Complexities underlying the breeding and deployment of Dutch elm disease resistant elms

AbstractDutch elm disease (DED) is a vascular wilt disease caused by the pathogens Ophiostoma ulmi and Ophiostoma novo-ulmi with multiple ecological phases including pathogenic (xylem), saprotrophic (bark) and vector (beetle flight and beetle feeding wound) phases. Due to the two DED pandemics during the twentieth century the use of elms in landscape and forest restoration has declined significantly. However new initiatives for elm breeding and restoration are now underway in Europe and North America. Here we discuss complexities in the DED ‘system’ that can lead to unintended consequences during elm breeding and some of the wider options for obtaining durability or ‘field resistance’ in released material, including (1) the phenotypic plasticity of disease levels in resistant cultivars infected by O. novo-ulmi; (2) shortcomings in test methods when selecting for resistance; (3) the implications of rapid evolutionary changes in current O. novo-ulmi populations for the choice of pathogen inoculum when screening; (4) the possibility of using active resistance to the pathogen in the beetle feeding wound, and low attractiveness of elm cultivars to feeding beetles, in addition to resistance in the xylem; (5) the risk that genes from susceptible and exotic elms be introgressed into resistant cultivars; (6) risks posed by unintentional changes in the host microbiome; and (7) the biosecurity risks posed by resistant elm deployment. In addition, attention needs to be paid to the disease pressures within which resistant elms will be released. In the future, biotechnology may further enhance our understanding of the various resistance processes in elms and our potential to deploy trees with highly durable resistance in elm restoration. Hopefully the different elm resistance processes will prove to be largely under durable, additive, multigenic control. Elm breeding programmes cannot afford to get into the host–pathogen arms races that characterise some agricultural host–pathogen systems.

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Identification of major quantitative trait loci controlling field resistance to downy mildew in cultivated lettuce (Lactuca sativa L.)

Phytopathology ◽

10.1094/phyto-08-20-0367-r ◽

2020 ◽

Author(s):

Lorena B Parra ◽

Ivan Simko ◽

Richard Michelmore

Keyword(s):

Downy Mildew ◽

Lactuca Sativa ◽

Quantitative Trait ◽

Durable Resistance ◽

Gene Pyramiding ◽

Field Resistance ◽

Significant Qtls ◽

Resistant Cultivars ◽

Lactuca Sativa L ◽

Grand Rapids

Lettuce downy mildew caused by Bremia lactucae Regel is the most economically important foliar disease of lettuce (Lactuca sativa L.). The deployment of resistant cultivars carrying dominant resistance genes (Dm genes) plays a crucial role in integrated downy mildew disease management; however, high variability in pathogen populations leads to the defeat of plant resistance conferred by Dm genes. Some lettuce cultivars exhibit field resistance that is only manifested in adult plants. Two populations of recombinant inbred lines (RILs), originating from crosses between the field resistant cultivars Grand Rapids and Iceberg and susceptible cultivars Salinas and PI491224, were evaluated for downy mildew resistance under field conditions. One hundred and sixty RILs from the Iceberg × PI491224 and 88 RILs from the Grand Rapids × Salinas RIL populations were genotyped using genotyping by sequencing, which respectively generated 906 and 746 high quality markers that were used for quantitative trait locus (QTL) analysis. We found a QTL in Chromosome 4 that is present in both Grand Rapids × Salinas and Iceberg × PI491224 populations that has a major effect on field resistance. We also found two additional significant QTLs in Chromosomes 2 and 5 in the Iceberg × PI491224 RIL population. Marker-assisted gene pyramiding of multiple Dm genes in combination with QTLs for field resistance provides the opportunity to develop cultivars with more durable resistance to B. lactucae.

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Identification of powdery mildew resistance genes in Polish common oat (Avena sativa L.) cultivars using host-pathogen tests

Acta Agrobotanica ◽

10.5586/aa.2012.008 ◽

2012 ◽

Vol 65 (3) ◽

pp. 63-68 ◽

Cited By ~ 10

Author(s):

Sylwia Okoń

Keyword(s):

Powdery Mildew ◽

Resistance Genes ◽

Powdery Mildew Resistance ◽

Resistance Pattern ◽

Mildew Resistance ◽

Differential Set ◽

Host Pathogen ◽

Resistance Patterns ◽

Breeding Programmes ◽

New Gene

The aim of the present study was to characterize and identify powdery mildew resistance genes in Polish common oat cultivars using host-pathogen tests. A differential set of six <em>Blumeria graminis </em>f.sp<em>. avenae </em>isolates virulent or avirulent to four cultivars and one line that has known resistance to powdery mildew were used. Among the investigated cultivars, only four of them (13.3%) had resistance patterns similar to genotypes belonging to the differential set. The resistance of OMR group 1 was found in the cultivar ‘Dragon’, while that of OMR2 in the cultivar ‘Skrzat’. The cultivars ‘Deresz’ and ‘Hetman’ showed a resistance pattern that corresponded with OMR group 3. The resistance corresponding to OMR4 was not found, which suggests that until now this gene has not been used in Polish oat breeding programmes. The cultivar ‘Canyon’ had a different pat- tern of resistance than the genotypes that have already known OMR genes, which indicates that the resistance of this cultivar is determined by a new gene or a combination of known genes.

