Isolation Of Antagonistic Bacterium Strains Against Pathogen Casuing Black Scurf Of Potato And Its Acting Mechanism

Potato black scurf caused by Rhizoctonia solani Kuhn is a soil-borne fungi disease，and it is one of the most serious and common diseases of potato in China.With the rapiddevelopment of potato industry, the potato rotation period has been gradually shortened,resulted in the serious obstackels of continuous potato crooping,which aggravated thePotato black scurf,and the damage of disease has become one of the most serious restrictionfactors affecting the potato tuber yield and quality in the major producing areas in China.In this study, from tiaoshan farm of jingtai county,Gansu province, bacteria withantagonistic activity against potato black scurf pathogen(Rhizoctonia solani)were isolatedfrom the rhizosphere soils of the different continuous cropping years.Based onidentification, growing conditions optimization, promoting substances detection and pottedbio-control effect test, reveals the bio-control mechanism of bio-control bacteria, aimed atproviding theoretical basis for biological control of potato black scurf. The main results areas follows:1. In this study,108bacterial strains were isolated from rhizosphere soil of potato withdilution method. One Strain was isolated from soil and could effectively inhibit the potatoblack scurf pathogen(Rhizoctonia solani). It produced an inhibition zone of6.0mm widthand above2.5cm diameter and an inhibitory rate at66.7%. Strain G1showedbroad-spectrum antibiotic property, such as Rhizoctonia solani of rice, Fusariumoxysporum f. sp. Melonis, Fusarium oxysporum f. sp.niveum, potato Fusarium sambucinum,potato Fusarium solani, Fusarium oxysporum f. sp. Potato. Based on the morphologicalcharacters, physiological and biochemical tests and16SrDNA sequence analysis, the strain,named as strain G1, was preliminarily identified as Paenibacillus jamilae.2. The strain G1could get the maximum growth under conditions as following, theculture time8~28h, temperature of37℃, initial pH7.0, salt concentration of10g.L-1,sucrose as carbon source, and yeast powder as nitrogen source. However strain G1hasgood suitability, also it can grow at4~45℃, pH5~10, and salt concentration of0to50g.L-1. it can use carbon, nitrogen extensively. Its growing conditions consistent with thepotato growing environment. 3. Strain G1produced cellulose enzyme, protease, pectinase, Siderophores, indoleacetic acid (IAA), and also have the ability of Phosphorus solubilization. Microscopy toobserve the Rhizoctonia solani of confrontation training5d, found that the hyphaemisshapen, hypha top expands, shorter, bending, twisting. It has great potential to controlPotato black scurf.4. Pot experiment showed: strain G1inoculated into soil,it promoted potatogrowth,especily the plant height, stem circumference, biomass, root absorption area, rootactivity, improved the activity of superoxide dismutase (SOD), peroxidase (POD), catalase(CAT) activity, and significantly reduces the malondialdehyde (MDA) content in potatoleaves. Strain G1promoted the growth and improved the resistance of potato plants.Above all, our studies showed that strain G1could effectively suppress the potatoblack scurf pathogen(Rhizoctonia solani), promote the growth of potato plants andimprove the resistance system of potato. It is the theoretical basis for the research anddevelopment of bio-control bacteria agent and bio-organic fertilizers to suppress the potatoblack scurf pathogen(Rhizoctonia solani).