Barley grass as a source of pathogenic variation in Rhynchosporium secalis

1981 ◽  
Vol 32 (1) ◽  
pp. 21 ◽  
Author(s):  
SM Ali
Keyword(s):  
Resistance Genes ◽  
Genetic Basis ◽  
Rhynchosporium Secalis ◽  
Pathogenic Variation ◽  
Pathogenic Variability ◽  
F2 Progeny

The pathogenic variability of 150 isolates of Rhynchospovium secalis collected in southern Australia was examined on 20 biotypes of barley grass (Hordeum lepovinum). The isolates were differentiated into 20 pathotypes on the basis of the reactions of the barley grass. The genetic basis of resistance and susceptibility of barley grass to R. secalis was determined from F2 progeny of crosses among three resistant and two susceptible biotypes of barley grass. The resistance genes identified were all dominant.

scholarly journals Pathogenic Variation in Rhynchosporium secalis on Barley in Ethiopia

2000 ◽  
Vol 5 (2) ◽  
pp. 75
Author(s):  
K. Meles ◽  
M. Hulluka ◽  
M.L. Deadman
Keyword(s):  
Resistance Genes ◽  
Geographical Location ◽  
Effective Resistance ◽  
Rhynchosporium Secalis ◽  
Malting Barley ◽  
Differential Host ◽  
Barley Cultivars ◽  
Pathogenic Variation ◽  
Pathogenic Variability

This paper presents the first detailed study on pathogenic variability in Rhynchosporium secalis in Ethiopia. Twenty four isolates of R. secalis, collected from Arsi, Bale and Shoa, major barley growing locations in Ethiopia, were tested on ten differential host cultivars, with known genes for resistance to the disease. The most frequent pathotypes were those inducing susceptible reactions on cvs Steudelli and Kitchen and the least complex pathotype identified was able to induce a susceptible reaction on these two cultivars only. Pathotypes 16 and 7 were the most complex and were able to induce susceptible reactions on 10 and 9 of the differential host cultivars respectively. These pathotypes were collected from research stations and were isolated from improved barley cultivars belonging to the malting barley type. The most frequent pathotype was pathotype 6 which was represented by four isolates from different locations in Arsi, Bale and Shoa. Pathogenic variation was detected amongst spores collected from the same field and from the same geographical location. The most effective resistance genes were those possessed by Turk, La-Mesita, Bey, Nigrinudum, Jet and Forrajera.   

Inheritance of scald resistance in barley. I. Resistance of genes of group A barley cultivars

1975 ◽  
Vol 26 (2) ◽  
pp. 243 ◽  
Author(s):  
SM Ali
Keyword(s):  
Western Australia ◽  
Resistance Genes ◽  
Genetic Basis ◽  
Rhynchosporium Secalis ◽  
Common Gene ◽  
Resistant Cultivars ◽  
Barley Cultivars ◽  
Group A ◽  
The Common

The genetic basis of resistance and susceptibility of barley cultivars to Rhynchosporium secalis (Oud.) Davis was determined from F2 and F3 progenies of crosses among five resistant and four susceptible cultivars. The resistant cultivars Psaknon, Atlas 46, Atlas 57, Hudson and Turk were found to share a common gene in addition to other genes for resistance. No race of the pathogen found in Western Australia was able to overcome the resistance conferred by the common gene. The effectiveness of the identified resistance genes to two isolates of R. secalis was studied under glasshouse conditions in winter and summer, and in the field during winter.

Hierarchical structure of pathogenic variation among Rhynchosporium secalis populations in Idaho and Oregon

1992 ◽  
Vol 70 (4) ◽  
pp. 810-817 ◽  
Author(s):  
Stephen B. Goodwin ◽  
Robert W. Allard ◽  
Shirlee A. Hardy ◽  
Robert K. Webster
Keyword(s):  
Pacific Northwest ◽  
Resistance Genes ◽  
Local Population ◽  
Rhynchosporium Secalis ◽  
Causal Organism ◽  
Pathogenic Variation ◽  
Differential Cultivars ◽  
Electrophoretic Data ◽  
Differential Cultivar ◽  
Major Resistance Genes

