Qualitative and Quantitative Late Blight Resistance in the Potato Cultivar Sarpo Mira Is Determined by the Perception of Five Distinct RXLR Effectors

Potato defends against Phytophthora infestans infection by resistance (R)-gene-based qualitative resistance as well as a quantitative field resistance. R genes are renowned to be rapidly overcome by this oomycete, and potato cultivars with a decent and durable resistance to current P. infestans populations are hardly available. However, potato cultivar Sarpo Mira has retained resistance in the field over several years. We dissected the resistance of ‘Sarpo Mira’ in a segregating population by matching the responses to P. infestans RXLR effectors with race-specific resistance to differential strains. The resistance is based on the combination of four pyramided qualitative R genes and a quantitative R gene that was associated with field resistance. The qualitative R genes include R3a, R3b, R4, and the newly identified Rpi-Smira1. The qualitative resistances matched responses to avirulence (AVR)3a, AVR3b, AVR4, and AVRSmira1 RXLR effectors and were overcome by particular P. infestans strains. The quantitative resistance was determined to be conferred by a novel gene, Rpi-Smira2. It was only detected under field conditions and was associated with responses to the RXLR effector AvrSmira2. We foresee that effector-based resistance breeding will facilitate selecting and combining qualitative and quantitative resistances that may lead to a more durable resistance to late blight.

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

International Journal of Molecular Sciences ◽

10.3390/ijms22010313 ◽

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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Cloning and Characterization of R3b; Members of the R3 Superfamily of Late Blight Resistance Genes Show Sequence and Functional Divergence

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-11-10-0276 ◽

2011 ◽

Vol 24 (10) ◽

pp. 1132-1142 ◽

Cited By ~ 71

Author(s):

Guangcun Li ◽

Sanwen Huang ◽

Xiao Guo ◽

Ying Li ◽

Yu Yang ◽

...

Keyword(s):

Late Blight ◽

Positional Cloning ◽

Sequence Similarity ◽

Functional Divergence ◽

Durable Resistance ◽

Coiled Coil ◽

Avirulence Gene ◽

R Gene ◽

Gene Stacking ◽

High Sequence Similarity

Massive resistance (R) gene stacking is considered to be one of the most promising approaches to provide durable resistance to potato late blight for both conventional and genetically modified breeding strategies. The R3 complex locus on chromosome XI in potato is an example of natural R gene stacking, because it contains two closely linked R genes (R3a and R3b) with distinct resistance specificities to Phytophthora infestans. Here, we report about the positional cloning of R3b. Both transient and stable transformations of susceptible tobacco and potato plants showed that R3b conferred full resistance to incompatible P. infestans isolates. R3b encodes a coiled-coil nucleotide-binding site leucine-rich repeat protein and exhibits 82% nucleotide identity with R3a located in the same R3 cluster. The R3b gene specifically recognizes Avr3b, a newly identified avirulence factor from P. infestans. R3b does not recognize Avr3a, the corresponding avirulence gene for R3a, showing that, despite their high sequence similarity, R3b and R3a have clearly distinct recognition specificities. In addition to the Rpi-mcd1/Rpi-blb3 locus on chromosome IV, the R3 locus on chromosome XI is the second example of an R-gene cluster with multiple genes recognizing different races of P. infestans.

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Fungicide Spray Programs for Defender, A New Potato Cultivar with Resistance to Late Blight and Early Blight

Plant Disease ◽

10.1094/pdis-91-10-1327 ◽

2007 ◽

Vol 91 (10) ◽

pp. 1327-1336 ◽

Cited By ~ 14

Author(s):

W. R. Stevenson ◽

R. V. James ◽

Debra Ann Inglis ◽

Dennis A. Johnson ◽

R. Thomas Schotzko ◽

...

