Disease resistance and pathogen population genetic

2002 ◽  
Vol 38 (SI 1 - 6th Conf EFPP 2002) ◽  
pp. 245-248
Author(s):  
B.A. McDonald ◽  
C. Linde
Keyword(s):  
Resistance Gene ◽  
Resistance Genes ◽  
Durable Resistance ◽  
Genetic Resistance ◽  
Pathogen Population ◽  
Evolutionary Forces ◽  
Boom And Bust ◽  
Major Resistance Genes ◽  
Pathogen Populations ◽  
Plant Pathosystems

Plant pathologists have seen many boom-and-bust cycles following the deployment of resistant varieties. These cycles result when pathogen populations adapt to the presence of a major resistance gene by evolving a new population that can overcome this resistance gene. The breakdown of genetic resistance is due to the evolution of the local pathogen population because of selection for mutants, recombinants, or immigrants that are better adapted to the resistant cultivar. To understand the process that leads to breakdown of a resistance gene, we need to understand the processes that govern pathogen evolution. Population geneticists have identified five evolutionary forces that interact to affect the evolution of organisms. We ranked these risks and developed a quantitative framework to predict the risk that a pathogen will evolve to overcome major resistance genes. Our hypothesis is that much of the durability of resistance genes is due to the nature of the pathogen population rather than to the nature of the resistance gene. The framework we developed can be used as a hypothesis to test against a large number of plant pathosystems. The underlying principles of the framework can be tested individually or in combination according to the available knowledge of the population genetics for any pathogen. We propose that this framework can be used to design breeding strategies to break the boom-and-bust cycle and lead to durable resistance.

scholarly journals Adaptation of Blumeria graminis f.sp. hordei to barley resistance genes in the Czech Republic in 1971–2000

2011 ◽  
Vol 49 (No. 6) ◽  
pp. 241-248 ◽  
Author(s):  
A. Dreiseitl
Keyword(s):  
Powdery Mildew ◽  
Resistance Genes ◽  
Spring Barley ◽  
Direct Selection ◽  
Pathogen Population ◽  
The Czech Republic ◽  
Evolutionary Forces ◽  
Major Resistance Genes ◽  
Barley Resistance ◽  
Resistance Of Varieties

Results of scoring the resistance of 35 selected spring barley varieties to powdery mildew, exhibiting high powdery mildew severity, in 307 variety trials of the Central Institute for Supervising and Testing in Agriculture were analysed. The varieties can be divided into two groups: the varieties that could not induce any changes in the pathogen population (the varieties with no effective resistance gene and varieties carrying gene mlo) and the varieties possessing major resistance genes [a total of 12 Ml-genes: a1, a3, a6, a7, a9, a12, a13, at, k1, La, g and (Kr)] to which the pathogen population adapted in 1971–2000. The time slope of decreasing resistance of varieties is described. The importance of individual evolutionary forces (mutations, migration, direct selection, indirect selection and recombinations) for the erosion of efficiency of respective major resistance genes and the effects of pathogen adaptation on population complexity and diversity are discussed.

Phytophthora sojae pathotype distribution and fungicide sensitivity in Michigan

Plant Disease ◽  
2021 ◽  
Author(s):  
Austin Glenn McCoy ◽  
Zachary Albert Noel ◽  
Janette L Jacobs ◽  
Kayla M Clouse ◽  
Martin I Chilvers
Keyword(s):  
Resistance Genes ◽  
Phytophthora Sojae ◽  
Significant Shift ◽  
Seed Treatments ◽  
Fungicide Sensitivity ◽  
History Of ◽  
Plant Stand ◽  
Rps Gene ◽  
Major Resistance Genes ◽  
Pathogen Populations

