blight on detached leaves. The area of late blight lesions on
treated leaves was lower than control, and higher protective
efficacy was recorded at concentrations of 12 and 6
l
g/L,
providing average disease reduction of 100 and 92.63%,
respectively.
In potted plant tests, 6.0 and 3.0
l
g/L Xcn1 inhibited
blight disease development 7 days after inoculation with
P. infestans
, exhibiting an average reduction in disease of
80.27 and 70.53% compared with control, respectively.
This was slightly lower than that of the chemical fungicide
Metalaxy (Table
4
), indicating that Xcn1 is able to sup-
press lesion expansion and reduce disease severity in
potato leaves.
Previously, we showed that metabolites of
Xenorhabdus
nematophilus
var.
pekingensis
have higher antifungal
activity against species of
Phytophthora
(Yang et al
.
1998
,
2000
,
2002
) and that Xcn1 is the main antibacterial com-
pound (Huang et al.
2005
). This study provides further
evidence of the antibiotic activities of Xcn1 against
P. infestans
in vitro and in vivo. These results indicate the
potential of Xcn1 as a novel fungicide for bio-control of
potato late blight disease.