Structural Identification of Antibiotics from Pseudomonas sp. RRj 228, a Antifungal Activity of Collectotrichum acutatum Causing Anthracnose on Pepper

Abstract

Microorganisms near the plant rhizosphere usually inhabit the surface or the inside of the plant roots and have a direct effect on plant growth by secreting plant growth promoters or antagonistic materials which protect the root zone system from various pathogens. This study was carried out to identify and isolate the antagonistic materials after isolation of microorganisms showing high antagonistic activities, in hopes of contributing to the development of sustainable agriculture and the preservation of agricultural environments. A number of antagonistic bacteria were isolated from paddy soil. Among isolates, RRj 228 showed plant growth promotion and antagonistic activity. RRj 228 was identified as Pseudomonas sp. according to the results of physiological properties and genetic methods. On the basis of the results of anti-fungal spectrum against several pathogens by RRj 228, the antagonistic effect of the isolate against Botrytis cinerea, Pythium ultimum, Phytopthola capsici, and Rhizoctonia solani, especially against red-pepper anthracnose caused by Colletotrichum acutatum, was remarkable. The experiment evaluating the biological control effect by RRj 228 revealed that the ED50 value by the RRj 228 culture against C. acutatum, R. solani and P. ultimum were 0.14 mg/ml, 0.16 mg/ml and 0.29 mg/ml, respectively. An antagonistic substance was isolated and purified by several chromatographies from the RRj 228 culture. The 1 H and 13 C assignment of the antagonistic substance was achieved from two-dimensional 1 H-1 H COSY, HMQC, and HMBC. Finally, the antagonistic substance was identified as Phenazine-1-carboxylic acid (C13H8N2O2, M.W.=224).

Antagonistic Activities of Bacillus spp. Strains Isolated from Tidal Flat Sediment Towards Anthracnose Pathogens Colletotrichum acutatum and C. gloeosporioides in South Korea

“…Although PGPR properties responsible for plant growth promotion have not been fully elucidated, PGPR is known to produce plant growth regulators such as indole-3-acetic acid (IAA) and promote asymbiotic N fixation and solubilization of soil P compounds ( Idris et al, 2007 ; Malik et al, 1997 ; Rodriguez and Fraga, 1999 ). Antagonistic microorganisms include Bacillus spp., Pseudomonas spp., Paenibacillus spp., and Streptomyces spp., which are mainly isolated to control the pepper anthracnose from the rhizosphere and plant microflora ( Garbeva et al, 2004 ; Jeon et al, 2010 ; Lamsal et al, 2012 ; Lee et al, 2011 ; Lim, 2005 ; Weller, 2007 ; Yoo et al, 2012 ). However, there is wide range of environments where more beneficial microorganisms have not been discovered.…”