scholarly journals Induced Resistance to Blackleg (Leptosphaeria maculans) Disease of Canola (Brassica napus) Caused by a Weakly Virulent Isolate of Leptosphaeria biglobosa

Plant Disease ◽  
2006 ◽  
Vol 90 (8) ◽  
pp. 1059-1064 ◽  
Author(s):  
Y. Chen ◽  
W. G. D. Fernando
Keyword(s):  
Brassica Napus ◽  
Field Experiments ◽  
Leptosphaeria Maculans ◽  
Fungal Species ◽  
Control Treatment ◽  
Water Control ◽  
Pathogenicity Group ◽  
Weakly Virulent ◽  
Leptosphaeria Biglobosa ◽  
Highly Virulent

Blackleg of canola is a disease complex of at least two fungal species: Leptosphaeria maculans and L. biglobosa. Isolates of L. biglobosa typically are weakly virulent or avirulent and are assigned to pathogenicity group 1 (PG-1). Isolates of L. maculans are highly virulent and encompass pathogenicity groups PG-2, PG-3, and PG-4. In greenhouse tests, percent lesion/leaf area (PLLA) on cotyledons of two Brassica napus cultivars, Westar and Invigor 2153, was smaller when L. biglobosa (PG-1) was either pre- or co-inoculated at 0, 12, 24, and 48 h with virulent isolates of L. maculans in PG-2, PG-3, and PG-4. On six-leaf-stage plants of Westar, the PLLA declined significantly compared with the control when the lower leaves were treated with either PG-1 or salicylic acid, then challenged with a PG-2 isolate 24 h later. In addition, the activity of four enzymes (chitinase, β-1,3-glucanase, peroxidase, and phenylalanine ammonia lyase) was greatly enhanced at 48 and 72 h when cotyledons of Westar were inoculated first with PG-1 followed by PG-2 24 h later, compared with a water control treatment. Field experiments conducted in 2003 and 2004 showed decreased blackleg severity in plants inoculated with PG-1 alone or prior to PG-2 compared with plants inoculated with PG-2 alone or prior to PG-1.

The teleomorph of the weakly aggressive segregate ofLeptosphaeriamaculans

2001 ◽  
Vol 79 (4) ◽  
pp. 412-419 ◽  
Author(s):  
R A Shoemaker ◽  
Hortense Brun
Keyword(s):  
New Species ◽  
Brassica Napus ◽  
Helianthus Annuus ◽  
Leptosphaeria Maculans ◽  
Interspecific Crosses ◽  
Phoma Lingam ◽  
Type Specimens ◽  
Brassica Napus L ◽  
Weakly Virulent ◽  
Leptosphaeria Biglobosa

Leptosphaeria biglobosa n.sp. is described for the weakly virulent (or non-aggressive) pathogen causing blackleg of oilseed rape and canola. The new species differs from the aggressive blackleg organism, Leptosphaeria maculans (Desm.) Ces. & De Not. in having a very prominent beak on the ascomata that is greatly enlarged at the apex. Ascomata of both species were produced on canola stems either by inoculation of compatible strains of the Phoma anamorph or by single ascospore isolates at a distance of 1 cm and letting them grow together. Both species exhibit bipolar heterothallism. Interspecific crosses were negative. In a study of type specimens of Leptosphaeria species with 5-septate ascospores infecting Cruciferae, none were found that matched the features of L. biglobosa. Leptosphaeria napi (Fuckel) Saccardo on Brassica napus L., and Leptosphaeria virginica (Cooke & Ellis) Saccardo on Lepidium virginica L., are synonyms of L. maculans. Leptosphaeria submaculans Holm on Sisymbrium, Berteroa, and Erysimum has distinctively enlarged ascospores. Leptosphaeria alliariae (Desm.) Ces. & De Not. on Alliaria officinalis Andrz., has much smaller ascospores. Leptosphaeria lindquistii Frezzi on Helianthus annuus L. of the Asteraceae has ascospores with only one, two, or rarely, three septa but was considered because it too has a Phoma anamorph.Key words: Phoma lingam, B group, ascomata.

scholarly journals First Report on the Presence of Phoma Blackleg Pathogenicity Group 1 (Leptosphaeria biglobosa) on Brassica napus (Canola/Rapeseed) in Iran

Plant Disease ◽  
2007 ◽  
Vol 91 (4) ◽  
pp. 465-465 ◽  
Author(s):  
W. G. D. Fernando ◽  
K. Ghanbarnia ◽  
M. Salati
Keyword(s):  
Brassica Napus ◽  
Relative Humidity ◽  
Rating Scale ◽  
Group Identification ◽  
Northern Iran ◽  
First Report ◽  
Pathogenicity Group ◽  
Weakly Virulent ◽  
Stem Lesions ◽  
Leptosphaeria Biglobosa

