IDENTIFICATION OF RHIZOSPHERIC AND ENDOPHYTIC DIAZOTROPHIC BACTERIA ASSOCIATED TO Lycopersicon esculentum Mill FROM THE NORTE OF SANTANDER, COLOMBIA

Abstract

Diazotrophic bacteria can stimulate the growth of the tomato (Lycopersicon esculentum Mill.) crop by hormone synthesis, with N fixation and the production of siderophores, or other processes. The predominant diazotrophic bacteria in agroecosystems may be potential biofertilizers. The aim of this study was to quantify and characterize the population of rhizospheric diatrophic bacteria in samples of rhizospheric soil (RS) and endophytic diazotrophic bacteria in root (R) and foliar material (FM) samples, with phenotypical and molecular tests. The study was exploratory and with random sampling, with 18 RS, roots (R) and FM samples of tomato plantations in six farms. The differences in the most probable number (MPN) of diazotrophic bacteria were not significant between the FM and R sampling sites. The mean of the Mfb displayed highly significant differences in Azotobacter sp. and Azospirillum sp. between the RS, R and FM samples, with a higher and lower MPN in RS and FM. This relates with the phenotypical and biochemical characterization of RS, in which 14 isolations were identified as Azotobacter sp., and seven as Azospirillum sp. The genera Burkholderia and Gluconacetobacter showed no significant differences in the number of isolations between RS and R samples, but they did with FM, with the lower cell population. The differences between the farms were not significant in the soil parameters, related to the dissimilarity of the MPN. Molecular characterization helped identify A. chroococcum, A. nigricans, A. vinelandii, A. brasilense, B. glumae and G. azotocaptans/G. johannae in samples of RS; B. glumae, G. azotocaptans/G. johannae in samples of R and G. azotocaptans/G. johannae in FM samples.

Key words: Diazotrophic, endophytic, rhizospheric, Lycopersicon esculentum, North Santander.