Isolation,identification And Study Of Control Efficiency Against Cylindrocarpon Destructans Of Antagonistic Actinomycetes YBUF5 And YBUF7

In this paper,115 strains of antagonistic actinomycetes for biological control of Cylindrocarpon destructans were isolated and purified from 6 kinds of Ginseng Soil samples,4 kinds of campus soil samples and 2 varieties of ginseng rhizomes and epidermis by dilution plate method,42 of them were antagonistic strains.After indoor confrontation experiment of 42 strains and Cylindrocarpon destructans,23 strains of antagonistic actinomycetes were found to inhibit the growth of the mycelium of Cylindrocarpon destructans by more than 50%.Eight strains of antagonistic actinomycetes with the best antagonistic effect were selected,and the colony morphological characteristics of these 8 strains of actinomycetes on Gao’s No.1 medium were observed and recorded.The antagonistic spectrum of 8 strains of antagonistic actinomycetes was determined by laboratory confrontation test with 9 plant pathogens.The results showed that 4 strains(YBUF5,YBUF7,YBUF15,YBUF76)had broad antagonistic spectrum and had high antagonistic effect on 9 plant pathogens.The fermentation concentrates of four strains of antagonistic actinomycetes were prepared by constant temperature shaker method.The antagonistic spectrum of the fermentation concentrates of 4 antagonistic strains was determined by laboratory confrontation test with 9 plant pathogens.After comprehensive data analysis two high-efficient antagonistic actinomycetes strains(YBUF5 and YBUF7)were screened.The identification of YBUF5 and YBUF7 strains was carried out by means of combining classical taxonomy with molecular taxonomy.The culture characteristics,morphological characteristics and physiological and biochemical characteristics of the strains were observed and determined,combined with the homology comparison sequences of YBUF5 and YBUF7 16S rDNA sequences and the phylogenetic tree of the strains based on the sequences,the strain YBUF5 was identified as Streptomyces caniferus and the strain YBUF7 was identified as Streptomyces humidus.The effects of culture conditions on the antagonistic activity of YBUF5 and YBUF7 strains and fermentation concentrates showed that YBUF5 and YBUF7 strains had strong antagonistic activity against the three ginseng pathogens at 20～25℃,but did not reflect their inhibition at 30℃.In the slightly acidic environment,YBUF5 and YBUF7 strains and their fermentation concentrates had the strongest antagonistic activity against the three ginseng pathogens,and the antagonistic effect was weak under strong alkaline conditions.The effects of nutritional conditions on the antagonistic activity of YBUF5 and YBUF7 strains showed that the biocontrol effects of YBUF5 and YBUF7 strains on the three plant pathogens were not completely nutritional competition.The stability of YBUF5 and YBUF7 fermentation concentrates(temperature,pH,UV)was studied.The results showed that YBUF5 fermentation concentrate had low thermal stability,YBUF7 fermentation concentrate had better thermal stability,and the adaptive temperature range was very wide.YBUF5 and YBUF7 fermentation concentrates had a wide range of stability to pH;YBUF5 fermentation concentrate had a wide range of irradiation time to ultraviolet stability,YBUF7 fermentation concentrate had low stability to ultraviolet light.Field safety and disease prevention experiment of YBUF5 and YBUF7 strains were carried out by artificial inoculation after emergence of ginseng.In the middle of October,the root was removed and tested for disease control effect.YBUF5 and YBUF7 strains and mixed strains are not harmful to ginseng plants,and have certain promoting effects on ginseng growth.Main defensive enzyme activity(peroxidase POD,catalase CAT,superoxide dismutase SOD,phenylalanine ammonialyase PAL)of ginseng in ginseng tissues increased after treatment of healthy ginseng by YBUF5 and YBUF7 strains suspension.During the field disease prevention experiment,YBUF5 and YBUF7 strains had significant effects on the control of Cylindrocarpon destructans.Among them,YBUF5 and YBUF7 strains had the best control effect on Cylindrocarpon destructans,followed by the mixed strain.The yield index and yield of ginseng treated by YBUF5 strain and YBUF7 strain were significantly higher than that of the control,and in terms of the single weight YBUF5 strain was superior to YBUF7 strain and the mixed strain of the two.The results of the activities of the main defense enzymes in the roots and leaves of ginseng were determined that the main defense enzymes in the roots and leaves of healthy ginseng infected by Cylindrocarpon destructans were significantly increased,the main defense enzymes in the roots and leaves with the use of YBUF5 and YBUF7 slightly lower than the treatment with Cylindrocarpon destructans but higher than the sterile water treatment.