A study of molecular variation among Botrytis spp., the causal pathogen of scape and umbel blights of onion, as well as the biocontrol of the virulent pathogen using Bacillus subtilis PHYS7 under greenhouse conditions was carried out. Twenty-three isolates of Botrytis spp. were recovered from onion plants showing umbel blight symptoms. They were able to infect onion plants with varied severity. All Botrytis spp. produced cellulases; however, almost all of them produced pectinase. The highest activities of cellulases and pectinase were achieved by B. allii PHYOA1; however, B. cinerea PHYOC3 showed a high activity of cellulases but it failed to produce pectinase. The genetic variability among the pathogens was assessed by random amplified polymorphic DNA (RAPD) markers, using 5 random 10-mer primers: OPA03, OPA05, OPA06, OPI09, and OPW15. The results showed that 50 DNA bands ranging from 100 bp (OPA03) to 1600 bp (OPA05) were generated by the 5 primers that differentiated 9 isolates of Botrytis spp. The dual culture test showed that Bacillus subtilis PHYS77 and PHYS78 had a high antagonistic potentiality against the pathogen and involved in 60–62% reduction in its growth. Application of Ridomil Gold MZ and Bacillus subtilis PHYS77 on onion plants, 2 days after or before infection with the pathogen, significantly reduced the disease severity than the control. The study approved the molecular tool as a reliable and quick method to differentiate among the virulent and non-virulent strains of Botrytis spp. The application of B. subtilis PHYS77 as an effective biocontrol agent in the management of the onion blight disease can be recommended.

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Molecular disparities among Botrytis species involved in onion umbel blight disease and its management using Bacillus subtilis PHYS7

The increased dependence of farmers on chemical fertilizers poses a risk to soil fertility and ecosystem stability. Plant growth‐promoting rhizobacteria (PGPR) are at the forefront of sustainable agriculture, providing multiple benefits for the enhancement of crop production and soil health. Bacillus subtilis is a common PGPR in soil that plays a key role in conferring biotic and abiotic stress tolerance to plants by induced systemic resistance (ISR), biofilm formation and lipopeptide production. As a part of bioremediating technologies, Bacillus spp. can purify metal contaminated soil. It acts as a potent denitrifying agent in agroecosystems while improving the carbon sequestration process when applied in a regulated concentration. Although it harbours several antibiotic resistance genes (ARGs), it can reduce the horizontal transfer of ARGs during manure composting by modifying the genetic makeup of existing microbiota. In some instances, it affects the beneficial microbes of the rhizosphere. External inoculation of B. subtilis has both positive and negative impacts on the endophytic and semi‐synthetic microbial community. Soil texture, type, pH and bacterial concentration play a crucial role in the regulation of all these processes. Soil amendments and microbial consortia of Bacillus produced by microbial engineering could be used to lessen the negative effect on soil microbial diversity. The complex plant–microbe interactions could be decoded using transcriptomics, proteomics, metabolomics and epigenomics strategies which would be beneficial for both crop productivity and the well‐being of soil microbiota. Bacillus subtilis has more positive attributes similar to the character of Dr. Jekyll and some negative attributes on plant growth, soil health and the environment akin to the character of Mr. Hyde.

Bacillus subtilis impact on plant growth, soil health and environment: Dr. Jekyll and Mr. Hyde

Cultivation of cannabis plants (Cannabis sativa L., marijuana) has taken place worldwide for centuries. In Canada, legalization of cannabis in October 2018 for the medicinal and recreational markets has spurned interest in large-scale growing. This increased production has seen a rise in the incidence and severity of plant pathogens, causing a range of previously unreported diseases. The objective of this review is to highlight the important diseases currently affecting the cannabis and hemp industries in North America and to discuss various mitigation strategies. Progress in molecular diagnostics for pathogen identification and determining inoculum sources and methods of pathogen spread have provided useful insights. Sustainable disease management approaches include establishing clean planting stock, modifying environmental conditions to reduce pathogen development, implementing sanitation measures, and applying fungal and bacterial biological control agents. Fungicides are not currently registered for use and hence there are no published data on their efficacy. The greatest challenge remains in reducing microbial loads (colony-forming units) on harvested inflorescences (buds). Contaminating microbes may be introduced during the cultivation and postharvest phases, or constitute resident endophytes. Failure to achieve a minimum threshold of microbes deemed to be safe for utilization of cannabis products can arise from conventional and organic cultivation methods, or following applications of beneficial biocontrol agents. The current regulatory process for approval of cannabis products presents a challenge to producers utilizing biological control agents for disease management. © 2021 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

