TITLE	Growth promotion and induction of systemic resistance in rice cultivar Co-47 (Oryza sativa L.) by Methylobacterium spp.
AUTHOR	Munusamy MADHAIYAN Department of Agricultural Chemistry, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea Selvaraj POONGUZHALI Department of Agricultural Microbiology, Tamilnadu Agricultural University, Coimbatore 641 003, Tamilnadu, India Murugaiyan SENTHILKUMAR Department of Agricultural Microbiology, Tamilnadu Agricultural University, Coimbatore 641 003, Tamilnadu, India Sundaram SESHADRI Department of Agricultural Chemistry, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea Heekyung CHUNG Department of Agricultural Chemistry, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea Jinchul YANG Department of Agricultural Chemistry, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea Subbiah SUNDARAM Department of Agricultural Microbiology, Tamilnadu Agricultural University, Coimbatore 641 003, Tamilnadu, India Tongmin SA Department of Agricultural Chemistry, Chungbuk National University, Cheongju, Chungbuk, 361-763, Republic of Korea
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ABSTRACT	Pink-pigmented facultatively methylotrophic bacteria (PPFMs), persistent colonizers of plant leaf surfaces, belong to the genus Methylobacterium and are mostly transmitted through seeds. Plant growth-promoting activity of methylotrophic bacteria and their effects on disease suppression were evaluated on rice under greenhouse conditions. Rice seeds were inoculated with Methylobacterium sp. strain PPFM-Os-07 and seed germination was evaluated in terms of morphometric measurements, seedling growth, rate of germination (RG), and seedling vigour index (SVI). Another experiment was carried out to study the induction of pathogenesis-related proteins (PR-proteins) in rice plants that were inoculated with methylotrophic bacteria by seed imbibition or foliar spray. In the third experiment, sixty-day-old rice plants grown in pots were challenge inoculated with Rhizoctonia solani strain TNAU-01. Methylobacterium inoculation promoted seed germination and plant growth. Increased plant height, number of tillers, plant biomass, and grain yield were observed. The average yield increases for seed imbibition and phyllosphere spray were, respectively, 22.1% and 24.3% greater than control. The bacteria also significantly reduced the sheath blight incidence when applied as either bacterial culture through seed imbibition and/or phyllosphere spray. The percent disease reduction recorded for seed imbibition alone and for combined applications of seed imbibition and phyllosphere spray were 17.8% and 23.5%. Rice plants sprayed with PPFM-Os-07 strain showed increased presence of PR-proteins and phenolic contents on day 1 after application. Maximum phenylalanine ammonia lyase (PAL) and peroxidase activity on day 4 and b-1,3-glucanase and chitinase activity on day 5 were recorded. The results suggest that Methylobacterium inoculation may alter rice susceptibility to R. solani. This work emphasizes the importance of evaluating induced systemic resistance while studying plant-associated growth promoting bacteria.
KEYWORD	Methylobacterium sp.; Oryza sativa L.; Induced systemic resistance; Pathogenesis-related proteins; Rhizoctonia solani;
ARTICLE INFO	Botanical Bulletin of Academia Sinica, Volume 45 Number 4 October 2004, page 315-324, 10 pages
PUBLISHER	Institute of Plant and Microbial Biology, Academia Sinica, Taipei, Taiwan, Republic of China