Identifying the pathotype structure of a Phytophthora sojae population is crucial for the effective management of Phytophthora stem and root rot of soybean (PRR). P. sojae has been successfully managed with major resistance genes, partial resistance, and fungicide seed treatments. However, prolonged use of resistance genes or fungicides can cause pathogen populations to adapt over time, rendering resistance genes or fungicides ineffective. A statewide survey was conducted to characterize the current pathotype structure and fungicide sensitivity of P. sojae within Michigan. Soil samples were collected from 69 fields with a history of PRR and fields having consistent plant stand establishment issues. Eighty-three isolates of P. sojae were obtained, and hypocotyl inoculations were performed on 14 differential soybean cultivars, all of which carry a single Rps gene or no resistance gene. The survey identified a loss of effectiveness of Rps genes 1b, 1k, 3b and 6, compared to a previous survey conducted in Michigan from 1993-1997. Three effective resistance genes were identified for P. sojae management in Michigan; Rps 3a, 3c, and 4. Additionally, the effective concentration of common seed treatment fungicides to inhibit mycelial growth by 50% (EC50) was determined. No P. sojae isolates were insensitive to the tested chemistries with mean EC50 values of 2.60x10-2 µg/ml for ethaboxam, 3.03x10-2 µg/ml for mefenoxam, 2.88x10-4 µg/ml for oxathiapiprolin, and 5.08x10-2 µg/ml for pyraclostrobin. Results suggest that while there has been a significant shift in Rps gene effectiveness, seed treatments are still effective for early season management of this disease.

Pathogenic variability of Erysiphe graminis f.sp. hordei in South Australia, 1981-1985

1993 ◽  
Vol 44 (8) ◽  
pp. 1931 ◽  
Author(s):  
MA Hossain ◽  
MS Rahman
Keyword(s):  
Resistance Gene ◽  
Resistance Genes ◽  
Virulence Genes ◽  
South Australia ◽  
Virulence Gene ◽  
Gene Frequencies ◽  
Individual Gene ◽  
Detached Leaf ◽  
Pathogenic Variability ◽  
Pathogen Populations

Two techniques (mobile seedling nursery and detached leaf) were used to study the pathogenic variability of Erysiphe gramznis DC. ex Merat f.sp. hordei Em. Marchal in four barley growing areas of South Australia (S.A.). The mobile nurseries were conducted over 5 years (1981-1985) to monitor changes in the spectrum of virulence and individual gene frequencies. The race-specific resistance genes M1-a6, M1-k, M1-v and M1-ra were found to be susceptible to the pathogen populations in all surveyed areas. The same virulence genes spectrum (V-a6, V-k, V-v and V-ra) was present in the pathogen populations in the surveyed areas throughout the period of 1981-1984. During the 1985 season, one new virulence matching the resistance gene in cv. Forrest was detected. The resistance in cv. Galleon did not 'break down' over the cultivation period when its cultivation rose to 55% of the barley areas of S.A. The probable reasons for apparent durability of Galleon resistance are discussed. The relative frequencies of the matching virulence genes varied only slightly over time and space. The relative frequency of V-k was always almost 100%. The relative frequencies of V-a6, V-ra and V-v occurred at a higher rate than expected, since the matching resistance genes were not deployed in barley cultivars. The results of the detached leaf experiments (1982-1984) confirmed the virulence spectrum of the pathogen populations found in the mobile nursery experiments. Three individual single colony isolates from different cultivars (Clipper, Sonja and Goldmarker) were isolated and purified. Each isolate can produce a susceptible infection on other cultivars having different resistance genes in addition to its matching cultivar. Thus, each isolate carries more than one virulence gene. In the mobile nursery tests, the resistance gene M1-v (Varunda and LaMi) showed variable infection types (I.T.l-3), but in most cases it was moderately susceptible (I.T.3). Under the controlled conditions of the detached leaf tests, it gave an I.T.3 indicating the presence of virulence gene for M1-v in the pathogen populations. Reasons for this variable reaction are discussed. Midas with an ineffective gene (M1-a6) produced a resistant reaction to all isolates, suggesting the presence of additional resistance genes in the cultivar. The Mildew resistance genes M1-a, M1-a7, M1-a9, 141-al2, M1-g, M1-h, M1-(CP) and ml-o3 were found to be resistant in all surveyed areas in both experiments throughout S.A. Either the matching virulence genes for these resistance genes were absent or they were present at a very low frequency in the pathogen populations that could not be detected by the sampling techniques used.

scholarly journals Specific Resistance of Barley to Powdery Mildew, Its Use and Beyond: A Concise Critical Review

Genes ◽  
2020 ◽  
Vol 11 (9) ◽  
pp. 971 ◽  
Author(s):  
Antonín Dreiseitl
Keyword(s):  
Powdery Mildew ◽  
Resistance Genes ◽  
Plant Pathogens ◽  
Specific Resistance ◽  
Wide Spectrum ◽  
Quantitative Resistance ◽  
Spring Barley ◽  
Durable Resistance ◽  
Genetic Resistance ◽  
Barley Cultivars

