Ia. Khmel et al., BIOLOGICAL-CONTROL OF CROWN GALL IN GRAPEVINE AND RASPBERRY BY 2 PSEUDOMONAS SPP. WITH A WIDE SPECTRUM OF ANTAGONISTIC ACTIVITY, Biocontrol science and technology, 8(1), 1998, pp. 45-57
Pseudomonas aureofaciens B-4117 and P. fluorescens CR330D inhibited th
e growth of a wide range of plant pathogens, including Agrobacterium t
umefaciens, when tested on agar media. In a series of nursery-based tr
ials with natural pathogen inoculum, application of either B-4117 or C
R330D significantly reduced the incidence and severity of crown gall c
aused by A. tumefaciens on grapeville and raspberry. The extent of dis
ease control depended upon the variety tested. Both bacteria reduced d
isease during seedling root production and grafting. The disease incid
ence on root cuttings of three grapevine varieties was reduced by 56-8
0% and the disease severity index (DSI) was decreased by 75-86%. Depen
ding on the scion variety, the number of healthy rooted grafts increas
ed by 2-3.5-fold, while the DSI was reduced by 1.5-3-fold. The results
suggest that there is potential in using these antagonists to diminis
h the influence of latent rootstock infection on graft sensitivity to
crown gall. Pretreatment of rooted raspberry seedlings with P. aureofa
ciens B-4117 prevented the development of crown galls caused by A. tum
efaciens strain K24 or by a mixture of A. tumefaciens pathogenic strai
ns previously isolated from raspberry. Both Pseudomonas spp. persisted
on the root surfaces of inoculated vine cuttings and in non-sterile s
oil. The advantages of using the antagonistic bacteria as biocontrol a
gents of crown gall are discussed.