scholarly journals Breakdown of a Brassica rapa subsp. sylvestris Single Dominant Blackleg Resistance Gene in B. napus Rapeseed by Leptosphaeria maculans Field Isolates in Australia

Plant Disease ◽  
2003 ◽  
Vol 87 (6) ◽  
pp. 752-752 ◽  
Author(s):  
H. Li ◽  
K. Sivasithamparam ◽  
M. J. Barbetti
Keyword(s):  
Brassica Napus ◽  
Resistance Gene ◽  
Disease Severity ◽  
Brassica Rapa ◽  
Oilseed Rape ◽  
Leptosphaeria Maculans ◽  
Blackleg Disease ◽  
Field Isolates ◽  
Western Australian ◽  
Lower Stem

Blackleg, caused by Leptosphaeria maculans, is a major disease of oilseed rape (Brassica napus) grown in Canada, Europe, and Australia. Cv. Surpass 400 was released in Australia in 2000 as the most resistant cultivar to L. maculans. It carries a single dominant resistance gene from B. rapa subsp. sylvestris. This cultivar usually shows a hypersensitive response to L. maculans characterized by small, dark brown lesions that are necrotic, localized, and without pycnidia on cotyledons, leaves, and stems. However, in 2001 on a Western Australian experimental farm, a small proportion of the lesions on the lower stem and crown region of cv. Surpass 400 were typical of those observed in susceptible cultivars, which were brown, necrotic lesions with a darker margin, but they contained fewer pycnidia. Forty seedlings of cv. Surpass 400 and susceptible cv. Westar were inoculated with pycnidiospore suspensions (106/ml) of each of 18 isolates taken from lesions on cv. Surpass 400. All 18 isolates caused collapse of cotyledons of susceptible cv. Westar. Four of these isolates caused large cotyledon lesions with some pycnidia on cv. Surpass 400. Three of these four isolates were subsequently inoculated onto 60 seedlings per isolate, at each of the four cotyledon lobes of each seedling of the two cultivars. Inoculated plants were assessed for disease severity on cotyledons and transplanted to the field 14 days after inoculation. The cotyledons of inoculated cv. Surpass 400 showed characteristic large, necrotic lesions with pycnidia, while the cotyledons of cv. Westar had collapsed and contained a mass of pycnidia. Blackleg disease severity in the crown region of the stem was assessed at 2 weeks before harvest. Fifty-four percent of the cv. Surpass 400 transplanted inoculated plants subsequently developed susceptible symptoms of crown cankers on stems. These symptoms were deep, girdling, brown lesions on the plant crowns with some pycnidia. One hundred percent of cv. Westar plants were infected and dead at this stage. This confirmed the ability of these field isolates to overcome the single dominant resistance gene present in cv. Surpass 400. To our knowledge, this is the first report of breakdown of a single dominant B. rapa subsp. sylvestris gene based resistance to blackleg in oilseed rape in the field.

scholarly journals Limitations of transcriptome-based prediction of pathogenicity genes in the plant pathogen Leptosphaeria maculans

2019 ◽  
Vol 366 (7) ◽  
Author(s):  
Andrew S Urquhart ◽  
Alexander Idnurm
Keyword(s):  
Gene Expression ◽  
Brassica Napus ◽  
Leptosphaeria Maculans ◽  
Simple Expression ◽  
Gene Transcript ◽  
Blackleg Disease ◽  
Fungal Pathogenicity ◽  
Transcript Levels ◽  
Oilseed Crops ◽  
High Gene

ABSTRACT Identification of pathogenicity determinants in Leptosphaeria maculans, a major cause of disease of oilseed crops, has been a focus of research for many years. A wealth of gene expression information from RNA sequencing promises to illuminate the mechanisms by which the fungus is able to cause blackleg disease. However, to date, no studies have tested the hypothesis that high gene transcript levels during infection correlate with importance to disease progression. In this study, we use CRISPR-Cas9 to disrupt 11 genes that are highly expressed during the early stages of disease and show that none of these genes are crucial for fungal pathogenicity on Brassica napus. This finding suggests that in order to understand the pathogenicity of this fungus more sophisticated techniques than simple expression analysis will need to be employed.

