Screening and diversity of plant growth promoting endophytic bacteria from peanut

Abstract

In order to study potential abilities to promote the growth of the plants and population diversity of endophytic bacteria in peanut plant at four different growth stages, 94 endophytic bacteria strains were isolated. Result indicate that numbers of endophytic bacteria of different growth stages ranged from 2.6 to 7.1×104 cfu/g FW with the maximum presented at the full pod stage. Based on 16S- restriction fragment length polymorphism (RFLP) and 16S rDNA sequences, these 94 strains were identified as 14 genera among which Bacillus and Pantoea were the dominant genera. The genus of the endophytic bacteria varied tremendously during annual growth period with the highest species richness at the full pod stage. Of the 15 antibacterial strains for the five phytopathogenic fungi, 12 strains were known to express antimicrobial activity againstFusarium solani, Colletotrichum gloeosporioides, Botrytis cinerea Pers andPseudoperonospora cubensis, but only three against Sclerotium rolfsii. Bacillus was dominant of these antibacterial strains. Among the 48 indole acetic acid (IAA) producing strains, Pantoea agglomerans, Bacillus megaterium and Enterobacter asburiae were remarkable for their high levels of IAA production and only three siderophore-producing bacteria were isolated which belong to Pseudomonas spp. At the same time, growth-promoting effects of three strains (Y21, F10 and H2) were proved by treatment of peanut seedling with bacterial supernatants. This study revealed the diversity of endophytic bacteria in peanuts at different growth stages. The obtained isolates have potential applications as inoculants that can adapt to poor soils and peanut. Basis is also provided for the manufacture of a multifunction bacterium agent.   Key words: Peanut, endophytic bacteria, growth-promoting, antifungal activity