Isolation and application of effective nitrogen fixation rhizobial strains on low-phosphorus acid soils in South China |
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Authors: | FengXian Cheng GuiQin Cao XiuRong Wang Jing Zhao XiaoLong Yan Hong Liao |
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Institution: | (1) Root Biology Center, South China Agricultural University, Guangzhou, 510642, China |
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Abstract: | Soybean (Glycine max L.) is a very important food and oil crop in China. Legume-rhizobium symbiotic nitrogen (N) fixation is an important biological
character and also the base of improving soil fertility of soybean. However, soybean production and development is severely
limited in tropical and subtropical areas in China due to a lack of effective rhizobial inoculants adapting to low-phosphorus
(P) acid soils. In the present study, 12 soybean rhizobial strains were isolated and purified from the nodules of two soybean
genotypes contrasting in P efficiency, which were grown on different low-P acid soils with different soybean cultivation histories.
Results from 16S rDNA sequence analysis showed that these 12 rhizobial strains belonged to the genus of Bradyrhizobium, which had higher nitrogenase activities compared to the control strain, Bradyrhizboium japonicum USDA110. A field experiment was carried out by applying rhizobial inoculants, a mixture of three rhizobial strains that showed
the highest nitrogenase activity, on a typical low-P acid soil in South China. The results showed that, without inoculation,
no nodules were formed in the three soybean genotypes tested; with inoculation, the nodulation rates in all were 100%. Inoculation
with rhizobial inoculants not only made many nodules formed, but also increased soybean shoot biomass and yield, and improved
nitrogen (N) and P nutrient status. Among which, shoot dry weight, N and P content of a soybean genotype, Huachun 3, inoculated
with rhizobium were increased 154.3%, 152.4% and 163.2% compared to that without inoculation, respectively. We concluded that:
(i) The effective indigenous rhizobial strains isolated in this study from soybeans on low-P acid soils in South China have
the characters of broad host range, high nodulation efficiency, efficient N fixation, great low pH and low P tolerance. (ii)
Soil environment and host types are the key factors to screen the effective rhizobial strains. Considering soil pH values
and P efficiency of the host genotypes might increase the screening efficiency. (iii) Improving N status and facilitating
root growth might be the mechanisms of increasing the P uptake in soybean plants inoculated with the effective rhizobial strains
on low-P acid soils. (iv) Inoculation with the effective rhizobial inoculants could significantly improve growth, N and P
content of soybean on low-P acid soils, which might be an effective approach to enhance soybean cultivation and development
in these areas. Therefore, application and extension of inoculation techniques with effective rhizobial inoculants in legumes
would result in great economical, environmental and ecological benefits.
The authors contributed equally to this work
Supported by National Key Basic Research and Development of China (Grant No. 2005CB120902), McKnight Foundation Collaborative
Crop Research Program (USA) (Grant No. 05-780) and National Natural Science Foundation of China (Grant No. 30571111) |
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Keywords: | acid soils low-P soybean rhizobium |
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