Caracterização cultural e fisiológica de estirpes de rizóbios oriundas da Região de Baixo Acaraú no Ceará

Abstract

Nitrogen availability is a limiting factor for plant production systems, bacteria that fix nitrogen, play an important role in this type of production, reducing costs, environmental impacts and increase productivity. The objective of this work was to isolate, characterize, test the salinity levels and evaluate the tolerance to extreme pH (pH 4 and pH 10) at elevated temperatures of rhizobia from the Acaraú region in Ceará. Out of the 19 strains, just one turn the medium pH to alkaline and 18 maintained the medium pH at neutral. All presented slow growth and mucus with butyric consistency. According with colony diameter evaluation, one is punctiform, fifteen have a diameter less than 1 mm and three have a diameter greater than 1 mm. None of the strains were able to tolerate pH 4, growing at pH 10 only. In the temperature test 18 strains were grown at 45 ° C and in salinity test 8 were grown at 10gL-1 NaCl concentration.The did not show significant variations in the cultural characteristics, however there were variations in the resistance to high temperatures and tolerance to different levels of salinity.