Among the progenitors, the Alagoano shows most promising results in components of nodulation and production.Due to the variability of leguminous plants as regards their efficiency in the biological fixation of nitrogen (BFN), the importance of plant breeding to improve nitrogen fixation has been emphasized. The objective of this study was to evaluate the symbiotic efficiency of parents of Brazilian cultivars of the cowpea, and give scientific support to the inclusion of BFN in the breeding program for the cowpea crop in Brazil. The experiment was conducted in Teresina, Piauí. An experimental design of randomized blocks in a 5 x 6 factorial arrangement was used, with three replications, consisting of six sources of N: four strains of diazotrophic bacteria (BR 3267, BR 3299, BR 3262 and INPA 03-11B); one treatment with mineral nitrogen and another with no inoculation and no N, and five cowpea genotypes: four parents (TVu 1190, Pitiúba, CNC 0434 and Alagoano) and one cultivar (BRS Guariba). For the variance analysis SAS software was used, and the averages compared by Tukey test. The parent, Alagoano, stood out from the others in nodulation efficiency, was higher than Pitiúba for nodule dry mass, and differed from TVu 1190 in nitrogen accumulation in the shoots. For nitrogen derived from biological fixation there was a mean variation of from 49.42 to 65.50%. As for production components, the Alagoano excelled in pod weight, pod length and 100 seed weight. It was concluded that the evaluated parents are responsive to BFN, and that there is evidence for specificity between the parents and the strains of rhizobia. Of the parents, the Alagoano presents the most promising results for the components of nodulation and production.
Cowpea-breeding; Plants-inoculation; Plants-nitrogen effect