Canola/rapeseed (Brassica napus L.) is a new crop in Iran, grown since 1996. In 2006, 180,000 ha were planted. During the same year, leaf and upper stem lesions (3) were observed on cv. Hyola 401 at rosette and flowering stages in the Gorgan Province in northern Iran. Field disease incidence ranged from 1 to 40%. Several isolates from stem lesions were sent to the Department of Plant Science, Blackleg Research Lab, University of Manitoba, Canada from the Agricultural and Natural Resources Research Center of Golestan Province of Iran for pathogenicity group identification. The blackleg pathogen is divided into several pathogenicity groups on the basis of phenotypic interaction (IP) of isolates on differential cvs. Westar, Glacier, and Quinta. Isolates PG2, PG3, PG4, and PGT are highly virulent, but PG1, which recently has been named Leptosphaeria biglobosa (2), is weakly virulent. Colonies of the blackleg pathogen were reisolated from their original medium, potato dextrose agar, and grown onV8 agar medium and incubated under light for 2 weeks. Pure cultures of the pathogen were then characterized by colony morphology, pycnidia, and measurement and microscopic observation of pycnidio-spores. Fungal colonies formed with concentric rings containing pycnidia with pink ooze on V8 agar. Pycnidia were globose and as much as 200 μ 200 μm. They had a prominent beak on the ascomata that was enlarged, cylindrical, central, terete, erect, and 150 to 200 × 100 μm. Pycnidiospores were cylindrical, straight, 4 to 5 × 2 μm, and hyaline (2). To identify the pathogenicity group of the Iranian isolates, pycnidiospores were harvested from single-spore cultures after 14 days of incubation under continuous cool-white fluorescent light (1). One-week-old cotyledons from the differential cvs. Westar, Glacier, and Quinta were inoculated with pycnidiospore suspension concentration of 2 × 107 spores per ml of the four Iranian isolates. Each cotyledon lobe was punctured with forceps and inoculated with a 10-μl droplet of spore suspension. Disease evaluations were made 10 to 14 days after inoculation using a 0 to 9 rating scale. Inoculations were repeated twice with identical results yielding only the PG1 type reaction. To our knowledge, this is the first report of the presence of L. biglobosa (PG1; B-type) on canola in Iran. Differential testing fulfilled Koch's postulates. L. biglobosa seems to be less damaging compared with L. maculans, but severe phoma stem lesion epidemics have been associated with the L. biglobosa in Poland (3). The importance of this weakly virulent pathogen, whenever the relative humidity increases, has been demonstrated in greenhouse conditions (A. El-Hadrami, W. G. D. Fernando, and F. Daayf, unpublished data). Since the relative humidity in northern Iran is high, an epidemic may occur if appropriate management practices are not utilized to minimize inoculum levels. References: (1) W. G. D. Fernando and Y. Chen. Plant Dis. 87:1268, 2003. (2) R. A. Shoemaker and H. Brun. Can. J. Bot. 79:412, 2003. (3) J. S.West et al. Plant Pathol. 48:161, 2001.

Feasibility of boron fertilization for yield, seed quality and B uptake of canola in northeastern Saskatchewan

2003 ◽  
Vol 83 (1) ◽  
pp. 99-108 ◽  
Author(s):  
S. S. Malhi ◽  
M. Raza ◽  
J. J. Schoenau ◽  
A. R. Mermut ◽  
R. Kutcher ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Field Experiments ◽  
Seed Quality ◽  
Leptosphaeria Maculans ◽  
Foliar Spray ◽  
Growth Chamber ◽  
Control Treatment ◽  
Sclerotinia Stem Rot ◽  
Brassica Napus L ◽  
B Uptake

