Symbiotic and Phenotypic Characterization of Common Bean ( .Phaseolus Vulgaris)- Nodulating Rhizobia from Some Areas of Southern Ethiopia

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Addis Ababa Universty


Eighteen isolates of common bean rhizobium from Konso (GI), Arbaminch (GII), Sodo (GUI), and Zeway- Awassa-Dilla (GIV ) regions in Southern Ethiopia were isolated and characterized by their phenotypic diversity and symbiotic properties on Red Welaita (RW) and Mexican142 (Ml 42). All isolates were infective on either of one or both Phciseolus vulgaris cultivars Red wolaita (RW ) and Mexican 142 (Ml 42) in glasshouse experiment. The cluster analysis grouped the isolates into two major diversity groups based on 80-100% similarity levels (Group I) and 39%-76%, similarity levels (Group II). Group I contained 78% of the isolates with two clusters la and lb with presumed similar characters of Rhizobium legwninosarum/Rhizobium etli group except AUPR10. Isolates such as AUPR8 from Group II displayed creamy colony appearance on Peptone Yeast Extract Agar medium (PY), tolerance to extreme pH, salt, and temperature and inability to utilize dulcitol and utilization of glycine that resembled with characters of Rhizobium tropici. Two isolates, AUPR9 (Group II) and AUPR 10 (Group I), exhibited rough colony appearance on PY that resemble the characteristics of Rhizobium gallicum. There was significant difference in shoot dry, nodule fresh and dry weight on both cultivars (P<0.05). RW accumulated more shoot dry weight than M142 (t=1.24, P<0.05). There was also association between seed color of the cultivar cropped at site of bacterial isolation and isolates performance. In addition to authentication of bean isolates, three tree isolates were included for cross-inoculation to non-host P.vulgaris in that AUPR21 ( Erythrina brucei) was effective on M142. Test on symbiotic properties of the five more effective isolates on RW cultivar on two soils of contrasting pH showed that all of them were equally effective in accumulating high diy matter and nitrogen on Gentameche soil. Kemogerbi soil poorly responded to inoculation by all the isolates. Soil factors such as high sum of cations and cation exchange capacity and low available phosphorus P (5.7 ppm) may have contributed to the difference of the two soils. We conclude that great variation exists among rhizobia spp. nodulating bean cultivars and selection of efficient symbiotic partners appears possible. Key words: Common bean , Rhizobia, Southern Ethiopia, Symbiotic effectiveness.



Common bean, Rhizobia, Southern Ethiopia, Symbiotic effectiveness