Fixação biológica de nitrogênio em genótipos de Pennisetum purpureum Schum

Abstract

Biological nitrogen fixation (BNF) in forage grasses can contribute significant amounts of nitrogen accumulated by the plant. The objective of this study was to evaluate five Pennisetum purpureum Schum. about the potential of BNF and endophytic association of diazotrophs in the root and stem, at two different times, as well as the dry matter yield and plant height of these genotypes due to nitrogen levels. The experiment was established in 2009 at the Experimental Station belonging to Itambé Agronomic Institute of Pernambuco (IPA), adopting the split plot design in randomized blocks with three replications. The main plot was formed by N fertilization levels of 0, 30, 60 and 90 kg ha-1 N per cut, and the subplot with genotypes Mineirão Elephant B, IRI 381, Taiwan A- 146 and ‘Pioneiro’. The effect of nitrogen fertilization on production aspects and plant height, and in plots with zero fertilizer level, BNF has been reported in four cycles of review. The occurrence of endophytic bacteria associated with the roots and stems of genotypes Elephant B, Venezuela and ‘Pioneiro’, were evaluated in dry and rainy seasons. Genotypes Taiwan A-146, Elephant B and IRI 381 were the most promising in the BNF, with contributions of up to 57.2 , 58.0 and 61.9 % of the total N accumulated in shoots. The presence of diazotrophs associated with roots of ‘Pioneiro’ was higher in the dry season. The cultivar Venezuela had the highest density of endophytes in the stem. There was no effect of nitrogen fertilization for the production of MS, with genotypes Taiwan A- 146, Elephant B and IRI 381 the most productive, with 870, 1208 and 899 g m-2 per cut DM. For height effect of nitrogen fertilization on the Pioneer and legume genotypes showed linear and quadratic effects, respectively was observed. The elephant grass genotypes studied are potentially fixers N. The occurrence of endophytic bacteria associated with elephant grass genotypes is influenced by tissue colonization and season, being necessary that these isolates were genetically characterized and evaluated for their potential to FBN.