Symbiotic and Phenotypic Characterization of Rhizobia Nodulating Common Bean (Phaseolus Vulgaris L.) From Eastern Ethiopia
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Date
2007-07
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Addis Ababa University
Abstract
Common bean (Phaseolus vulgaris L.) is the most widely distributed and has the broadest range of
genetic resources. In Ethiopia, the yield of common bean is extremely low mainly due to nitrogen
deficiency and also little information is available regarding diversity of rhizobia nodulating common
bean. Hence, this study initiated to know their phenotypic diversity and maximize the symbiotic
nitrogen fixation with common bean in Eastern Ethiopia in particular, 72 isolates of bean rhizobia were
isolated from three zones, where common bean is commonly cultivated. The efficiency of infectivity
and effectiveness of isolates was examined using the Awash Melka variety. Results revealed that 62
isolates were able to form nodules on the roots of the common bean variety and 10 isolates failed to
nodulate the host. The tested isolates showed two different ranges of growth rates: 61 isolates as fast
growing and isolate NSPVR-62 from Goro Gutu woreda as slow growing. The numerical analysis of
the phenotypic characteristics of 62 isolates formed two major diversity groups based on 75% level of
relative similarity. The phenotypic characterization and the numerical analysis indicated that 57 isolates
as Rhizobium leguminosarum-like or Rhizobium etli-like, 4 isolates as Rhizobium gallicum-like and 1
isolate as Bradyrhizobium-like rhizobia were isolated from Eastern Ethiopia soils nodulating common
bean. On the basis of preliminary screening of symbiotic effectiveness on sand culture from 62 isolates,
89% of them are effective and very effective in terms of symbiotic effectiveness. Based on SDW
yield, strains NSPVR-2 from Eastern Shewa Zone and NSPVR-26, NSPVR-29, and NSPVR-31 from
Western Hararghe Zone were selected to study symbiotic effectiveness on Ayenew and Awash Melka
varieties on Melkassa and Babille soils. From the selected isolates, isolate NSPVR-31 showed different
effectiveness of nitrogen fixation on Awash Melka and Ayenew varieties. While isolate NSPVR-29
showed significantly (p<0.01) higher SDW than uninoculated plants on both Ayenew and Awash Melka
varieties. Therefore, isolate NSPVR-29 could be used as an inoculum on Babille soil on both tested
varieties. Nevertheless, on Melkassa soil on Ayenew and Awash Melka varieties showed that nonstatistical
difference of SDW, plant nitrogen contents, nodule number, and weight among all treatments.
This is due to Melkassa soil has sufficient number of effective rhizobia nodulating common bean.
Isolates NSPVR-8 and NSPVR-11 both from Bost woreda showed TCP solubilizer under preliminary
screening of phosphorus solubilization and effective nitrogen fixers. We conclude that significant
variation exists among rhizobial isolates nodulating common bean in Eastern Ethiopia and can be
possible to select superior rhizobia that is in terms of symbiotic effectiveness, competitiveness ability
and tolerate to adverse conditions.
Key Words/Phrases: Common bean; Rhizobia; Eastern Ethiopia, Phenotypic; Symbiotic effectiveness;
TCP solubilizer.
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Keywords
Common bean; Rhizobia; Eastern Ethiopia, Phenotypic; Symbiotic effectiveness; TCP solubilizer.