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Screening common bean germplasm for resistance to genetically diverse Sclerotinia sclerotiorum isolates from Argentina

Acta Scientiarum Agronomy ◽

10.4025/actasciagron.v42i1.42786 ◽

2020 ◽

Vol 42 ◽

pp. e42786

Author(s):

Carla Luciana Abán ◽

Gisel Maria Taboada ◽

Norma Beatriz Casalderrey ◽

Maria Elisa Maggio ◽

Mario Osvaldo Chocobar ◽

...

Keyword(s):

Common Bean ◽

Sclerotinia Sclerotiorum ◽

Durable Resistance ◽

Weather Conditions ◽

White Mold ◽

Post Inoculation ◽

Progress Curve ◽

Breeding Programmes ◽

Favorable Weather ◽

Production Areas

White mold caused by Sclerotinia sclerotiorum (Lib.) de Bary is a devastating disease that affects the common bean (Phaseolus vulgaris. L) crop worldwide. In Argentina, white mold has been detected in all bean production areas, reaching seed yield and quality losses up to 100% on susceptible common bean cultivars under favorable weather conditions. The aim of this study was to screen the physiological resistance of 20 common bean accessions to five genetically distinct isolates of S. sclerotiorum collected from the main common bean growing area of Argentina, using the greenhouse straw test. The white mold reaction was scored at 7, 14, and 21 days post-inoculation using a 1 (no disease symptoms) to 9 (severely diseased or dead plants) scale and the area under the disease progress curve (AUDPC) was determined. Highly significant differences (p < 0.001) were observed between isolates, accessions and genotype x isolate interaction at the three evaluations dates. All cultivars and lines were susceptible at the end of the assessment, except line A 195 which was resistant to white mold against the five isolates tested and was significantly different from all accessions. This work represents a valuable contribution to regional breeding programmes aimed to obtain cultivars with durable resistance.

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Correction to: Breeding and scientific advances in the fight against Dutch elm disease: Will they allow the use of elms in forest restoration?

New Forests ◽

10.1007/s11056-018-9645-5 ◽

2018 ◽

Vol 50 (3) ◽

pp. 519-519 ◽

Cited By ~ 2

Author(s):

Juan A. Martín ◽

Juan Sobrino-Plata ◽

Jesús Rodríguez-Calcerrada ◽

Carmen Collada ◽

Luis Gil

Keyword(s):

Forest Restoration ◽

Dutch Elm Disease ◽

Scientific Advances

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Durable Resistance and Host-Pathogen-Environment Interaction

Durable Resistance in Crops ◽

10.1007/978-1-4615-9305-8_12 ◽

1983 ◽

pp. 125-140 ◽

Cited By ~ 4

Author(s):

J. C. Zadoks ◽

J. A. G. van Leur

Keyword(s):

Durable Resistance ◽

Environment Interaction ◽

Host Pathogen

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A novel source of resistance to verticillium wilt in alfalfa

Canadian Journal of Plant Science ◽

10.4141/p03-096 ◽

2004 ◽

Vol 84 (1) ◽

pp. 401-404 ◽

Cited By ~ 3

Author(s):

B. D. Gossen ◽

P. G. Jefferson

Keyword(s):

Medicago Sativa ◽

Key Words ◽

Verticillium Wilt ◽

Field Resistance ◽

Canadian Prairies ◽

Disease Reaction ◽

Resistant Cultivars ◽

Verticillium Albo Atrum

Verticillium wilt (VW) can cause substantial losses in yield and stand longevity in alfalfa. Resistant cultivars are available, but susceptible cultivars continue to be grown on the Canadian Prairies, where VW generally occurs only under irrigation. A study was conducted to assess the yield and persistence of 11 alfalfa lines under irrigation on three commercial fields in southern Saskatchewan. An epidemic of verticillium wilt developed at one site; the disease reaction of the susceptible Medicago sativa ssp. falcata line ‘SC Mf3713’ was similar to that of the resistant cv. Barrier. SC Mf3713 may carry a novel form of field resistance to VW, and merits further study. Key words: Medicago sativa ssp. falcata, Verticillium albo-atrum

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Expression of Inoculum and Family Specific Responses in the Ponderosa Pine-Western Gall Rust Pathosystem

Plant Disease ◽

10.1094/pdis.1997.81.1.57 ◽

1997 ◽

Vol 81 (1) ◽

pp. 57-62 ◽

Cited By ~ 2

Author(s):

James A. Walla ◽

Gerald A. Tuskan ◽

John E. Lundquist ◽

Chengguo Wang

Keyword(s):

