Characterization of nodulation capacity with native rhizobia in germplasm of underutilized forage species of Macroptilium (Benth.) Urb.

In order to generate reliable characterization and selection schemes in germplasm of Macroptilium for biological nitrogen fixation with native rhizobia, we carried out a trial to evaluate the germplasm variability for initial growth, crude protein in shoots and nodulation capacity with native soil of subtropical environment. The trial was carried out under two conditions, substrate with (N+) and without nitrogen added (N-). The growth variables and nitrogen content were analyzed through a nested ANOVA with the factors species (S), accessions nested within species (ANS), nitrogen level (NL) and the corresponding interactions. Because the plants did not nodulate in the N + treatment, a simple one-way ANOVA was performed in the N- treatment to analyze nodulation capacity. Relationships between variables and accessions were examined using principal component analysis. All accessions evaluated formed effective nodules in N- treatment. Accessions showed different initial growth and nitrogen content at different nitrogen levels. There was variability in the symbiotic response and initial growth, and most of the variance was explained by differences between ANS. Nodule number and nodule weight were related to Macroptilium plant dry matter and crude protein in shoots. Our hypotheses were confirmed in this work. In evaluated germplasm we found variability for nodulation capacity. In the other hand, nodulation capacity was related with biological nitrogen fixation (BNF), since the accessions with higher NC showed higher initial growth and higher protein content in shoot.