scholarly journals A Field Method for Evaluating the Potential Durability of New Resistance Sources: Application to the Leptosphaeria maculans-Brassica napus Pathosystem

2000 ◽  
Vol 90 (9) ◽  
pp. 961-966 ◽  
Author(s):  
H. Brun ◽  
S. Levivier ◽  
I. Somda ◽  
D. Ruer ◽  
M. Renard ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Field Experiment ◽  
Resistance Genes ◽  
Leptosphaeria Maculans ◽  
Rapid Change ◽  
Natural Populations ◽  
Field Method ◽  
Addition Line ◽  
Resistant Lines ◽  
High Level

To increase the longevity of new resistance genes by avoiding a rapid change in pathogen populations, we established a new field method to determine, before the release of a resistant cultivar, whether and how rapidly the pathogen population is capable of responding to the selective pressure we impose. This method was applied to the Leptosphaeria maculans-Brassica napus pathosystem. The potential durability of two new major resistance genes introgressed into B. napus from the Brassica B genome was tested separately for each gene under field conditions for 4 years. Successive inoculations with residues of the resistant lines mixed with susceptible contaminated plant material recovered at harvest the previous year were performed in autumn. The Jlm1 resistance gene originating from B. juncea conferred complete resistance on the B. napus-B. juncea recombinant lines MX and MXS to inoculation of the cotyledons with a large diversity of L. maculans isolates. It also gave a high level of stem canker resistance in the field against natural populations of the pathogen. A similar level of resistance was obtained in the B. napus-B. nigra addition line LA4+, containing B. nigra chromosome 4 in a B. napus background. In the second year of the field experiment (i.e., the first in which residues from the resistant lines were included in the inoculation material), both MX and LA4+ maintained a high level of resistance. In the third and fourth years of the field experiment, the resistance of MX and MXS exposed to inoculum produced from their own residues broke down, but against fungal populations from susceptible B. napus or resistant B. nigra material remained effective. In contrast, LA4+ remained highly resistant to all sources of inoculum for the 4-year experiment.

The Role of Phytoalexins in the Seedling Resistance to Leptosphaeria maculans in Some Crucifers

1995 ◽  
Vol 50 (1-2) ◽  
pp. 15-20 ◽  
Author(s):  
Michael Storck ◽  
Maria D. Sacristán
Keyword(s):  
Brassica Napus ◽  
Leptosphaeria Maculans ◽  
Brassica Species ◽  
Fungal Isolate ◽  
Time Intervals ◽  
Seedling Resistance ◽  
Sinapis Arvensis ◽  
Resistant Lines ◽  
Resistance Reaction

Abstract Brassica juncea, Brassica carinata and Sinapis arvensis resistant lines to Leptosphaeria maculans and four Brassica napus cuitivars susceptible to this pathogen in seedling stage were analyzed in relation to the accumulation of phytoalexins after inoculation with L. maculans. Cotyledon inoculations with spore suspensions of an aggressive and a non-aggressive isolate of L. maculans were performed on seedlings of these lines. The quantity of accumulated phytoalexins in the cotyledons was determined at different time intervals after inoculation. The content and composition of phytoalexins differed considerably among the tested species and according to the fungal isolate used. In the tested Brassica species seedling resistance against L. maculans could not be related to phytoalexin accumulation. However, in Sinapis arvensis phytoalexins might contribute to the resistance reaction to this pathogen.

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.

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.

scholarly journals Genome-wide identification and comparative analysis of NBS-LRR resistance genes in Brassica napus

2018 ◽  
Vol 69 (1) ◽  
pp. 72 ◽  
Author(s):  
Salman Alamery ◽  
Soodeh Tirnaz ◽  
Philipp Bayer ◽  
Reece Tollenaere ◽  
Boulos Chaloub ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Brassica Napus ◽  
Resistance Genes ◽  
Plant Disease Resistance ◽  
Interleukin 1 ◽  
Critical Role ◽  
Coiled Coil ◽  
Genome Wide ◽  
High Level ◽  
Plant Disease Resistance Genes

Plant disease-resistance genes play a critical role in providing resistance against pathogens. The largest family of resistance genes are the nucleotide-binding site (NBS) and leucine-rich repeat (LRR) genes. They are classified into two major subfamilies, toll/interleukin-1 receptor (TIR)-NBS-LRR (TNL) and coiled-coil (CC)-NBS-LRR (CNL) proteins. We have identified and characterised 641 NBS-LRR genes in Brassica napus, 249 in B. rapa and 443 in B. oleracea. A ratio of 1 : 2 of CNL : TNL genes was found in the three species. Domain structure analysis revealed that 57% of the NBS-LRR genes are typical resistance genes and contain all three domains (TIR/CC, NBS, LRR), whereas the remaining genes are partially deleted or truncated. Of the NBS-LRR genes, 59% were found to be physically clustered, and individual genes involved in clusters were more polymorphic than those not clustered. Of the NBS-LRR genes in B. napus, 50% were identified as duplicates, reflecting a high level of genomic duplication and rearrangement. Comparative analysis between B. napus and its progenitor species indicated that >60% of NBS-LRR genes are conserved in B. napus. This study provides a valuable resource for the identification and characterisation of candidate NBS-LRR genes.

scholarly journals Cytological Investigation of Resistance to Leptosphaeria maculans Conferred to Brassica napus by Introgressions Originating from B. juncea or B. nigra B Genome

1999 ◽  
Vol 89 (12) ◽  
pp. 1200-1213 ◽  
Author(s):  
S. Roussel ◽  
M. Nicole ◽  
F. Lopez ◽  
M. Renard ◽  
A. M. Chèvre ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Leptosphaeria Maculans ◽  
Hypersensitive Reaction ◽  
Plant Responses ◽  
Addition Line ◽  
B Genome ◽  
Hr Cell Death ◽  
Wall Apposition ◽  
Cell Changes ◽  
High Degree

