Biological Characteristics Of The Peach Brown Rot Pathogens From Different Peach-growing Areas And The Biocontrol Mechanism Of Bacillus Licheniformis W10 Against Peach Brown Rot

Peach brown rot is an important disease on peach trees,which seriously restricts the sustainable development of peach industry.In this paper,the biological characteristics of peach brown rot pathogens from different peach-growing areas and the biocontrol mechanism of Bacillus licheniformis W10 against peach brown rot were studied,providing a scientific basis for the effective control of peach brown rot in different peach-growing areas,and laying a theoretical basis for Bacillus licheniformis W10 biocontrol peach brown rot.The results showed that the optimum temperature for overall mycelial growth of 15 peach brown rot pathogen strains from different growing-areas strains was 25 ?,PDA was the best culture medium,the befitting pH was 6.0 to 7.0,and 12 h light each day was suitable for mycelial growth.The optimum carbon source and nitrogen source were starch and beef extract,respectively.The average rate of conidial germination of different strains was the highest under the condition of 25?,pH 7.0,and 12 hours of illumination each day.There were biological differences among peach brown rot pathogens from different peach-growing areas,indicating that there were abundant physiological and biochemical diversities in brown rot pathogen strains.In general,different nutrition,temperature,light,pH conditions had a significant impact on the mycelial growth and spore germination of different peach brown rot pathogens from different peach-growing areas.The test of Bacillus licheniformis W10 against peach brown rot showed that the treatment of inoculation brown rot pathogen 1 d after spraying W10 could significantly inhibit the occurrence and expansion of peach brown rot lesions,the enzymatic activities of POD,PPO,PAL,SOD,?-1,3-GA and CHI,LOX,CAT in peach fruits increased rapidly to a certain peak,then slowly decreased or tended to be flat,and the eight enzyme activities were higher than the treatment of W10 inoculation and brown rot pathogen inoculation.However,the W10 inoculation treatment also showed a trend of increasing enzymatic activity,which was similar to the trend of the treatment of inoculation brown rot pathogen 1 d after spraying W10,but the latter variation was small.At the same time,it was found that the content of malondialdehyde(MDA)and protein carbonyl in all treated peach fruits showed a gradual increase trend,but the contents of MDA and protein carbonyl in peach fruits treated with W10 inoculation and inoculation brown rot pathogen 1 d after spraying W10 were significantly lower than other treatments.In addition,the W10 inoculation treatment significantly reduced the protoplast leakage of peach fruit cells.Therefore,B.licheniformis W10 could confer peach-resistant brown rot by inducing changes in resistance-related defense enzyme activities,delaying lipid oxidation of proteins and protein carbonylation,and protecting the plasma membrane.This paper further studied the proteomics of peach fruit after W10 treatment to explain the molecular mechanism of protein level of W10 against peach brown rot.According to the results of the proteomics,the 1.2-fold differential expression was selected as the standard.When brown rot pathogen inoculation treatment compared with W10 inoculation treatment,there were 505 differentially expressed proteins in total,in which 370 proteins(73%)were up-regulated and 135 proteins(27%)were down-regulated.When W10 inoculation treatment compared with CK,there were 771 differentially expressed proteins in total,in which 441 proteins(57%)were up-regulated and 270 proteins(43%)were down-regulated.Contransing inoculation brown rot pathogen 1 d after spraying W10 treatment and CK,there were 479 proteins(70%)up-regulated and 207 proteins(30%)down-regulated.When inoculation brown rot pathogen 1 d after spraying W10 treatment compared with inoculation W10 treatment,there were 274 up-regulated proteins(54%)and 234 down-regulated proteins(46%);When inoculation brown rot pathogen 1 d afterspraying W10 treatment compared with inoculation peach brown rot pathogen,there were 951differentially expressed proteins in total,in which 479 proteins(50%)were up-regulated and 472 proteins were down-regulated(50%).The differentially expressed proteins were mainly involved in transcriptional translation,carbohydrate metabolism,amino acid metabolism,transport and catabolism.Subcellular localization analysis revealed that differentially expressed proteins were mainly located in the nucleus and chloroplast,and other differentially expressed proteins were located in the cytoplasm,plasma membrane,and mitochondria.