scholarly journals Hormonal Responses to Susceptible, Intermediate, and Resistant Interactions in the Brassica napus–Leptosphaeria maculans Pathosystem

2021 ◽  
Vol 22 (9) ◽  
pp. 4714
Author(s):  
Cunchun Yang ◽  
W. G. Dilantha Fernando
Keyword(s):  
Brassica Napus ◽  
Plant Defense ◽  
Fungal Pathogen ◽  
Durable Resistance ◽  
Leptosphaeria Maculans ◽  
Hormone Signaling ◽  
Hormonal Responses ◽  
Microbe Interactions ◽  
Quantitative Analyses ◽  
The Relationship

Hormone signaling plays a pivotal role in plant–microbe interactions. There are three major phytohormones in plant defense: salicylic acid (SA), jasmonic acid (JA), and ethylene (ET). The activation and trade-off of signaling between these three hormones likely determines the strength of plant defense in response to pathogens. Here, we describe the allocation of hormonal signaling in Brassica napus against the fungal pathogen Leptosphaeria maculans. Three B. napus genotypes (Westar, Surpass400, and 01-23-2-1) were inoculated with two L. maculans isolates (H75 8-1 and H77 7-2), subsequently exhibiting three levels of resistance: susceptible, intermediate, and resistant. Quantitative analyses suggest that the early activation of some SA-responsive genes, including WRKY70 and NPR1, contribute to an effective defense against L. maculans. The co-expression among factors responding to SA/ET/JA was also observed in the late stage of infection. The results of conjugated SA measurement also support that early SA activation plays a crucial role in durable resistance. Our results demonstrate the relationship between the onset patterns of certain hormone regulators and the effectiveness of the defense of B. napus against L. maculans.

scholarly journals A Six-Year Investigation of the Dynamics of Avirulence Allele Profiles, Blackleg Incidence, and Mating Type Alleles of Leptosphaeria maculans Populations Associated with Canola Crops in Manitoba, Canada

Plant Disease ◽  
2018 ◽  
Vol 102 (4) ◽  
pp. 790-798 ◽  
Author(s):  
W. G. Dilantha Fernando ◽  
Xuehua Zhang ◽  
Carrie Selin ◽  
Zhongwei Zou ◽  
Sakaria H. Liban ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Sexual Reproduction ◽  
Oilseed Rape ◽  
Mating Type ◽  
Fungal Pathogen ◽  
Leptosphaeria Maculans ◽  
Fungal Population ◽  
Pcr Assays

Blackleg, caused by the fungal pathogen Leptosphaeria maculans, is one of the most economically important diseases of canola (Brassica napus, oilseed rape) worldwide. This study assessed incidence of blackleg, the avirulence allele, and mating type distributions of L. maculans isolates collected in commercial canola fields in Manitoba, Canada, from 2010 to 2015. A total of 956 L. maculans isolates were collected from 2010 to 2015 to determine the presence of 12 avirulence alleles using differential canola cultivars and/or PCR assays specific for each avirulence allele. AvrLm2, AvrLm4, AvrLm5, AvrLm6, AvrLm7, AvrLm11, and AvrLmS were detected at frequencies ranging from 97 to 33%, where the AvrLm1, AvrLm3, AvrLm9, AvrLepR1, and AvrLepR2 alleles were the least abundant. When the race structure was examined, a total of 170 races were identified among the 956 isolates, with three major races, AvrLm-2-4-5-6-7-11, AvrLm-2-4-5-6-7-11-S, and Avr-1-4-5-6-7-11-(S) accounting for 15, 10, and 6% of the total fungal population, respectively. The distribution of the mating type alleles (MAT1-1 and MAT1-2) indicated that sexual reproduction was not inhibited in any of the nine Manitoba regions in any of the years L. maculans isolates were collected.

Molecular mapping and validation of Rlm1 gene for resistance to Leptosphaeria maculans in canola (Brassica napus L.)

