Aims: Native rhizobia from root nodules of mungbean could reduce atmospheric nitrogen to ammonia for assimilation. The objective of this study was to find the best native rhizobium from mungbean. Methodology and results: Three rhizobia isolates from three mungbean varieties (Maejo 3, Khampangsan 2 and Chainat 72) were collected from 10 undamaged fresh nodules at Prince Chakrabandh Pensiri Center for Plant Development, Saraburi Province, Thailand in 2016. 16S rDNA analysis identified the three rhizobia isolates as Bradyrhizobium sp. (SB1), Bradyrhizobium elkanii (SB2) and Rhizobium sp. (SB3). All the isolates could grow well in yeast mannitol agar (YMA) at pH 7, and all isolates could tolerate up to 35 °C, with isolate SB3 tolerate up to 45 °C. Isolate SB2 produced the highest amount of indole acetic acid (IAA; 8.37 mg/L) and had the highest phosphate solubilization index (7.60 SI). In a Leonard jar trial, inoculation with isolate SB2 resulted in the highest shoot fresh and dry biomass of mungbean host. Further, the mungbean inoculated with SB2 had the highest number of root nodules, nodule fresh dry weight, chlorophyll content index, and shoot and root nitrogen contents. Conclusion, significance and impact of study This study suggested that the strain SB2 (B. elkanii) is a suitable bioinoculant to improve mungbean growth and yield.
Vigna--microbiology ; Rhizobiaceae

Heavy metal pollution of soil is a significant environmental problem and has its negative impact on human health and agriculture. Rhizosphere, as an important interface of soil and plant, plays a significant role in phytoremediation of contaminated soil by heavy metals, in which, microbial populations are known to affect heavy metal mobility and availability to the plant through release of chelating agents, acidification, phosphate solubilization and redox changes, and therefore, have potential to enhance phytoremediation processes. Phytoremediation strategies with appropriate heavy metal-adapted rhizobacteria have received more and more attention. This article paper reviews some recent advances in effect and significance of rhizobacteria in phytoremediation of heavy metal contaminated soils. There is also a need to improve our understanding of the mechanisms involved in the transfer and mobilization of heavy metals by rhizobacteria and to conduct research on the selection of microbial isolates from rhizosphere of plants growing on heavy metal contaminated soils for specific restoration programmes.
Biodegradation, Environmental ; Biological Availability ; Metals, Heavy ; metabolism ; Plant Development ; Plants ; metabolism ; microbiology ; Rhizobiaceae ; metabolism ; Soil Microbiology ; Soil Pollutants ; metabolism