Evaluation of a novel endophytic Pseudomonas lactis strain for control of boxwood blight1

Abstract Boxwood blight, caused by Calonectria pseudonaviculata (Cps) (Synonyms: Cylindrocladium buxicola, Cylindrocladium pseudonaviculatum), is a devastating disease which affects boxwood (Buxus) in private and public gardens worldwide. SW, an endophyte identified as a strain of Pseudomonas lactis, was isolated along with seven other bacterial strains from symptom-reversed boxwood leaves infected by Cps. SW had the largest population among the 8 isolates. SW inhibited Cps culture growth similar to three other antagonistic isolates but was the strongest suppressor of Cps conidial germination and germling development. When the cell-free supernatant (CFS) from SW liquid cultures was used to treat boxwood plants 48 h prior to inoculation with Cps, it resulted in a 69.4% disease reduction; suggesting involvement of its metabolites in disease suppression. Boxwood blight control efficacy was further evaluated with resuspended SW cell at 108-9 cfu.ml−1 at different treatment lead times. When SW was applied 2 or 10 days before inoculation with Cps, boxwood blight disease decreased by 72% and 67%, respectively. Further extending the lead time to 20 and 30 days, the efficacy was reduced to 26-27%. However, with its features of moderate control efficacy, high population in plant tissue and safety towards humans, SW shows great potential as a biocontrol agent for boxwood blight. Index words: Biocontrol agent, endophyte, plant pretreatment, Calonectria pseudonaviculata suppression. Species used in this study: Bacterium strain SW (Pseudomonas lactis). Plant species: Buxus sempervirens ‘Justin Brouwers'.

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First record of Cydalima perspectalis (Walker, 1859) (Lepidoptera: Crambidae) in Greece

Hellenic Plant Protection Journal ◽

10.1515/hppj-2015-0010 ◽

2015 ◽

Vol 8 (2) ◽

pp. 66-72

Author(s):

I. Strachinis ◽

C. Kazilas ◽

F. Karamaouna ◽

N.E. Papanikolaou ◽

G.K. Partsinevelos ◽

...

Keyword(s):

Urban Environment ◽

First Record ◽

Control Measures ◽

Public Gardens ◽

Buxus Sempervirens ◽

Private And Public ◽

And Control

Summary The study concerns the first records for the presence of the box tree moth Cydalima perspectalis in Greece and subsequent infestations on ornamental box trees in urban environment. Adults of the pest were first spotted in six locations around the country from October 2013 until April 2015, when infestation was also detected (mid April). The pest was found infesting plants of Buxus sempervirens in several private and public gardens and parks in the urban environment of Kifissia, Attica. Possible introduction scenarios, as well as preventive and control measures are discussed.

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A Potent Burkholderia Endophyte against Boxwood Blight Caused by Calonectria pseudonaviculata

Microorganisms ◽

10.3390/microorganisms8020310 ◽

2020 ◽

Vol 8 (2) ◽

pp. 310 ◽

Cited By ~ 4

Author(s):

Ping Kong ◽

Chuanxue Hong

Keyword(s):

Burkholderia Cepacia ◽

Lead Time ◽

Biocontrol Agent ◽

Burkholderia Cepacia Complex ◽

Broth Culture ◽

Great Promise ◽

Bacterial Concentration ◽

Control Efficacy ◽

Landscape Plant ◽

Blight Disease

Calonectria pseudonaviculata (Cps) poses an increasing threat to boxwood, a major nursery crop and iconic landscape plant worldwide. Here, we report on a potent biocontrol agent that produces small sage green (SSG) colonies on potato dextrose agar. SSG is a bacterial strain recovered from Justin Brouwers boxwood leaves with unusual response to Cps inoculation. Water-soaked symptoms developed on leaves 2 days after inoculation then disappeared a few days later. This endophyte affected several major steps of the boxwood blight disease cycle. SSG at 107 cfu/mL lysed all conidia in mixed broth culture. SSG at 108 cfu/mL reduced blight incidence by >98% when applied one day before or 3 h after boxwood were inoculated with Cps. Its control efficacy decreased with decreasing bacterial concentration to 103 cfu/mL and increasing lead time up to 20 days. When applied on diseased leaf litter under boxwood plants, SSG reduced Cps sporulation and consequently mitigated blight incidence by 90%. SSG was identified as a new member of the Burkholderia cepacia complex with distinct characters from known clinical strains. With these protective, curative, and sanitizing properties, this Burkholderia endophyte offers great promise for sustainable blight management at production and in the landscape.

