Effect Of Nitrogen On The Incidence Of Bitter Pit Of Hanfu Apples

Apple is the world’s first four fruits,and plays an important role in China’s fruit productions,but the unreasonable application of nitrogen fertilizer seriously affected fruit quality,yield and postharvest storage.The imbalance of fruit nitrogen content can easily lead to physiological diseases such as bitter pit,seriously affect the quality of apple fruit,and pose a great threaten on the fruit production.Therefore,the study of the incidence of bitter pit,fruit quality and the relationship between nitrogen and calcium at different nitrogen levels can provide a theoretical basis for revealing the relationship between nitrogen and apple bitter pit disease,and has important guiding significance for the prevention and treatment of apple bitter pit.In this study,the incidences of bitter pit at different nitrogen levels were analyzed using Hanfu apples as the experimental materials.To explore the relationship between the occurrence of apple bitter pit and nitrogen,the internal quality of fruits,enzyme activity,hormone and other materials content at the development storage stages were determined.The research results can provide theoretical basis for taking appropriate measures to reduce the incidence of apple bitter pit.The main results were as follows:(1)In this study,the incidence of Hanfu apple bitter pox increased by 7.5% and 11.5%,respectively,when the plants were treated with ammonium sulfate 1800 g(HN)per year,compared with the plants treated with ammonium sulfate 150 g(LN)per year after harvest and 30 days of storage.(2)High nitrogen treatment increased the single fruit weight,soluble solid content and sugar-acid ratio of Hanfu apples,reduced the fruit hardness and titratable acid content,changed the fruit texture,and thus increased the incidence of bitter acne disease.(3)In the late stage of fruit development,high nitrogen treatment reduced the calcium content of Hanfu apple fruit,increased the nitrogen to calcium ratio,affected the calcium components of fruit,reduced the content of pectin calcium,and thus resulted in the increased incidence of bitter pox disease.(4)High nitrogen treatment increased the activity of antioxidant enzyme,pectin methyl esterase and cellulase in Hanfu apple fruits,as well as the accumulation of IAA and GA3 in the middle and late stage of development,reduced the activity of cell wall peroxidase,accelerated the decomposition of cell wall,and then reduced the strength of cell wall,resulting in the increased incidence of bitter pox disease.