https://onlinelibrary.wiley.com/doi/pdf/10.1002/ps.6307

Emerging Diseases of Cannabis sativa and Sustainable Management.

Simple Summary Microbial bio-stimulants are attracting increasing attention in agricultural research. In particular, plant growth-promoting rhizobacteria (PGPR) have great potential to improve crops’ productivity and tolerance of biotic and abiotic stresses. It is anticipated that PGPR could eventually replace synthetic fungicides in agriculture. This research evaluated Pseudomonas aeruginosa strain FG106—which was isolated from tomato plants– as a potential biocontrol agent against several plant pathogens. This strain displayed multiple plant growth-promoting attributes and high in vitro and in vivo inhibition of growth and pathogenicity of tested phytopathogens. It is thus a multifunctional PGPR with potential applications as a biocontrol agent to control fungal and bacterial pathogens. Abstract P. aeruginosa strain FG106 was isolated from the rhizosphere of tomato plants and identified through morphological analysis, 16S rRNA gene sequencing, and whole-genome sequencing. In vitro and in vivo experiments demonstrated that this strain could control several pathogens on tomato, potato, taro, and strawberry. Volatile and non-volatile metabolites produced by the strain are known to adversely affect the tested pathogens. FG106 showed clear antagonism against Alternaria alternata, Botrytis cinerea, Clavibacter michiganensis subsp. michiganensis, Phytophthora colocasiae, P. infestans, Rhizoctonia solani, and Xanthomonas euvesicatoria pv. perforans. FG106 produced proteases and lipases while also inducing high phosphate solubilization, producing siderophores, ammonia, indole acetic acid (IAA), and hydrogen cyanide (HCN) and forming biofilms that promote plant growth and facilitate biocontrol. Genome mining approaches showed that this strain harbors genes related to biocontrol and growth promotion. These results suggest that this bacterial strain provides good protection against pathogens of several agriculturally important plants via direct and indirect modes of action and could thus be a valuable bio-control agent.

/pdf/plant-growth-promoting-activity-of-pseudomonas-aeruginosa-3p06isb2.pdf

Plant Growth-Promoting Activity of Pseudomonas aeruginosa FG106 and Its Ability to Act as a Biocontrol Agent against Potato, Tomato and Taro Pathogens

Powdery mildew on cannabis (Cannabis sativa L., marijuana), caused by Golovinomyces cichoracearum, reduces plant growth and overall quality. To investigate disease management options, biological, c...

https://www.tandfonline.com/doi/pdf/10.1080/07060661.2020.1836026

Evaluation of disease management approaches for powdery mildew on Cannabis sativa L. (marijuana) plants

Efficacy of Bacillus subtilis strain QST 713 (Rhapsody) against four major diseases of greenhouse cucumbers