2012 ◽  
Vol 63 (10) ◽  
pp. 1007 ◽  
Author(s):  
Rosy Raman ◽  
Belinda Taylor ◽  
Kurt Lindbeck ◽  
Neil Coombes ◽  
Denise Barbulescu ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Ssr Markers ◽  
Genomic Sequence ◽  
Molecular Mapping ◽  
Durable Resistance ◽  
Leptosphaeria Maculans ◽  
Doubled Haploid Population ◽  
Brassica Napus L ◽  
Breeding Populations ◽  
Independent Population

European winter canola (Brassica napus L.) cultivars harbour genes for durable resistance to the fungus Leptosphaeria maculans, which causes blackleg disease under Australian environmental conditions. Previous studies have shown that resistance in winter-type cultivars Maxol and Columbus is controlled by two genes, Rlm1 and Rlm3, which have been mapped using randomly amplified polymorphic DNA markers onto chromosome A7. We mapped a doubled-haploid population that consisted of 101 lines from a cross between Maxol*1 and Westar-10 using diversity arrays technology and simple sequence repeat (SSR)-based markers. Two SSR marker loci, Xol12-e03 and Xra2-a05b, flanked the Rlm1 locus at an interval of 6.7 cM, which corresponds to ~3.2 Mb of the Brassica rapa genomic sequence; this region contains several genes encoding putative kinase and leucine-rich repeat-type disease-resistance proteins. SSR markers were further tested for their linkage with the Rlm1 locus in an independent population derived from Columbus*3/Westar-10. Our results showed that SSR markers linked to Rlm1 can be useful for monitoring Rlm1 gene introgression in breeding populations derived from Maxol and Columbus.

scholarly journals Recognition of Avirulence Gene AvrLm1 from Hemibiotrophic Ascomycete Leptosphaeria maculans Triggers Salicylic Acid and Ethylene Signaling in Brassica napus

2012 ◽  
Vol 25 (9) ◽  
pp. 1238-1250 ◽  
Author(s):  
Vladimír Šašek ◽  
Miroslava Nováková ◽  
Barbora Jindřichová ◽  
Károly Bóka ◽  
Olga Valentová ◽  
...  
Keyword(s):  
Salicylic Acid ◽  
Brassica Napus ◽  
Single Molecule ◽  
Fungal Pathogen ◽  
Leptosphaeria Maculans ◽  
Defense Responses ◽  
Avirulence Gene ◽  
Ethylene Signaling ◽  
Incompatible Interaction ◽  
Biotrophic Pathogens

Interaction of a plant with a fungal pathogen is an encounter with hundreds of molecules. In contrast to this, a single molecule often decides between the disease and resistance. In the present article, we describe the defense responses triggered by AvrLm1, an avirulence gene from a hemibiotrophic ascomycete, Leptosphaeria maculans, responsible for an incompatible interaction with Brassica napus. Using multiple hormone quantification and expression analysis of defense-related genes, we investigated signaling events in Rlm1 plants infected with two sister isolates of L. maculans differentiated by the presence or absence of AvrLm1. Infection with the isolate carrying AvrLm1 increased the biosynthesis of salicylic acid (SA) and induced expression of the SA-associated genes ICS1, WRKY70, and PR-1, a feature characteristic of responses to biotrophic pathogens and resistance gene–mediated resistance. In addition to SA-signaling elements, we also observed the induction of ASC2a, HEL, and CHI genes associated with ethylene (ET) signaling. Pharmacological experiments confirmed the positive roles of SA and ET in mediating resistance to L. maculans. The unusual cooperation of SA and ET signaling might be a response to the hemibiotrophic nature of L. maculans. Our results also demonstrate the profound difference between the natural host B. napus and the model plant Arabidopsis in their response to L. maculans infection.

scholarly journals Impact of a resistance gene against a fungal pathogen on the plant host residue microbiome: The case of the Leptosphaeria maculans–Brassica napus pathosystem

2020 ◽  
Vol 21 (12) ◽  
pp. 1545-1558 ◽  
Author(s):  
Lydie Kerdraon ◽  
Matthieu Barret ◽  
Marie‐Hélène Balesdent ◽  
Frédéric Suffert ◽  
Valérie Laval
Keyword(s):  
Brassica Napus ◽  
Resistance Gene ◽  
Fungal Pathogen ◽  
Leptosphaeria Maculans ◽  
Plant Host

scholarly journals Comparison of non-subjective relative fungal biomass measurements to quantify the Leptosphaeria maculans—Brassica napus interaction

Plant Methods ◽  
2021 ◽  
Vol 17 (1) ◽  
Author(s):  
Wendelin Schnippenkoetter ◽  
Mohammad Hoque ◽  
Rebecca Maher ◽  
Angela Van de Wouw ◽  
Phillip Hands ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Fungal Pathogen ◽  
Fungal Biomass ◽  
Quantitative Resistance ◽  
Leptosphaeria Maculans ◽  
Post Inoculation ◽  
Blackleg Disease ◽  
In Planta ◽  
Visual Assessments ◽  
Host Tissues