Keyword(s):

Late Blight ◽

Early Blight ◽

Total Yield ◽

Development Program ◽

Potato Cultivar ◽

Field Tests ◽

Field Resistance ◽

Russet Burbank ◽

Ranger Russet ◽

Progress Curve

Defender (A90586-11) is a new late blight-resistant potato cultivar which was released from the Tri-State Potato Variety Development Program in 2004. Conventional and reduced fungicide spray programs were compared on Defender and Russet Burbank (3 years) and Ranger Russet (1 year) in Wisconsin experimental field trials. Useful levels of field resistance to both late blight and early blight were observed in Defender in the absence of fungicide sprays and reduced fungicide input programs. Disease progressed slowest on Defender regardless of fungicide program, relative to Russet Burbank and Ranger Russet. Organic, conventional, and reduced fungicide spray programs also were compared on Defender and Russet Burbank in experimental greenhouse and field tests in Washington. Fungicide spray programs performed similarly on both Defender and Russet Burbank; however, area under the disease progress curve values for no-fungicide treatments were either three times (greenhouse) or six times (field) lower on Defender compared with Russet Burbank. Regardless of the fungicide program, total yield was higher for Defender than Russet Burbank. Mean economic returns associated with Defender also were higher than for Russet Burbank ($6,196 versus $4,388/ha). Fungicide and nonfungicide treatment programs generated similar returns on Defender whereas conventional and reduced fungicide programs generated comparable but higher returns than the nonfungicide program on Russet Burbank.

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The RPi-mcd1 Locus from Solanum microdontum Involved in Resistance to Phytophthora infestans, Causing a Delay in Infection, Maps on Potato Chromosome 4 in a Cluster of NBS-LRR Genes

Molecular Plant-Microbe Interactions ◽

10.1094/mpmi-21-7-0909 ◽

2008 ◽

Vol 21 (7) ◽

pp. 909-918 ◽

Cited By ~ 59

Author(s):

M. Y. Adillah Tan ◽

Ronald C. B. Hutten ◽

Carolina Celis ◽

Tae-Ho Park ◽

Rients E. Niks ◽

...

Keyword(s):

Late Blight ◽

Late Blight Resistance ◽

Field Resistance ◽

R Gene ◽

Chromosome 4 ◽

Solanum Microdontum ◽

Plant Maturity ◽

Trait Locus ◽

Plant Pathogen Interactions ◽

Resistance Data

The distinction between field resistance and resistance based on resistance (R) genes has been proven valid for many plant–pathogen interactions. This distinction does not seem to be valid for the interaction between potato and late blight. In this study, a locus involved in late blight resistance, derived from Solanum microdontum, provides additional evidence for this lack of distinction. The resistance is associated with a hypersensitive response and results in a delay of infection of approximately 1 to 2 weeks. Both a quantitative as well as a qualitative genetic approach were used, based on data from a field assay. Quantitative trait locus (QTL) analysis identified a QTL on chromosome 4 after correction of the resistance data for plant maturity. A qualitative genetic analysis resulted in the positioning of this locus on the short arm of chromosome 4 in between amplified fragment length polymorphism marker pCTmACG_310 and cleaved amplified polymorphic sequence markers TG339 and T0703. This position coincides with a conserved Phytophthora R gene cluster which includes R2, R2-like, RPi-blb3, and RPi-abpt. This implies that RPi-mcd1 is the fifth R gene of this nucleotide-binding site leucine-rich repeat cluster. The implications of our results on R-gene-based and field resistance are discussed.

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The effect of the presence of R-genes for resistance to late blight (Phytophthora infestans) of potato (Solanum tuberosum) on the underlying level of field resistance

Plant Pathology ◽

10.1046/j.1365-3059.2003.00811.x ◽

2003 ◽

Vol 52 (2) ◽

pp. 193-198 ◽

Cited By ~ 68

Author(s):

H. E. Stewart ◽

J. E. Bradshaw ◽

B. Pande

Keyword(s):

Solanum Tuberosum ◽

Late Blight ◽

Phytophthora Infestans ◽

Field Resistance ◽

R Genes

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Identification of Genes Underlying the Resistance to Melampsora larici-populina in an R Gene Supercluster of the Populus deltoides Genome

Plant Disease ◽

10.1094/pdis-08-19-1699-re ◽

2020 ◽

Vol 104 (4) ◽

pp. 1133-1143

Author(s):

Suyun Wei ◽

Huaitong Wu ◽

Xiaoping Li ◽

Yingnan Chen ◽

Yonghua Yang ◽

...

