Characterization of New Efficient and Competitive Strains for the Bean (Phaseolus Vulgaris L.) Crop in Brazil
A lack of response to bean inoculation in field experiments performed in Brazil has been frequently reported, but a long term program of selection of strains genetically stable and adapted to environmentally stressing conditions is missing. In the State of Paraná, three strains were identified, PRF 35, PRF 54, and PRF 81, which have shown high rates of N2 fixation, competitiveness, and tolerance to high temperatures under greenhouse conditions. The good performance, especially of PRF 81, was confirmed in several field trials and this strain has then been recommended, since 1996, for the use in Brazilian commercial inoculants. The three strains from Paraná were better characterized trying to define parameters which could help the selection of bean rhizobia. The strains have shown the same Nod factor profile as Rhizobium tropici type IIA CFN 299 and type IIB CIAT 899. The colony morphology, ability to grow in vitro at low pH and high temperatures, and PCR products with Yl-Y2 primers were similar to CIAT 899, but the strains were not able to grow in LB or PY minus Ca media, similarly to CFN 299. The results reported here stimulate the search of new R. tropici strains for tropical and subtropical bean cropping areas.
KeywordsUrea Microbe Oligosaccharide Rhizobium Naringenin
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