Study on the Relationship Between Leaf Content of Manganese and Internal Bark Necrosis Disease of Apple Trees
Ye Youliang, Zhang Fusuo, Yu Zhongfan,and Jiang Xueling(China Agricultural University, Beijing 100094 China; Shandong Agricultural university ,Taian 271018 China; Yantai Academy of Agricultural Science, Yantai 265500 China)
Several apple orchards with internal bark necrosis (IBN) in Jiaodong peninsula were investigated, and the manganese concentrations in soils, leaves, flowers, and phloem, xylem tissues were analyzed. The results showed that the soil available manganese were higher in apple orchards with IBN. Manganese concentrations in flowers were higher in apple trees infected with severe IBN. Manganese concentrations in flowers of apple trees damaged by the most serious IBN at Jianggezhuang were 139.28,122.34 and 182.19 mg/kg higher than those at Guanshui and Jijiabu orchards. From April to October, the severity of IBN were increased, and Mn concentrations in leaves were raised with the severity of disorder; and the highest and average Mn concentration in leaves at Jianggezhuang were 1 717.85 and 1 119.69 mg/kg on October, while it were 306.03 mg/kg at Jijiabu with slight IBN, the former were 265.88% higher than the latter. Among the different parts of the tree, manganese concentrations in phloem were much higher than it in xylem, but lower than it in leaves. It showed that the internal bark necrosis disease of apple trees in Jiaodong peninsula were caused by Mn toxicity, due to the high Mn concentration in soils, low soil pH, high precipitation and unreasonable fertilizer application.