Powdery mildew caused by the airborne ascomycete fungus Blumeria graminis f. sp. hordei (Bgh) is one of most common diseases of barley (Hordeum vulgare). This, as with many other plant pathogens, can be efficiently controlled by inexpensive and environmentally-friendly genetic resistance. General requirements for resistance to the pathogens are effectiveness and durability. Resistance of barley to Bgh has been studied intensively, and this review describes recent research and summarizes the specific resistance genes found in barley varieties since the last conspectus. Bgh is extraordinarily adaptable, and some commonly recommended strategies for using genetic resistance, including pyramiding of specific genes, may not be effective because they can only contribute to a limited extent to obtain sufficient resistance durability of widely-grown cultivars. In spring barley, breeding the nonspecific mlo gene is a valuable source of durable resistance. Pyramiding of nonspecific quantitative resistance genes or using introgressions derived from bulbous barley (Hordeum bulbosum) are promising ways for breeding future winter barley cultivars. The utilization of a wide spectrum of nonhost resistances can also be adopted once practical methods have been developed.

scholarly journals A Comprehensive Review of the Major Genes Conditioning Resistance to Anthracnose in Common Bean

HortScience ◽  
2004 ◽  
Vol 39 (6) ◽  
pp. 1196-1207 ◽  
Author(s):  
James D. Kelly ◽  
Veronica A. Vallejo
Keyword(s):  
Common Bean ◽  
Resistance Genes ◽  
Durable Resistance ◽  
Gene Pyramiding ◽  
Resistance Breeding ◽  
Gene Clusters ◽  
Allelic Series ◽  
Multiple Alleles ◽  
Differential Cultivars ◽  
Major Resistance Genes

Resistance to anthracnose in common bean is conditioned primarily by nine major independent genes, Co-1 to Co-10 as the Co-3/Co-9 genes are allelic. With the exception of the recessive co-8 gene, all other nine are dominant genes and multiple alleles exist at the Co-1, Co-3 and Co-4 loci. A reverse of dominance at the Co-1 locus suggests that an order of dominance exists among individual alleles at this locus. The nine resistance genes Co-2 to Co-10 are Middle American in origin and Co-1 is the only locus from the Andean gene pool. Seven resistance loci have been mapped to the integrated bean linkage map and Co-1 resides on linkage group B1; Co-2 on B11, Co-3 on B4; Co-4 on B8; Co-6 on B7; and Co-9 and Co-10 are located on B4 but do not appear to be linked. Three Co-genes map to linkage groups B1, B4 and B11 where clusters with genes for rust resistance are located. In addition, there is co-localization with major resistance genes and QTL that condition partial resistance to anthracnose. Other QTL for resistance may provide putative map locations for the major resistance loci still to be mapped. Molecular markers linked to the majority of major Co-genes have been reported and these provide the opportunity to enhance disease resistance through marker-assisted selection and gene pyramiding. The 10 Co-genes are represented in the anthracnose differential cultivars, but are present as part of a multi-allelic series or in combination with other Co-genes, making the characterization of more complex races difficult. Although the Co-genes behave as major Mendelian factors, they most likely exist as resistance gene clusters as has been demonstrated on the molecular level at the Co-2 locus. Since the genes differ in their effectiveness in controlling the highly variable races of the anthracnose pathogen, the authors discuss the value of individual genes and alleles in resistance breeding and suggest the most effective gene pyramids to ensure long-term durable resistance to anthracnose in common bean.

Resistance genes and gene pyramids controlling rice blast pathogen populations in eight African countries

2020 ◽  
Author(s):  
Symphorien Awande ◽  
Kossi Kini ◽  
Kassankogno Abalo Itolou ◽  
Harinjaka Raveloson ◽  
Robert Amayo ◽  
...  
Keyword(s):  
Resistance Genes ◽  
Hot Spots ◽  
Blast Resistance ◽  
Durable Resistance ◽  
Screening Tests ◽  
R Genes ◽  
Improved Varieties ◽  
Neck Blast ◽  
Or Gene ◽  
Pathogen Populations

