Characterization of chickpea root nodule bacteria in Turkey

Chickpea (Cicer arietinum L.) is among the first cultivated pulses in Turkey. Since Turkey soils are deficient in nitrogen, rhizobia can replace chemical fertilizers to increase chickpea yield at low cost. Also, nodules harbor non-nodulating endophytes (NEB) that can promote the plant growth. In this study, we aimed to investigate the diversity of RNR and NEB bacteria inside chickpea nodules. A total of 120 RNR and 13 NEB isolates, from 17 cities in 6 provinces in Turkey, were characterized on the basis of morphological, physiological, and biochemical traits. Besides, the NEB isolates were further identified on molecular basis using REP-PCR and 16S rRNA. Ninty percent of the RNR isolates displayed mucously, circular, smooth-margined colonies. Also, 11 out of 13 non-nodulating isolates displayed light pink colonies. All isolates in both groups endured up to 2% NaCl, grew optimally at 25-35°C and at pH 6-8. They all were gram-negative, fast growers and catalase and oxidase positive, while negative for amylase and methyl red. More than 95% of isolates in both groups utilized different compounds as sole carbon and nitrogen sources. The majority of isolates in both groups were insensitive to the heavy metals Zn, Cu and Cr, and resistant to the antibiotics such as kanamycin, streptomycin and tetracycline. Numerical analysis separated the isolates in each group into three clusters. Clusters 1, 2 and 3 of the RNR group came with 113, 5 and 2 isolates, respectively, and were respectively close to Mesorhizobium ciceri, M. mediterraneum and Mesorhizobium sp. Eight representative isolates of NEB group were identified via 16S rRNA sequencing with 99% similarity to 4 genera: Rahnella, Enterobacter, Pseudomonas, and Rhizobium. This showed that NEB inside nodules were as diverse as RNR bacteria. Key Words: Rhizobia, Chickpea, Phenotypic Characterization, Diversity