Biocontrol of clubroot disease: how successful are endophytic fungi and bacteria?

Abstract

The commercial aspect of growing Brassica crops has always been influenced by the worldwide occurrence of the clubroot pathogen, Plasmodiophora brassicae. Clubroot symptoms reduce crop yield dramatically and the resilient protist is hard to eradicate from infested soils. Chemical treatments are not so efficient and their use is allowed only in a few areas of the world, none of them in the EU. The majority of clubroot control is mediated by using resistant crops, but not all species have good or durable resistance sources available, and these can be overcome by evolving or new Plasmodiophora pathotypes. Some commercially available biocontrol agents have been tested and found to reduce clubroot on crops such as rapeseed, cauliflower and Chinese cabbage to some extent. More biocontrol organisms have been isolated and described in recent decades but for many commercial application is still a long way off. In this review we summarize trends for bacterial and fungal endophytes for clubroot biocontrol as well as mechanisms behind the effects reported, such as antibiosis, defense induction or competition for space and nutrients. There are indeed plenty of studies on biocontrol of clubroot but not many have reached a point where the biocontrol agents are ready to be applied at field scale. The potential of endophytic microbes in pest management against clubroot disease is huge.

The potential of PGPR and Trichoderma-based bioproducts and resistant cultivars as tools to manage clubroot disease in cruciferous crops

“…Although the amount of research on biocontrol of P. brassicae –cruciferous is not as vast as in other soil-borne pathosystems, the increasing scientific literature on this area shows the interest and the potential of this method against clubroot ( Auer and Ludwig-Müller, 2023 ). Since some fungicides with demonstrated efficacy to control clubroot are banned in the European Union, and there is interest in developing sustainable clubroot management around the world, further work based on the combination of crop management practices, resistant cultivars, and biological control approaches must be carried out.…”

“…A low number of Trichoderma species have been tested against P. brassicae , and in some works, the species were not reported. From the review by Auer and Ludwig-Müller (2023) , just a few species have been tested, mainly T. harzianum followed by T. virens , T. asperellum , and T. koningiopsis . Moreover, no studies on modes of action by the biocontrol agents against P. brassicae were done, with the exception of that described in Yu et al.…”

“…It is interesting to see, from the work of Auer and Ludwig-Müller (2023) , the high variability of the biocontrol effect by each group of beneficial microorganisms, and even more those cases in which clubroot development was favored under certain biological treatments, including Trichoderma . Moreover, studies that elucidate why the biocontrol agents promote disease are not usual, but those should be executed to further understand the complex biocontrol agent–plant–pathogen interactions.…”

“…However, its use is questionable, since soil treatment with such fungicides can change soil physicochemical properties and alter soil microbial communities ( Liao et al., 2022 ). For instance, promising fungicides such as fluazinam and cyazofamid are banned in the European Union, where farmers must use alternative control measures ( Auer and Ludwig-Müller, 2023 ).…”

Testing Effects of Seed Treatments against Clubroot Disease in Various Oilseed Rape Hybrids

“…A trend can be observed in the isotianil treatments, particularly for experimental year 2. Auer and Ludwig-Müller [35] reviewed the control efficacies of various biocontrol agents against clubroot and found that the majority of studies reported a reduction in clubroot symptoms following treatments with biological control agents (BCA). Interestingly, some studies reported efficacies with more severe symptoms observed after BCA treatment.…”