Department of Biotechnology and Plant Breeding, Sari Agricultural Sciences and Natural Resources University, Sari, Iran.
Agriculture & Natural resources Campus, Faculty of Agricultural Engineering & Technology, Department of Soil Science, University of Tehran, Tehran 31587-77871, Iran.
Ecotoxicol Environ Saf. 2018 Oct 30;162:129-138. doi: 10.1016/j.ecoenv.2018.06.092. Epub 2018 Jul 11.
There are fewer reports on plant growth promoting (PGP) bacteria living in nodules as helper to tolerance to abiotic stress such as salinity and drought. The study was conducted to isolate rhizobial and non-rhizobial drought and salinity tolerant bacteria from the surface sterilized root nodules of alfalfa, grown in saline soils, and evaluate the effects of effective isolates on plant growth under salt stress. Based on drought and salinity tolerance of bacterial isolates and having multiple PGP traits, two non-rhizobial endophytic isolates and one rhizobial endophytic isolate were selected for further identification and characterization. Based on partial sequences of 16 S rRNA genes, non-rhizobial isolates and rhizobial isolate were closely related to Klebsiella sp., Kosakonia cowanii, and Sinorhizobium meliloti, respectively. None of the two non-rhizobial strains were able to form nodules on alfalfa roots under greenhouse and in vitro conditions. Co-inoculation of alfalfa plant with Klebsiella sp. A36, K. cowanii A37, and rhizobial strain S. meliloti ARh29 had a positive effect on plant growth indices under salinity stress. In addition, the single inoculation of non-rhizobial strains without rhizobial strain resulted in an increase in alfalfa growth indices compared to the plants non-inoculated and the ones inoculated with S. meliloti ARh29 alone under salinity stress, indicating that nodule non-rhizobial strains have PGP potentials and may be a promising way for improving effectiveness of Rhizobium bio-fertilizers in salt-affected soils.
关于生活在根瘤中有助于耐受非生物胁迫（如盐度和干旱）的植物促生（PGP）细菌的报道较少。本研究旨在从生长在盐渍土壤中的苜蓿表面消毒根瘤中分离耐干旱和耐盐的根瘤菌和非根瘤菌，并评估有效分离株在盐胁迫下对植物生长的影响。基于细菌分离株的耐旱和耐盐性以及具有多种 PGP 特性，选择了两个非根瘤内生菌和一个根瘤内生菌进行进一步鉴定和表征。基于 16S rRNA 基因的部分序列，非根瘤菌分离株和根瘤菌分离株分别与克雷伯氏菌、考克氏菌和苜蓿中华根瘤菌密切相关。在温室和体外条件下，这两个非根瘤菌株都不能在苜蓿根上形成根瘤。将苜蓿植物与克雷伯氏菌 A36、考克氏菌 A37 和根瘤菌 S. meliloti ARh29 共接种对盐胁迫下植物生长指数有积极影响。此外，与未接种和单独接种 S. meliloti ARh29 的植株相比，非根瘤菌单独接种也会增加苜蓿生长指数，这表明根瘤非根瘤菌具有 PGP 潜力，可能是提高盐渍土壤中根瘤菌生物肥料有效性的一种有前途的方法。
