Influence of inoculation technique on the endophytic colonization of rice by Pantoea sp. isolated from sweet potato and by Enterobacter sp. isolated from sugarcane

Abstract

The colonization abilities of two endophytic diazotrophs, Pantoea sp. strain 18 isolated from sweet potato and Enterobacter sp. strain 35 isolated from sugarcane, in cultivated rice (Oryza sativa cv. Nipponbare) and wild rice (Oryza officinalis) were investigated using two inoculation methods: rhizosphere inoculation and the root dip method. Higher bacterial densities resulted from the root dip method for both strains. Higher bacterial numbers of both strains were detected in cultivated rice than in wild rice. The use of green fluorescent protein-labeled strains indicated that Pantoea sp. 18-2 was able to better colonize and more effectively reduce the acetylene in both hosts compared with Enterobacter sp. 35-1. Specifically, the combination of cultivated rice and Pantoea sp. strain 18-2 gave the best association for colonization and nitrogen fixing. The present study provides evidence that Pantoea sp. strain 18-2 and Enterobacter sp. strain 35-1 can be established in rice plants other than their original hosts, suggesting a lack of host specificity, although the extent of colonization may vary depending on the combination of host and endophyte. © 2008 Japanese Society of Soil Science and Plant Nutrition.