Nodule bacteria (rhizobia) in symbiotic associations with legumes enable considerable entries of biologically fixed nitrogen into soil. Efforts are therefore made to intensify the natural process of symbiotic nitrogen fixation by legume inoculation. Studies of field populations of rhizobia open up the possibility to preserve and probably exploit some indigenous strains with hidden symbiotic or ecological potentials. The main aim of the present study is to determine genetic diversity of common bean rhizobia isolated from different field sites in central Croatia and to evaluate their symbiotic efficiency and compatibility with host plants. The isolation procedure revealed that most soil samples contained no indigenous common bean rhizobia. The results indicate that the cropping history had a significant impact on the presence of indigenous strains. Although all isolates were found to belong to species Rhizobium leguminosarum, significant genetic diversity at the strain level was determined. Application of both random amplification of polymorphic DNA (RAPD) and enterobacterial repetitive intergenic consensus-polymerase chain reaction (ERIC- -PCR) methods resulted in similar grouping of strains. Symbiotic efficiency of indigenous rhizobia as well as their compatibility with two commonly grown bean varieties were tested in field experiments. Application of indigenous rhizobial strains as inoculants resulted in significantly different values of nodulation, seed yield as well as plant nitrogen and seed protein contents. The most abundant nodulation and the highest plant nitrogen and protein contents were determined in plants inoculated with R. leguminosarum strains S_17/2 and S_21/6. Although, in general, the inoculation had a positive impact on seed yield, differences depending on the applied strain were not determined. The overall results show the high degree of symbiotic efficiency of the specific indigenous strain S_21/6. These results indicate different symbiotic potential of indigenous strains and confirmed the importance of rhizobial strain selection. These are the first studies of indigenous common bean rhizobia in Croatia that provide the basis for further characterization and selection of highly efficient indigenous strains and their potential use in agricultural practice and future research.

中文翻译：

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克罗地亚本土菜豆根瘤菌的遗传多样性和共生效率。

与豆类共生的根瘤细菌（根瘤菌）使大量固定生物氮进入土壤。因此努力通过豆类接种来增强共生固氮的自然过程。根瘤菌田间种群的研究为保存和开发具有潜在共生或生态潜能的某些本地菌株提供了可能性。本研究的主要目的是确定从克罗地亚中部不同田地分离的普通豆根瘤菌的遗传多样性，并评估其共生效率和与寄主植物的相容性。分离过程表明，大多数土壤样品均不含本土的普通豆根瘤菌。结果表明，种植历史对本地菌株的存在有重大影响。确定了豆科根瘤菌，在菌株水平上具有显着的遗传多样性。随机扩增多态性DNA（RAPD）和肠细菌重复性基因间共有-聚合酶链反应（ERIC--PCR）方法的应用导致了相似的菌株分组。在田间试验中测试了本土根瘤菌的共生效率以及它们与两个常用豆品种的相容性。本地根瘤菌菌株作为接种剂的应用导致结瘤，种子产量以及植物氮和种子蛋白质含量的显着不同。在接种豆科植物_念珠菌菌株S _17/2的植物中确定了最丰富的根瘤形成以及最高的植物氮和蛋白质含量和S _21/6。尽管通常接种对种子产量有积极影响，但仍未确定取决于所施加菌株的差异。总体结果表明，特定的本地菌株S _21/6具有很高的共生效率。这些结果表明本土菌株具有不同的共生潜力，并证实了选择根瘤菌菌株的重要性。这些是克罗地亚对土著普通豆根瘤菌的首次研究，为进一步鉴定和选择高效本地菌株及其在农业实践和未来研究中的潜在用途提供了基础。