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Inoculation of stigma colonizing microbes to apple stigmas alters microbiome structure and reduces the occurrence of fire blight disease

Phytobiomes Journal ◽

10.1094/pbiomes-04-20-0035-r ◽

2020 ◽

Author(s):

Zhouqi Cui ◽

Regan B. Huntley ◽

Neil Schultes ◽

Blaire Steven ◽

Quan Zeng

Keyword(s):

Fire Blight ◽

Plant Diseases ◽

Disease Suppression ◽

Bacterial Strains ◽

Microbiome Composition ◽

Microbial Inoculation ◽

Short Life Span ◽

Blight Disease ◽

Different Strains

Flowers secrete nutrient rich exudates that support the growth of an assemblage of microorganisms, including both beneficial and pathogenic members, most of which belong to the phylum Proteobacteria. Given the potential role of the microbiome in plant health, manipulating the microbiome to promote growth of beneficial members holds promise in controlling plant diseases. In this study we inoculated four different bacterial strains that were originally isolated from apple stigmas, alone or in mixtures of increasing complexity, onto apple flowers during bloom. We tested if such treatments would influence fire blight occurrence, a disease caused by Erwinia amylovora, and if we could detect a shift in the structure of the microbiome due to the treatments. We show that various inoculations did influence the occurrence of fire blight, although the level of disease suppression was dependent upon specific bacterial strains. Furthermore, treatments using different strains or strain mixtures predominantly resulted in increased representation of the inoculated strains, suggesting that disease suppression was due to an alteration of the stigma microbiome structure. Compared to treatments with single strains, a Pantoea-Pseudomonas strain mixture produced a homogeneous microbiome structure with less inter-flower variability. Findings from this study suggest the microbiome on the flower stigma can be manipulated through microbial inoculation. Due to flowers’ short life span yet important role in plant disease infection, even a shot-term influence on microbiome composition may result in significant decreases in disease susceptibility.

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Synergistic Effect of Combined Application of a New Fungicide Fluopimomide with a Biocontrol Agent Bacillus methylotrophicus TA-1 for Management of Gray Mold in Tomato

Plant Disease ◽

10.1094/pdis-01-19-0143-re ◽

2019 ◽

Vol 103 (8) ◽

pp. 1991-1997 ◽

Cited By ~ 3

Author(s):

Xiaoxue Ji ◽

Jingjing Li ◽

Zhen Meng ◽

Shouan Zhang ◽

Bei Dong ◽

...

Keyword(s):