Prevalence of blackleg (Leptosphaeria maculans) on canola (Brassica napus) in Western Australia

2001 ◽  
Vol 41 (1) ◽  
pp. 71 ◽  
Author(s):  
R. K. Khangura ◽  
M. J. Barbetti
Keyword(s):  
Western Australia ◽  
Disease Incidence ◽  
Leptosphaeria Maculans ◽  
Sowing Date ◽  
Blackleg Disease ◽  
The Mean ◽  
Seed Yields ◽  
Blackleg Fungus ◽  
Western Australian

Canola crops were monitored throughout the Western Australian wheatbelt during 1996–99 to determine the incidence and severity of crown cankers caused by the blackleg fungus (Leptosphaeria maculans). All crops surveyed had blackleg. The incidence of crown canker was 48–100%, 15–100%, 9–94% and 48–100% during 1996, 1997, 1998 and 1999, respectively. The mean incidence of crown cankers statewide was 85, 63, 55 and 85% in 1996, 1997, 1998 and 1999, respectively. The severity of crown canker (expressed as percentage disease index) ranged between 30 and 96%, 3 and 94%, 5 and 78% and 21 and 96% during 1996, 1997, 1998 and 1999, respectively. These high levels of blackleg can possibly be attributed to the accumulation of large amounts of infested canola residues. In 1999, there were effects of variety, application of the fungicide Impact, distance to last year’s canola residues and rainfall on the incidence and severity of blackleg. However, there were no effects of sowing date or region on the disease incidence or severity once the other factor effects listed above had been considered. In 1995, an additional survey of 19 sites in the central wheatbelt of Western Australia assessed the survival of the blackleg fungus on residues from crops grown in 1992–94. The residues at all sites carried blackleg. However, the extent of infection at any particular site varied from 12 to 100% of stems with the percentage of stems carrying pseudothecia containing ascospores varying between 7 and 96%. The high levels of blackleg disease found in commercial crops are indicative of significant losses in seed yields, making it imperative that management of blackleg be improved if canola is to remain a viable long-term cropping option in Western Australia.

scholarly journals Genome-Wide Identification and Analysis of VQ Motif-containing Gene Family in Brassica napus and Functional Characterization of BnMKS1 in Response to Leptosphaeria maculans

2020 ◽  
Author(s):  
Zhongwei Zou ◽  
Fei Liu ◽  
Shuanglong Huang ◽  
DILANTHA GERARD FERNANDO
Keyword(s):  
Brassica Napus ◽  
Gene Family ◽  
Functional Characterization ◽  
Leptosphaeria Maculans ◽  
Defense Responses ◽  
Marker Genes ◽  
Blackleg Disease ◽  
Genome Wide ◽  
A Genome

Proteins containing Valine-glutamine (VQ) motifs play important roles in plant growth and development, as well as in defense responses to both abiotic and biotic stresses. Blackleg disease, which is caused by Leptosphaeria maculans, is the most important disease in canola (Brassica napus L.) worldwide. H; however, the identification of B. napus VQs and their functions in response to blackleg disease have not yet been reported. In this study, we conducted a genome genome-wide identification and characterization of the VQ gene family in B. napus, including chromosome location, phylogenetic relations, gene structure, motif domain, synteny analysis, and cis-elements categorization of their promoter regions. To understand B. napus VQ gene function in response to blackleg disease, we overexpressed BnVQ7 (BnaA01g36880D, also known as the mitogen-activated protein kinase4 substrate1 (MKS1) gene) in a blackleg-susceptible canola variety Westar. Overexpression The overexpression of BnMKS1 in canola did not improve its resistance to blackleg disease at the seedling stage. H; however, transgenic canola plants overexpressing BnMKS1 displayed an enhanced resistance to L. maculans infection at the adult plant stage. Expression levels of downstream and defense marker genes in cotyledons increased significantly at the necrotrophic stage of L. maculans infection in the overexpression line of BnMKS1, suggesting that the SA salicylic acid (SA)- and jasmonic acid (JA )-mediated signaling pathways were both involved in the defense responses. Together, these results suggest that BnMKS1 might play an important role in the defense against L. maculans.

scholarly journals Fine mapping of Brassica napus blackleg resistance gene Rlm1 through bulked segregant RNA sequencing