Abstract Background Blackleg disease, caused by the fungal pathogen Leptosphaeria maculans, is a serious threat to canola (Brassica napus) production worldwide. Quantitative resistance to this disease is a highly desirable trait but is difficult to precisely phenotype. Visual scores can be subjective and are prone to assessor bias. Methods to assess variation in quantitative resistance more accurately were developed based on quantifying in planta fungal biomass, including the Wheat Germ Agglutinin Chitin Assay (WAC), qPCR and ddPCR assays. Results Disease assays were conducted by inoculating a range of canola cultivars with L. maculans isolates in glasshouse experiments and assessing fungal biomass in cotyledons, petioles and stem tissue harvested at different timepoints post-inoculation. PCR and WAC assay results were well correlated, repeatable across experiments and host tissues, and able to differentiate fungal biomass in different host-isolate treatments. In addition, the ddPCR assay was shown to differentiate between L. maculans isolates. Conclusions The ddPCR assay is more sensitive in detecting pathogens and more adaptable to high-throughput methods by using robotic systems than the WAC assay. Overall, these methods proved accurate and non-subjective, providing alternatives to visual assessments to quantify the L. maculans-B. napus interaction in all plant tissues throughout the progression of the disease in seedlings and mature plants and have potential for fine-scale blackleg resistance phenotyping in canola.

scholarly journals Can Actin Depolymerization Actually Result in Increased Plant Resistance to Pathogens?

2018 ◽  
Author(s):  
Hana Krutinová ◽  
Lucie Trdá ◽  
Tetiana Kalachova ◽  
Lucie Lamparová ◽  
Romana Pospíchalová ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Plant Resistance ◽  
Fungal Pathogen ◽  
Leptosphaeria Maculans ◽  
Bacterial Pathogen ◽  
Isochorismate Synthase ◽  
Actin Depolymerization ◽  
Pathogen Attack ◽  
Plant Pathosystems ◽  
The Relationship

Introductory paragraphThe integrity of the actin cytoskeleton is essential for plant immune signalling1. Consequently, it is generally assumed that actin disruption reduces plant resistance to pathogen attack2-4. However, in a previous study, it was shown that actin depolymerisation triggers the salicylic acid (SA) signalling pathway5, which is interesting because increased SA is associated with enhanced plant resistance to pathogen attack6,7. Here, we attempt to resolve this seeming inconsistency by showing that the relationship between actin depolymerization and plant resistance is more complex than currently thought. We investigate the precise nature of this relationship using two completely different plant pathosystems: i) a model plant (Arabidopsis thaliana) and a bacterial pathogen (Pseudomonas syringae), and ii) an important crop (Brassica napus) and a fungal pathogen (Leptosphaeria maculans). We demonstrate that actin depolymerization induces a dramatic increase in SA levels and that the increased SA is biosynthesized by the isochorismate synthase pathway. In both pathosystems, this phenomenon leads to increased plant resistance.

Establishing the relationship of ascospore loads with blackleg (Leptosphaeria maculans) severity on canola (Brassica napus)

2004 ◽  
Vol 55 (8) ◽  
pp. 849 ◽  
Author(s):  
A. D. Wherrett ◽  
K. Sivasithamparam ◽  
M. J. Barbetti
Keyword(s):  
Brassica Napus ◽  
Crop Residues ◽  
Leptosphaeria Maculans ◽  
Disease Index ◽  
Adult Plant ◽  
Exponential Relationship ◽  
Glufosinate Ammonium ◽  
Highly Correlated ◽  
Relationship Of ◽  
The Relationship

