In vitro antagonistic efficacy of a Paenibacillus sp. BTA27 against tea blister blight associated fungal pathogens

A bacterial isolate designated BTA27 was isolated from soil samples of Bateli tea estate of Assam, India. Morphological and phylogenetic analysis identified the isolate to be Paenibacillus sp. which shared 86.48% sequence similarity with Paenibacillus xylanisolvens strain X11-1 (NR_112906.1). The isolate showed antagonistic activity against several plant pathogenic fungi including tea blister blight associated fungal pathogens Pestalotiopsis sp. MGA4 (MN5660032), Pestalotiopsis sp. MGA6 (MN565994), Pestalotiopsis sp. MGA22 (MT707211), Pestalotiopsis sp. MGA37 (MN567942), and Nigrospora sp. MGA38 (MN566004). This was confirmed by techniques that included spot inoculation, well diffusion, and disc diffusion methods. The BTA27 isolate produced maximum antifungal metabolites from 8th to 10th day post-inoculation. Additionally, the BTA27 isolate exhibited a possible fungistatic effect against Pestalotiopsis sp. MGA4, Pestalotiopsis sp. MGA6, Pestalotiopsis sp. MGA22, Pestalotiopsis sp. MGA37, and Nigrospora sp. MGA38. Extract preparation of BTA27 was done in ethyl acetate from broth liquid culture following the organic solvent extraction method. The minimum inhibitory concentration (MIC) of the ethyl acetate extract of BTA27 was found in the range 0.912 to 7.42 µg/ml with the lowest MIC being recorded against Nigrospora sp. MGA38 (0.912 µg/ml) and the highest was seen against Pestalotiopsis sp. MGA37 (7.42 µg/ml). Increased concentrations of the ethyl acetate extract of BTA27 caused decreased spore germination of the fungal pathogens. Using GC-MS the chemical composition of the ethyl acetate extract of BTA27 was analyzed and the presence of different chemical compounds was detected having biological activities. Therefore, these results highlight potential suitability of BTA27 isolate for the development of biocontrol agent against blister blight.