Production Technique And Effects On Soil Biological Community Of Streptomyces Rubrogriseus HDZ-9-47

Meloidogyne spp. is one of the most important plant parasitic nematodes that cause significant damage to a broad range of host plants. Biocontrol provides a strategy for sustainable nematode control, which is eco-friendly and safe for human health. Streptomyces rubrogriseus HDZ-9-47 was isolated from the eggs of Meloidogyne spp. and has shown great potential as an effective biocontrol agent against Meloidogyne incognita under in vitro and field conditions in our previous reseaches. In this study, we explore the biocontrol mechanism, optimize the industrial medium, and evaluate the field control efficacy of S. rubrogriseus HDZ-9-47 to provide reliable data for the industrial production of S. rubrogriseus HDZ-9-47.1、The biocontrol mechanism of S. rubrogriseus HDZ-9-47 against M. incognita was studied in vitro and pot. The study found that S. rubrogriseus HDZ-9-47 produced both chitinase and proteases. Microscopic observation results showed that S. rubrogriseus HDZ-9-47 had the ability to parasitize the eggs of M. incognita. To determine which component of the S. rubrogriseus HDZ-9-47 is responsible for the activity against M. incognita, greenhouse tests were set up to evaluate individually spores, cultures and secondary metabolites of S. rubrogriseus HDZ-9-47. All components reduced the root knot score. Furthermore, the activities of defense enzymes were increased to some extent after inoculation with S. rubrogriseus HDZ-9-47. It suggested that S. rubrogriseus HDZ-9-47 induced systemic resistance of tomato. In addition, the soluble sugar increased but the soluble acid decreased in the frult of tomato after inoculation with S. rubrogriseus HDZ-9-47.2、The molecular weights of the major nematicidal constituents were greater than 3 kDa. The S. rubrogriseus HDZ-9-47 nematicidal metabolites had high tolerance to heat, UV light and pH change, but were sensitive to proteinase K. In addition, the S. rubrogriseus HDZ-9-47 culture filtrates showed broad-spectrum activity against Meloidogyne spp., Heterodera spp., and Gaeumannomyces graminis. In pot experiment, the control efficacy of S. rubrogriseus HDZ-9-47 against G. graminis was comparable to that of a conventional chemical agent-raxil.3、In this study, the optimized industrial medium SPR-2 of S. rubrogriseus HDZ-9-47 was determined by single factor experiments and orthogonal experimental design. S. rubrogriseus HDZ-9-47 was inoculated into 200 ml SRP-2 medium and incubated in the shaker with 160 rpm at 28 ℃ for 3 days. There were 108/ml spores in the culture. The 2.0%(v/v) of optimized ferment filtrate caused more than 90% second-stage juveniles (J2s) mortality of M. incognita.Fermentation studies were conducted in a 50 L fermenter containing 30 L SPR-2 medium. The maximum nematicidal activity is obtained at the inoculation volume 3%, initial rotary speed of 160 rpm, ventilated volume of 2 L/min, fermentator pressure of 0.2 MPa, dissolved oxygen> 35%, fermentation time of 72 h, temperature 28℃ and initial pH 7.3. After fermentation, spores was 1010 /ml and the 2.5%(v/v) of the ferment filtrate caused more than 90% J2s mortality of M. incognita.4, Fermentation filtrate and spores were stored. Spores could reach to 108/ml after 12 months with peat ash as carriers. Fermentation filtrate lost activity again nematode after 4 months storage at room temperature.5、The efficacy of S. rubrogriseus HDZ-9-47 against M. incognita was evaluated under field condition during 2011 to 2014 cropping seasons. The results showed that S. rubrogriseus HDZ-9-47 cultured in SPR-2 medium could control M. incognita effectively and the control efficacy was 48% on tomato. Application of S. rubrogriseus HDZ-9-47 plus fosthiazate could not reduce the application dose of fosthiazate. Combined application of S. rubrogriseus HDZ-9-47 with biofumigation had obtained a synergistic effect against M. incognita, and resulted in control efficacy (67%) higher than that of fosthiazate.6、Cultivation-based analysis and PCR-denaturing gradient gel electrophoresis (DGGE) analyses demonstrated that combined application of S. rubrogriseus HDZ-9-47 with biofumigation affect soil microbial community and influenced some unique bacteria and fungi that may aid in controlling M. incognita.