| Myxobacteria are a group of higher prokaryotes with social behavior.Secondary metabolites of myxobacteria have anti-bacterial,anti-fungal,anti-tumor and anti-virus activities,which are good resources for screening natural drugs.Potato is the fourth largest food crop after rice,wheat and corn in the world and the fourth staple food in China.During the growing process,potatoes are vulnerable to various kinds of attacks,such as early blight,late blight,black shank disease,ring rot,black scurf,and insect bites,which eventually lead to a decrease in potato production.A myxobacterial strain B25-I-3 was isolated.It was showed that the secondary metabolites of the strain had a broad-spectrum inhibitory effect on potato pathogens.However,the field control effect of the secondary metabolites of the strain on potato diseases is still unknown.In this study,the control effect of secondary metabolites of strain B25-I-3 on potato diseases in field was preliminarily detected.The results showed that the secondary metabolite of strain B25-I-3 could effectively inhibit the growth of Phytophthora infestans at the concentration of 10 g /m L,and the secondary metabolite with Organosilicon auxiliary agent was safe for potted potato plants.The secondary metabolites of strain B25-I-3 had no significant effects on the basic growth indexes,chlorophyll content,quality and yield of potato tubers at seedling,flowering and tuber formation stage,starch accumulation stage and maturity stage,indicating that the secondary metabolites of strain B25-I-3 were safe for potato plants.The disease index and treatment effect of different treatment groups in each period were analyzed.The disease index of CK group was the highest in each growth period.The disease index of B1 group was lower in all growth stages,and the disease index of this group was the lowest in flowering and tuber formation stage and maturity stages.There was no significant difference in disease index among all the groups.The disease control effects of each group were calculated compared with CK group.The control effects of B1 group were higher in each growth stage,which were 72.18%,66.47%,17.87% and 92.31%,respectively.The control effects of B2 group were 51.41%,36.50%,19.46% and 68.94%,respectively.The control effects of conventional group were 76.76%,56.08%,6.20% and 67.55%,respectively.Statistical analysis of the rate of diseased tubers and commodity tubers showed that the rate of diseased tubers in B1 and conventional groups was significantly lower than that in B2 and CK groups,while the rate of commodity tubers in B1 and conventional groups was higher than that in B2 and CK groups,but there was no significant difference in the rate of commodity tubers in each group.These results indicated that the secondary metabolites of strain B25-I-3 had a control effect on potato diseases,which was similar to that of common pesticides.The isolation,purification and identification of the pathogen of this potato disease were carried out,and a total of 12 strains of pathogen were isolated.The results of biological morphology and molecular identification showed that the pathogen might be Alternaria Solani and Alternaria alternata.The disease may be early blight of potato.This work laid a foundation for the further development of the disease control effect of myxobacterial secondary metabolites in field. |
