Biodiversity And Biogeography Of Rhizobia Associated With Phaseolus Vulgaris Grown In Different Ecological Regions Of Shaanxi

Phaseolus vulgaris, native to the Central and South America region, was introduced to China in the 1400 s and china is a secondary center of origin. It has been widely cultivated around the world. As edible beans, becase of high nutritional value as well as one of the most important source of plant protein, it is the world's most important economic crop. The total output accounted for almost 50% of global consumption of edible beans yield. However, the correlation between the variety of rhizobia from root nodules of Phaseolus vulgaris and ecological environment hasn't been studied systematically. Also, it is urgent that common bean, as the widely cultivated crops, how find the matched rhizobia to soon form the symbiosis in a variety of different habitats.To deplore the problem above, 194 symbiotic rhizobial isolates from root nodules of common bean, collected from N31° to N39° in 13 sites in Shaanxi, were characterized on the basis of genetic analysis(16S r DNA PCR-RFLP and the sequences analysis of 16 S r DNA, rec A, atp D, gln?, nod C, nif H). Then, the rhizobial variety, their symbiotic evolution and the related ecological environment factors were studied. The main results were followed.1.16 of 20 representative isolates of different genotypes could form nodules on the roots of Phaseolus vulgaris by nodulation tests on their original host plant. The most 67, the least 1, averaged 11 nodules were observed on each inoculated plant. Most of nodules located on the lateral roots. The majority of nodules shaped in spherical and short rod, with the size of about 0.4 cm, in white or pink color.2. 16 S r DNA PCR-RFLP and sequences analysis of 16 S r DNA and rec A-atp D-gln? gene showed that 194 isolates belonged to 5 genura, Agrobacterium, Sinorhizobium, Rhizobium, Bradyrhizobium and Ochrobactrum and 11 species, A. radiobacter, R. phaseoli, S. adhaerens, S. fredii, S. kummerowiae, R. vallis, R. giardinii, R. yanglingense, R. leguminosarum, B. liaoningense and O. anthropic. It showed the high species diversity of rhizobia from root nodules of Phaseolus vulgaris. R. phaseoli 52.58%, A. radiobacter 23.71%, S. fredii 14.43%, R. leguminosarum 3.09%, and other species(0.52 ~ 1.03%), and presents the difference of the regional distribution. S. adhaerens, S. kummerowiae, B. liaoningense, R. vallis mainly distributed in N34°; R. giardinii and R. yanglingense mainly distributed in the N37°; O. anthropic mainly distributed in N35°; R. leguminosarum mainly distributed in N32° ~ N33°; S. fredii mainly distributed in N34° ~ N37°; A. radiobacter and R. phaseoli widely distributed in the whole province N32° ~ N38°, but different kinds of genotypes in different ecological regions.3. nod C sequences analysis showed they belonged to Rhizobium and Sinorhizobium, but Rhizobium was the dorminant, including 10 genotypes isolates all with R. vallis and R. phaseoli for together, and Sinorhizobium including 5 genotypes isolates all with S. fredii for together. It indicated nod C gene of Rhizobium and Sinorhizobium were probably from the R. vallis, R. phaseoli and S. fredii respectively, through the lateral transfer and long-term adaptation, finally evolved towards differentiation.5. nif H PCR-RFLP and sequences analysis showed all genotypes of rhizobia from root nodules of Phaseolus vulgaris, belonging to Rhizobium and Sinorhizobium. The phylogenetic trees based on 16 S r DNA, nod C and nif H displayed obvious differences, implied that possible lateral transfer of the symbiotic genes occurred between different species or genera.6. It was done that the correlation analysis of diversity rhizobia from root nodules of Phaseolus vulgaris in different latitude 13 sampling sites and the ecological environment factors, including geography, soil and climate. The results showed that Shannon-Wiener index and Simpson index had significantly correlation with soil profile and monthly rainfall. Richness index had significantly correlation with longitude, soil profile and the groundwater level. Evenness index had significantly correlation with altitude, soil species, soil profile, ripe cycle, Annual effective accumulative temperature, average geothermal at the depth of 20 cm, average monthly temperature at sampling, average monthly relative humidity at sampling and average monthly sunshine durationat. For Species richness biogeographic distribution, groundwater level, A-P and A-K had significantly positive correlation with S. fredii and S. adhaerens and significantly negative correlation with R. phaseoli. But few effect on B. liaoningense, O. anthropic and R. vallis. Longitude had significantly positive correlation with A. radiobacter and R. leguminosarum, and had significantly negative correlation with S. kummerowiae, B. liaoningense, O. anthropic and R. vallisi. The thickness of plow layer had significantly positive correlation with S. kummerowiae, B. liaoningense, O. anthropic and R. vallis, had significantly negative correlation with A. radiobacter and R. leguminosarum. In general, environmental factor has a great influence on distribution of Shaanxi Phaseolus vulgaris rhizobia, all environmental factors explained 82.35%, which 34.03% from geographical factors, its the largest influence.