Field Experiments ◽

Biocontrol Agent ◽

Severe Disease ◽

Combined Treatment ◽

Field Trials ◽

Antimicrobial Activities ◽

Gray Mold ◽

Control Efficacy ◽

Bacillus Methylotrophicus

Gray mold caused by Botrytis cinerea can be a severe disease of tomato infecting leaves and fruits of tomato plants. Chemical control is currently the most effective and reliable method; however, application of fungicides has many drawbacks. The combination of biological control agents with newly developed fungicides may be a practicable method to control B. cinerea. Fluopimomide is a newly developed fungicide with a novel mode of action. Bacillus methylotrophicus TA-1, isolated from rhizosphere soil of tomato, is a bacterial strain with a broad spectrum of antimicrobial activities. Little information is currently available about the effect of fluopimomide and its integrated effect on B. cinerea. Therefore, laboratory, pot, and field experiments were carried out to determine the effects of fluopimomide alone and in combination with B. methylotrophicus TA-1 against gray mold on tomato. The in vitro growth of B. methylotrophicus TA-1 was unaffected by 100 mg liter−1 fluopimomide. Inhibition of B. cinerea mycelial growth was significantly increased under combined treatment of fluopimomide and B. methylotrophicus TA-1. In greenhouse experiments, efficacy against gray mold was significantly greater by an integration of fluopimomide and B. methylotrophicus TA-1 than by either alone; control efficacy of fluopimomide at 50 and 100 g ha−1 in combination with B. methylotrophicus TA-1 at 108 colony-forming units (cfu) ml−1 reached 70.16 and 69.32%, respectively, compared with the untreated control. In both field trials during 2017 and 2018, control efficacy was significantly higher for the combination of fluopimomide at 50 and 100 g ha−1 in combination with B. methylotrophicus TA-1 than for either treatment alone. The results from this study indicated that integration of the new fungicide fluopimomide with the biocontrol agent B. methylotrophicus TA-1 synergistically increased control efficacy of the fungicide against gray mold of tomato.

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Effectiveness of 3 antagonistic bacterial isolates to control Rhizoctonia solani Kühn on lettuce and potato

Canadian Journal of Microbiology ◽

10.1139/w05-002 ◽

2005 ◽

Vol 51 (4) ◽

pp. 345-353 ◽

Cited By ~ 61

Author(s):

Rita Grosch ◽

Franziska Faltin ◽

Jana Lottmann ◽

A Kofoet ◽

Gabriele Berg

Keyword(s):

Rhizoctonia Solani ◽

Pseudomonas Fluorescens ◽

Biological Control Agent ◽

Dry Mass ◽

Control Agent ◽

Disease Suppression ◽

Growth Chamber ◽

Bacterial Strains ◽

Serratia Plymuthica ◽

Suppression Effect

Rhizoctonia solani causes yield losses in numerous economically important European crops. To develop a biocontrol strategy, 3 potato-associated ecto- and endophytically living bacterial strains Pseudomonas fluorescens B1, Pseudomonas fluorescens B2, and Serratia plymuthica B4 were evaluated against R. solani in potato and in lettuce. The disease-suppression effect of the 3 biocontrol agents (BCAs) was tested in a growth chamber and in the field. In growth chamber experiments, all 3 BCAs completely or significantly limited the dry mass (DM) losses on lettuce and the disease severity (DS) caused by R. solani on potato sprouts. Strain B1 showed the highest suppression effect (52% on average) on potato. Under field conditions, the DS on both crops, which were bacterized, decreased significantly, and the biomass losses on lettuce decreased significantly as well. The greatest disease-suppression effect on potato was achieved by strain B1 (37%), followed by B2 (33%) and then B4 (31%), whereas the marketable tuber yield increased up to 12% (B1), 6% (B2), and 17% (B4) compared with the pathogen control at higher disease pressure. Furthermore, in all experiments, B1 proved to be the most effective BCA against R. solani. Therefore, this BCA could be a candidate for developing a commercial product against Rhizoctonia diseases. To our knowledge, this is the first report on the high potential of endophytes to be used as a biological control agent against R. solani under field conditions.Key words: biocontrol, Rhizoctonia solani, field grown lettuce and potato, antagonistic bacteria, endophytes.

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Biological and Application-Oriented Factors Influencing Plant Disease Suppression by Biological Control: A Meta-Analytical Review

Phytopathology ◽

10.1094/phyto-96-1168 ◽

2006 ◽

Vol 96 (11) ◽

pp. 1168-1174 ◽

Cited By ~ 44

Author(s):

P. S. Ojiambo ◽

H. Scherm

Keyword(s):

