Enhancement of Soybean Yield Using Pink Pigmented Facultative Methylotrophic Bacteria

摘要

Emphasis is now focusing on discovering new microbes that can enhance growth and yield of field crops. So far we have known that rhizobia and bradyrhizobia fix atmospheric nitrogen for plant use and increase yield of leguminous plants. In this paper, we are reporting the discovery of the use of another bacteria, Pink Pigmented Facultative Methyiotrophs (PPFM) of the genus Methylobacterium to enhance growth and yield of soybean. These bacteria produce a plant normone cytokinin and enzyme urease. Cytokinins are involved in several stages of plant growth and development such as cell elongation, cell division, tissue differentiation and delay in senescence. Urease activates the breakdown of urea to ammonia and carbon dioxide and eventually makes N available to the plant. Field experiments were conducted on soybean [Glycine max (L.) Merr.] to evaluate the effects of PPFM bacteria on crop growth and yield. These bacteria were sprayed on the foliage at the reproductive growth stage (R_5). Application of PPFM gave a yield of 2.34 t ha~(-1), reflecting a 73% yield increase over the control under drought conditions. Similarly, PPFM significantly increased seed yield per plant and apparent harvest index (HI). As a result of PPFM spray, seed weight per plant was 13.9 g compared to the control that had seed weight of 7.9 g. Application of PPFM resulted in an apparent harvest index of 64.4%, while the control was 46.9%. Emphasis on development and use of PPFM can enhance soybean yield especially under moisture stress. It has so far not been shown that increasing PPFM population in the environment has any deleterious effect on the ecosystem. We believe that its use is environmentally safe because these bacteria are naturally occurring on the foliage of almost all angiosperms.