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S. Kotepong , A. Nuntagij , S. Jitacksorn , N. Teaumroong , N. Boonkerd
'Soil Microbiology Research Group, Division of Soil Science, Department of Agriculture, Bangkok, Thailand
2School of Biotechnology, Suranaree University of Technology, Nakhon Ratchasima, Thailand
Leguminous trees such as Acacia, Pterocartpus, and Leuceana have been recommended for reforesting in denuded and degraded lands in Thailand. These leguminous trees successfully compete with native grasses and adapted to adverse conditions, i.e. drought, fires, acid, saline and low fertility soils. The advantage of leguminous trees is their association with Rhizobium, a symbiotic microorganism. Since the legume-rhizobial symbiosis can fix atmospheric nitrogen, thus nitrogen status of soil is improved even though no chemical nitrogen fertilizer is applied. Root nodules of five tropical leguminous trees (Acacia mangium, Acacia auricultiformis, Pterocarpus macrocarpus, Xylia kerii and Millettia leucantha) were collected from reforested sites around the country. Five trees were examined and nodules were collected for each of the species at each sites. About 300 rhizobial strains were isolated, purified and subcultured. The rhizobial strains were inoculated into their host plant and evaluated for their ability to increase host plant biomass, nodule forming and acetylene reduction assay. The data indicated that effective rhizobial strain resulted in higher plant biomass than ineffective and uninoculated treatments. Further study is carried out with the ten highest efficiency strains per each host plant.
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