Usefulness of nonhost plants in managing Plasmodiophora brassicae

Abstract

Germination of resting spores of Plasmodiophora brassicae , causal agent of clubroot in crucifers, may be stimulated by certain nonhost plants. Without a host plant to infect, such germination would lead to a reduced persistence of resting spores in the soil. The effect of four nonhost plants on P. brassicae was investigated in a 3-year field experiment and a 14-month glasshouse experiment. Three of the plant species used, leek ( Allium porrum ), winter rye ( Secale cereale ) and perennial ryegrass ( Lolium perenne ), have been reported to stimulate resting spore germination, while the fourth, red clover ( Trifolium pratense ), does not. In the field experiment, none of the plant species reduced the concentration of P. brassicae in soils when tested with bioassay plants (Chinese cabbage, Brassica rapa var. pekinensis ). In the glasshouse experiment, there was a lower disease level in all plant treatments compared with the plant-free control following incorporation and decomposition of plant roots. At this time, pH in the soils with plant treatments was higher than that in the control soil. There were no indications of a species-specific interaction between any of the nonhost plants investigated and P. brassicae , and it cannot be concluded that any of them would be useful in the sanitation of P. brassicae -infested soils within short time periods.

A comparison of clubroot development and management on canola and Brassica vegetables

“…A crop that stimulates germination of resting spores of P. brassicae was grown as a bait crop to stimulate resting spore germination, and then ploughed down before the pathogen completed its life cycle, thus reducing the inoculum load in the field. However, the results of empirical studies to assess the efficacy of this approach were inconsistent (Friberg et al, 2006). Use of bait crops to stimulate germination of resting spores did not reduce clubroot incidence or severity in northern Europe (Friberg et al, 2005(Friberg et al, , 2006, but a 5-year fallow period resulted in a substantial decrease in resting spore populations compared with continuous cultivation of a clubroot-resistant Japanese radish (Raphanus sativus var.…”

“…Resting spore germination is stimulated by proximity to the roots of both host and non-host plants (Friberg et al, 2006). This appears to be a general response to root exudates, because the root exudates of several non-hosts such as perennial ryegrass, leeks (Allium ampeloprasum var.…”

“…This appears to be a general response to root exudates, because the root exudates of several non-hosts such as perennial ryegrass, leeks (Allium ampeloprasum var. porrum (L.) Gay), rye (Secale cereale L.) and Downloaded by [Harvard College] at 06:07 18 September 2013 red clover (Trifolium pratense L.) induced resting spore germination (Friberg et al, 2006). Root hair infection has been reported in a wide range of plant species, including common velvet-grass (Holcus lanatus L.), perennial ryegrass (Lolium perenne L.) and Indian cress (Tropaeolum majus L.) (Webb, 1949;MacFarlane, 1952).…”

“…Inducing resting spore germination in the absence of host plants was assessed as a management technique to accelerate reduction in resting spore populations (Friberg et al, 2006). A crop that stimulates germination of resting spores of P. brassicae was grown as a bait crop to stimulate resting spore germination, and then ploughed down before the pathogen completed its life cycle, thus reducing the inoculum load in the field.…”

Cultural Practices Influencing Biological Management of Crop Diseases

“…In the glasshouse experiment, there was a reduction in disease incidence in all plant treatments, compared with plant-free controls, following incorporation and decomposition of plant roots. The results indicated that use of nonhost plant species for reducing club root disease incidence would not be an effective approach (Friberg et al 2006 ) . On the other hand, intercropping fi eld vegetables with other crops has been shown to have potential to be used as alternative to the application of chemicals for reducing the disease incidence.…”