scholarly journals Assessment of physiological races of Exserohilum turcicum isolates from maize in Argentina and Brazil

2021 ◽  
Author(s):  
Barbara Ludwig Navarro ◽  
Lucia Ramos Romero ◽  
María Belén Kistner ◽  
Juliana Iglesias ◽  
Andreas von Tiedemann
Keyword(s):  
Exserohilum Turcicum ◽  
Breeding Programs ◽  
Physiological Races ◽  
Maize Leaves ◽  
Race 1 ◽  
Resistance Reaction ◽  
Qualitative Resistance ◽  
Maize Plants ◽  
Corn Leaf Blight ◽  
Resistant Genotypes

AbstractNorthern corn leaf blight (NCLB) is one of the most important diseases in maize worldwide. It is caused by the fungus Exserohilum turcicum, which exhibits a high genetic variability for virulence, and hence physiological races have been reported. Disease control is based mainly on fungicide application and host resistance. Qualitative resistance has been widely used to control NCLB through the deployment of Ht genes. Known pathogen races are designated according to their virulence to the corresponding Ht gene. Knowledge about of E. turcicum race distribution in maize-producing areas is essential to develop and exploit resistant genotypes. Maize leaves showing distinct elliptical grey-green lesions were collected from maize-producing areas of Argentina and Brazil, and 184 monosporic E. turcicum isolates were obtained. A total of 66 isolates were collected from Argentina during 2015, 2018 and 2019, while 118 isolates from Brazil were collected during 2017, 2018 and 2019. All isolates were screened on maize differential lines containing Ht1, Ht2, Ht3 and Htn1 resistance genes. In greenhouse experiments, inoculated maize plants were evaluated at 14 days after inoculation. Resistance reaction was characterized by chlorosis, and susceptibility was defined by necrosis in the absence of chlorosis. The most frequent race was 0 in both Argentina (83%) and Brazil (65%). Frequencies of race 1 (6% and 24%) and race 23N (5% and 10%) were very low in Argentina and Brazil, respectively. The high frequency of race 0 isolates provides evidence that qualitative resistance based on the tested Ht genes is not being used extensively in Argentina and Brazil to control NCLB. This information may be relevant for growers and breeding programs as the incidence of NCLB is increasing in both countries.

scholarly journals Occurrence and Distribution of Physiological Races of Exserohilum turcicum in Ontario, Canada

Plant Disease ◽  
2019 ◽  
Vol 103 (7) ◽  
pp. 1450-1457 ◽  
Author(s):  
Krishan K. Jindal ◽  
Albert U. Tenuta ◽  
Tsegaye Woldemariam ◽  
Xiaoyang Zhu ◽  
Dave C. Hooker ◽  
...  
Keyword(s):  
Resistance Genes ◽  
Exserohilum Turcicum ◽  
Corn Hybrids ◽  
Physiological Races ◽  
The Past ◽  
Geographical Regions ◽  
Symptomatic Leaf ◽  
New Races ◽  
Corn Leaf Blight ◽  
Virulence Frequency

Northern corn leaf blight (NCLB) caused by Exserohilum turcicum is the most common and economically significant fungal leaf disease of corn in Ontario, Canada. During the past 10 years in Ontario, severity and incidence of NCLB have increased, possibly owing to the appearance of new races. Several races have been identified in various parts of the world; however, information on occurrence and distribution of races in Ontario is lacking. In the current study, 677 single conidial isolates of E. turcicum were isolated from 687 symptomatic leaf samples collected between 2012 and 2016. These isolates were evaluated for pathogenicity on six corn differential inbreds (A619, A619Ht1, A619Ht2, A619Ht3, A632Htn1, and H102Htm1) under controlled environmental conditions and then grouped into 17 physiological races (0, 1, 2, 3, M, N, 12, 1M, 1N, 3M, 13M, 12N, 13N, 1MN, 12MN, 13MN, 123MN) based on the reaction of the inbreds to infection (resistant or susceptible). Four races (0, 1M, 1N, and 1MN) were most frequent, with an isolation frequency of 13, 10, 12, and 41%, respectively. Seventy-six percent of the isolates were virulent on more than one Ht resistance gene, with 2.4% (16 isolates) virulent on all five Ht resistance genes used in this study. Further analysis of the distribution of races in four regions over the years revealed that the occurrence and distribution of the races changed with time in Ontario. Overall, the frequency of virulence of the 677 isolates screened on the differentials with resistance genes Ht1, Ht2, Ht3, Htm1, and Htn1 varied from 6 to 81% (Ht1 81%, Ht2 6%, Ht3 12%, Htm1 64%, and Htn1 64%). Virulent isolates produced fewer lesions on the Htm1 differential, and smaller lesions that were slower and having less sporulation on the Htn1 differential, compared with infection of the differentials with Ht1, Ht2, and Ht3 resistance genes. Virulence frequency also changed within the four geographical regions of Ontario, with fewer isolates virulent on all resistance genes in eastern Ontario compared with southern and western Ontario. Isolates from southern Ontario had greater virulence frequency against Ht1 and Htm1, whereas isolates from western Ontario were more frequently virulent on Ht1 and Htn1. The information generated in this study on the distribution of E. turcicum races in Ontario corn will help growers to select appropriate hybrids with required resistance genes and will assist seed companies in deploying resistance genes in corn hybrids across the province or within a particular region.