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Fuyou Fu ◽  
Xunjia Liu ◽  
Rui Wang ◽  
Chun Zhai ◽  
Gary Peng ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Resistance Gene ◽  
Rna Sequencing ◽  
Catalytic Domain ◽  
Leptosphaeria Maculans ◽  
Snp Markers ◽  
Specific Pcr ◽  
Dual Specificity ◽  
Kinase Catalytic Domain ◽  
Allele Specific

Abstract The fungal pathogen Leptosphaeria maculans causes blackleg disease on canola and rapeseed (Brassica napus) in many parts of the world. A B. napus cultivar, ‘Quinta’, has been widely used for the classification of L. maculans into pathogenicity groups. In this study, we confirmed the presence of Rlm1 in a DH line (DH24288) derived from B. napus cultivar ‘Quinta’. Rlm1 was located on chromosome A07, between 13.07 to 22.11 Mb, using a BC1 population made from crosses of F1 plants of DH16516 (a susceptible line) x DH24288 with bulked segregant RNA Sequencing (BSR-Seq). Rlm1 was further fine mapped in a 100 kb region from 19.92 to 20.03 Mb in the BC1 population consisting of 1247 plants and a F2 population consisting of 3000 plants using SNP markers identified from BSR-Seq through Kompetitive Allele-Specific PCR (KASP). A potential resistance gene, BnA07G27460D, was identified in this Rlm1 region. BnA07G27460D encodes a serine/threonine dual specificity protein kinase, catalytic domain and is homologous to STN7 in predicted genes of B. rapa and B. oleracea, and A. thaliana. Robust SNP markers associated with Rlm1 were developed, which can assist in introgression of Rlm1 and confirm the presence of Rlm1 gene in canola breeding programs.

scholarly journals Effect of Water Flooding on Survival of Leptosphaeria biglobosa ‘brassicae’ in Stubble of Oilseed Rape (Brassica napus) in Central China

Plant Disease ◽  
2015 ◽  
Vol 99 (10) ◽  
pp. 1426-1433 ◽  
Author(s):  
Xiang Cai ◽  
Jing Zhang ◽  
Mingde Wu ◽  
Daohong Jiang ◽  
Guoqing Li ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Field Experiment ◽  
Oilseed Rape ◽  
Leptosphaeria Maculans ◽  
Soil Surface ◽  
Dry Weight ◽  
Central China ◽  
Water Flooding ◽  
Cotton Field ◽  
Winter Oilseed Rape

Blackleg (Phoma stem canker) caused by Leptosphaeria maculans and L. biglobosa is an economically important disease on oilseed rape and many cruciferous vegetables. Oilseed rape–rice rotation is a routine cultivation practice in central China. This study was conducted to assess the effect of flooding on survival of L. biglobosa ‘brassicae’ in the stubble of winter oilseed rape (Brassica napus). Basal stems with typical blackleg symptoms were collected and cut into small pieces (2 cm) that were either submerged in water at 16 and 20, 20 and 28, 28 and 33, and 33 and 40°C (12 and 12 h) or kept dry at room temperature (control). Moreover, in a field experiment, the stem pieces were placed on the soil surface in a rice field or in a cotton field and either flooded in water or not flooded, respectively. After 1, 2, 4, 6, and 8 weeks, the stem pieces were sampled for retrieval of L. biglobosa ‘brassicae’ on V8-juice agar and for determination of dry weight. Selected L. biglobosa ‘brassicae’ isolates from the stem pieces were identified by polymerase chain reaction (PCR). Results from the two experiments showed that, compared with the controls, flooding for 1 to 2 weeks substantially reduced recovery of L. biglobosa ‘brassicae’ and flooding for 4 weeks resulted in negligible recovery of L. biglobosa ‘brassicae’. All of the 99 selected isolates produced a 444-bp DNA fragment in the PCR, confirming that they belong to L. biglobosa ‘brassicae’. Results also indicated that flooding caused rapid decomposition of the stem pieces. After flooding for 8 weeks, the dry weight of the stem pieces was reduced by 28 to 42% in the laboratory experiment and by 26 to 36% in the field experiment. These results suggest that oilseed rape–rice rotation is probably an efficient way to reduce longevity of L. biglobosa ‘brassicae’ in stubble of winter oilseed rape in central China.

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