Morphophysiological diversity of rhizobia nodulating pigeon pea (Cajanus cajan L. Millsp.) growing in Ethiopia

Abstract

Pigeon pea (Cajanus cajan (L.) Millsp.) is an important protein source grown in several tropical and subtropical countries, and is considered a multi-purpose plant that is resistant to the conditions where drought and salinity is a common phenomenon. The aim of this study was to evaluate the diversity of rhizobial isolates obtained from root nodules of pigeon pea plants grown in central and southern Ethiopia. A total of 116 nitrogen-fixing rhizobial strains were isolated. The bacterial isolates were characterized by 91 phenotypic traits including cultural characteristics, intrinsic antibiotic and heavy metal resistance, salt, pH and incubation temperature tolerance, and carbon and nitrogen sources utilization ability. Preliminary symbiotic properties of the isolates were also evaluated. The isolates were compared with seven reference strains of rhizobia by application of the unweighted pair group method with arithmetic means (UPGMA) using NTSYSpc Version 2.1 software program. The dendrogram constructed from cluster analysis of 91 phenotypic traits, grouped them into six clusters and eight un-clustered positions at 80% relative similarity. Cluster I contained 83% of the test isolates that were grouped together with the reference strains Bradyrhizobium japonicum (HAMBI 2314 T ) and Bradyrhizobium elkanii (LMG 6164), suggesting that pigeon pea is commonly nodulated by bradyrhizobia. Results from symbiotic effectiveness test revealed that majority of the isolates were found to be effective. Generally, this investigation demonstrated that rhizobial population nodulating C. cajan on the study area were phenotypically diverse and symbiotically effective. Furthermore, the result indicates the existence of strains in the collection, which can tolerate environmental stresses, thus can be developed into inoculant for pigeon pea inoculation and production in Ethiopia and beyond.

Eco-physiological and physiological characterization of cowpea nodulating native rhizobia isolated from major production areas of Ethiopia

“…Isolates HUCR-3 (South Ari) and HUCR-7 (Humbo, Wolaita) showed the highest tolerance to salt concentration up to 6% NaCl (Table 4). A report by Degefu et al (2018) also indicated that rhizobia isolates collected from southern Ethiopia were able to tolerate the highest salt concentration of 5.5%. This ability can make them highly competitive in colonizing the rhizosphere and fixing nitrogen in salinity affected soils.…”

“…Besides, the isolates can be used as potential inoculants to realize higher yields under a wide range of environmental conditions. A study by Degefu et al (2018) also reported that rhizobial isolates which tolerated a broader range of temperature are often used as inoculant and/or for production of biofertilizer under wider ecological conditions.…”

“…According to Degefu et al (2018), rhizobia selection as inoculant and for biofertilizer production requires isolates with higher tolerance to numerous ecological stresses and their utmost ability to compete for nutrient utilization. In the present study, isolates HUCR-3, HUCR-7, HUCR-11, HUCR-15, and HUCR-25 showed growth on all the provided carbon sources and these isolates have known to use a broader range of carbon sources (Table 5).…”

“…Therefore, these isolates have a better advantage over those having limited utilization of carbon sources. Degefu et al (2018) further delineated that isolates that use a broader range of carbon sources are of paramount importance for the production of inoculum that can be used in soils with different carbon sources.…”

Performance Evaluation of Pigeon Pea (Cajanus cajan L. Millsp.) Variety for Registration in the Lowland Areas of Ethiopia

“…is study focused on providing information on the current prospects of pigeon pea adaptation and production potential in Ethiopia. It is expected to provide information regarding whether the farmers will cultivate more or reduce the land allotted to pigeon pea production [16]. Although there is no systematic scoring and a national database, it is distributed all over the geographies in the North (Wollo), South East (Bale), Southern Region, Western regions, and central parts of Ethiopia, growing in patches and intercropped [17].…”