Introgressions into Brassica napus from the B genome, either the B. nigra chromosome B4 or the B. juncea fragment carrying the Jlm1 gene, have given rise to the B. napus-B. nigra addition line (LA4+) and the B. napus-B. juncea recombinant line (MXS), respectively. The resistance of these two lines to Leptosphaeria maculans is characterized by a hypersensitive reaction (HR) on both the cotyledons and leaves, while the collar displays a high degree of resistance. Responses induced in cotyledons of the two lines by L. maculans inoculation were investigated with emphasis on cytological events underlying the HR and on host defense reactions. Features of host cell changes including condensation and lobing of nuclei, fragmentation of chromatin, disruption of the nuclear membranes, and plasma membrane withdrawal were reminiscent of HR cell death in MXS and LA4+ plants. Restriction of pathogen growth to the infection areas in LA4+ was correlated to reinforcement of cell wall barriers, including wall apposition, papillae, and vessel plugging. In MXS, the lower expression of resistance was associated with a delay in plant responses. These results indicate that mechanisms underlying the HR in the B. napus recombinant and addition lines are differently controlled according to the introgressed genes.

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.

scholarly journals A Cluster of Major Specific Resistance Genes to Leptosphaeria maculans in Brassica napus

2004 ◽  
Vol 94 (6) ◽  
pp. 578-583 ◽  
Author(s):  
R. Delourme ◽  
M. L. Pilet-Nayel ◽  
M. Archipiano ◽  
R. Horvais ◽  
X. Tanguy ◽  
...  
Keyword(s):  
Brassica Napus ◽  
Resistance Genes ◽  
Specific Resistance ◽  
Quantitative Resistance ◽  
Specific Interaction ◽  
Leptosphaeria Maculans ◽  
Field Resistance ◽  
Genetic Identification ◽  
Adult Plant ◽  
Avirulence Genes

Two types of genetic resistance to Leptosphaeria maculans usually are distinguished in Brassica napus: qualitative, total resistance expressed at the seedling stage and quantitative, partial resistance expressed at the adult plant stage. The latter is under the control of many genetic factors that have been mapped through quantitative trait loci (QTL) studies using ‘Darmor’ resistance. The former usually is ascribed to race-specific resistance controlled by single resistance to L. maculans (Rlm) genes. Three B. napus-originating specific Rlm genes (Rlm1, Rlm2, and Rlm4) previously were characterized. Here, we report on the genetic identification of two novel resistance genes, Rlm3 and Rlm7, corresponding to the avirulence genes AvrLm3 and AvrLm7. The identification of a novel L. maculans- B. napus specific interaction allowed the detection of another putative new specific resistance gene, Rlm9. The resistance genes were mapped in two genomic regions on LG10 and LG16 linkage groups. A cluster of five resistance genes (Rlm1, Rlm3, Rlm4, Rlm7, and Rlm9) was strongly suggested on LG10. The relation between all these specific resistance genes and their potential role in adult-plant field resistance is discussed. These two Rlm-carrying regions do not correspond to major QTL for Darmor quantitative resistance.

Seedling and adult plant resistance to blackleg (Leptosphaeria maculans (Desm.) Ces. et de Not.) in spring rape (Brassica napus L.)

1980 ◽  
Vol 31 (1) ◽  
pp. 37 ◽  
Author(s):  
LA Cargeeg ◽  
N Thurling
Keyword(s):  
Brassica Napus ◽  
Leptosphaeria Maculans ◽  
Adult Plant ◽  
Selection Line ◽  
Selected Lines ◽  
Brassica Napus L ◽  
Seedling Resistance ◽  
Causal Organism ◽  
Resistant Lines ◽  
The Mean

In a glasshouse test with a large number of lines derived by self-pollination of rape plants (Brassica napus L.) randomly selected from each or four spring cultivars, considerable variation in the responses of seedlings to blackleg infection (causal organism Leptosphaeria maculans (Desm.) Ces. et de Not.) was observed between and within cultivars. Although the mean disease scores of lines within each cultivar ranged between the extremes of susceptibility and resistance, a much higher frequency of resistant lines were detected in the cultivar Nosovsky than in Ceska and Zollerngold. The lines used in this initial test provided a basis for developing a susceptible and resistant line from each cultivar, and these were tested together with six other lines previously rated as being resistant in the field, under both glasshouse and field conditions. Responses to seedling infection in four different glasshouse environments showed only three field-selected lines (Wesreo, Mutu and R46) to have adequate seedling resistance. All glasshouse-selected lines were susceptible in these glasshouse tests, and the resistant selections were In all cases slightly more susceptible than the corresponding susceptible selections. In the field test, the field-selected lines as a group were clearly more resistant than any of the glasshouse-selected lines except the Nosovsky resistant selection line. The Ceska and Zollerngold resistant selections, although susceptible in comparison with the field selections, were more resistant than the corresponding susceptible selections. Considerable variation in the mean disease scores of individual plants obtained at maturity was observed within all lines except the two Tower glasshouse selections. The frequency of resistant plants was fairly high in all field-selected lines except 73N22-1 and very low in all glasshouse-selected lines except the Nosovsky resistant selection. Coefficients of correlation between disease scores at maturity in the field and scores of young plants in each of four different glasshouse environments were significant for all but one environment. The highest correlation was observed in the case of the procedure involving a single inoculation 10 days after sowing and growth of seedlings under a daily temperature regime of 25/20�C. The five lines ranked most resistant in this test were also the five most resistant lines in the field.

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