Endophytic Bacillus spp. from Zingiber zerumbet rhizome, rhizosphere and axenic cultures: characterisation and identification of isolates with plant growth promoting activities and antagonism to soft-rot causative Pythium myriotylum

Abstract

Prospecting for plant growth promoting (PGP) endophytes is of particular relevance especially for soil-borne Pythium species that pose major productivity constraint for spice crop, ginger. Pythium- resistant wild ginger congener, Zingiber zerumbet L Smith constitutes a good source for prospecting PGP endophytes. Present study towards characterising bacterial flora from Z. zerumbet endosphere and rhizosphere yielded a total of 109 isolates from different tissue sets viz., leaves, rhizomes, axenically grown in vitro plantlets and rhizosphere. Morphological and PCR-RFLP analysis categorised isolates to 16 groups with representatives from each group identified by 16S rRNA sequence analysis. Isolates ZzTC6, ZzER11 and ZzER62 identified respectively as Bacillus pumilus, B. amyloliquefaciens and B. subtilis exhibited antagonism to P. myriotylum. Isolates also exhibited PGP traits like catalase and ammonia production with ZzTC6 also being IAA producer while ZzER62 positive for HCN. Endophytic isolates constitutes a valuable resource for development of BCAs against Pythium mediated soft-rot disease.