Biological Control ◽

Effect Size ◽

Untreated Control ◽

Plant Disease ◽

Biocontrol Agent ◽

Disease Suppression ◽

Effect Sizes ◽

Biological Control Agents ◽

Control Effect ◽

Soilborne Diseases

Studies to evaluate the effectiveness of biological control in suppressing plant disease often report inconsistent results, highlighting the need to identify general factors that influence the success or failure of biological control in plant pathology. We conducted a quantitative synthesis of previously published research by applying meta-analysis to determine the overall effectiveness of biocontrol in relation to biological and application-oriented factors. For each of 149 entries (antagonist-disease combinations) from 53 reports published in Biological & Cultural Tests between 2000 and 2005, an effect size was calculated as the difference in disease intensity expressed in standard deviation units between the biocontrol treatment and its corresponding untreated control. Effect sizes ranged from -1.15 (i.e., disease strongly enhanced by application of the biocontrol agent) to 4.83 (strong disease suppression by the antagonist) with an overall weighted mean of 0.62, indicating moderate effectiveness on average. There were no significant (P >0.05) differences in effect sizes between entries from studies carried out in the greenhouse versus the field, between those involving soilborne versus aerial diseases, or among those carried out in conditions of low, medium, or high disease pressure (expressed relative to the disease intensity in the untreated control). However, effect sizes were greater on annual than on perennial crops, regardless of whether the analysis was carried out for all entries (P = 0.0268) or for those involving only soilborne diseases (P = 0.0343). Effect sizes were not significantly different for entries utilizing fungal versus bacterial biocontrol agents or for those targeting fungal versus bacterial pathogens. However, entries that used r-selected biological control agents (i.e., those having short generation times and producing large numbers of short-lived offspring) were more effective than those that applied antagonists that were not r-selected (P = 0.0312). Interestingly, effect sizes for entries that used Bacillus spp. as biological control agents were lower than for those that applied other antagonists (P = 0.0046 for all entries and P = 0.0114 for soilborne diseases). When only aerial diseases were considered, mean effect size was greater for entries that received one or two sprays than for those that received more than eight sprays of the biocontrol agent (P = 0.0002). This counterintuitive result may indicate that investigators often attempt unsuccessfully to compensate for anticipated poor performance in antagonist-disease combinations by making more applications.

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The pink hibiscus mealybug Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae) in Greece

Hellenic Plant Protection Journal ◽

10.1515/hppj-2017-0009 ◽

2017 ◽

Vol 10 (2) ◽

pp. 80-83 ◽

Cited By ~ 1

Author(s):

P.G. Milonas ◽

G.K. Partsinevelos

Keyword(s):

Urban Environment ◽

First Report ◽

Public Gardens ◽

Maconellicoccus Hirsutus ◽

Hibiscus Rosa Sinensis ◽

Pink Hibiscus Mealybug ◽

Private And Public ◽

First Time

SummaryThe invasive pink hibiscus mealybug, Maconellicoccus hirsutus (Green) (Hemiptera: Pseudococcidae), is reported for first time in Greece. Individuals of the mealybug were found infesting Hibiscus rosa-sinensis (Linnaeus) (Malvaceae) in private and public gardens in the urban environment in Rhodes, Dodecanese islands, East Greece. This is the first report of genus Maconellicoccus in Greece.

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Comparison of Two Commercial Recirculated Aquacultural Systems and Their Microbial Potential in Plant Disease Suppression

10.20944/preprints202101.0155.v1 ◽

2021 ◽

Author(s):

Sammar Khalil ◽

Preeti Panda ◽

Farideh Ghadamgahi ◽

AnnaKarin Rosberg ◽

Ramesh R Vetukuri

Keyword(s):

Plant Growth ◽

Fish Species ◽

Plant Pathogens ◽

Extracellular Enzymes ◽

Production Systems ◽

Sampling Site ◽

Disease Suppression ◽

Bacterial Strains ◽

Promising Tool

Aquaponics are food production systems advocated for food security and health. Their sustainability from a nutritional and plant health perspective is, however, a significant challenge. Recirculated aquaculture systems (RAS) form a major part of aquaponic systems but knowledge about their potential to benefit plant growth and suppress their pathogens is limited. The current study tested if the diversity and function of microbial communities in two commercial RAS were specific to the fish species used (Tilapia or Clarias) and sampling site (fish tanks and wastewaters), and whether they confer benefits to plants and have in vitro antagonistic potential towards plant pathogens. Microbial diversity and composition was found to be dependent on fish species and sample site. The Tilapia RAS hosted higher bacterial diversity than the Clarias RAS; but the latter hosted higher fungal diversity. Both Tilapia and Clarias RAS hosted bacterial and fungal communities that promoted plant growth, inhibited plant pathogens and encouraged biodegradation. The production of extracellular enzymes, related to nutrient availability and pathogen control, by bacterial strains isolated from the Tilapia and Clarias systems, makes them a promising tool in aquaponics and in their system design.

