Seleção de rizóbios e compatibilidade simbiótica em diferentes variedades de feijão-caupi (Vigna unguiculata (L.) Walp)

Abstract

The cowpea [Vigna unguiculata (L.) Walp] is a autogamous plant that presents cleistogamy, widely cultivated in the North and Northeast regions of Brazil. It’s rusticity and phenotypic plasticity allow it’s cultivation in adverse weather conditions and soil and it is capable of establishing symbiosis with rhizobia, with biological nitrogen fixation (BNF). BNF fixes atmospheric N2 by an enzymatic complex called nitrogenase. Rhizobia strains, to fix nitrogen with plants, depend on factors intrinsic to the bacteria-legume symbiosis process and on environmental factors that affect the survival of the plant. The objective was to evaluate symbiotic compatibility and efficiency of isolates obtained from the soils semi-arid region of Pernambuco and the recommended strain BR 3262, and its symbiotic stability in cultivars BR 17-Gurguéia, IPA 206 and BRS Novaera selected for different regions of Brazil. A greenhouse experiment was conducted with these cultivars, 25 isolates, the recommended strain and uninoculated treatments with and without N. Harvest was 45 days after inoculation and dry matter of shoots, roots and nodules, nodule number, dry weight of nodules by number of nodules, N accumulated in shoots dry matter by nodules, N content in the shoot, N accumulation in the shoots on the recommended efficiency strain based on the accumulation of nitrogen, on the recommended efficiency strain based on dry matter of shoots were determined. The plants of all inoculated treatments nodulated. Sixteen isolates did not differ from BR 3262 nodules dry matter. For dry weight of nodules by number of nodules, 20 isolates did not differ from BR 3262, and 18 isolates were similar to nitrogen accumulated in the shoot dry matter by the nodules. The nitrogen treatment with and without inoculation were among the lowest average for N content in shoot and relative efficiency of N accumulation compared to the inoculated treatments. The strains with improved stability and adaptability to cultivar with high potential for biological nitrogen fixation are G7.85 and BR 3262.