COLONIZATION OF SORGHUM BICOLOR (L.) MOENCH BY THE N2-FIXING ENDOPHYTE GLUCONACETOBACTER DIAZOTROPHICUS

Gluconacetobacter diazotrophicus is a N2-fixing endophyte to study biological nitrogen fixation in cereal crops. The objectives of this study were to establish colonization of sorghum with G. diazotrophicus and to evaluate the effects of the environment and sucrose on colonization. Seven sorghum cultivars inoculated with the bacterium were grown under greenhouse and field conditions. In the sweet and grain cultivars, G. diazotrophicus was either detected in the roots, stems and/or leaves. Differences in colonization were observed among the different plant cultivars and plant growth conditions. G. diazotrophicus was detected in a higher proportion of sweet sorghum plants than grain sorghum plants. Bacterial presence was detected in a higher proportion of field-grown plants than greenhouse-grown plants. Strong positive correlations between sucrose concentration and the proportion of plants showing bacterial presence and bacterial population numbers were observed, indicating that colonization is dependent on the sucrose concentration of the plant