Variability of Xanthomonas Campestris pv. vasculorum From Sugarcane and Other Gramineae in Reunion Island. Characterization of a Different Xanthomonad

Abstract

Strai ns presumed to be of Xanthomonas campestris pv. vascu lomm (Cobb.) Dye, obtained from sugarcane and other gramineae in Reunio n Island, were compared in terms of cultural aspects, pathoge ni c and ph ys iological reactions, fatty acid profiles and restriction fragment length polymorphism (RFLP) of genomi c DNA. The strains could be divided into two sepa rate groups (G I and G2). The G l stra.ins were id entical to strains described as X. campestris pv. vasmlorum; they showed an important varia bility in their cultural characteristi cs and in their aggressiveness. The G2 strains did not induce the usual symptoms of gumming disease on sugarcane cultiva rs infected under natural conditi ons or inocul ated in the gree nhouse. The G2 strains grew faster on agar medi um, their colonies were more pigmented and less fluidal and had a different morphology on agar slant. Unlike the G I strai ns, G2 strains hydrolyzed sta rch weakly and casei n strongly; they utilized L-fucose and, to a lesser extent, melibioze. The fatty aci d and genomi c DNA profiles differed between the groups. Differences seemed large enough to support separation of Gl and G2 strains into distinct taxonomic entities, namely G l as Xanthomonas campestris pv. vascttlorum and G2 as a different pathovar of X. campestris. The taxono mi c position of G2 strains is discussed.