Variation in the responses of rapeseed (Brassica napus and B. campestris) cultivars to blackleg (Leptosphaeria maculans) infection

1977 ◽  
Vol 17 (86) ◽  
pp. 445 ◽  
Author(s):  
N Thurling ◽  
LA Venn
Keyword(s):  
Brassica Napus ◽  
Significant Variation ◽  
Brassica Campestris ◽  
Leptosphaeria Maculans ◽  
The Other ◽  
Controlled Environment ◽  
Disease Development ◽  
Fungal Populations ◽  
Different Populations ◽  
Blackleg Fungus

The responses of 53 cultivars of the rapeseed species Brassica napus and Brassica campestris to infection by three different populations of the blackleg fungus, Leptosphaeria maculans, were examined in a controlled environment. Significant variation in disease development was observed between cultivars as well as between fungal populations which had been derived from diseased stubble collected at widely separated sites in Western Australia. A large proportion of the cultivars tested were either susceptible or only slightly resistant to infection by each of the three fungal populations whereas only one cultivar, Zollerngold, was highly resistant to all fungal populations. Several other cultivars, however, were resistant to one population and susceptible or slightly resistant to the other two. In these cases, marked interactions between host and parasite were evident, some cultivars being substantially more resistant than others to infection by spores from a particular population.

scholarly journals Decreased Sensitivity of Leptosphaeria maculans to Pyraclostrobin in Alberta, Canada

Plant Disease ◽  
2020 ◽  
Vol 104 (9) ◽  
pp. 2462-2468
Author(s):  
Yixiao Wang ◽  
Alireza Akhavan ◽  
Sheau-Fang Hwang ◽  
Stephen E. Strelkov
Keyword(s):  
Brassica Napus ◽  
Growth Inhibition ◽  
Growth Plate ◽  
Leptosphaeria Maculans ◽  
Fungal Growth ◽  
Microtiter Plate ◽  
Single Spore ◽  
First Report ◽  
Fungal Populations ◽  
The Mean

Leptosphaeria maculans, the causal agent of blackleg of canola (Brassica napus), can be managed with pyraclostrobin and other strobilurin fungicides. Their frequent application, however, poses a risk for the development of insensitivity in fungal populations. A collection of L. maculans single-spore isolates recovered from infected canola stubble in Alberta, Canada, in 2016 was evaluated for its pyraclostrobin sensitivity. In conventional growth plate assays, the concentration of pyraclostrobin required to inhibit fungal growth by 50% (EC50) was determined to be 0.28 mg/liter in a subset of 38 isolates. This EC50 was four times greater than the mean EC50 (0.07 mg/liter) of baseline isolates collected in 2011. Two hundred sixty-three isolates were screened further with two discriminatory doses of 0.28 and 3.5 mg/liter of pyraclostrobin, resulting in growth inhibition values ranging from 16 to 82% and 41 to 100%, respectively. In microtiter plate assays with the same isolates, the mean EC50 was determined to be 0.0049 mg/liter, almost 3.3 times greater than the mean EC50 (0.0015 mg/liter) of the baseline isolates. The sensitivity of the isolates was also evaluated in microtiter plate assays with discriminatory doses of 0.006 and 0.075 mg/liter of pyraclostrobin, resulting in inhibition values ranging from 20 to 88% and 49 to 100%, respectively. This is the first report of isolates of L. maculans with increased insensitivity to pyraclostrobin in Canada, suggesting the need for improved fungicide stewardship.

Identifying resistance genes to Leptosphaeria maculans in Australian Brassica napus cultivars based on reactions to isolates with known avirulence genotypes

2012 ◽  
Vol 63 (4) ◽  
pp. 338 ◽  
Author(s):  
Steve J. Marcroft ◽  
Vicki L. Elliott ◽  
Anton J. Cozijnsen ◽  
Phillip A. Salisbury ◽  
Barbara J. Howlett ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Resistance Genes ◽  
Adult Plant Resistance ◽  
Leptosphaeria Maculans ◽  
Mortality Data ◽  
Adult Plant ◽  
Blackleg Disease ◽  
Seedling Resistance ◽  
Breeding Lines ◽  
Fungal Populations