Ninety-four isolates of Rhynchosporium secalis, the causal organism of the barley scald disease, from four populations (infected fields) in Idaho and eight in Oregon, were tested for pathogenicity to 14 barley differential cultivars; 60 distinct pathotypes, 33 in Idaho and 28 in Oregon, were found among the 94 isolates. Pathogenicity to most of the differentials was found in each local population sampled. One differential cultivar, CI 5831, was resistant to all isolates tested. Isolates from the same cultivar in different locations usually had different pathogenicities, and most pathotypes were genetically heterogeneous mixtures of many different genotypes based on previous electrophoretic data. The sampled cultivars generally had few or no resistance genes, suggesting that the R. secalis populations in Idaho and Oregon are characterized by large amounts of seemingly unnecessary pathogenicity. When the total pathogenic diversity was partitioned into hierarchical components using the Shannon information statistic, 58% was accounted for by the within-population component, 33% among populations within regions, and only 9% by the between-region component. Because most of the pathogenic variation is within local populations, these populations should adapt rapidly to introduced resistance genes; therefore traditional methods of breeding for resistance to R. secalis using single major resistance genes are not likely to be effective in the Pacific Northwest. Key words: pathogenicity index.

Inheritance of scald resistance in barley. II.* Resistance genes of group B barley cultivars

1975 ◽  
Vol 26 (2) ◽  
pp. 251 ◽  
Author(s):  
SM Ali
Keyword(s):  
Environmental Factors ◽  
Resistance Genes ◽  
Genetic Basis ◽  
Rhynchosporium Secalis ◽  
Inheritance Of Resistance ◽  
West China ◽  
Barley Cultivars ◽  
Group B

The genetic basis of resistance to Rhynchosporium secalis (Oud.) Davis of barley cultivars La Mesita, West China and Sakigake differentiated as group B were determined from F2, F3 and BC1 progenies. The resistance genes identified are situated at different loci from each other. The effectiveness of the identified resistance genes to two isolates of Rhynchosporium secalis was studied under glasshouse conditions in winter and in summer, and also in the field. The inheritance of resistance genes of group B cultivars was found to be greatly influenced by environmental factors. *Part I, Aust. J. Agric. Res., 26: 243 (1975).

scholarly journals Pathogenic Variation of Phakopsora pachyrhizi Isolates on Soybean in the United States from 2006 to 2009

Plant Disease ◽  
2012 ◽  
Vol 96 (1) ◽  
pp. 75-81 ◽  
Author(s):  
M. Twizeyimana ◽  
G. L. Hartman
Keyword(s):  
United States ◽  
Resistance Genes ◽  
The United States ◽  
Soybean Rust ◽  
Phakopsora Pachyrhizi ◽  
Soybean Genotype ◽  
Pathogenic Variation ◽  
Differential Set ◽  
Soybean Genotypes ◽  
Soybean Leaves

The introduction of Phakopsora pachyrhizi, the cause of soybean rust, into the United States is a classic case of a pathogen introduction that became established in a new geographical region overwintering on a perennial host (kudzu, Pueraria lobata). The objective of our study was to classify the pathogenic variation of P. pachyrhizi isolates collected in the United States, and to determine the spatial and temporal associations. In total, 72 isolates of P. pachyrhizi collected from infected kudzu and soybean leaves in the United States were purified, then established and increased on detached soybean leaves. These isolates were tested for virulence and aggressiveness on a differential set of soybean genotypes that included six genotypes with known resistance genes (Rpp), one resistant genotype without any known characterized resistance gene, and a susceptible genotype. Three pathotypes were identified among the 72 U.S. P. pachyrhizi isolates based on the virulence of these isolates on the genotypes in the differential set. Six aggressiveness groups were established based on sporulating-uredinia production recorded for each isolate on each soybean genotype. All three pathotypes and all six aggressiveness groups were found in isolates collected from the southern region and from both hosts (kudzu or soybean) in 2008. Shannon's index based on the number of pathotypes indicated that isolates from the South region were more diverse (H = 0.83) compared with the isolates collected in other regions. This study establishes a baseline of pathogenic variation of P. pachyrhizi in the United States that can be further compared with variation reported in other regions of the world and in future studies that monitor P. pachyrhizi virulence in association to deployment of rust resistance genes.

