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

Marcroft, S. J.; Elliott, Vicki L.; Cozijnsen, Anton; Salisbury, P. A.; Howlett, Barbara J.; Wouw, Angela P. Van de

doi:10.1071/cp11341

Cited by 84 publications

(110 citation statements)

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“…This result was not unexpected, as high rates of virulence towards Rlm3 [66] and Rlm4 [23] have been previously reported for Australian L. maculans isolates. Analysing the cotyledon reactions to single L. maculans isolates avirulent towards the respective R genes produced high LOD, high variance ‘CotQTL’ loci associated with each gene, as expected.…”

Section: Discussionsupporting

confidence: 82%

“…There has also been a widely-held view that blackleg APR is race non-specific [17], based largely on experience of the French variety Jet Neuf, which provided durable resistance to blackleg disease over many years in Europe and was also utilised in early efforts to improve blackleg resistance in Australian germplasm [21, 22]. However, more recent studies utilising single L. maculans isolates have questioned the “race non-specific” nature of blackleg APR [19, 23]. …”

Section: Introductionmentioning

confidence: 99%

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Multi-environment QTL studies suggest a role for cysteine-rich protein kinase genes in quantitative resistance to blackleg disease in Brassica napus

et al. 2016

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BackgroundResistance to the blackleg disease of Brassica napus (canola/oilseed rape), caused by the hemibiotrophic fungal pathogen Leptosphaeria maculans, is determined by both race-specific resistance (R) genes and quantitative resistance loci (QTL), or adult-plant resistance (APR). While the introgression of R genes into breeding material is relatively simple, QTL are often detected sporadically, making them harder to capture in breeding programs. For the effective deployment of APR in crop varieties, resistance QTL need to have a reliable influence on phenotype in multiple environments and be well defined genetically to enable marker-assisted selection (MAS).ResultsDoubled-haploid populations produced from the susceptible B. napus variety Topas and APR varieties AG-Castle and AV-Sapphire were analysed for resistance to blackleg in two locations over 3 and 4 years, respectively. Three stable QTL were detected in each population, with two loci appearing to be common to both APR varieties. Physical delineation of three QTL regions was sufficient to identify candidate defense-related genes, including a cluster of cysteine-rich receptor-like kinases contained within a 49 gene QTL interval on chromosome A01. Individual L. maculans isolates were used to define the physical intervals for the race-specific R genes Rlm3 and Rlm4 and to identify QTL common to both field studies and the cotyledon resistance response.ConclusionThrough multi-environment QTL analysis we have identified and delineated four significant and stable QTL suitable for MAS of quantitative blackleg resistance in B. napus, and identified candidate genes which potentially play a role in quantitative defense responses to L. maculans.Electronic supplementary materialThe online version of this article (doi:10.1186/s12870-016-0877-2) contains supplementary material, which is available to authorized users.

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Section: Discussionsupporting

confidence: 82%

Section: Introductionmentioning

confidence: 99%

Multi-environment QTL studies suggest a role for cysteine-rich protein kinase genes in quantitative resistance to blackleg disease in Brassica napus

et al. 2016

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“…The number of samples isolated from B. napus cultivars may also be too small to clearly display this association on the heatmap in the form of LD. Furthermore, the majority of Australian cultivars that have been genotyped contain Rlm4 and therefore there has been strong selection pressure at the AvrLm4-7 locus for a number of years in Australia (Marcroft et al, 2012). However, detailed studies comprising more isolates derived from B. juncea isolates will need to be conducted to confirm the validity of this association to B. napus cultivars.…”

Section: Phylogmentioning

confidence: 99%

“…(Balesdent et al, 2001); Not all data on these isolates was available, "-" denotes an unknown variable. IBCN numbers represent the IDs of "International Blackleg Collection Network" isolates (Marcroft et al, 2012).…”

Section: Fungal Samplesmentioning

confidence: 99%

Population Diversity of Leptosphaeria maculans in Australia

Patel¹,

Zander²,

Wouw³

et al. 2015

IJB

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The fungal pathogen Leptosphaeria maculans, causal agent of blackleg disease, is a primary cause of canola (Brassica napus) crop loss in Australia. Expanding our knowledge of the occurrence of this pathogen in Australia will provide valuable insights into developing methods of resistance against it. In this study, we examine the population diversity of L. maculans in Australia using single nucleotide polymorphisms (SNPs). An Illumina GoldenGate 384 SNP assay was developed and used to genotype 59 blackleg isolates collected from across Australia, in different years and from different stubble sources. Limited linkage disequilibrium, absence of significant clustering in the principal component analysis and a mixed dendrogram suggest that the Australian L. maculans population as a whole is panmictic. Some evidence of clonality concentrated in each state was also observed. There was a lack of correlation between SNP haplotypes, stubble cultivar and year of collection. These results suggest a high rate of sexual reproduction and evolutionary diversification in the pathogen. These features could enable the pathogen to overcome resistance and continue to cause disease in Brassica crops. Analysis of these fungal population isolates will help shed some light on evolution and pathogenicity questions in this important crop pathogen.

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“…Resistance genes in canola cultivars are identified by the use of 12 differential L. maculans isolates (with different sets of avirulence genes) in glasshouse infection trials. On this basis of responses (susceptible or resistant) to these isolates, seven resistance groups (A-G) that include a range of resistance genes have been defined (Marcroft et al 2012a). Stubble from each site represents local fungal populations, which can be analyzed in high throughput laboratory assays to quantify regional frequencies of alleles of avirulence genes.…”

Section: Monitoring Changes In Virulence Frequencies In Australian Pomentioning

confidence: 99%

Evolution of virulence in fungal plant pathogens: exploiting fungal genomics to control plant disease

2015

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The propensity of a fungal pathogen to evolve virulence depends on features of its biology (e.g. mode of reproduction) and of its genome (e.g. amount of repetitive DNA). Populations of Leptosphaeria maculans, a pathogen of Brassica napus (canola), can evolve and overcome disease resistance bred into canola within three years of commercial release of a cultivar. Avirulence effector genes are key fungal genes that are complementary to resistance genes. In L. maculans these genes are embedded within inactivated transposable elements in genomic regions where they are readily mutated or deleted. The risk of resistance breakdown in the field can be minimised by monitoring disease severity of canola cultivars and virulence of fungal populations using high throughput molecular assays and by sowing canola cultivars with different resistance genes in subsequent years. This strategy has been exploited to avert yield losses due to blackleg disease in Australia.

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

Cited by 84 publications

References 36 publications

Multi-environment QTL studies suggest a role for cysteine-rich protein kinase genes in quantitative resistance to blackleg disease in Brassica napus

Multi-environment QTL studies suggest a role for cysteine-rich protein kinase genes in quantitative resistance to blackleg disease in Brassica napus

Population Diversity of Leptosphaeria maculans in Australia

Evolution of virulence in fungal plant pathogens: exploiting fungal genomics to control plant disease

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