Ponderosa Pine ◽

Field Resistance ◽

Red Pigment ◽

Host Pathogen Interactions ◽

Red Pigments ◽

Host Family ◽

Inoculum Source ◽

Mother Tree ◽

Host Pathogen

Host-pathogen interactions in the ponderosa pine-western gall rust pathosystem were studied using seedlings from eight open-pollinated mother-tree families and Peridermium harknessii aeciospores from two geographically separate sources. Pregall symptoms occurred on seedlings by 4 days after inoculation (DAI). Gall occurrence was essentially complete by 230 DAI. Of three measured pigments, light red and dark red pigments on the needles developed most rapidly. Light red pigment on the base of the needles between 21 and 66 DAI was the pregall symptom most often (i) affected by inoculum source and host family, and (ii) correlated to gall width. Pre- and postgall symptoms varied significantly (i) between inocula, and (ii) among mother-tree families. No relationship was found between field resistance ratings of the mother trees and the expression of resistance in their progeny. The inocula varied in pathogenicity, and the seedling families varied in response to infection, as shown by differences in level of incidence and site of development of pigmentation and gall size on inoculated seedlings.

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Mapping and DNA sequence characterisation of the Rysto locus conferring extreme virus resistance to potato cultivar ‘White Lady’

10.1101/809152 ◽

2019 ◽

Author(s):

Mihály Kondrák ◽

Andrea Kopp ◽

Csilla Uri ◽

Anita Sós-Hegedűs ◽

Edina Csákvári ◽

...

Keyword(s):

Dna Sequence ◽

Resistance Genes ◽

Virus Resistance ◽

Genomic Sequence ◽

Durable Resistance ◽

Potato Cultivar ◽

Wild Plant ◽

Commercial Potato ◽

Breeding Programmes ◽

Extreme Virus Resistance

AbstractVirus resistance genes carried by wild plant species are valuable resources for plant breeding. The Rysto gene, conferring a broad spectrum of durable resistance, originated from Solanum stoloniferum and was introgressed into several commercial potato cultivars, including ‘White Lady’, by classical breeding. Rysto was mapped to chromosome XII in potato, and markers used for marker-assisted selection in breeding programmes were identified. Nevertheless, there was no information on the identity of the Rysto gene. To begin to reveal the identification of Rysto, fine-scale genetic mapping was performed which, in combination with chromosome walking, narrowed down the locus of the gene to approximately 1 Mb. DNA sequence analysis of the locus identified six full-length NBS-LRR-type (short NLR-type) putative resistance genes. Two of them, designated TMV2 and TMV3, were similar to a TMV resistance gene isolated from tobacco and to Y-1, which co-segregates with Ryadg, the extreme virus resistance gene originated from Solanum andigena and localised to chromosome XI. Furthermore, TMV2 of ‘White Lady’ was found to be 95% identical at the genomic sequence level with the recently isolated Rysto gene of the potato cultivar ‘Alicja’. In addition to the markers identified earlier, this work generated five tightly linked new markers which can serve potato breeding efforts for extreme virus resistance.

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Field resistance and molecular detection of the orange rust resistance gene linked to G1 marker in Brazilian cultivars of sugarcane

Summa Phytopathologica ◽

10.1590/0100-5405/221803 ◽

2020 ◽

Vol 46 (2) ◽

pp. 92-97 ◽

Cited By ~ 1

Author(s):

Ícaro Fier ◽

Thiago Willian Almeida Balsalobre ◽

Roberto Giacomini Chapola ◽

Hermann Paulo Hoffmann ◽

Monalisa Sampaio Carneiro

Keyword(s):

Molecular Detection ◽

Durable Resistance ◽

Marker Locus ◽

Field Resistance ◽

Breeding Programs ◽

Saccharum Spp ◽

Resistant Phenotype ◽

Marker Efficiency ◽

Diagrammatic Scale ◽

Sugarcane Industry

ABSTRACT Sugarcane (Saccharum spp.), an important crop for tropical and subtropical countries, is used in the production of sugar and biofuel. Orange rust, a disease caused by the fungus Puccinia kuehnii, can reduce the yield and harm the sugarcane industry. Molecular markers linked to resistance genes can help breeding programs confirm introgression of favorable alleles, find new resistance sources and release new cultivars that have durable resistance. In the current study, the aims were (i) to evaluate in the field the resistance to orange rust of 24 Brazilian commercial cultivars; (ii) to assess the frequency of the allele at G1 marker locus in the set of cultivars, and (iii) to study the usefulness of G1 marker to predict the resistant phenotype and its potential for marker assisted selection. A diagrammatic scale, which ranged from 1 (plants without symptoms) to 9 (highly susceptible plants), was used to determine the disease severity. Considering resistant cultivars those with mean severity up to 3, G1 marker efficiency in predicting the resistant phenotype was 71.43%. In addition, there was a reduction of 35% in the overall mean severity when G1 marker was present. G1 marker is an important molecular tool that can be used by breeding programs in the search for sugarcane cultivars resistant to orange rust.

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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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