Colonization of sorghum and wheat by seed inoculation with Gluconacetobacter diazotrophicus

Colonization of sorghum and wheat after seed inoculation with Gluconacetobacter diazotrophicus strains PAL 5 and UAP 5541/pRGS561 (containing the marker gene gusA) was studied by colony counting and microscopic observation of plant tissues. Inoculum levels as low as 102 CFU per seed were enough for root colonization and further spreading in aerial tissues. Rhizoplane colonization was around 7 log CFU g−1 (fresh weight). G. diazotrophicus was found inside sorghum and wheat roots with populations higher than 5 log CFU g−1 (fresh weight). Stem colonization remained stable for 30 days post inoculation with endophyte concentrations from 4 to 5 log CFU g−1 (fresh weight) (in both plants). Population in leaves decreased continuously being undetectable after 17 days post inoculation.