Blackleg disease, caused by the fungus Leptosphaeria maculans, is the major disease of canola (Brassica napus) worldwide. A set of 12 Australian L. maculans isolates was developed and used to characterise seedling resistance in 127 Australian cultivars and advanced breeding lines. Plant mortality data used to assess the effectiveness of seedling resistance in canola growing regions of Australia showed that Rlm3 and Rlm4 resistance genes were less effective than other seedling resistance genes. This finding was consistent with regional surveys of the pathogen, which showed the frequency of Rlm4-attacking isolates was >70% in fungal populations over a 10-year period. Differences in adult plant resistance were identified in a subset of Australian cultivars, indicating that some adult gene resistance is isolate-specific.

Molecular mapping of resistance to Leptosphaeria maculans in Australian cultivars of Brassica napus

Genome ◽  
1997 ◽  
Vol 40 (3) ◽  
pp. 294-301 ◽  
Author(s):  
R. Mayerhofer ◽  
A. G. Good ◽  
V. K. Bansal ◽  
M. R. Thiagarajah ◽  
G. R. Stringam
Keyword(s):  
Brassica Napus ◽  
Molecular Mapping ◽  
Bulked Segregant Analysis ◽  
Leptosphaeria Maculans ◽  
Rflp Markers ◽  
Dh Population ◽  
Dna Mapping ◽  
Resistant Varieties ◽  
Dh Lines ◽  
Blackleg Fungus

Doubled haploid (DH) lines together with a cotyledon bioassay were employed for the molecular analysis of resistance to the blackleg fungus Leptosphaeria maculans in the Australian Brassica napus cultivars Shiralee and Maluka. We used bulked segregant analysis to identify 13 RAPD and two RFLP markers linked to the resistance phenotype and mapped these markers in the segregating DH population. Our data suggest the presence of a single major locus controlling resistance in the cultivar Shiralee, confirming our previous results obtained from Mendelian genetic analyses. In addition, preliminary mapping data for the cultivar Maluka also support a single locus model for resistance and indicate that the resistance genes from 'Shiralee' and 'Maluka' are either linked or possibly identical. The molecular markers identified in this study should be a useful tool for breeding blackleg resistant varieties using marker-assisted selection, and are the essential first step towards the map-based cloning of this resistance gene.Key words: blackleg, Leptosphaeria maculans, Brassica napus, DNA mapping, disease resistance.

Synergistic Mixes of DPX-A7881 and Clopyralid in Canola (Brassica napus)

1989 ◽  
Vol 3 (4) ◽  
pp. 690-695 ◽  
Author(s):  
Robert E. Blackshaw
Keyword(s):  
Brassica Napus ◽  
Seed Yield ◽  
The Other ◽  
Quality Data ◽  
Controlled Environment ◽  
Common Lambsquarters ◽  
Wild Buckwheat ◽  
Redroot Pigweed ◽  
Wild Mustard ◽  
Yield And Quality

The interaction of DPX-A7881 and clopyralid applied as tank mixtures was studied under controlled environment and field conditions on several commonly occurring weeds in canola. Control of wild mustard and wild buckwheat was not affected by mixing these herbicides. DPX-A7881 controlled wild mustard, and clopyralid controlled wild buckwheat independently of the other herbicide. However, redroot pigweed and common lambsquarters were controlled better with DPX-A7881 plus clopyralid than with either herbicide alone. The herbicides interacted in an additive to synergistic manner on redroot pigweed depending on the rate of each herbicide. DPX-A7881 and clopyralid interacted synergistically at all rates on common lambsquarters. Plant height, date of flowering, seed yield, and quality data all indicated that canola completely tolerated DPX-A7881 and clopyralid applied alone or in combination.

scholarly journals The Effect of Temperature on the Hypersensitive Response (HR) in the Brassica napus–Leptosphaeria maculans Pathosystem

