Infection of perennial ryegrass (Lolium perenne L.), Italian ryegrass
(Loliumunultiflorum L.), and timothy (Phleum pratense L.) by Xanthomon
as campestris pv. graminis and Xanthomonas campestris pv. graminis and
Xanthomonas campestris pv. phlei occurred mainly via wounds rather th
an natural openings. Nevertheless, bacteria were detected by isolation
and immunofluorescence in plants sprayed with the pathogen, without p
rior wounding, and in plants in which intact ears had been dipped in i
nocula. High concentrations of bacteria were observed around the stoma
ta of perennial ryegrass and timothy by scanning electron microscopy 4
8 h after inoculation. Perennial ryegrass and Italian ryegrass and ind
ividual plants of ryegrass and timothy differed in susceptibility to t
he pathogens.