Endophytic bacteria in grapevine

Abstract

The nonfastidious, xylem-inhabiting bacteria from a selection of grape cultivars in Nova Scotia have been examined. The size of this population varied with the method of extraction: 2.65 × 10² to 3.46 × 10³/mL xylem sap with vacuum extraction, 3.83 × 10³ to 1.31 × 10⁴/g xylem tissue with homogenization, 3.33 × 10⁴ to 9.89 × 10⁴/mL xylem sap with Acridine Orange direct counts. These figures suggest that many endophytic bacteria may be attached to vessel walls and that the majority are fastidious. There was no significant difference in the number of endophytic bacteria found in two grape varieties, Michurinetz and Marechal Foch. There was a significant difference between vineyards. The frequency distribution followed a log normal model. Seventy-eight percent of isolates were Gram negative, with Pseudomonas and Enterobacter being the predominant genera. Only six strains were identified as potential phytopathogens. A comparison of eight hydrolytic exo–enzymes in a subset of endophytic bacteria to those in a random sample of rhizosphere bacteria revealed that the two populations were distinct and that the former possessed less hydrolytic enzyme capacity than the latter. It therefore seems unlikely that this endophytic population gains entry to the xylem symplastically (intracellularly).Key words: endophytic bacteria, grapevine, xylem-inhabiting.