Abstract BackgroundThe behavior of rice varieties under natural environments in fields often differs from the expected one. For developing varieties, breeders give then a particular importance to multi-local field screening to confirm the resistance of their germplasm. We assembled 81 accessions e.g. blast differential, traditional and improved varieties and tested them for resistance to blast (Pyricularia grisea) in eight African hot spots under different ecologies. We thus expected to identify accessions and genes or gene pyramids that provide durable resistance locally or across sites.Methods81 accessions (e.g. blast differential, traditional and improved varieties were tested in hot spots in Benin, Burkina Faso, Côte d'Ivoire, Madagascar, Mali, Rwanda, Togo and Uganda for resistance to leaf and neck blast. An Alpha design (randomized incomplete block) with four replications was used. Correlation between leaf blast and neck blast severity and between incidence and severity were analyzed.Results:From 2013 to 2016, multi-local screening tests were conducted at yje selected sites. Among the 81 rice accessions tested, seven accessions were consistently susceptible while 12 were resistant across locations and seasons. Interestingly, effective individual resistance genes (R genes) or gene pyramids efficient across the sites were identified. In addition, we noticed on some sites, changes in the responses of some rice accessions to the disease from one season to the other. Responses of some accessions also showed great variations from one site to another. In addition, several accessions sharing the same resistance genes exhibited different responses to blast. Regarding the neck blast, only fewer accessions could be assessed as very susceptible ones died at early stages. Although differential responses were observed in the four sites considered for the analysis, several accessions consistently resisted. In addition, results showed that leaf and neck blast resistances were correlated.ConclusionsResults obtained provide useful information on the tested germplasm resistance. In addition, it was possible to identify resistant accessions and sometimes the R genes associated which were effective locally or across sites. Results also showed shifts in pathogenicity of the pathogen populations over seasons and sites. Finally, breeders can now use this valuable information for sustainable blast resistance breeding.

scholarly journals Achieving Durable Resistance Against Plant Diseases: Scenario Analyses with a National-Scale Spatially Explicit Model for a Wind-Dispersed Plant Pathogen

2017 ◽  
Vol 107 (5) ◽  
pp. 580-589 ◽  
Author(s):  
Marjolein Elisabeth Lof ◽  
Claude de Vallavieille-Pope ◽  
Wopke van der Werf
Keyword(s):  
Resistance Genes ◽  
Single Gene ◽  
Genetic Resistance ◽  
Plant Diseases ◽  
Spatially Explicit ◽  
Explicit Model ◽  
Pathogen Population ◽  
Spatially Explicit Model ◽  
Resistant Varieties ◽  
Useful Life

Genetic resistance in crops is a cornerstone of disease management in agriculture. Such genetic resistance is often rapidly broken due to selection for virulence in the pathogen population. Here, we ask whether there are strategies that can prolong the useful life of plant resistance genes. In a modeling study, we compared four deployment strategies: gene pyramiding, sequential use, simultaneous use, and a mixed strategy. We developed a spatially explicit model for France and parameterized it for the fungal pathogen Puccinia striiformis f. sp. tritici (causing wheat yellow rust) to test management strategies in a realistic spatial setting. We found that pyramiding two new resistance genes in one variety was the most durable solution only when the virulent genotype had to emerge by mutation. Deploying single-gene-resistant varieties concurrently with the pyramided variety eroded the durability of the gene pyramid. We found that continuation of deployment of varieties with broken-down resistance prolonged the useful life of simultaneous deployment of four single-gene-resistant varieties versus sequential use. However, when virulence was already present in the pathogen population, durability was low and none of the deployment strategies had effect. These results provide guidance on effective strategies for using resistance genes in crop protection practice.

The allelic relationships among Russian wheat aphid resistance genes in two Iranian wheat lines and known genes

2002 ◽  
Vol 138 (3) ◽  
pp. 281-284 ◽  
Author(s):  
A. ESTAKHR ◽  
M. T. ASSAD
Keyword(s):  
Resistance Gene ◽  
Resistance Genes ◽  
Genetic Resistance ◽  
Russian Wheat Aphid ◽  
Diuraphis Noxia ◽  
Virulent Strains ◽  
Resistant Lines ◽  
Additional Protection ◽  
Wheat Lines ◽  
Effective Source

