Abstract
The Valsa canker caused by Valsa mali seriously harmed the production of East Asian apples and caused very significant economic losses. Considering the chemical residues and the improvement of people’s awareness of environmental protection, there is a need for screening new green pesticides for the control of Valsa canker. Therefore, we conducted systematic evaluations on the antifungal activity of wood tar. In this research, the effective concentration (EC50) of six strains of V. mali to wood tar was determined, and the EC50 ranged from 69.54 to 92.81 μg/mL. After treatment with wood tar, the hyphae of V. mali broke, swelled, and deformed; the permeability of the cell membrane increased; and the activity of pectinase reduced. Moreover, the expression levels of five genes related to pectinase also decreased significantly. In addition, the activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD) of apple leaves treated with wood tar also increased. On detached apple branches, wood tar also showed therapeutic and protective activities. In the 2016–2019 field experiments, wood tar also showed good efficacy against Valsa canker and promoted the formation of callus. (In the experiments from 2016 to 2019, it can be seen that the control effect of 50% wood tar and 100% wood tar in the field is above 75% and promoted the formation of callus.) This study is the first to report the bidirectional efficacy of wood tar against Valsa mali and for trunk wound healing. The above results evidenced that wood tar has great potential to be developed as a natural alternative to commercial fungicides for the management of apple Valsa canker.
Highlights
Apple Valsa canker is a devastating disease caused by V. mali
The EC50 values of wood tar inhibiting the mycelia growth of the six V. mali strains ranged from 69.54~92.81 μg/mL, with an average EC50 value of 81.16 ± 3.24 μg/mL
The commonly used fungicides have been to the achieve the ideal control efareas
Summary
Apple Valsa canker is a devastating disease caused by V. mali. In recent years, V. mali has seriously hindered the production of apples, with an average incidence of more than50% in the Shaanxi Province of China, and the affected area is between 30% and 90%. Apple Valsa canker is a devastating disease caused by V. mali. V. mali has seriously hindered the production of apples, with an average incidence of more than. V. mali infects branches, trunks, and fruit, causing necrosis of the diseased part, spreading to the entire trunk, and even causing the tree to the death in severe cases. It has caused great harm to apple production in East Asia, which is the main area of apple production, causing great economic losses to farmers. This pathogen can infect, especially when the tree is damaged or frostbite. Because the disease is occult and spreads rapidly, it is difficult to control the disease effectively [1]
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