大豆根瘤菌SCAUs8的接种效果、促生性及系统发育研究

Field assessment of symbiotic efficiency, growth-promoting ability and phylogeny of soybean rhizobial strain SCAUs8

摘要:

【目的】大豆是我国重要的农作物，利用大豆-根瘤菌共生体系能有效减少化学氮肥的用量。将初筛的大豆根瘤菌SCAUs8在四川两个重要的大豆种植生态区进行田间接种验证试验，同时对该菌株进行分类地位研究。【方法】在四川丘陵区和攀西地区，采用大田试验调查接种大豆根瘤菌SCAUs8对大豆的增产效果。采用点接种法研究SCAUs8的抗逆性，用Salkowski比色法检测供试菌分泌吲哚乙酸(IAA)的能力。用多位点基因(16S rRNA，atpD，recA，glnⅡ，nodC，nifH)序列分析对供试菌株SCAUs8进行分类地位的确定。【结果】大田试验表明，接种大豆根瘤菌SCAUs8后，大豆植株的产量、鲜重、干重等指标明显高于不接种对照(CK)处理，其中大豆植株产量比不接种CK增产21.4%?29.7%，其差异达显著水平。对供试菌株SCAUs8进行的耐酸碱性、耐盐性、生长温度范围以及分泌IAA能力测定的结果表明，供试菌株SCAUs8能在ph 5.0?10.0正常生长，可耐受NaCl浓度为0.5%，生长温度范围是10?40 °C，能分泌IAA。综合16S rRNA、atpD、recA、glnⅡ、nodC、nifH基因的序列分析，发现供试菌株SCAUs8与Bradyrhizobium diazoefficiens USDA110T相似性高达100%。【结论】供试菌株SCAUs8是与四川主栽大豆品种共生匹配性较好的广谱菌株。该菌株耐盐性较差，但具有较强的耐酸碱性、较宽的生长温度范围及分泌IAA的能力。系统发育研究将供试菌株SCAUs8确定为B. diazoeffciens。

Abstract:

[Objective] Soybean is the important legume crops in China. We can reduce chemical nitrogen fertilizer effectively by soybean-rhizobia symbiosis. The former screened soybean rhizobial strain SCAUs8 was used in field inoculation to two important soybean planting regions, in Sichuan. In addition, we identified the taxonomic position of this strain. [Methods] Field experiments were conducted to investigate the effect on soybean production by inoculating soybean rhizobia strain SCAUs8 in Sichuan hilly area and Panxi area. We studied the stress-tolerance of SCAUs8 with the point inoculation method. Growth-promoting ability was determined through Salkowski colorimetric method. Multilocus sequence analyses (16S rRNA, atpD, recA, glnⅡ, nodC, nifH) were amplied to identify the phylogenetic position of SCAUs8. [Results] Field experiments showed that plant fresh weight and dry weight inoculated with SCAUs8 were significantly higher than that of no inoculation control (CK). The yield increased significantly by 21.4%?29.7% compared with CK. The strain SCAUs8 could grow at pH 5.0?10.0. It could be resistant to 0.5% NaCl, and the growth temperature range was 10?40 °C. Growth-promoting capability of secreting heteroauxinc (IAA), was also be detected. By analyses of 16S rRNA, atpD, recA, glnⅡ, nodC and nifH sequences, we found that SCAUs8 clustered closely to Bradyrhizobium diazoefficiens USDA110T with 100% similarities. [Conclusion] SCAUs8 was a good candidate matching with main planting cultivars of Sichuan soybean. This strain had alkaline and acid tolerance, wide growth temperature range and could secrete growth-promoting IAA, although the salt tolerance of it was weak. Phylogenic study proved that strain SCAUs8 was assigned as B. diazoeffciens.