Host range and physiologic specialization in Rhynchosporium secalis

1974 ◽  
Vol 25 (1) ◽  
pp. 21 ◽  
Author(s):  
SM Ali ◽  
WJR Boyd
Keyword(s):  
Genetic Diversity ◽  
Host Range ◽  
Environmental Conditions ◽  
Host Specialization ◽  
Rhynchosporium Secalis ◽  
Host Reaction ◽  
Genetic Studies ◽  
Barley Cultivars ◽  
Adequate Sampling ◽  
Pathogenic Variability

The pathogenic variability of isolates of R. secalis collected in Western Australia has been examined on different host genera of the Gramineae and on selected barley cultivars. Depending on the host-isolate combination and the conditions of the test, evidence has been obtained of inter- and intra-isolate variability in both host reaction and isolate pathogenicity. This complicates definitive interpretation of the results, militates against identification of conventional 'races' of the pathogen and shows that R. secalis does not exhibit strict host specialization. Hosts which consistently express resistance or susceptibility under different environmental conditions, and isolates which express their pathogenic characteristics consistently, have been identified. The need for more precise genetic studies and adequate sampling of genetic diversity is emphasized.

scholarly journals Identification of Phaeoisariopsis griseola pathotypes from five States in Brazil

2002 ◽  
Vol 27 (1) ◽  
pp. 78-81 ◽  
Author(s):  
ALOISIO SARTORATO
Keyword(s):  
Phaseolus Vulgaris ◽  
Common Bean ◽  
Resistance Genes ◽  
Leaf Spot ◽  
Angular Leaf Spot ◽  
Phaeoisariopsis Griseola ◽  
Moist Chamber ◽  
Differential Cultivars ◽  
Pathogenic Variability ◽  
Resistant Genotypes

Due to the increased importance of angular leaf spot of common bean (Phaseolus vulgaris) in Brazil, monitoring the pathogenic variability of its causal agent (Phaeoisariopsis griseola) is the best strategy for a breeding program aimed at developing resistant genotypes. Fifty one isolates of P. griseola collected in five Brazilian States were tested on a set of 12 international differential cultivars in the greenhouse. When inoculated plants showed symptoms but no sporulation was observed, they were transferred to a moist chamber for approximately 20-24 h. After this period of time, if no sporulation was observed, the plants were considered resistant; otherwise, they were considered susceptible. From the fifty-one tested isolates, seven different pathotypes were identified. No Andean pathotypes were identified; consequently, all isolates were classified as Middle American pathotypes. Pathotype 63-31 was the most widespread. Pathotype 63-63 overcame resistance genes present in all differential cultivars and also the resistance gene(s) present in the cultivar AND 277. This fact has important implications for breeding angular leaf spot resistance in beans, and suggests that searching for new resistance genes to angular leaf spot must be pursued.

scholarly journals Pathogenic Variation of Colletotrichum lindemuthianum causing Anthracnose of Beans (Phaseolus vulgaris) in Uganda

2017 ◽  
Vol 5 (3) ◽  
pp. 89-98
Author(s):  
Moses J. Kiryowa ◽  
Aston Ebinu ◽  
Vincent Kyaligonza ◽  
Stanley T. Nkalubo ◽  
Pamela Paparu ◽  
...  
Keyword(s):  
Broad Spectrum ◽  
Single Gene ◽  
Colletotrichum Lindemuthianum ◽  
Breeding Programs ◽  
Pathogenic Variation ◽  
Broad Spectrum Resistance ◽  
Differential Cultivars ◽  
Differential Cultivar ◽  
Bean Anthracnose ◽  
Pathogenic Variability

