Colonization efficiency of different sorghum genotypes by Gluconacetobacter diazotrophicus.
Yoon, V., Tian, G., Vessey, K., Macfie, S. M., Dangi, O.P., Kumer, A.K., and Tian, L.-N. (2016). "Colonization efficiency of different sorghum genotypes by Gluconacetobacter diazotrophicus.", Plant and Soil, 398(1-2), pp. 243-256. doi : 10.1007/s11104-015-2653-8 Access to full text
Background: Gluconacetobacter diazotrophicus is a nitrogen-fixing bacterium initially isolated from sugarcane plants. Endophytic diazotrophs have the potential to fix nitrogen, but the extent of nitrogen fixation is variable and is dependent on the sugarcane genotype and other factors. Exploration of colonization of G. diazotrophicus in other plant species will provide a possibility for the development of nitrogen fixation potential in new host plants. Aims: The aim of the present study is to measure the efficiency of G. diazotrophicus colonization in different sorghum genotypes, which is an important precondition for substantial nitrogen fixation in sorghum plants. Methods: Using root-dip inoculation, G. diazotrophicus wild-type PAL5 was introduced into five grain and two sweet sorghum genotypes. The bacterium colonization in sorghum plants was assessed by the polymerase chain reaction using specific DNA primers to G. diazotrophicus, by analyzing and visualizing the expression of reporter gene uid that marked G. diazotrophicus and by reisolating the bacterium from plant tissues. The sugar content of each sorghum genotype was also measured. Results: G. diazotrophicus was detected in all sorghum genotypes tested, and the bacterium was detected in roots, stems, and leaves of sorghum genotypes via polymerase chain reaction (PCR) analysis. Analysis of the uid reporter gene expression and visualization of embedded samples also indicated full colonization of the bacterium in sorghum plants. The colonization efficiency varied among different plant genotypes and organs, with the number of bacteria ranging from 1.08 × 102 to 7.16 × 103 per g fresh tissue. Colonization of the bacterium was higher in sweet sorghum genotypes than in grain genotypes, and a positive correlation (r = 0.82, p = 0.025) was found between sucrose content of the plants and bacterium colonization efficiency. Conclusion: The nitrogen-fixing bacterium, G. diazotrophicus, can be introduced into different types of sorghum, and the bacterium can be detected in different organs of the plants. Successful and high levels of colonization are an important step to further explore this bacterium for biological nitrogen fixation in sorghum.
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