Plants ◽  
2021 ◽  
Vol 10 (5) ◽  
pp. 843
Author(s):  
Cunchun Yang ◽  
Zhongwei Zou ◽  
Wannakuwattewaduge Gerard Dilantha Fernando
Keyword(s):  
Brassica Napus ◽  
Leptosphaeria Maculans ◽  
The Other ◽  
Effect Of Temperature ◽  
Marker Genes ◽  
Temperature Sensitive ◽  
Temperature Changes ◽  
Pathogenesis Related ◽  
Two Temperature ◽  
Incompatible Interactions

Temperature is considered one of the crucial environmental elements in plant pathological interactions, and previous studies have indicated that there is a relationship between temperature change and host–pathogen interactions. The objective of this research is to investigate the link between temperature and the incompatible interactions of the host and pathogen. In this study, two Leptosphaeria maculans isolates (HCRT75 8-1 and HCRT77 7-2) and two Brassica napus genotypes (Surpass400 and 01-23-2-1) were selected. The selected B. napus genotypes displayed intermediate and resistant phenotypes. The inoculated seedlings were tested under three temperature conditions: 16 °C/10 °C, 22 °C/16 °C and 28 °C/22 °C (day/night: 16 h/8 h). Lesion measurements demonstrated that the necrotic lesions from the 28 °C/22 °C treatment were enlarged compared with the other two temperature treatments (i.e., 16 °C/10 °C and 22 °C/16 °C). The results of expression analysis indicated that the three temperature treatments displayed distinct differences in two marker genes (PATHOGENESIS–RELATED (PR) 1 and 2) for plant defense and one temperature-sensitive gene BONZAI 1 (BON1). Additionally, seven dpi at 22 °C/16 °C appeared to be the optimal pre-condition for the induction of PR1 and 2. These findings suggest that B. napus responds to temperature changes when infected with L. maculans.

scholarly journals Pathogenicity of Leptosphaeria maculans Isolates on a Brassica napus-B. juncea Recombinant Line

1999 ◽  
Vol 89 (2) ◽  
pp. 169-175 ◽  
Author(s):  
Irénée Somda ◽  
Régine Delourme ◽  
Michel Renard ◽  
Hortense Brun
Keyword(s):  
Brassica Napus ◽  
Plant Breeding ◽  
Leptosphaeria Maculans ◽  
The Other ◽  
Interspecific Crosses ◽  
Sources Of Resistance ◽  
Recombinant Line ◽  
B Genome ◽  
Cotyledon Stage ◽  
Breeding Schemes

The Brassica napus-B. juncea recombinant line (MX), resistant to Leptosphaeria maculans, was produced by interspecific crosses and bears one gene (Jlm1) from the B. juncea B genome. We investigated whether this new resistance was race specific by characterizing protection against a large sample of L. maculans isolates. The pathogenicity of 119 isolates of L. maculans comprising 105 A-group isolates and 14 B-group isolates was studied at the cotyledon stage under controlled conditions using the MX line, the susceptible B. napus cultivar Westar, and the resistant B. juncea cultivar Picra. All but one of the isolates were pathogenic on ‘Westar’. Only 3 of the 105 A-group isolates caused very mild symptoms on ‘Picra’. Two of these strains were isolated from the MX line and the other from Sinapis arvensis. The other 102 strains caused hypersensitive-type responses. Most B-group isolates were pathogenic on ‘Picra’. There were differences in pathogenicity among A-group isolates tested on the MX line, whereas all B-group isolates were pathogenic on this line. A-group isolates obtained from the MX line were more frequently pathogenic on the MX line than those obtained from B. napus cultivars. One isolate from S. arvensis infected the MX line. These results suggest that the resistance of the MX line is unlikely to be durable. Thus, the new resistance gene Jlm1 should probably be used in association with other sources of resistance, in plant breeding schemes, to prevent the breakdown of this resistance.

scholarly journals Insights into fighting against blackleg disease of Brassica napus in Canada

2018 ◽  
Vol 69 (1) ◽  
pp. 40 ◽  
Author(s):  
Xuehua Zhang ◽  
W. G. Dilantha Fernando
Keyword(s):  
Brassica Napus ◽  
Disease Control ◽  
Resistance Genes ◽  
Leptosphaeria Maculans ◽  
Western Canada ◽  
R Genes ◽  
Blackleg Disease ◽  
Evolutionary Potential ◽  
Fungal Populations ◽  
Major Resistance Genes

