Boxwood blight: an ongoing threat to ornamental and native boxwood

LeBlanc, Nicholas; Salgado‐Salazar, Catalina; Crouch, Jo Anne

doi:10.1007/s00253-018-8936-2

Cited by 48 publications

(43 citation statements)

References 62 publications

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“…boxwood), Pachysandra and Sarcococca . Among these genera, this disease is of greatest concern for the production of ornamental boxwood in Europe and the USA as well as the health of non‐cultivated boxwood found as predominant flora growing in native ecosystems bordering Asia and Europe (reviewed in LeBlanc et al ., ).…”

Section: Introductionmentioning

confidence: 97%

Limited genetic diversity across pathogen populations responsible for the global emergence of boxwood blight identified using SSRs

LeBlanc

Gehesquière²,

Salgado‐Salazar

et al. 2019

Plant Pathology

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Boxwood blight is an emerging disease of ornamental as well as native boxwood. The disease became widely established in Europe at the beginning of the 21st century, prior to its more recent discovery in North America and Asia. Two sister‐species of fungi cause the disease, Calonectria pseudonaviculata (Cps) and C. henricotiae (Che). Prior efforts to quantify intraspecific genetic polymorphisms of Cps and Che have yielded little information, limiting the ability to understand the evolution and migration of these pathogens. This study describes the development and implementation of simple sequence repeat (SSR) markers to analyse genetic diversity from a global collection of Cps and Che isolates, representing major blight outbreaks since the disease was first identified in the UK in the late 1990s. Analysis of the Cps CB002 genome sequence identified 180 single copy SSR loci using stringent search criteria, 11 of which were polymorphic and used to screen a global sample of 306 isolates. Fourteen multilocus genotypes of Cps and two multilocus genotypes of Che were identified. Twelve of the 14 Cps genotypes differed from each other by a single allele. The most common Cps genotype was found on all continents where boxwood blight is confirmed. Based on measurement of linkage disequilibrium, Cps showed no evidence of sexual recombination. Further in silico analysis identified 1594 SSRs using relaxed SSR definition criteria. Comparison of these SSR‐containing loci with Cps and Che genome sequences representing three different genotypes demonstrated that single nucleotide polymorphisms might serve as informative genetic markers for future studies.

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Section: Introductionmentioning

confidence: 97%

Limited genetic diversity across pathogen populations responsible for the global emergence of boxwood blight identified using SSRs

LeBlanc

Gehesquière²,

Salgado‐Salazar

et al. 2019

Plant Pathology

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“…Boxwood blight is a deadly disease of boxwood caused by Cps (Daughtrey, 2019;LeBlanc, Salgado-Salazar & Crouch, 2018). Leaves inoculated with the pathogen can develop blight symptoms within 72 h (Kong & Hong, 2018).…”

Section: Introductionmentioning

confidence: 99%

EndophyticBurkholderiasp. SSG as a potential biofertilizer promoting boxwood growth

Kong

Hong

2020

PeerJ

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Background Burkholderia sp. SSG is a bacterial endophyte isolated from boxwood leaves showing a resistant response to infection by the boxwood blight pathogen Calonectria pseudonaviculata. SSG acted as a protective and curative biocontrol agent for boxwood blight and as a bio-sanitizer of disease inoculum in the field. Many gene clusters involved in antibiotic production and plant growth promotion (PGP) were found in the genome, giving this endophyte great application potential as a treatment for plant protection. However, the PGP features have not been documented. This study investigated the plant growth promotion activity of SSG in boxwood. Methods To determine whether SSG is a plant growth promoting bacterium, four PGP traits, auxin and siderophore production, nitrogen fixation and phosphate solubilization, were examined in the laboratory with colorimetric or agar plate assays. The plant growth promoting activity of SSG was tested on three boxwood varieties characterized by slow, intermediate and fast growth rates, namely Justin Brouwers, Buddy and Winter Gem, respectively. These plants were drenched with an SSG cell suspension or water and washed plant weight was compared before and after treatment to determine growth changes after 10 months. Results The SSG culture was sustainable on nitrogen free media, suggesting that SSG may fix atmospheric nitrogen. It was also a strong phosphate solubilizer and a potent siderophore and indole-3-acetic acid (IAA) producer. Significant growth promotion was observed on boxwood cultivars Justin Brouwers, Buddy and Winter Gem 10 months after plant roots were drenched with SSG cells. The growth rate of treated plants was 76.1, 58.3, and 37.3% higher than that of the control, respectively. The degree of growth promotion was significantly different among plant varieties, notably more pronounced with the slow and intermediate growers. This study demonstrates that the SSG bacterium has multiple PGP traits and is a prospective plant biofertilizer.

