Uso da técnica de DGGE para monitorar o estabelecimento de bactérias diazotróficas endofíticas inoculadas em duas variedades de cana-de-açúcar

Abstract

Many inoculation experiments conducted in several countries had shown the benefits of inoculation with endophytic diazotrophic bacteria in sugar cane crop, facing the reduction of chemical inputs and the production increase. The aim of this study was to observe the effect of a standard inoculant containing a mixture of diazotrophic entophytic bacteria (BR 11504, BR 11335, BR 11115, BR 11281, and BR 11366), in two sugarcane varieties (RB867515 and RB72454) cultivated in the Brazilian Northeast region. The monitoring of both the inoculated and the native bacterial population by Denaturating Gradient Gel Electrophoresis technique (DGGE) showed a low establishment of the inoculant, and that it was not possible to detect all of the inoculated bacteria. Variations of the endophytic microbial diversity were observed during the crop cycle, suggesting that the plant controls its endophytic bacterial community. A reduction on the diversity between the experiments was observed, probably because of hydric stress. Bacteria of Herbaspirillum genus were identified with greatest frequency and the number of bands corresponding to unknown bacteria was higher than that of bands corresponding to the bacteria used in the inoculant. Furthermore, the results showed that inoculation with the mixture of bacteria increased up to 7% in the production of stalks of sugar cane varieties RB72454 and RB867515, for the experiment conducted in the city of Itambé Pernambuco State. In contrast, the effect was not observed in the inoculation experiment conducted in the city of Goiana, Pernambuco State, suggesting that the effect on the stems productivity depends of edaphic and climatic factors, among others.