(Brassica napus L . and B. rapa L.) grown on the sandy soils of northeastern Saskatchewan has been observed to exhibit symptoms similar to B deficiency, and soil testing laboratories often recommend B fertilization on these soils. The objective of the present study was to determine if yield, seed quality and diseases of canola are related to different rates, times and methods of B fertilization on some northeastern Saskatchewan soils (Gray Luvisol) expected to be B deficient. Two growth chamber and seven field experiments were conducted in 1997, 1998, 1999 and 2000. In the field experiments, the treatments included application of B fertilizers as broadcast followed by incorporation (1 to 4 kg B ha-1) prior to seeding, seedrow placement at seeding (0.5 to 2 kg B ha-1) and foliar spray at 10–20% bloom stage (0.25 and 0.50 kg B ha-1) plus a zero B control treatment. In the growth chamber experiments, rates of 1 to 3 mg B kg-1 soil were tested. In the field experiments, seed and straw yields tended to increase in very few of the treatments, with significant increases from incorporated B fertilization at one site for seed and at three sites for straw. The protein content in the seed was significantly increased by B fertilization at one site, while oil content in the seed was not influenced by B fertilization in any field experiment. The B fertilization treatments either increased or tended to increase the B concentration and uptake of B in seed and straw in most cases, with significant contrasts for control vs. incorporated B and seedrow B methods of applications in many cases. The increase in B concentration and uptake of B was usually greater in straw than in seed. Among the methods of B application, the effectiveness of B application could be considered as incorporated B > seedrow B > foliar B. Averaged across the sites and two treatments for each application method for example, B uptake in seed increased by 6.7, 3.8 and 1.0 g ha-1 with incorporated, seedrow and foliar B treatments, respectively. Corresponding methods showed an increase of B uptake in straw by 46, 33 and 23 g ha-1. Disease levels were low for sclerotinia stem rot (Sclerotinia sclerotorum) and low to moderate for blackleg (Leptosphaeria maculans) and alternaria pod spot (Alternaria brassica and A. raphani), and B fertilizer treatments had no impact on the amount or severity of infection for these diseases. In the growth chamber experiments, B fertilization tended to increase the yield of seed and straw (up to 13%) in both soils, with significant contrasts for 0 k g B ha-1 vs. 1, 2 and 3 kg B ha-1 in many cases. In conclusion, the findings of this study suggest that canola rarely responds to B fertilization in field conditions on soils suspected to be B deficient, but canola response to B was influenced by the method of B application. Key words: Boron concentration and uptake, boron fertilizer, canola (Brassica napus L. and Brassica rapa L.), oil and proteincontent, yield

scholarly journals Mycovirus-Induced Hypervirulence of Leptosphaeria biglobosa Enhances Systemic Acquired Resistance to Leptosphaeria maculans in Brassica napus

2020 ◽  
Vol 33 (1) ◽  
pp. 98-107 ◽  
Author(s):  
Unnati A. Shah ◽  
Ioly Kotta-Loizou ◽  
Bruce D. L. Fitt ◽  
Robert H. A. Coutts
Keyword(s):  
Brassica Napus ◽  
Systemic Acquired Resistance ◽  
Acquired Resistance ◽  
Leptosphaeria Maculans ◽  
Stem Canker ◽  
Systemic Resistance ◽  
Phoma Stem Canker ◽  
Isogenic Lines ◽  
Related Proteins ◽  
Leptosphaeria Biglobosa

Phoma stem canker (blackleg) is one of the most important diseases of winter oilseed rape (Brassica napus) worldwide and is caused by a complex that comprises at least two species: Leptosphaeria maculans and L. biglobosa. Screening a panel of field Leptosphaeria isolates from B. napus for the presence of mycoviruses revealed the presence of a novel double-stranded RNA quadrivirus in L. biglobosa and no viruses in L. maculans. Following elimination of the mycovirus, virus-infected and virus-free isogenic lines of L. biglobosa were created. A direct comparison of the growth and virulence of these isogenic lines illustrated that virus infection caused hypervirulence and resulted in induced systemic resistance toward L. maculans in B. napus following lower leaf preinoculation with the virus-infected isolate. Analysis of the plant transcriptome suggests that the presence of the virus leads to subtle alterations in metabolism and plant defenses. For instance, transcripts involved in carbohydrate and amino acid metabolism are enriched in plants treated with the virus-infected isolate, while pathogenesis-related proteins, chitinases and WRKY transcription factors are differentially expressed. These results illustrate the potential for deliberate inoculation of plants with hypervirulent L. biglobosa to decrease the severity of Phoma stem canker later in the growing season. [Formula: see text] Copyright © 2020 The Author(s). This is an open access article distributed under the CC BY 4.0 International license .

scholarly journals Characterization of Callose Deposition and Analysis of the Callose Synthase Gene Family of Brassica napus in Response to Leptosphaeria maculans

2018 ◽  
Vol 19 (12) ◽  
pp. 3769 ◽  
Author(s):  
Fei Liu ◽  
Zhongwei Zou ◽  
W. Fernando
Keyword(s):  
Brassica Napus ◽  
Expression Patterns ◽  
Critical Role ◽  
Leptosphaeria Maculans ◽  
Tissue Expression ◽  
Callose Synthase ◽  
Callose Deposition ◽  
Protein Properties ◽  
Gene Structures ◽  
Leptosphaeria Biglobosa

