Evaluation of 0.3% Agricultural Antibiotic 702 AS against Three Pathogenic Fungi of Rice

Abstractsolution （AS） against Rhizocto- nia solani, Magnaporthe grisea and Ustilaginoidea virens. [ Method] The toxicity effect of 0.3% agricultural antibiotic 702 AS against R., solani, M. grisea and U. virens were studied by mycelial growth rate method and mycelial wet weight method. [ Result ] The EC50 and EC50 values of agricultural antibiotics 702 AS to R. solani, M. grisea and U. virens in vitro condition were 4.16 and 16.17 mg/L, 16.05 and 41.85 mg/L, 111.2 and 389.0 mg/L, respectively. Agricultural antibi- otics 702 AS had good inhibition effect against R. solani and M. grisea and could basically achieve the effects of commercially available Jinggangmycin and kaanga- mycin, but the inhibition effect against U. v/rens was relatively weak. The preventive activity of aqueous solution was obviously higher than treatment activity. [Conclusion] 0.3% Agricultural antibiotic 702 AS is considered to be a potential biological control agent against R. solani, M. grisea and U. virens, and can be used as the potential alternative pesticide of Jinggangmycin.

Field Efficacy of Agricultural Antibiotic 702 against Rice Leaf Blast and Panicle Blast

The control effects of agricultural antibiotic 702 （ ag-antibiotic 702） on rice leaf blast and panicle blast were evaluated in field trials. With ag-antibiotic 702 and the two-line early hybrid rice 287 as test materials, different concentrations of ag-antibiotic 702 liquids were sprayed at tiUering stage and full heading stage of rice. In leaf blast test, the disease indexes of leaf blast at tillering stage were surveyed at 1 d prior to the first spraying and at 15 d post spraying, respectively. The disease indexes （DI） and the rice yield in panicle blast test was investigated at milky stage. Meanwhile, enzyme activities, including peroxidase （ POD）, catalase （CAT）, superoxide dismutase （SOD）, phenylalanine ammonia-lyase （PAL）, and polyphanol oxidase （PPO）, were measured. Kasugamycin （45 μg/mL） and deionized water were designed as positive and negative controls. When the concentrations of ag-antibiotie 702 were 15, 30 and 45 μg/mL, the control effects against leaf blast were 72.14%, 80.32% and 85.22%, respectively; the control effects on panicle blast were 74.08%, 84.87% and 86.58%, respectively; and the yield increase rates were 17.28%, 21.40% and 22.57%, respectively. So, ag-antibiotic 702, as a new agricultural antibiotic fungicide, could effectively cantrel rice blast by inducing defensive enzymes, and increase rice yield. The results will contribute to further development of ag-antibiotic 702 and its application in rice blast control.

A LuxR family transcriptional regulator AniF promotes the production of anisomycin and its derivatives in Streptomyces hygrospinosus var.beijingensis

The protein synthesis inhibitor anisomycin features a unique benzylpyrrolidine system and exhibits potent selective activity against pathogenic protozoa and fungi.It is one of the important effective components in Agricultural Antibiotic120,which has been widely used as naturally-originated agents for treatment of crop decay in China.The chemical synthesis of anisomycin has recently been reported,but the complex process with low productivity made the biosynthesis still to be a vital mainstay in efforts.The biosynthetic gene cluster(BGC)of anisomycin in Streptomyces hygrospinosus var.beijingensis has been identified in our previous work,while poor understanding of the regulatory mechanism limited the yield enhancement via regulation engineering of S.hygrospinosus var.beijingensis.In this study here,we characterized AniF as an indispensable LuxR family transcriptional regulator for the activation of anisomycin biosynthesis.The genetic manipulations of aniF and the real-time quantitative PCR(RT-qPCR)revealed that it positively regulated the transcription of the anisomycin BGC.Moreover,the overexpression of aniF contributed to the improvement of the production of anisomycin and its derivatives.Dissection of the mechanism underlying the function of AniF revealed that it directly activated the transcription of the genes aniR-G involved in anisomycin biosynthesis.Especially,one AniF-binding site in the promoter region of aniR was identified by DNase I footprinting assay and an inverted repeat sequence(5′-GGGC-3′)composed of two 4-nt half sites in the protected region was found.Taken together,our systematic study confirmed the positive regulatory role of AniF and might facilitate the future construction of engineering strains with high productivity of anisomycin and its derivatives.