Study On Biological Control And Mechanism Of Potato Common Scab

Potato common scab is one of the common potato diseases,which widely exists in major planting areas,resulting in the depreciation of potato commodity value,and its treatment is extremely urgent.The treatment effect of traditional methods is limited and there are some drawbacks.The application of microbial agents for biological control of potato common scab is the current research hotspot.At present,the number of strains to be selected to make microbial agents is limited.More strains with biocontrol potential still need to be excavated.In this study,bacteria with significant antagonistic effect on the pathogen of potato common scab were isolated and screened from diseased potato soil,in order to provide high quality strain resources and theoretical basis for biological control of potato common scab.The bacteria were isolated from diseased potato soil by dilution coating plate method,and the antagonistic strains were screened by plate confrontation method,and the antagonistic bacteria were identified according to morphology,physiology,biochemistry and molecular biology,and their potted control effect was determined.In order to explore the mechanism of CY1 in controlling Streptomyces scabies,the possible bacteriostatic substances were extracted and the effects of CY1 on mycelium morphology and spore production of Streptomyces scabies were observed.To investigate the effects of CY1 and Streptomyces scabies on defense enzymes,plant height,root system and biocontrol of potato;to determine the effects of antagonistic bacteria on the number of potato rhizosphere microflora by traditional microbial culture methods;exploring the effects of antagonistic bacteria on the activities of urease,sucrase and cellulase in potato rhizosphere soil.The results show that:(1)The 38 strains of bacteria were isolated from diseased potato soil,among which strain CY1 had significant antagonistic effect against Streptomyces scabies.The identification results showed that the strain CY1 had the closest genetic relationship with Bacillus atrophaeus,so the strain was identified as Bacillus atrophaeus,named Bacillus atrophaeus CY1.The pot results showed that strain CY1 reduced the incidence of scab caused by Streptomyces scabies from 87.32% to 60.77%,the disease index from 58.89% to 25%,and the control effect was 57.46%.(2)Through the production of bacteriostatic active substances,strain CY1 can obviously distort the mycelium of Streptomyces scabies and can not form sporulation septum,inhibit the production of spores and antagonize pathogenic bacteria.Antagonistic bacteria CY1 induced the overexpression of potato defense enzymes and improved the disease resistance of potato.During the growing period of potato,the activities of PPO,POD and CAT in potato leaves treated with antagonistic bacteria were significantly higher than those in infected groups.Antagonistic bacteria CY1 increased the resistance of potato leaves and resisted the stress of accidental outbreak of whitefly in potato growing period.Compared with the infected group,the content of MDA in potato tubers treated with antagonistic bacteria significantly decreased by 15.17%.The activities of POD,CAT and PPO increased by 71.49%,21.98% and116.15%,respectively.Antagonistic bacteria CY1 could improve the resistance of mature potato tubers and reduce the incidence of potato common scab.(3)Compared with the infected group,the plant height,root length and root number of potato in the antagonistic group increased by 148.5%,16.9% and 30.1%,respectively,and this growth advantage continued until the tuber-forming stage.Strain CY1 could recruit potato rhizosphere bacteria,inhibit fungal growth,increase urease activity(20.62%)and cellulase activity(43.93%)in rhizosphere soil,but had no significant effect on sucrase activity.Antagonistic strain CY1 could change soil types,promote the number of bacteria in potato rhizosphere and inhibit the growth of pathogens.Bacillus atrophaeus CY1 has a good control effect on potato common scab caused by Streptomyces scabies.It can promote seed potato germination and seedling growth,increase the activity of defense enzymes in potato tubers,improve soil microecology,and has the prospect of application and development.