Callose plays a critical role in different biological processes including development as well as in the response to multiple biotic and abiotic stresses. In this study, we characterized the callose deposition in cotyledons of different Brassica napus varieties post-inoculated with different Leptosphaeria maculans isolates. Further, members of the callose synthase gene were identified from the whole genome of B. napus using the 12 Arabidopsis thaniana callose synthase protein sequences, and were then classified into three groups based on their phylogenetic relationships. Chromosomal location and duplication patterns indicated uneven distribution and segmental duplication patterns of BnCalS genes in the B. napus genome. Subsequently, gene structures, conserved domains analysis, and protein properties were analyzed for BnCalS genes. In addition, 12 B. napus orthologs of the AtCalS were selected for investigating the tissue expression pattern, indicating diverse expression patterns for these BnCalS genes. Responses of the selected 12 orthologs and all the BnCalS genes were characterized in the different types (AvrLm1-Rlm1, AvrLm4-Rlm4, AvrLepR1-LepR1) of B. napus–L. maculans interactions and B. napus-Leptosphaeria biglobosa interactions, implying their potential roles in response to Leptosphaeria infection.

scholarly journals Pathogenicity of Botryosphaeriaceae Species Isolated from Grapevine Cankers in California

Plant Disease ◽  
2009 ◽  
Vol 93 (6) ◽  
pp. 584-592 ◽  
Author(s):  
J. R. Úrbez-Torres ◽  
W. D. Gubler
Keyword(s):  
Fungal Species ◽  
Botryosphaeria Dothidea ◽  
The Family ◽  
Vascular Discoloration ◽  
Grapevine Dieback ◽  
Weakly Virulent ◽  
Highly Virulent ◽  
Neofusicoccum Luteum ◽  
Botryosphaeriaceae Species

Fungal species in the family Botryosphaeriaceae have been recently recognized as the most common fungi isolated from grapevine (Vitis vinifera) cankers in California. However, the role of these fungi in causing grapevine dieback as well as their status as canker-causing agents was unknown. Therefore, pathogenicity studies were conducted to determine their importance as grapevine pathogens in California. A total of 72 isolates representing all nine Botryosphaeriaceae species isolated from grapevine cankers from California were used in five different pathogenicity studies. Overall, experiments showed all nine Botryosphaeriaceae species able to infect both young and mature tissues as well as green shoots of the new vegetative growth causing cankers, vascular discoloration, and/or otherwise dark streaking of the wood. However, virulence varied among species. Lasiodiplodia theobromae was the most virulent species followed by Neofusicoccum luteum, N. parvum, and N. australe, all categorized as highly virulent. Botryosphaeria dothidea was considered intermediately virulent and Diplodia mutila, D. seriata, Dothiorella iberica, and D. viticola were shown to be weakly virulent. This study shows species of Botryosphaeriaceae to be much more important pathogens on grapevines than originally thought, and some of them, in view of their virulence, should be considered high risk for causing severe and rapid canker and dieback diseases in the grapevine industry in California.

scholarly journals Assessing the role of fungal diversity in decomposition: A meta-analysis

2021 ◽  
Author(s):  
Sytske M. Drost ◽  
Annemieke van der Wal ◽  
Wietse de Boer ◽  
Paul. L.E. Bodelier
Keyword(s):  
Fungal Diversity ◽  
Selection Criteria ◽  
Field Experiments ◽  
Meta Analysis ◽  
C:N Ratio ◽  
Negative Relationship ◽  
Fungal Species ◽  
Control Treatment ◽  
Plant Materials ◽  
Diversity Gradient

AbstractFungi play an important role in carbon - and nutrient cycling. It is, however, unclear if diversity of fungi is essential to fulfill this role. With this meta-analysis, we aim to understand the relationship between fungal diversity and decomposition of plant materials (leaf litter and wood) in terrestrial and aquatic environments. The selection criteria for papers were the presence of a fungal diversity gradient and quantification of decomposition as mass loss. In total 40 papers met the selection criteria. We hypothesized that increase of fungal species will result in stronger decomposition, especially in species poor communities. Both artificial inoculated and naturally assembled fungal communities were included in the analysis in order to assess whether manipulated experiments are representative for field situations. We found a significant positive effect of increased fungal diversity on decomposition. However, in manipulated experiments this relationship was only positive when a control treatment of one fungus was compared with multispecies communities. This relationship became negative when comparisons of higher initial richness (at least two fungal species as “control”) were included. In contrast, under natural field conditions increased fungal diversity coincided with increased decomposition. This suggests that manipulated experiments are not representative for field situations. Possible reasons for this are discussed. Yet, both in manipulated and field experiments, environmental factors can influence diversity – decomposition relationships as indicated by a negative relationship of increasing C:N ratio on the effect of fungal diversity on decomposition. Overall, our results show that fungal diversity can have an important role in decomposition, but that design of experiments (manipulated or field) and quality of the plant material should be taken into account for interpretation of this diversity-functioning relationship.