Blackleg disease, caused by the ascomycete fungal pathogen Leptosphaeria maculans, is a devastating disease of canola (Brassica napus) in Australia, Canada and Europe. Although cultural strategies such as crop rotation, fungicide application, and tillage are adopted to control the disease, the most promising disease control strategy is the utilisation of resistant canola varieties. However, field populations of L. maculans display a high evolutionary potential and are able to overcome major resistance genes within a few years, making disease control relying on resistant varieties challenging. In the early 1990s, blackleg resistance gene Rlm3 was introduced into Canadian canola varieties and provided good resistance against the fungal populations until the early 2000s, when moderate to severe blackleg outbreaks were observed in some areas across western Canada. However, the breakdown of Rlm3 resistance was not reported until recently, based on studies on R genes present in Canadian canola varieties and the avirulence allele frequency in L. maculans populations in western Canada. The fact that Rlm3 was overcome by the evolution of fungal populations demands canola breeding programs in Canada to be prepared to develop canola varieties with diversified and efficient R genes. In addition, frequent monitoring of fungal populations can provide up-to-date guidance for proper resistance genes deployment. This literature review provides insights into the outbreaks and management of blackleg disease in Canada.

Non-aggressive Strains of the Blackleg Fungus, Leptosphaeria maculans, Are Present in Australia and Can Be Distinguished From Aggressive Strains by Molecular Analysis

1994 ◽  
Vol 42 (1) ◽  
pp. 1 ◽  
Author(s):  
KM Plummer ◽  
K Dunse ◽  
BJ Howlett
Keyword(s):  
Brassica Napus ◽  
North America ◽  
Molecular Analysis ◽  
Ribosomal Rna ◽  
Random Amplified Polymorphic Dna ◽  
Rapd Marker ◽  
Leptosphaeria Maculans ◽  
Morphological Characters ◽  
Molecular Techniques ◽  
Blackleg Fungus

Isolates of the pathogenic ascomycete Leptosphaeria maculans have been cultured from blackleg-affected oilseed rape (Brassica napus) stubble from Horsham, Victoria. These isolates are indistinguishable on the basis of morphological characters, but can be classified as either aggressive or non-aggressive by their ability to infect B. napus cultivars Midas and Westar. These aggressive and non-aggressive isolates of L. maculans can be distinguished by molecular techniques including electrophoretic karyotyping, Southern analysis of the ribosomal RNA gene repeat, Random Amplified Polymorphic DNA (RAPD) marker analysis, and pigment production. The presence of aggressive and non-aggressive strains of L. maculans in North America and Europe has been previously described. This is the first report of non-aggressive L. maculans strains isolated from B. napus in Australia.

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.

Development of an agronomically superior blackleg resistant canola cultivar in Brassica napus L. using doubled haploidy

1995 ◽  
Vol 75 (2) ◽  
pp. 437-439 ◽  
Author(s):  
G. R. Stringam ◽  
V. K. Bansal ◽  
M. R. Thiagarajah ◽  
D. F. Degenhardt ◽  
J. P. Tewari
Keyword(s):  
Brassica Napus ◽  
Doubled Haploid ◽  
Leptosphaeria Maculans ◽  
Resistance Breeding ◽  
Breeding Method ◽  
Brassica Napus L ◽  
Breeding Lines ◽  
University Of Alberta ◽  
Blackleg Resistance ◽  
The University

The doubled haploid breeding method and greenhouse screening using cotyledon bio-assay were successfully applied to transfer blackleg resistance from the Australian cultivar Maluka (Brassicas napus), into susceptible advanced B. napus lines from the University of Alberta. This approach for blackleg resistance breeding was effective and efficient as several superior blackleg resistant breeding lines were identified within 4 yr from the initial cross. One of these lines (91–21864NA) was entered in the 1993 trials of the Western Canada Canola/Rapeseed Recommending Committee. Key words: Blackleg resistance, Leptosphaeria maculans, doubled haploid, Brassica napus

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