Endophytic colonization of sorghum and wheat by seed inoculation with Gluconacetobacter diazotrophicus

MARÍA F. LUNA; MARÍA L. GALAR; JULIETA APREA; MARÍA L. MOLINARI; JOSÉ L. BOIARDI

PLANT AND SOIL

Año: 2008

0032-079X

Colonization patterns of Sorghum caffrorum and Triticum aestevium by the diazotrophic endophytic bacterium Gluconacetobacter diazotrophicus were studied under gnotobiotic conditions. Surface sterilized seeds were inoculated with the strains PAL 5 and UAP 5541/pRGS561 (containing the marker gene gusA) of G. diazotrophicus and endophytic colonization evaluated by colony counting of disrupted tissues and microscopic observation of organ sections. Bacteria were first detected on root surfaces and hair roots and later at lateral root emergence sites. Root tip colonization was observed only in wheat. Inoculated bacteria were observed in the intercellular spaces of sorghum and, apparently, intracellular colonization occurred in wheat plants. Bacteria were not detected on steam or leaves surfaces but they were found on internal shoot tissues. G. diazotrophicus was found inside sorghum and wheat roots with population densities higher than 5 log CFU.g-1 (fresh weight). Significant colonization of aerial parts, particularly steams, was also detected with endophyte concentrations varying from 4 - 5 log CFU.g-1. Key words: Gluconacetobacter diazotrophicus, endophytes, colonization, wheat, sorghum