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“…Hill). The pathogen appears to be clonal with limited genetic diversity within its known range (LeBlanc et al 2018). The disease was first identified in the USA in 2011 (Ivors et al 2012) and resulted in very significant losses in the ornamental nursery industry due to direct losses of plants due to disease, the removal of potentially infected plant debris, destruction of exposed plants and the subsequent costs associated with changes in plant production to prevent re-introduction of the pathogen (AmericanHort 2017).…”

Section: Introductionmentioning

confidence: 99%

Curative Fungicide Activity Against Calonectria pseudonaviculata, the Boxwood Blight Pathogen1

LaMondia¹

2020

Journal of Environmental Horticulture

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Azoxystrobin, azoxystrobin plus benzovindiflupyr, kresoxim-methyl, propiconazole, pyraclostrobin, pyraclostrobin plus fluxapyroxad, tebuconazole, tetraconazole, thiophanate-methyl, and triflumizole fungicides were evaluated for curative and anti-sporulant activity against boxwood blight caused by Calonectria pseudonaviculata on detached leaves and whole boxwood plants (Buxus spp.). Pretreating detached leaves with 30 or 300 ppm a.i. 24 h prior to inoculation reduced disease compared to the untreated control for all fungicides. Fungicides were also applied 24 to 96 h post-inoculation. Only propiconazole reduced diseased leaf incidence to at least half of the control. When leaves were treated post-infection with 300 ppm propiconazole, tetraconazole, tebuconazole, or triflumizole, the pathogen did not sporulate over 2 wks. Propiconazole also reduced the percent of leaf area diseased; lesions were nearly 80% smaller with 300 ppm applied 48 h after inoculation. ‘True Dwarf' boxwood plants treated with 450 ppm thiophanate-methyl, 120 ppm pyraclostrobin or 150 ppm propiconazole 48 h after inoculation demonstrated that only propiconazole reduced the number of diseased leaves, blight lesions and the frequency of pathogen re-isolation. Experiments with ‘Green Mound' and ‘Green Mountain' boxwood cultivars and additional fungicides applied 48 h after inoculation demonstrated that propiconazole at 300 ppm, pyraclostrobin plus fluxapyroxad (150 ppm each) and azoxystrobin (135 ppm) plus benzovindiflupyr (67.5 ppm) reduced disease. Index words: fungicide management, Buxus, chemical disease management Chemicals used in this study: azoxystrobin (Heritage 50 WG), azoxystrobin plus benzovindiflupyr (Mural 30, 50 WG), kresoxim-methyl (Cygnus 50 WG), propiconazole (ProCon-Z 14.3 L), pyraclostrobin (Insignia 20 WG), pyraclostrobin plus fluxapyroxad (Orkestra Intrinsic 21.26 SC), tebuconazole (Torque 38.7 SC), tetraconazole (Minerva 11.6 SC), thiophanate-methyl (3336 50% WP), triflumizole (Procure 480 SC). Species used in this study: boxwood (Buxus L.), boxwood blight (Calonectria pseudonaviculata (Crous, J.Z. Groenew. & C.F. Hill) L. Lombard, M. J. Wingf. & Crous.

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Boxwood blight: an ongoing threat to ornamental and native boxwood

Cited by 48 publications

References 62 publications

Limited genetic diversity across pathogen populations responsible for the global emergence of boxwood blight identified using SSRs

Limited genetic diversity across pathogen populations responsible for the global emergence of boxwood blight identified using SSRs

EndophyticBurkholderiasp. SSG as a potential biofertilizer promoting boxwood growth

Curative Fungicide Activity Against Calonectria pseudonaviculata, the Boxwood Blight Pathogen1

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