Symbiotic efficiency of Hup+, Huphr and Hup- Bradyrhizobium japonicum and Bradyrhizobium elkanii strains in cowpea cultivars

• Autor(a) principal: Souza, Alessandra Alves de
• Data de Publicação: 1999
• Outros Autores: Burity, Hélio Almeida, Figueiredo, Márcia do Vale Barreto, Silva, Maria Luiza Ribeiro Bastos da, Melotto, Maeli, Tsai, Siu Mui
• Tipo de documento: Artigo
• Idioma: por
• Título da fonte: Pesquisa Agropecuária Brasileira (Online)
• Texto Completo: https://seer.sct.embrapa.br/index.php/pab/article/view/5518
• topic: Hup; hydrogenase; N2 fixation; nodulation; Vigna unguiculata; Hup; hidrogenase; fixação de N2; nodulação; Vigna unguiculata

The effectiveness of Bradyrhizobium strains with characteristics Hup+ (SR and USDA-110), Hup- (29W) and Huphr (SEMIA-587), was evaluated in cowpea (Vigna unguiculata L.), cultivars IPA-202, BR-3 and VITA-4. Results showed that nodulation in VITA-4 was superior, with a positive interaction when inoculated with strains SEMIA-587 and USDA-110. However, when comparing nodule efficiency, the combination IPA-202 x SEMIA-587 presented the highest nitrogenase activity, with a relative efficiency around 1.0. Nitrogenase activities were similar in plants inoculated with the strains SR and SEMIA-587, and higher, with strains USDA-110 and 29W. These results indicate that strains with Hup+ and Huphr were able to achieve higher enzymatic activities. Leghemoglobin (Lb) content detected in strains SR and USDA-110 was positively correlated to nitrogenase activity. However, correlations between Lb and nitrogenase activity were highly variable in nodules containing strain 29W-Hup-, indicating that imbalances in the nitrogenase system in the absence of hydrogenase may affect the flow of Lb to the bacteroids. Significant differences on the plant N content were found among the strains studied, but not among cultivars. Plant inoculated with Hup+ strains were more efficient to accumulate N, indicating that N-fixing systems retaining H2 may accumulate additional N in the host.