Colletotrichum lindemuthianum is a highly variable pathogen of common beans that easily overcomes resistance in cultivars bred with single-gene resistance. To determine pathogenic variability of the pathogen in Uganda, samples of common bean tissues with anthracnose symptoms were collected in eight districts of Uganda, namely Kabarole, Sironko, Mbale, Oyam, Lira, Kapchorwa, Maracha and Kisoro. 51 isolates sporulated successfully on Potato Dextrose Agar and Mathur’s media and were used to inoculate 12 differential cultivars under controlled conditions. Five plants per cultivar were inoculated with each isolate and then evaluated for their reaction using the 1 – 9 severity scale. Races were classified using the binary nomenclature system proposed by Pastor Corrales (1991). Variation due to cultivar and isolate effects was significant (P≤0.001) for severity. The 51 isolates from eight districts grouped into 27 different races. Sironko district had the highest number of races followed by Mbale and Kabarole. Races 2047 and 4095 were the most frequently found, each with 10 isolates grouped under them. Race 4095 was the most virulent since it caused a susceptible (S) reaction on all 12 differential cultivars and the susceptible check. This was followed by races 2479, 2047 and 2045 respectively. Two races, 4094 and 2479, caused a susceptible reaction on the differential cultivar G2333, which nevertheless, showed the most broad spectrum resistance followed by cultivars Cornell 49-242, TU, and AB136 respectively. These cultivars are recommended for use in breeding programs aiming at breeding for broad spectrum resistance to bean anthracnose in Uganda.

scholarly journals 480. Molecular Characterization of Multidrug-Resistant Gram-Negative Pathogens in Three Tertiary Care Hospitals in Egypt

2019 ◽  
Vol 6 (Supplement_2) ◽  
pp. S235-S235
Author(s):  
Amani Kholy ◽  
Samia A Girgis ◽  
Arwa R Elmanakhly ◽  
Mervat A F Shetta ◽  
Dalia El- Kholy ◽  
...  
Keyword(s):  
Molecular Characterization ◽  
Resistance Genes ◽  
Genetic Basis ◽  
Tertiary Care ◽  
Carbapenem Resistance ◽  
Resistance Mechanisms ◽  
Gram Negative ◽  
E Coli ◽  
Tertiary Care Hospitals

Abstract Background High rates of AMR among Gram-negative bacilli (GNB) have been reported from Egypt for almost 2 decades. Surveillance and identifying the genetic basis of AMR provide important information to optimize patient care. As there is no adequate data on the genetic basis of AMR in Egypt, we aimed to identify the molecular characterization of multi-drug-resistant (MDR) Gram-negative pathogens (GNP). Methods Three major tertiary-care hospitals in Egypt participated in the “Study for Monitoring Antimicrobial Resistance Trends” (SMART) from 2014 to 2016. Consecutive GNPs were identified and their susceptibility to antimicrobials were tested. Molecular identification of ESBL, AmpC, and carbapenemase resistance genes was conducted on MDR isolates. Results We enrolled 1,070 consecutive Gram-negative isolates; only one isolate per patient according to the standard protocol of (SMART). During 2014–2015, 578 GNP were studied. Enterobacteriaceae comprised 66% of the total isolates. K. pneumoniae and E. coli were the most common (29.8% and 29.4%). K. pneumoniae and E. coli were the predominant organisms in IAI (30.5% and 30.1%, respectively) and UTI (and 38.9% and 48.6%, respectively), while Acinetobacter baumannii was the most prevalent in RTI (40.2%). ESBL producers were phenotypically detected in 53% of K. pneumoniae, and 68% of E. coli. During 2016, 495 GNP were studied. ESBL continued to be high. For E. coli and K. pneunomiea, the most active antimicrobials were amikacin (≥93%), imipenem/meropenem (≥87%) and colistin (97%). Genetic study of ertapenem-resistant isolates and 50% of isolates with ESBL phenotype revealed ESβL production in more than 90% of isolates; blaCTXM-15 was detected in 71.4% and 68.5% in K. pneumoniae and E. coli, respectively, blaTEM-OSBL in 48.5% and47.5% of K. pneumoniae and E. coli, respectively. Carbapenem resistance genes were detected in 45.4% of isolates. In K. pneumoniae, OXA-48 dominated (40.6%), followed by NDM1 (23.7%) and OXA-232 (4.5%). Conclusion Our study detected alarming rates of resistance and identified many resistance mechanisms in clinical isolates from Egyptian hospitals. These high rates highlight the importance of continuous monitoring of the resistance trend and discovering the novel resistant mechanisms of resistance, and the underscores a national antimicrobial stewardship plan in Egypt. Disclosures All authors: No reported disclosures.

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.

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