Effect Of Streptomyces PL11 Fermentation Broth On Improving Disease Resistance And Cold Resistance Of Peach Fruit

Peach as a typical climacteric fruit,its shelf-life and commodity value are severely influenced by rapidly ripening and deteriorating after harvest.Moreover,peach fruit is susceptible to mechanical injury in process of picking and storage,and the wound is easy to be infected by Monilinia fructicola..For fruits and vegetables,low temperature storage is a common method to keep fresh after harvest,which can effectively prolong the storage period of fruits and vegetables.However,peach fruits is sensitive to low temperature,which is easily prone to cold damage,leading to the decline of fruit quality.Various characteristics of peach fruits lead to intolerance to storage after harvest,which affects the development of peach industry.Streptomyces belongs to Streptomyces genus,Streptomyces family,which can produce a variety of active secondary metabolites due to its strong secondary metabolic capacity.Our previous study screened a strain of Streptomyces PL11 from soil,and found that the fermentation broth of Streptomyces PL11 had a good fresh-keeping effect on cherry tomatoes,bitter melon,pepper and fruits and vegetables,as well as prolong the storage period of these fruits and vegetables.Therefore,herein,the “Jinqiuhongmi” and “Yingshuanghong” peach was collected from Yiyuan County,Zibo City,as experimental materials.The preach fruits was treated by fermentation broth and extracts of Streptomyces PL11 to explore the inhibitory effect of fermentation broth and extracts of Streptomyces PL11 on brown rot and alleviating cold damage of peach fruits.Moreover,the extracts of Streptomyces PL11 fermentation broth aqueous phase have been preliminarily separated to find a new preservation method with comprehensive preservation effect on peach fruit.The main results as follows:(1)The mycelium growth and spore germination of Monilinia fructicola could significantly inhibited by the fermentation broth and aqueous extracts of Streptomyces PL11.Moreover,the apoptosis rate and ROS levels of Monilinia fructicola spores was significantly increased by Streptomyces PL11 fermentation broth and aqueous extracts using flow cytometry and inverted fluorescence microscopy.(2)The incidence and spot diameter of peach inoculated with Monilinia fructicola was significantly inhibited by Streptomyces PL11 fermentation broth,aqueous phase and organic phase extracts,and Streptomyces PL11 fermentation broth and aqueous phase has better inhibitory effect as compared to other treatment.After treated with Streptomyces PL11 fermentation broth and aqueous extracts,the activity of chitinase and β-1,3-glucanase could be significantly improved and the expression of PpPR1,PpNPR1,PpCHI,PpGNS and disease resistance-related genes was be significantly induced in peach fruits.Therefore,the resistance of peach fruits was induced,as well as inhibiting decay rate of peach fruits.(3)Peach fruits treated by Streptomyces PL11 fermentation broth,aqueous phase and organic phase extract can significantly relieve the symptoms of chilling injury,reduce the disease index,improve the antioxidant level,inhibit the accumulation of malondialdehyde,and maintain the fruit quality.In addition,the cold injury symptoms of peach fruits treated with organic phase extract of Streptomyces PL11 fermentation broth was significantly lower than other groups.