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Rice Phyllosphere Actinomycetes as Biocontrol Agent of Bacterial Leaf Blight Disease on Rice

Asian Journal of Plant Pathology ◽

10.3923/ajppaj.2016.1.8 ◽

2015 ◽

Vol 10 (1-2) ◽

pp. 1-8 ◽

Cited By ~ 4

Author(s):

Noor Andryan Ilsan ◽

Abdjad Asih Nawangsih ◽

Aris Tri Wahyudi

Keyword(s):

Biocontrol Agent ◽

Leaf Blight ◽

Bacterial Leaf Blight ◽

Blight Disease

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First Report of Blight on Buxus spp. Caused by Cylindrocladium buxicola in Belgium

Plant Disease ◽

10.1094/pdis.2003.87.12.1539a ◽

2003 ◽

Vol 87 (12) ◽

pp. 1539-1539 ◽

Cited By ~ 17

Author(s):

C. Crepel ◽

S. Inghelbrecht

Keyword(s):

Control Plant ◽

First Record ◽

Leaf Spots ◽

Laboratory Bench ◽

Buxus Sempervirens ◽

Similar Disease ◽

Stems And Leaves ◽

Blight Disease ◽

Stem Lesions ◽

Made In

In the fall of 2000, a new blight disease was observed on Buxus spp. in private gardens in Belgium. Since then, more and similar disease samples from other Belgian sites, nurseries, and several garden centers have been received, indicating that this disease is spreading. Similar observations have been made in the U.K. and France, where the disease is widespread and losses are sometimes dramatic (1). Diseased plants have dark brown-to-black leaf spots and streaky, black stem lesions which lead, in some cases, to complete defoliation. On some infected plants new leaves grew in defoliated areas, hiding the original blight symptoms. Infection was mainly observed on Buxus sempervirens cv. Suffruticosa, but B. sempervirens cv. Latifolia raculata, B. microphylla cv. Compacta, and B. microphylla var. japonica cv. Faulkner were also infected. In the U.K., infections have additionally been reported on varieties of B. sempervirens, B. sinica, and B. microphylla (1). On the basis of observed symptoms and comparison of the symptoms with descriptions by Henricot and Culham (2), we identified that this new form of Buxus blight in Belgium is caused by Cylindrocladium buxicola. Sporulating cultures on potato dextrose agar (PDA) had macroconidiophores with stipe extensions terminating in broadly ellipsoidal vesicles with pointed or papillate apices (6.5 to 11 μm in diameter) and a penicillate arrangement of fertile branches each terminating in two to five phialides. Phialides produced clusters of cylindrical conidia (42 to 68 × 4 to 6 μm) that were rounded at both ends and had a single septum. Pathogenicity of the isolate was demonstrated by inoculation of healthy stems and leaves of four 3-year-old plants of B. sempervirens cv. Suffruticosa. On each plant, agar pieces of 1-week-old cultures grown on PDA were placed on five stems and five leaves that had been wounded with a sterile scalpel, then sealed with Parafilm. As a control, five wounded stems and leaves from another B. sempervirens cv. Suffruticosa plant were inoculated with sterile agar plugs. Inoculated plants were incubated in humid chambers (approximately 95% relative humidity) on the laboratory bench. Two weeks after inoculation, no symptoms were visible on the control plant. The inoculated plants showed symptoms as previously described, and C. buxicola was successfully reisolated from diseased tissue completing Koch's postulates. To our knowledge, this is the first record of C. buxicola on Buxus spp. in Belgium. References: (1) B. Henricot et al. Plant Pathol. 49:805, 2000. (2) B. Henricot and A. Culham. Mycologia 94(6):980, 2002.

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