Keyword(s):

Populus Deltoides ◽

De Novo ◽

Quantitative Resistance ◽

Rust Fungus ◽

Constitutive Expression ◽

Transcriptome Profiling ◽

R Gene ◽

R Genes ◽

Sequencing Data ◽

Key Genes

Identification of the particular genes in an R genes supercluster underlying resistance to the rust fungus Melampsora larici-populina in poplar genome remains challenging. Based on the de novo assembly of the Populus deltoides genome, all of the detected major genetic loci conferring resistance to M. larici-populina were confined to a 3.5-Mb region on chromosome 19. The transcriptomes of the resistant and susceptible genotypes were sequenced for a timespan from 0 to 168 hours postinoculation. By mapping the differentially expressed genes to the target genomic region, we identified two constitutive expression R genes and one inducible expression R gene that might confer resistance to M. larici-populina. Nucleotide variations were predicted based on the reconstructed haplotypes for each allele of the candidate genes. We also confirmed that salicylic acid was the phytohormone mediating signal transduction pathways, and PR-1 was identified as a key gene inhibiting rust reproduction. Finally, quantitative reverse transcription PCR assay revealed consistent expressions with the RNA-sequencing data for the detected key genes. This study presents an efficient approach for the identification of particular genes underlying phenotype of interest by the combination of genetic mapping, transcriptome profiling, and candidate gene sequences dissection. The identified key genes would be useful for host resistance diagnosis and for molecular breeding of elite poplar cultivars exhibiting resistance to M. larici-populina infection. The detected R genes are also valuable for testing whether the combination of individual R genes can induce durable quantitative resistance.

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POPULATION STRUCTURE OF PHYTOPHTHORA INFESTANS ON WORLDWIDE SCALE: A REVIEW

Pakistan Journal of Phytopathology ◽

10.33866/phytopathol.029.02.0402 ◽

2017 ◽

Vol 29 (2) ◽

pp. 281

Author(s):

Khalid Naveed ◽

Nasir A. Rajputt ◽

Sajid A. Khan ◽

Arbab Ahmad

Keyword(s):

Population Structure ◽

Late Blight ◽

Phytophthora Infestans ◽

Potato Cultivar ◽

R Genes ◽

Solanum Bulbocastanum ◽

Tuber Resistance ◽

Commercial Potato ◽

Rb Gene ◽

Late Blight Of Potato

Phytophthora infestans is a destructive pathogen that causes late blight of potato worldwide. Several sexually and asexually reproducing lineages of the pathogen have been identified and new lineages are more virulent as compared to their parental lineages. A new highly aggressive clonal lineage EU13_A2 has spread into potato fields of Europe, Africa and Asia in place of the older lineages. In North America, 24 clonal lineages US1to US24 have been identified. Despite of sexual reproduction, the overall population of P. infestans in potato and tomato fields is dominated by asexual lineages. Breeding has been done to transfer 'R' genes into commercial potato cultivars through classical breeding and by pyramiding of genes. Defender is the only potato cultivar that has foliar and tuber resistance to late blight. Genetically modified potato with RB gene from Solanum bulbocastanum has been developed but it lacks tuber resistance to disease. This review discusses population structure of P. infestans worldwide and breeding efforts to produce late blight resistant potato.

