Abstract: 【Objective】Due to climate and other factors，Southern regions gray mold outbreaks for many years, seriously affecting blueberry fruit yield, quality and industrial economic benefits. Emerald is one of the susceptible to gray mold disease varieties, which can even lead to complete crop failure in severe cases.Chemical control is widely used in the control of gray mold of blueberries due to its low cost and fast effectiveness. However, with the abuse of chemical agents, the pathogen has developed serious resistance. Chemical control due to pesticide residue exceeds the standard not only easy to limit China's blueberry export foreign exchange, but also bring food safety hidden danger. Currently, using natural plant physiological active substances to induce plant resistance against gray mold disease is regarded as a new method of disease control. This method is non-toxic and healthy, but has been studied less in blueberry cultivation and needs field trials to verify its effectiveness. In order to screen the green control measures of gray mold in 'Emerald' blueberry in southern Anhui Province, and to improve the fruit yield and quality, we have developed the following study.【Methods】In this study, we screened natural plant physiological active substances through the plate confrontation test that can significantly inhibit the important causal organism of gray mold, 'Botrytis cinerea ' by salicylic acid (SA), methyl jasmonate (MeJA), chitooligosaccharide, and Bacillus subtilis, and the selected four active agents were applied to field-cultivated blueberries, with a total of (0.1 mmol/L, 0.5 mmol/L,1 mmol/L) SA, (0.01 mmol/L, 0.1 mmol/L, 0.5 mmol/L ) MeJA, (1.5 g/L,5 g/L ) chitooligosaccharide, 2g/L Bacillus subtilis and the control group were applied four times at the flowering stage and before the color-changing period of the fruits.They are respectively the flowering period (March 22, 2024,;April 1, 2024), the period of young fruit (April 20, 2024), and the period of fruit expansion(May 10, 2024),to investigate the effects of different treatments on the incidence of gray mold in blueberries, and to further analyze the effects of different treatments on the development and quality of blueberry fruits. The best group was selected by correlation analysis and principal component analysis. The unique advantages of the well-performing treatment group are identified and the reasons behind them are analyzed.【Results】The four physiologically active substances could significantly inhibit the growth of gray staphylococcus mycelium.The higher the concentration of chitooligosaccharides and salicylic acid, the better the inhibition effect. And the overall inhibition effect of gray mold in the field was 0.1 mmol/LSA, 5g/L chitosan, (0.5, 0.01 mmol/L) MeJA, and 2g/L Bacillus subtilis, in descending order. All treatments (except 5g/L chitooligosaccharides) could significantly improve the transverse diameter and weight of blueberries at the ripening stage, and maintain their hardness without significant changes.By inhibiting the expression of gray mold in the field and its influence on fruit development, we selected 0.1 mmol/LSA, 1.5g/L chitooligosaccharides and 0.5 mmol/L MeJA as three treatment groups with excellent comprehensive performance. 11 key indexes were screened by principal components of 16 indexes related to the internal and external quality of ripening fruits, and further evaluated comprehensively through the weighted average of the subordinate function, which showed that the treatment groups with the effect of improving the quality of fruits from the highest to the lowest were, in descending order, 0.1 mmol/LSA, 1.5g/L chitooligosaccharides and 0.5 mmol/L MeJA, and all three treatments can significantly increase the glucose, fructose, total soluble sugar content, total phenolic content, as well as the DPPH free radical clearance rate of blueberry, and significantly decrease the malondialdehyde content of fruits, and basically maintain the titratable acid content unchanged.The antioxidant capacity of fruits is mainly affected by the content of proanthocyanidins. 0.1mmol/LSA affects the enzyme activity, while 0.5mmol/LMeJA and 1.5g/L chitooligosaccharides regulate the antioxidant capacity and appearance quality of fruits by affecting the sugar content and flavonoids. All the three treatments can regulate the sweetness of fruits through flavonoids.【Conclusion】For the prevention and control of gray mold in the field, the effect of 1.5g/L chitooligosaccharides on reducing incidence rate of wilting inflorescence is optimal;0.5 mmol/L MeJA for reducing the ratio of moldy flowers, enhancing the effect of DPPH free radical clearance rate of ripe fruit is optimal; for fruit quality enhancement, 0.1mmol/LSA in the improvement of ripe fruit weight and transverse diameter, and can be a small increase in the hardness of fruit, and for the enhancement of proanthocyanidins, total flavonoids, total phenolic content is optimal. The effect of 1.5 g/L chitooligosaccharides on the total sugar, titratable acid, and glucose of ripe fruits in each period of time is optimal, and this study can provide theoretical and practical guidance for coping with gray mold and improving the quality and yield of fruits in the green cultivation of blueberries.
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