Rhizobacteria able to express multiple plant growth-promoting (PGP) traits has been frequently failed to enhance the chickpea-Mesorhizobium symbiosis possibly because a relatively large amount of organic acids exudated by chickpea root to form an acid rhizosphere reduced the survival and colonisation of plant growth-promoting rhizobacteria (PGPR). Therefore, this study was initiated to screen rhizobacteria that would enhance the chickpea-Mesorhizobium symbiosis using a plant-basedstrategyA total of 743 Bacillus-, Burkholderia- and Pseudomonas-like bacteria were isolated from 74 agricultural soil samples collected across Australia. Only 167 isolates were selected, based upon their individual performance in a seedling growth bioassay, to test their effect on nodulation and growth of chickpea in sterile growth pouches. Also, their ability to produce 1-aminocyclopropane-1-carboxylate (ACC) deaminase and indole acetic acid (IAA) was investigated in relation to their mode of action. The diversity of the 167 isolates was investigated using 16S rDNA sequencing. Of 743 isolates, 697 (83%) were able to produce IAA in the presence of L-tryptophan. ACC deaminase production was detected in 57 isolates (7.7%). Commercial inoculant strain Mesorhizobium ciceri CC1192 produced 7 μg mL⁻¹ IAA and lacked ACC deaminase activity. In further investigation, the promotion of seedling root elongation by rhizobacteria predicted their effect on nodulation and growth of chickpea after dual inoculation in aseptic conditions. The effect of rhizobacteria on seedling root growth as well as shoot growth and nodulation was associated with the capacity of the isolates to produce IAA and ACC deaminase. These isolates were superior in plant growth promotion than those PGPR unable to produce PGP traits. The synthesis of IAA along with ACC deaminase activity by rhizobacteria gave an added advantage in promoting the ability of rhizobia to form an efficient chickpea-Mesorhizobium symbiosis as measured by biomass production and nodulation. Most of these rhizobacteria belonged to the genus Burkholderia. The use of a plant-based first-stage screening strategy in combination with assays for in vitro production of IAA and ACC deaminase enabled the identification of efficient PGPR that were able to enhance the legume-rhizobia symbiosis.

能够表达多种植物促生长（PGP）特性的根际细菌常常未能增强鹰嘴豆-中生根共生，这可能是由于鹰嘴豆根分泌的大量有机酸形成酸性根际降低了植物的存活和定植。 -促进根际细菌（PGPR）。因此，开始这项研究以使用植物为基础的策略筛选可增强鹰嘴豆-中生根瘤菌共生的根际细菌共743芽孢杆菌，伯克霍尔德氏菌和假单胞菌从澳大利亚各地收集的74个农业土壤样品中分离出类似的细菌。根据其在幼苗生长生物测定中的个体表现，仅选择了167个分离株，以测试它们对无菌生长袋中鹰嘴豆结瘤和生长的影响。此外，还针对它们的作用方式，研究了它们产生1-氨基环丙烷-1-羧酸酯（ACC）脱氨酶和吲哚乙酸（IAA）的能力。使用16S rDNA测序研究了167个分离株的多样性。在743个分离株中，有697个（83％）在L-色氨酸存在下能够产生IAA。在57个分离株（7.7％）中检测到了ACC脱氨酶的产生。商业接种菌菌株Mesorhizobium ciceri CC1192产生7μgmL ^-1IAA和缺乏ACC脱氨酶活性。在进一步的研究中，根瘤菌促进了幼苗根系的伸长，预示了它们在无菌条件下双重接种后对鹰嘴豆的结瘤和生长的影响。根瘤菌对幼苗根系生长以及枝条生长和结瘤的影响与分离株产生IAA和ACC脱氨酶的能力有关。这些分离株在植物生长促进方面优于那些不能产生PGP性状的PGPR。根瘤菌合成IAA以及ACC脱氨酶活性在增加根瘤菌形成有效鹰嘴豆-中生根瘤菌共生能力方面具有额外优势，如通过生物量生产和结瘤所测。这些根际细菌大多数属于伯克霍尔德氏菌属。基于植物的第一阶段筛选策略与体外产生IAA和ACC脱氨酶的检测方法的结合使用，可以鉴定出能够增强豆科植物-根瘤菌共生的有效PGPR。