Potential biological control of clubroot on canola and crucifer vegetable crops

Abstract

Clubroot caused by Plasmodiophora brassicae is an emerging threat to canola (Brassica napus) production in western Canada, and a serious disease on crucifer vegetable crops in eastern Canada. In this study, seven biological control agents and two fungicides were evaluated as soil drenches or seed treatments for control of clubroot. Under growth cabinet conditions, a soil-drench application of formulated biocontrol agents Bacillus subtilis and Gliocladium catenulatum reduced clubroot severity by more than 80% relative to pathogen-inoculated controls on a highly susceptible canola cultivar. This efficacy was similar to that of the fungicides fluazinam and cyazofamid. Under high disease pressure in greenhouse conditions, the biocontrol agents were less effective than the fungicides. Additionally, all of the treatments delivered as a seed coating were less effective than the soil drench. In field trials conducted in 2009, different treatments consisting of a commercial formulation of B. subtilis, G. catenulatum, fluazinam or cyazofamid were applied as an in-furrow drench at 500 L ha )1 water volume to one susceptible and one resistant cultivar at two sites seeded to canola in Alberta and one site of Chinese cabbage in Ontario. There was no substantial impact on the susceptible canola cultivar, but all of the treatments reduced clubroot on the susceptible cultivar of Chinese cabbage, lowering disease severity by 54-84%. There was a period of 4 weeks without rain after the canola was seeded, which likely contributed to the low treatment efficacy on canola. Under growth cabinet conditions, fluazinam and B. subtilis products became substantially less effective after 2 weeks in a dry soil, but cyazofamid retained its efficacy for at least 4 weeks.

Liming and biofungicide for the control of clubroot in cauliflower1

“…The low efficiency of the biofungicide in the biological control of the disease is not uncommon (Peng et al 2011) and is due to different factors, such as environmental and soil microflora conditions and pathogen spore density and viability, among others, as shown in the present study. The low efficiency of T. harzianum and positive effect of a cyazofamid-based product in the control of clubroot are reported by Peng et al (2011) in canola, although these authors also showed a promising effect of other antagonists such as Bacillus subtilis and Gliocladium catenulatum.…”

“…The biotrophic pathogen P. brassicae is a common soil protozoan (Niwa et al 2008, Peng et al 2011. It has a complex life cycle divided into two phases: in the soil, where it survives in the form of robust resting spores (Dixon 2009), and in plants, infecting the roots and causing cell hyperplasia and hypertrophy with the consequent formation of galls.…”

“…Most studies on clubroot control (Penalber 2009, Peng et al 2011) are based on the reduction of disease intensity without considering other aspects, such as the increase in root volume, especially of healthy roots, or do not evaluate combinations of different forms of control. Thus, this study aimed to evaluate the use of a Trichoderma harzianum-based biofungicide combined with liming in reducing the severity of clubroot in cauliflower and their effects on root and inflorescence attributes under field conditions, as well as the effect of liming combined with the biofungicide and cyazofamid on disease symptoms and progress and on root attributes in cauliflower under greenhouse conditions.…”

Adaptation to Brassica Host Genotypes by a Single-Spore Isolate and Population of Plasmodiophora brassicae (Clubroot)

“…In another study examining the efficacy of seven biological control agents and two fungicides at reducing clubroot severity, two biological control agents. Bacillus subtilis Ehrenberg & Cohn and Gliocladium catenulatum Gilman & Abbott, were found to be as effective as the fungicides fluazinam and cyazofamid under greenhouse conditions (18). Unfortunately, these biological control agents were not effective under field conditions, perhaps due to the relatively dry weather experienced that year (18).…”

Boron reduces development of clubroot in canola

“…No pesticides are registered for clubroot management on canola (Howard et al, 2010). In response, research is being carried out to examine factors that could be part of an integrated and sustainable disease management package for clubroot that includes biological control (Peng et al, 2010), the impact of seeding date (Gossen et al, 2009), soil amendments and bait crops (Ahmed et al, 2011). Optimum management may reduce the development and spread of new pathotypes that can overcome the clubroot-resistant commercial cultivars that have recently been developed, and so could contribute to reducing the threat that clubroot poses to the canola industry in western Canada.…”