Abstract
This study aimed at screening rhizobial isolates of chickpea and evaluating their symbiotic nitrogen fixation efficiency and tolerance to abiotic stresses. A total of 107 (100%) isolates were collected of which 52 (48.6%) were confirmed as chickpea rhizobia using preliminary tests. Among 52 (48.6%) isolates, 46 (88.5%) have induced nodulation on chickpea under greenhouse and were screened under in vitro conditions and 6 (11.5%) of them were discarded due to fail to nodulate. The greenhouse data showed the highest nodule number (68.67 plant−1), nodule dry weight (0.17 g plant−1), and shoot dry weight (0.81 g plant−1) were scored by plants inoculated with isolates WUCR 17, WUCR 1, and WUCR 66, respectively. Among authenticated isolates, 73.9%, 21.7%, and 4.3% were highly effective, effective, and lowly effective, respectively. The physiological test showed 15% of isolates tolerated 13% salt concentration and 10.9% of isolates grew at pH 4–10 range. All isolates grew at 20–35°C and 13% grew at maximum temperature (50°C). The isolates showed better resistance to the tested antibiotics at low concentration (2.5 μg/ml) but the majorities were sensitive at high concentration (10 μg/ml). Among the isolates, 13% tolerated all tested heavy metals but 48% were sensitive to mercury. Regarding the carbohydrate utilization test, 52.2% catabolized all the tested 11 carbon sources but 6.5% of them utilized only 63.6% carbon sources. Amino acid utilization showed isolates (85%) utilized D-alanine except WUCR (14, 25, 31, 34, 39, 59, and 76) and 76% of the isolates utilized arginine and phenylalanine and 74% utilized leucine as a nitrogen source. Of the isolates, 43.5% of them utilized both D-alanine and arginine as a nitrogen source. In almost all tests conducted, isolates WUCR 1 and 5 performed top and were recommended as potential candidates for microbial inoculants.
Highlights
Chickpea (Cicer arietinum L.), a member of the family Leguminosae, is an important pulse crop valued as a rich source of proteins [1]
Researches that focused on the diversity and symbiotic properties of rhizobia and rhizobacteria associated with pulse crops including fava bean, field pea, chickpea, and lentil were carried out [26, 27]. ese studies mainly focused on isolation and in vitro characterization under laboratory conditions and nitrogen fixation under greenhouse conditions [10]. ese trials were limited to only a few areas of the country and no literature report in the study area so far [28,29,30,31,32]. e plant growth promoting and controlling role of chickpea rhizobia was forgotten except few works done in other areas outside from the study area and on other crop legumes [33, 34]. us, this study was aimed at isolating and characterization of chickpea (Cicer arietinum L.) nodulating rhizobia collected from South Wollo Zone, Ethiopia
Presumptive Test. e growth of the rhizobial isolates was determined by growing them on Peptone Glucose Agar (PGA), Keto-Lactose Test, Gram staining, and Yeast Extract Mannitol Agar containing Congo red (YEMA-CR) medium [18, 36, 37]. e rhizobia isolates were tested for determining their Gram reaction type using the KOH method [33, 38]. e isolates were incubated at 28 ± 2°C for 3–5 days to check the presence and absence of growth
Summary
Chickpea (Cicer arietinum L.), a member of the family Leguminosae, is an important pulse crop valued as a rich source of proteins [1] It is a cool-season legume crop that is grown in many countries around the world as a food source [2]. Chickpea is a staple basic food crop in many tropical and subtropical Afro-Asian countries and is one of the world’s major pulse crops which are traditionally cultivated in marginal areas and semiarid regions [4] It ranked the third most important pulse crop [5] with an average yield of 913 kg/ha and a total production of 10.9 million metric tons [6]. About 95% of chickpea cultivation and consumption is in developing countries [8]
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