Screening And Identification Of Bearing Lower Temperature And Controling Vegetable Root-knot Nematode Dominant Strain Streptomyces S205

Root-knot nematode disease is one of difficult diseases in vegetable production,and biological control is the hot spot of current research and development.Years of research and practice proved that it is important prerequisite that obtain rhizosphere predominant strains which had comprehensive features,especially low temperature properties to develop efficient and stable of biological control agents.In this study,297 different strains are isolated from the soils of tomato and cucumber rhizosphere,which contain 207 strains of bacteria and 90 strains of actinomycetes.Besides,three strains of Bacillus spp.and one strain of Streptomyces S506 which has some of the root-knot nematode resistance,are domesticated and selected.Laboratory screening results showed that the 5-fold diluted ferment filtrates of 9 strains,which are S511,B167,S205,B244,STU101,S252,LK101,S251 and S206,respectively,had more than 70% corrected knockdown efficiency to second stage juveniles(J2) after 24 hours.Of which there are four trains had more than 90% corrected knockdown efficiency,and the corrected mortality of S511 strain and B167 strain are come to the highest 98.22%.The above nine strains were used to measure the death-rates of J2 of root-knot nematodes respectively in diffierent concentration(2-fold,5-fold and10-fold)and treated time(4h,8h,12h and 24h).The results indicate that the 2-fold diluted ferment filtrates of the nine strains had more than 87.93% corrected knockdown efficiency to J2,the corrected knockdown efficiency of B167 and B244 are 99.16% and are highest in the all.At 10-fold,the knockdown efficiency of S511 expressed more effective to J2 to others.In diffierent treated time text,the five strains of B167,B244,S511,S205 and LK101 have respectively started more quickly than others.Through laboratory a screening,there are seven good strains were isolated,which are B167,B244,S511,STU1,S205 and LK101. The above seven strains were used in greenhouse screening by pot bioassay(insect defense,promote plant growth,stress resistance),antagonist and laboratory resistance to low temperature test.The results indicate that all strains treatment can promte plant growth in some extent compared with control,S205 treatment was significant difference compared with control﹙p<0.05﹚.The S205,STU101 and B244 treatments conductivity were lower than the control,and the S205 treatment conductivity was lowest,by 10.14%.Except S511,other strains had different inhibitory action to soil-borne pathogens,in which the strongest inhibition of rhizoctonia sp.,Fusarium wilt,phytophthora capsici is the strain B244, S205 and STU101,respectively,their inhibition rate was 55.44%,51.11% and 51.67%.The room temperature resistance test, S205 can grow at 4℃,with strong resistance to low temperature.The pot test results showed that the S205 treatment had the lowest disease index and had better control effect than others by 56.82% in average 15-18℃.Through comprehensive comparing some fine features, such as nematicidal, promote plant growth,improve plant resistance,broad-spectrum antimicrobial and low-temperature resistance,and so on,it is determined that Streptomyces S205 is the optimal strain.The advantage strain S205 was used to classification and determination.The results of the 16S rDNA sequence indicate S205 was 100% homology with Streptomyces antibioticus ( AY999776 ) and Streptomyces antibioticus(AB184184).S205 was classified as Streptomyces antibioticus,based on analyzeing its morphological,physiolodical-biochemical test and 16S rDNA sequence.