compound potassium nitrophenolate 1 mg·L~(-1)),T2(potassium phosphate 3 340 mg·L~(-1)),T3(potassium phosphite 1 mg·L~(-1) + potassium phosphate 3 340 mg·L~(-1))were sprayed on May 20,June 20 and July 20 in 2021,respectively.The growth of apple shoots, endogenous hormone content were measured, fruit yield and flowering rate of the next year were surveyed.At the same time, the expression levels of flowering-related genes in short shoot of terminal buds were verified by quantitative PCR.The results showed that from the treatment to the end of the growing season, T2 and T3 treatments could significantly control the late growth of shoots, and the growth of shoots decreased by 29.03%-31.64% and 27.18%-30.33% compared with the control, respectively. At the hormone level, from physiological differentiation stage to morphological differentiation stage, with the increase of spraying times, the content of ZR increased first and then decreased, the content of IAA and GA_3 decreased, the content of ABA increased first and then decreased, and the difference was significant at the third times of spraying. During the critical period of flowering, the expression levels of MdSOC1,MdFD,MdLFY and MdFT were up-regulated, and the expression levels of MdGA20ox and MdTFL-1 were significantly down-regulated. After sprayingof compound potassium nitrophenolate and potassium phosphite, the flowering rate of the next year was significantly increased by about 63.41% under T3 treatment compared with the control. In summary, spraying of compound potassium nitrophenolate and potassium phosphite can control the vigorous growth of shoots, balance the relationship between vegetative growth and reproductive growth, regulate the change of endogenous hormone content, promote the expression of flowering-related genes, and effectively promote the flowering of ‘Fuji' apple. It was recommended tobe used in ‘Fuji' apple orchards with suitable fruits load.