Studies On The Effects Of Calcium On Watercore And Sorbitol Content In 'Yueguan' Apple Fruit

Watercore is a common physiological disorders of apple?Malus domestica?.It has been reported that apple fruit watercore is related to calcium content and abnormal metabolism of sorbitol.The new apple cultivar‘Yueguan'was used as the test material in this study.We have investigated the occurrence of watercore under measures such as spraying calcium fertilizer,fruit bagging and so on.The contents of inclusions and Ca²⁺,and sorbitol dehydrogenase activity in different treatment were determined.The expression patterns of sorbitol transporter?SOT?and sorbitol dehydrogenase?SDH?in different fruit development stage and fruit of watercore were analyzed by Real-time quantitative PCR technology.The main results are as follows:1.Spraying chelated calcium had better effect on the prevention and control of apple fruit watercore than spraying calcium chloride treatment.2.Compared with spray water,spraying calcium fertilizer in three different stages after full bloom can reduced the occurrence of fruit watercore.Among them,the effect of spraying calcium fertilizer on the plants multiple times at 15 d,75 d and135 d after flowering were best.Spraying calcium fertilizer increased the expression of MdSOTs and MdSDHs and accelerated the transport and metabolism of sorbitol in apple fruit.In addition to reducing the accumulation of sorbitol in the intercellular space of fruit,it also controls the incidence and symptom index of fruit watercore.3.Fruit bagging would increase the incidence of watercore,and also reduce the effect of calcium spraying on watercore prevention and control.However,bagging will reduce the incidence of watercore.The expression of MdSOTs and MdSDHs was significantly impaired after fruit bagging,and the increase in the expression of plants after calcium fertilizer application was limited.4.By comparing the occurrence of watercore in the two rootstocks of‘Yueguan/Liaozhen 2'and‘Yueguan/Mark 9',different scion combinations had different resistance to watercore.5.The Ca²⁺content in normal fruit was significantly higher than that in fruit of watercore.The Ca²⁺content of the normal fruit and the normal part of watercore fruit were significantly increased after spraying with calcium fertilizer.However,there was no significancein the diseased part of watercore fruit.At the same time,diseased part of watercore fruit had higher content of sorbitol and lower sorbitol dehydrogenase activity.The expressions of MdSOTs and MdSDHs were significantly lower than that of normal fruit in the diseased part of watercore fruit.After Spraying calcium fertilizer,the expression level of MdSOTs in the watercore fruits increased significantly,while the expression level of MdSDHs had no significance.