Abstract

Sorghum is an important crop around the World. Burkholderia genus has emerged as an important plant associated bacteria in the last years. However, it is important to understand these processes and how they took place in the environment. In this study, we evaluated the occurrence of Burkholderia species associated with five varieties of sorghum cultivated in different places of Mexico. Burkholderia species were isolated using a selective medium for diazotrophic species and identified using a semi-selective set of primers and clustered by restriction analysis of 16S rRNA sequence. It was found a low geographical distribution of species Burkholderia tropica and Burkholderia vietnamiensis. Due to the low diversity of diazotrophic Burkholderia found, colonization and competition assays were performed in the rhizosphere of sorghum plants. By colonization assays we inoculated populations of 1 × 0⁸ cfu/ml of B. tropica, Burkholderia unamae, Burkholderiasilvatantlica and Burkholderia xenovorans. We showed that all strains could colonize the rhizosphere. In competition assays, B. unamae and B. tropica did not show any antagonistic effect among them, but we showed that both species colonized the rhizosphere with the same number of bacteria in sorghum plants. The present study confirms the low geographic distribution of diazotrophic B. tropica and B. vietnamiensisassociated with sorghum field-grown in México.

Key words: β-rhizobia, Burkholderia, sorghum, nitrogen fixation.