Ocorrência de bactérias endofíticas associadas a variedades de cana-de-açúcar cultivadas nos estados: Alagoas e Pernambuco

Abstract

The sugar cane is one of the major agricultural products in Brazil. The crop is able to associate with diazotrophic bacteria (fix nitrogen from the air), that may be located inside the plant tissue (entophytic). The diazotrophic bacteria are capable of promoting growth of sugar cane by means of biological nitrogen fixation (BNF) or production of hormones. But little is known about populations of these bacteria present in sugar cane. This work aimed to study diversity of the population and identify the isolates by molecular and physiological methods, as well as to assess the effectiveness of some isolates to promote plant growth of sugar cane in the field. In solid potato media, there were observed the formation of seven groups, with 95% of similarity, showing the great colonies morphology variation. Many isolates showed similar characteristics to the genus Gluconacetobacter, when analyzed in semi-solid LGI-P media and solid Potato-P and LGI-P media. Two isolates were most efficient in the endolar synthesis with production over 49 µg/mL. All isolates were classified as Gram negative. Of the 36 isolates, 27.5% were similar to the standard strain RB 11366 (Burkholderia tropica), 45% to BR 11281 strain (Gluconacetobacter diazotrophicus) and 5% to the other patterns BR 11335 (Herbaspirillum seropedicae), BR 11504 (Herbaspirillum rubrisubalbicans) and BR 11145 (Azospirillum amazonense). Through the comparison of the sequencing of 16S rDNA with the NCBI GenBank isolate 215 was identified as belonging to species Gluconacetobacter diazotrophicus, the 179-1a belonging to Burkholderia tropica and the isolated 151-B, 211-A, and 219 to the gender Burkholderia. The inoculated strains 160-1 and 215 promoted an increase in the straw dry biomass (up to 0.7 Mg ha-1) and total nitrogen of flag leaf (above 69,7 kg ha-1), respectively in the tested varieties RB 72454 and RB 918,639. Only the 160-1 isolate was able to promote increase in biomass in the RB 867515 variety. Stalk yield was higher for the variety RB 918639 with 191.96 Mg ha-1.