X. Nesme et al., DIFFERENTIAL HOST-PATHOGEN INTERACTIONS AMONG CLONES OF POPLAR AND STRAINS OF XANTHOMONAS-POPULI PV POPULI, Phytopathology, 84(1), 1994, pp. 101-107
To verify the occurrence of physiologic races in Xanthomonas populi pv
. populi, the causal agent of oozing canker of poplar, the virulence o
f 19 strains was compared by inoculating five poplar clones and one wi
llow clone in two sets of tests performed during June and September, r
espectively. Canker severity was measured 2 yr later by determining th
e lengths and the girdling index of cankers. Analysis of variance indi
cated a significant poplar clone-strain interaction and no significant
clone-strain-inoculation date interaction for most strains, using the
two variables. Five putative physiologic races were characterized. Ra
ce 3 was totally avirulent on the clone Italica, although the other ra
ces gave relatively small differences in canker severity. Strains belo
nging to races 1, 2, 3, and 5 were isolated in continental Europe (Bel
gium, France, and the Netherlands), whereas race 4, more virulent to P
opulus trichocarpa clones, was isolated in Britain or close to the Bel
gian coast.