Gs. Raupach et al., INDUCED SYSTEMIC RESISTANCE IN CUCUMBER AND TOMATO AGAINST CUCUMBER MOSAIC CUCUMOVIRUS USING PLANT GROWTH-PROMOTING RHIZOBACTERIA (PGPR), Plant disease, 80(8), 1996, pp. 891-894
Plant growth-promoting rhizobacteria (PGPR) strains 89B-27 (Pseudomona
s fluorescens) and 90-166 (Serratia marcescens), which previously demo
nstrated induced systemic resistance in cucumber against some fungal a
nd bacterial diseases, were tested for their capacity to protect Cucum
is sativus L. cv. Straight 8 from disease development of cucumber mosa
ic cucumovirus (CMV). Seed treatment with both PGPR strains significan
tly and consistently reduced mean numbers of symptomatic plants when C
MV was inoculated onto cotyledons. Plants treated with PGPR did not de
velop initial symptoms 14 days after CMV inoculation and remained symp
tomless throughout the experimental period. In a comprehensive study w
ith cucumber, no viral antigen could be detected by enzyme-linked immu
nosorbent assay (ELISA) in any asymptomatic PGPR-treated plants; where
as CMV was evident in every leaf of symptomatic plants. The same two P
GPR strains were evaluated for effects on CMV symptom development in t
omato in three experiments by measuring the disease severity at six ob
servation dates. In all experiments, the area under the disease progre
ss curve (AUDPC) was significantly lower with strain 89B-27 than in th
e nonbacterized control. The AUDPC with strain 90-166 was also signifi
cantly lower than with strain 89B-27. These results suggest that PGPR
should be further evaluated for their potential to contribute toward m
anagement of viral plant diseases.