A study was carried out to determine the relationship of blackleg (Leptosphaeria maculans) to ascospore loads from infested canola residue, and also to determine whether effects of chemicals on L. maculans development and ascospore discharge from residues would be reflected in subsequent disease on a freshly sown crop. Residues were dipped in a water-only control or solutions of flutriafol or glufosinate-ammonium and placed in the field prior to early winter rains where they remained through the growing season. Canola (Brassica napus cv. Dunkeld) was seeded adjacent to residues. Early seedling lesion and adult plant crown canker development were monitored. A significant exponential relationship between numbers of ascospores discharged from residues and seedling percentage disease index (SPDI; range 0–100%) and adult plant percentage disease index (APDI; range 0–100%) was evident. In particular, large variations in SPDI and APDI were evident in relation to changes in level of inoculum where less than 25 × 105 ascospores/stem (approx.) were discharged. A reduction in ascospore numbers discharged from 25 × 105 ascospores/stem to 5 × 105 ascospores/stem resulted in a significant reduction of SPDI and APDI. Above this ascospore/stem threshold, responses to inoculum increases were minimal, with relatively little further increase in SPDI or APDI. Our study established, for the first time, a clear response of disease severity to numbers of ascospores discharged. SPDI was lower in plots containing flutriafol- or glufosinate-ammonium-treated residues compared with water-only control plots. Nearly all seedlings remained symptom-free in flutriafol-treated plots compared with only 20% in the water-only control plots. Crown canker measurement on adult plants indicated significantly lower APDI in plots containing flutriafol- or glufosinate-ammonium-treated residues compared with the untreated control plots. SPDI was highly correlated to APDI.

Comparison of inoculation methods for selection of plants resistant to Leptosphaeria maculans in Brassica napus

1993 ◽  
Vol 73 (4) ◽  
pp. 1199-1207 ◽  
Author(s):  
W. M. McNabb ◽  
C. G. J. van den Berg ◽  
S. R. Rimmer
Keyword(s):  
Brassica Napus ◽  
Key Words ◽  
Correlation Coefficient ◽  
Leptosphaeria Maculans ◽  
Inoculation Methods ◽  
Inoculation Techniques ◽  
Large Populations ◽  
Disease Rating ◽  
The Relationship ◽  
Selection Of

The relationship between ratings following four inoculation techniques and field ratings and the usefulness of these techniques for screening large populations was determined. Plants of Brassica napus ’Westar,’ ’Wesroona’, ’Topas’, ’Hanna’ and ’R8314’ were inoculated with L. maculans using four techniques: cotyledon inoculation with cotyledon rating, leaf inoculation with leaf and stem rating, stem inoculation with stem rating and inoculation using infested oat kernels with stem rating. Plants from each combination of cultivar and technique were self-pollinated for evaluation of disease rating in the field. The highest precision was obtained with cotyledon rating following cotyledon inoculation. The correlation coefficient between the rating of inoculated plants and the field rating of their progeny ranged from 0.50** for oat kernel inoculation to 0.72** for cotyledon inoculation. Considerable variation for field rating was associated with each rating following artificial inoculation. Selection of resistant plants using low cotyledon reaction was a more efficient technique than leaf or stem inoculation; it was rapid, required less labour and space and correlated well with the field ratings. Key words: Leptosphaeria maculans, Brassica napus, blackleg, oilseed rape, inoculation methods, canola

scholarly journals Recent Findings Unravel Genes and Genetic Factors Underlying Leptosphaeria maculans Resistance in Brassica napus and Its Relatives

2020 ◽  
Vol 22 (1) ◽  
pp. 313
Author(s):  
Aldrin Y. Cantila ◽  
Nur Shuhadah Mohd Saad ◽  
Junrey C. Amas ◽  
David Edwards ◽  
Jacqueline Batley
Keyword(s):  
Brassica Napus ◽  
Genetic Factors ◽  
Quantitative Resistance ◽  
Genetic Resistance ◽  
Leptosphaeria Maculans ◽  
Gene Interaction ◽  
R Gene ◽  
R Genes ◽  
Blackleg Resistance ◽  
Avr Gene

Among the Brassica oilseeds, canola (Brassica napus) is the most economically significant globally. However, its production can be limited by blackleg disease, caused by the fungal pathogen Lepstosphaeria maculans. The deployment of resistance genes has been implemented as one of the key strategies to manage the disease. Genetic resistance against blackleg comes in two forms: qualitative resistance, controlled by a single, major resistance gene (R gene), and quantitative resistance (QR), controlled by numerous, small effect loci. R-gene-mediated blackleg resistance has been extensively studied, wherein several genomic regions harbouring R genes against L. maculans have been identified and three of these genes were cloned. These studies advance our understanding of the mechanism of R gene and pathogen avirulence (Avr) gene interaction. Notably, these studies revealed a more complex interaction than originally thought. Advances in genomics help unravel these complexities, providing insights into the genes and genetic factors towards improving blackleg resistance. Here, we aim to discuss the existing R-gene-mediated resistance, make a summary of candidate R genes against the disease, and emphasise the role of players involved in the pathogenicity and resistance. The comprehensive result will allow breeders to improve resistance to L. maculans, thereby increasing yield.

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