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Comparative analysis of late blight resistance R genes and their coding proteins in some potato genotypes

Czech Journal of Genetics and Plant Breeding ◽

10.17221/49/2021-cjgpb ◽

2021 ◽

Author(s):

Heba Amin Mahfouze ◽

Osama Ezzat El-Sayed

Keyword(s):

Amino Acid ◽

Late Blight ◽

Base Pair ◽

Durable Resistance ◽

Late Blight Resistance ◽

Nucleotide Sequences ◽

The Other ◽

Solid Base ◽

R Genes ◽

Sequence Alignments

Late blight (LB) disease can cause potato yield losses in both Egypt and the world. Therefore, the structural analysis of resistance (R) genes responsible for LB resistance will help in understanding their functions. This work aimed to identify the variations between the dominant and recessive alleles of two genes, R3a and R8 at the nucleotide and amino acid levels in five potato genotypes. Two genes of R3a and R8 representing the broad-spectrum LB resistance were amplified by specific primers, which gave one amplicon of 194 and 220 bp of each gene, respectively. Two fragments were sequenced after purification using an ABI 3730xl System DNA Sequencer. The DNA sequence alignments of two genes, R3a and R8, were determined among five selected potato genotypes. The percentage of genetic similarity of the nucleotide sequences of the R3a and R8 genes ranged between (82–83%) and (86–87%), respectively, in comparison to the reference sequences in the nucleotide BLAST. We report on the existence of positional differences in the nucleotide sequences, and base-pair substitutions of two fragments, resulting in amino acid changes between the resistant and susceptible potato genotypes. On the other hand, the highest total number of base-pair substitutions was recorded as 16 in the recessive allele r8 of the varieties Bellini and Cara. However, the lowest number was recorded as four in the dominant allele R3a of the variety Cara. The dendrograms of the five potato genotypes were made up of phylogenetically different clusters, separate from all the other named potato accessions of the two genes. The results of this study will create a solid base for the further understanding of the mechanism of plant-pathogen interactions and supply a theoretical reference for durable resistance to late blight diseases in the potato.

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Advances and Challenges in Bacterial Spot Resistance Breeding in Tomato (Solanum lycopersicum L.)

International Journal of Molecular Sciences ◽

10.3390/ijms21051734 ◽

2020 ◽

Vol 21 (5) ◽

pp. 1734

Author(s):

Pragya Adhikari ◽

Tika B. Adhikari ◽

Frank J. Louws ◽

Dilip R. Panthee

Keyword(s):

Quantitative Resistance ◽

Durable Resistance ◽

Resistance Breeding ◽

Field Resistance ◽

Control Measures ◽

Current Status ◽

Linkage Drag ◽

Bacterial Spot ◽

Regulatory Processes ◽

Solanum Lycopersicum L

Bacterial spot is a serious disease of tomato caused by at least four species of Xanthomonas. These include X. euvesicatoria (race T1), X. vesicatoria (race T2), X. perforans (races T3 and T4), and X. gardneri, with the distinct geographical distribution of each group. Currently, X. gardneri and X. perforans are two major bacterial pathogens of tomato in North America, with X. perforans (race T4) dominating in east-coast while X. gardneri dominating in the Midwest. The disease causes up to 66% yield loss. Management of this disease is challenging due to the lack of useful chemical control measures and commercial resistant cultivars. Although major genes for resistance (R) and quantitative resistance have been identified, breeding tomato for resistance to bacterial spot has been impeded by multiple factors including the emergence of new races of the pathogen that overcome the resistance, multigenic control of the resistance, linkage drag, non-additive components of the resistance and a low correlation between seedling assays and field resistance. Transgenic tomato with Bs2 and EFR genes was effective against multiple races of Xanthomonas. However, it has not been commercialized because of public concerns and complex regulatory processes. The genomics-assisted breeding, effectors-based genomics breeding, and genome editing technology could be novel approaches to achieve durable resistance to bacterial spot in tomato. The main goal of this paper is to understand the current status of bacterial spot of tomato including its distribution and pathogen diversity, challenges in disease management, disease resistance sources, resistance genetics and breeding, and future prospectives with novel breeding approaches.

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