Isolation and Characterization of Tomato Leaf Phyllosphere Methylobacterium and Their Effect on Plant Growth

Abstract

Phyllosphere methylotrophic bacteria from tomato leaves were isolated using selective Ammonia Mineral Salt (AMS) medium. Totally thirty two epiphytic bacterial isolates were selected based on their colony morphology and distinct pigmentation. All the isolates tested were Gram negative, rod shaped and positive for urease, catalase and oxidase activities. The preliminary screening of five randomly selected strains under in vitro for plant growth promoting characteristics and evaluated for their beneficial effects on the early growth of tomato showed positive for nitrogen fixation, ACC deaminase, siderophore and phytohormone productions were chosen for further studies. An in vitro experiment was conducted with 4 selected Methylobacterium spp. to evaluate their effect on tomato seed germination and vigor index. Among the isolates tested, Mt-Tm-13 had significantly increased the seed germination percentage (100%) earliness in radical emergence and vigor index. Plant inoculation studies indicated that Methylobacterium spp. strains provided a significant beneficial effect to the plants. In pot culture experiment, foliar application of Methylobacterium spp. (1% v/v concentration) showed that the inoculated plants had significant plant growth, biomass as well as yield attributes. The present study suggests that the Methylobacterium isolates may be used as bio-inoculants for sustainable tomato