Bacillus subtilis is a potential biocontrol agent for management of fungal diseases on greenhouse crops. Colonization of plant roots by B. subtilis enhances growth and reduces disease incidence and severity to minimize yield losses and improve quality. The mechanisms through which B. subtilis may contribute to control of fungal diseases include competition with other microbes, production of inhibitory chemicals, and induction of plant resistance. Specific strains of B. subtilis exhibit strong antagonistic activity against mycelial growth of different fungal pathogens through antibiotic production. The effectiveness of B. subtilis strain QST 713 against several important diseases of cucumber and tomato grown under greenhouse conditions was assessed. The major diseases on cucumber are Pythium crown and root rot (Pythium aphanidermatum), Fusarium root and stem rot (Fusarium oxysporum f. sp. radicis-cucumerinum), gummy stem blight (Didymella bryoniae, anamorph Phoma cucurbitacearum), and powdery mildew (Podosphaera xanthii). On greenhouse tomatoes, the most important diseases are gray mold (Botrytis cinerea), Pythium damping-off (Pythium aphanidermatum), Fusarium wilt (Fusarium oxysporum), and powdery mildew (Oidium neolycopersici). Applications of B. subtilis made on cucumber and tomato plants before or after the onset of pathogen inoculation demonstrated efficacy against various diseases. The potential for broad-spectrum activity against different pathogens on these crops is demonstrated.

Management of Fungal Diseases on Cucumber (Cucumis sativus L.) and Tomato (Solanum lycopersicum L.) Crops in Greenhouses Using Bacillus subtilis

Sclerotinia stem rot (Sclerotinia sclerotiorum Lib. De Bary) is one of the most destructive fungal diseases on canola (Brassica napus L.). The effect of a foliar fertilizer containing 3% boron (Active Flower™ [AF]) in reducing disease severity was evaluated. AF at 0.1, 0.3 and 0.5 ml/100 ml was first tested for growth inhibition of S. sclerotiorum in potato dextrose broth. Growth was reduced at 0.5 ml/100 ml by around 90%. Boric acid (BA), an important component of AF, was tested against fungal growth at 10 ml/L, and no significant effect (p = .05) was found. Foliar applications of AF and AF formulation that did not contain boron at 0.1, 0.3 and 0.5 ml/100 ml were made weekly to canola ‘Westar’ grown under greenhouse conditions. Treatments were also made with BA at 10 ml/L to canola plants. After four applications, AF at 0.5 ml/100 ml and BA at 10 ml/L enhanced boron levels in leaves by fivefold and threefold, respectively, compared with the control. Lesion size of S. sclerotiorum on detached leaves was significantly (p < .05) reduced by AF at 0.5 ml/100 ml, but lesion size was not reduced on AFWB‐treated leaves. Experiments were repeated twice with the same results. Levels of phenolic compounds in leaves treated with 0.5 ml/100 ml AF were enhanced by twofold compared with the control. There were no significant differences in lignin, peroxidase (POD) or polyphenoloxidase (PPO) between the control and AF treatments. These results suggest that enhanced boron levels in canola leaves were associated with a suppressive effect on disease due to S. sclerotiorum.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/jph.12865

Effects of a foliar fertilizer containing boron on the development of Sclerotinia stem rot (Sclerotinia sclerotiorum) on canola (Brassica napus L.) leaves

Bud rot pathogens cause diseases on Cannabis sativa L. (cannabis, hemp) worldwide through pre- and post-harvest infections of the inflorescence. Seven indoor or outdoor cannabis production sites an...

The bud rot pathogens infecting cannabis (Cannabis sativa L., marijuana) inflorescences: symptomology, species identification, pathogenicity and biological control

Powdery mildew, caused by Podosphaera xanthii (U. Braun & Shishkoff), is a widespread disease on greenhouse cucumber in many countries, including Canada. The efficacy of seven biological or chemica...

Li Ni

Papers

Efficacy of Bacillus subtilis strain QST 713 (Rhapsody) against four major diseases of greenhouse cucumbers

Management of Fungal Diseases on Cucumber (Cucumis sativus L.) and Tomato (Solanum lycopersicum L.) Crops in Greenhouses Using Bacillus subtilis

Effects of a foliar fertilizer containing boron on the development of Sclerotinia stem rot (Sclerotinia sclerotiorum) on canola (Brassica napus L.) leaves

The bud rot pathogens infecting cannabis (Cannabis sativa L., marijuana) inflorescences: symptomology, species identification, pathogenicity and biological control

Management of powdery mildew on greenhouse cucumber (Cucumis sativus L.) plants using biological and chemical approaches