Effect of root rot and stem canker caused by Leptosphaeria maculans on yield of Brassica napus and measures for control in the field

2010 ◽  
Vol 61 (1) ◽  
pp. 50 ◽  
Author(s):  
S. J. Sprague ◽  
J. A. Kirkegaard ◽  
B. J. Howlett ◽  
J. Graham
Keyword(s):  
Brassica Napus ◽  
Grain Yield ◽  
Root Rot ◽  
Field Experiments ◽  
Management Strategies ◽  
Leptosphaeria Maculans ◽  
Brassica Species ◽  
Grain Filling ◽  
Stem Canker ◽  
Eastern Australia

Leptosphaeria maculans causes blackleg of Brassica napus (canola), manifesting in symptoms including leaf lesions, stem canker, and root rot. Root rot is an extension of the stem canker phase of the disease resulting from foliar infection; however, the role of root rot in grain yield loss has not been investigated. Field experiments were conducted in south-eastern Australia to determine the efficacy of fungicides and host resistance to stem canker for the control of root rot, along with the association between root rot severity and grain yield. Fungicides applied as a seed dressing (fluquinconazole) or coated on fertiliser (flutriafol) reduced root rot severity by 16 and 41%, respectively. Root rot severity was 78% less in a B. napus cultivar with an Australian Blackleg Rating (ABR) of 9.0 (highly resistant to stem canker) than in a moderately resistant cultivar (ABR 5.5), and was also reduced in Brassica species with good resistance to stem canker. Root rot caused little or no additional reduction in yield or harvest index of individual B. napus plants above that caused by stem canker. Individual upright plants with greater than 80% of the stem cross-section blackened had significantly reduced seed yield; however, this was influenced by rainfall during the grain-filling period. This study shows that current management strategies for stem canker caused by L. maculans also control root rot in B. napus, as although the symptoms in roots are severe, these symptoms have no additional effect on yield.

scholarly journals Suppression of Bacterial Blight on Mustard Greens with Host Plant Resistance and Acibenzolar-S-Methyl

Plant Disease ◽  
2016 ◽  
Vol 100 (9) ◽  
pp. 1921-1926 ◽  
Author(s):  
Anthony P. Keinath ◽  
W. Patrick Wechter ◽  
Mark W. Farnham
Keyword(s):  
Host Plant ◽  
Plant Resistance ◽  
Host Plant Resistance ◽  
Bacterial Blight ◽  
Field Experiments ◽  
Foliar Spray ◽  
Control Treatment ◽  
Water Control ◽  
Trade Name ◽  
Brassica Vegetables

Bacterial blight, caused by Pseudomonas cannabina pv. alisalensis, attacks the leaves of most brassica vegetables, including mustard greens (Brassica juncea). ‘Carolina Broadleaf,’ a new mustard cultivar, is resistant to bacterial blight, whereas ‘Florida Broadleaf,’ a commonly grown cultivar, is susceptible. Acibenzolar-S-methyl (trade name Actigard) has been used to manage bacterial diseases caused by P. syringae on a variety of crops. The objective of this study was to evaluate host plant resistance and acibenzolar-S-methyl alone and in combination to manage bacterial blight. Three field experiments were done in spring and fall 2011 and fall 2014. In each experiment, acibenzolar-S-methyl was applied twice as a foliar spray, once before and once after plants were inoculated. Severity of bacterial blight was 81% less on nontreated Carolina Broadleaf than on nontreated Florida Broadleaf (P ≤ 0.0003). Acibenzolar-S-methyl applications reduced severity of bacterial blight by 55% compared with the water control treatment on susceptible Florida Broadleaf. Mean weight of diseased leaves, averaged across acibenzolar-S-methyl treatments, was 53% less with Carolina Broadleaf than with Florida Broadleaf (P < 0.0001). However, acibenzolar-S-methyl applied at the recommended rate (14.2 g/ha) significantly injured leaves of Carolina Broadleaf in two experiments and injured leaves of Florida Broadleaf in one experiment. Overall, host plant resistance was more effective than acibenzolar-S-methyl for managing bacterial blight on mustard greens.

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