The Effect Of Reduced Swelling Agent Combined With Different Plant Growth Regulators On The Quality And Yield Of Red-Fleshed Kiwifruit

Red-fleshed kiwifruit is a red flesh variety of Chinese kiwifruit,which is an extremely early maturing kiwifruit variety.Its offspring have stable genetic traits,strong stress resistance,large fruit,strong sweet and delicious flavor,and are more storable.Forchlorfenuron（CPPU）is a widely used swelling agent in kiwifruit production,which has the activity of promoting cell division.Reasonable use can increase the weight and yield of kiwifruit.However,excessive CPPU concentration can reduce the flavor and quality of kiwifruit,increase deformed fruit,affect commercial value,and shorten the storage time of the fruit.10mg/L CPPU is widely used in production to increase yield,but long-term use has had adverse effects on quality and storage,affecting economic benefits and health.In order to meet people’s demand for kiwifruit production and pursuit of fruit quality,this study selected’Hongyang’and’Donghong’,two main varieties of kiwifruit as materials,to carry out a test of reducing CPPU in combination with brassinolide,Jianda 990,zeatin and gibberellin during the fruit expansion period,and comprehensively analyze the effects of different chemical combinations on kiwifruit yield,quality and storage.Furthermore,transcriptome analysis was carried out for the best combination of chemicals to reveal the principle of minimizing the use of CPPU on the quality and yield of kiwifruit.The main research content and conclusions of this article are as follows:1.The regulatory effects of CPPU reduction combined with different growth regulators on the yield and quality of Red-fleshed kiwifruit are significantly different.There was a significant difference in the heart cavity rate between the reduced CPPU and BR,Jianda 990,and ZT treatments compared to the control,ranging from0.15mg/L BR<132mg/L Jianda 990<44mg/L Jianda 990<66mg/L Jianda990<0.075mg/L BR<0.01mg/L ZT,which decreased by 38.6%,31.8%,29.5%,25.0%,18.4%,and 18.2%,respectively;The combination of reduced CPPU with BR,Jianda 990,and ZT significantly reduced the abnormal fruit rate of’Donghong’.Among them,the combination of 0.075mg/L BR,0.15mg/L BR,and 0.3mg/L BR had the lowest abnormal fruit rate,which decreased by 50%,51.2%,and 39.3%compared to the control,respectively.CPPU combined with 0.15mg/L BR,66mg/L Jianda 990,0.01mg/L,0.05mg/L,and 0.1mg/L ZT can improve the fruit hardness of kiwifruit during the picking period;The combination of CPPU and 0.15mg/L BR can maintain a higher single fruit weight and yield of Red-fleshed kiwifruit,while the combination of 132mg/L Jianda 990,0.01mg/L ZT,and 130mg/L GA4+7 significantly reduces single fruit weight and yield.The yield of’Hongyang’is 78.3%,78.1%,and 80.7%of the control,and the yield of’Donghong’is 90.7%,88.0%,and 89.6%of the control,respectively.CPPU combined with 0.15mg/L BR,66mg/L Jianda 990,0.01mg/L,0.05mg/L,and 0.1mg/L ZT can improve the fruit hardness of kiwifruit during the picking period;The combination of CPPU and 0.15mg/L BR can maintain a higher single fruit weight and yield of Red-fleshed kiwifruit,while the combination of 132mg/L Jianda 990,0.01mg/L ZT,and 130mg/L GA4+7 significantly reduces single fruit weight and yield.The yield of’Hongyang’is 78.3%,78.1%,and 80.7%in comparison to the control,and the yield of’Donghong’is 90.7%,88.0%,and 89.6%in comparison to the control,respectively.CPPU combined with BR can significantly increase the soluble solids,solid acid ratio,and vitamin C content of fruits.Among them,the 0.15mg/L BR treatment has a significantly higher effect than other treatments,with an increase of 3.6%,11.6%,and 12.1%compared to the control,respectively;At the same time,CPPU combined with appropriate concentrations of BR,Jianda 990,ZT,and GA₄₊₇can increase the dry matter,calcium,and magnesium content of kiwifruit.2.Based on the comprehensive evaluation of fruits,it was found that the top three comprehensive evaluation indices for’Hongyang’were 0.15mg/L BR,0.075mg/L BR,and 0.3mg/L BR,while the top three comprehensive evaluation indices for’Donghong’were 0.15mg/L BR,0.3mg/L BR,and 0.075mg/L BR.Suggested that CPPU combined with BR can improve the comprehensive quality of red-fleshed kiwifruit,with the best effect being 0.15mg/L.3.Reduced CPPU combined with different plant growth regulators has a significant effect on improving the storage capacity of red-fleshed kiwifruit.The combination of CPPU with BR,Jianda 990,ZT,and Jianda 990 at appropriate concentrations can reduce the fruit drop rate during tree retention,delay the rate of fruit hardness decrease during storage,and delay the rate of fruit decay during storage;At the same time,CPPU combined with BR can also improve the soluble solid content of the fruit after storage.After comprehensive evaluation of storage properties,CPPU combined with 0.15mg/L BR has the best effect.This treatment can make red-fleshed kiwifruit go on the market for 10-20 days in staggered peaks and extend the fresh storage shelf life of the fruit by 3-5 days.4.Through RNA-seq analysis,it was found that CPPU combined with 0.15mg/L BR treatment was up-regulated in genes related to brassinolide（brassinolide）signal transduction,including brassinolide receptor BRI1,positive regulator BSK and transcription Factor BES1/BZR1.However,most of the auxin-responsive genes were downregulated,such as SAUR36,IAA4,SAUR24,22D and ARG7,while ABA signaling was enhanced by inhibiting the negative regulation of pp2c,and the regulation of brassinolide on the growth of’Donghong’kiwifruit was more dependent on ABA and GA signaling,but not auxin and cytokinins.Brassinolide promotes the growth of’Donghong’kiwi fruit mainly by enhancing the signal transduction of brassinolide,gibberellin,abscisic acid and jasmonic acid,inhibiting the signal transduction of auxin and cytokinin,and compensating for the decrease of forchlorfenuron content。To sum up,the treatment of reduced Forchlorfenuron combined with brassinolide can maintain high single fruit weight and yield,and improve the quality and storage tolerance of kiwifruit;Brassinolide mainly enhances signal transduction of brassinolide,gibberellin,abscisic acid and jasmonic acid,inhibits signal transduction of auxin and cytokinin,compensates for the decrease of Forchlorfenuron content,and promotes kiwifruit enlargement.Therefore,the combination of 5 mg/L of Forchlorfenuron（the production use is halved）and 0.15 mg/L of brassinolide can be used to improve the quality and storage tolerance of kiwifruit.