The availability of more resistance genes to Russian wheat aphid (RWA), Diuraphis noxia (Mordvilko) may provide additional protection from new virulent strains or biotypes of the insect. This genetic study was conducted to determine the allelic relationships of resistance genes in two Iranian wheat (Triticum aestivum L.) lines, SHZ.W.102 and SHZ.W.104 and lines PI 137739, PI 262660, PI 372129, PI 294994 and PI 243781, carrying resistance genes Dn1, Dn2, Dn4, Dn5 and Dn6 respectively. The two Iranian lines were crossed to each of the other resistant lines, and F1 and F2 seedlings were screened for RWA reaction. The resistance gene in 102 was allelic to Dn1, however, the resistance gene in 104 was different from other known genes. The resistant line 104 is an effective source of genetic resistance to RWA and the gene symbol Dn7 is proposed for its resistance gene.

scholarly journals Transgressive Segregation, Heritability, and Number of Genes Controlling Durable Resistance to Stripe Rust in One Chinese and Two Italian Wheat Cultivars

2001 ◽  
Vol 91 (7) ◽  
pp. 680-686 ◽  
Author(s):  
Z. J. Zhang ◽  
G. H. Yang ◽  
G. H. Li ◽  
S. L. Jin ◽  
X. B. Yang
Keyword(s):  
Resistance Gene ◽  
Stripe Rust ◽  
Resistance Genes ◽  
Durable Resistance ◽  
Transgressive Segregation ◽  
Stripe Rust Resistance ◽  
Narrow Sense ◽  
Narrow Sense Heritability ◽  
Gene Number ◽  
Number Of Genes

Wheat (Triticum aestivum) cvs. Libellula (LB), San Pastore (SP), and Xian Nong 4 (XN4) possess durable resistance to stripe rust, caused by Puccinia striiformis f. sp. tritici, and cv. Ming Xian 169 (MX169) is highly susceptible to the rust. Inheritance of stripe rust resistance was studied by crossing the four cultivars and evaluating the resistance of parental, F1, F2, backcross, and F3 plants in the fields. Transgressive segregation for resistance was observed in the resistant by resistant crosses of LB × XN4 and XN4 × SP, but not in cross LB × SP. These results indicate that (i) the resistance genes in XN4 are different from those in LB and SP, and (ii) LB and SP share common resistance genes. The number of genes segregating for the resistance was estimated by quantitative methods from the data of F2, backcross, and F3 populations. LB and XN4 appear to have two to three resistance genes, and SP appears to have two to four resistance genes when crossed with MX169. The resistance gene number in resistant by resistant cross LB × XN4 was four to five, approximately equal to the sum of the genes in LB and XN4. Similarly, the resistance gene number in cross XN4 × SP was approximately equal to the sum of the genes in XN4 and SP. Broad-sense heritability was high in all crosses except LB × SP. Compared with the three MX169-involved crosses, narrow-sense heritability was higher in LB × MX169 and SP × MX169 crosses than in the XN4 × MX169 cross. The LB × XN4 and XN4 × SP crosses showed moderate narrow-sense heritability.

scholarly journals Allocation of the oat powdery mildew resistance gene Pm3 to oat chromosome 1A

2021 ◽  
Author(s):  
Volker Mohler
Keyword(s):  
Powdery Mildew ◽  
Resistance Gene ◽  
Resistance Genes ◽  
Residual Effect ◽  
Major Effect ◽  
Adult Plant ◽  
Consensus Map ◽  
Breeding Programs ◽  
Genetic Studies ◽  
Major Resistance Genes

AbstractBesides the mode of inheritance, the knowledge of the chromosome location and allelic relationships are the essentials towards a successful deployment and stacking of divergent disease resistance genes for a given pathogen in breeding programs. Powdery mildew of oats, to which 11 major resistance genes in the host Avena sativa L. have been characterized so far, is a prevalent fungal disease of the crop in Northwestern Europe. In the present study, the resistance gene Pm3 was mapped by linkage analysis relative to molecular markers from oat consensus linkage group Mrg18 which was recently determined to represent oat chromosome 1A. Pm3 was located at 67.7–72.6 cM on Mrg18 of the oat consensus map, a position at which also stem and crown rust resistance genes Pg13 and Pc91 and a large cluster of resistance gene analogs have been previously mapped. The closely linked marker GMI_ES03_c2277_336 was found to be useful for the prediction of Pm3 in gene postulation studies. Although the major effect of the widespread gene got lost over time, the known genome location with associated markers will assist revealing in future genetic studies whether there is a possible residual effect of the gene contributing to adult plant resistance.

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