scholarly journals The determination of Exserohilum turcicum virulence factors in Serbia

Genetika ◽  
2008 ◽  
Vol 40 (3) ◽  
pp. 271-281 ◽  
Author(s):  
Jelena Levic ◽  
Slavica Stankovic ◽  
Tijana Petrovic
Keyword(s):  
Virulence Factors ◽  
Standard Procedure ◽  
Inbred Lines ◽  
Exserohilum Turcicum ◽  
Leaf Sample ◽  
Maize Inbred Lines ◽  
First Results ◽  
Race 1 ◽  
Corn Leaf Blight

The determination of Exserohilum turcicum virulence factors and resistance responses of three sets of maize inbred lines (four differential, eight isogenic and 22 commercial inbreeds) to three isolates of this pathogen under greenhouse conditions were studied. The maize inbreeds were selected according to previous testing of resistance based on lesion types in 194 inbreeds under field conditions of plant inoculation with the E. turcicum race 0 (designated as the isolate MRI-Et). The standard procedure was applied to obtained isolates MRIZP-1747 and MRIZP-1416 from resistant and susceptible lesion types, respectively. These lesions were developed on the same leaf of a plant of the experimental hybrid no. 163/99 grown in a nursery at Zemun Polje during 1999. The third isolate (MRIZP-1435) was isolated from a leaf sample originating from the location of Srbobran in which the occurrence of northern corn leaf blight (NCLB), caused by Exserohilum turcicum, was intensive. Based upon virulence/avirulence of three isolates of E. turcicum on differential maize inbred lines, it was found out that the isolate MRIZP-1747 could be classified as race 0, whereas isolates MRIZP-1416 and MRIZP-1435 could be classified as race 1. These are the first results that confirm the presence of race 1 of E. turcicum in Serbia. Not including differential lines, 22 and six lines were resistant to race 0 and race 1, respectively, while eight and five lines were resistant and susceptible to both races, respectively. All isogenic lines not containing the Ht gene were susceptible to both races 0 and 1.

scholarly journals RESISTANCE OF CUCURBITA SPP. TO FUSARIUM SOLANI FOR USE AS ROOTSTOCK

2020 ◽  
Vol 33 (2) ◽  
pp. 384-394
Author(s):  
JOICE SIMONE DOS SANTOS ◽  
RITA DE CÁSSIA SOUZA DIAS ◽  
KARINA BRANCO DE ALMEIDA ◽  
PEDRO MARTINS RIBEIRO JUNIOR ◽  
TIAGO LIMA DO NASCIMENTO
Keyword(s):  
Fusarium Solani ◽  
High Frequency ◽  
Breeding Programs ◽  
Soil Pathogen ◽  
Race 1 ◽  
Resistant Genotypes

ABSTRACT Fusarium solani f. sp. cucurbitae (Fsc) is a soil pathogen and the adoption of resistant rootstocks is an effective method of control. Hybrids of Cucurbita spp. are the main rootstock used for watermelon. This study aimed to evaluate the virulence of Fsc race 1 (Fsc1) in three cucurbits and check the reaction of Cucurbita spp. genotypes to the fungus for its use as rootstock. Four experiments were performed. The virulence of Fsc1 in melon, watermelon and Cucurbita spp. was evaluated in experiment I. In experiment two and three the severity of the pathogen in 19 cucurbits was analyzed. And experiment four evaluated the compatibility of these genotypes as a rootstock for watermelon. Cucurbita spp. proved to be more resistant to Fusarium solani f. sp. cucurbitae race 1 than the melon. The high frequency of plants resistant to Fsc1 was found in the genotypes BGC622, BGC620, BGC567, BGC530, BGC186, BGC381, BGC692, BGC082, ES0061 and ES0062. In addition, the evaluated genotypes may be used as watermelon rootstocks, except for the ES530 strain, which was incompatible with the cultivar BRS Opara, but could be used in pumpkin breeding programs, as well as other resistant genotypes.

scholarly journals Resistance Conferred by the Ht1 Gene in Sweet Corn Infected by Mixtures of Virulent and Avirulent Exserohilum turcicum

Plant Disease ◽  
2006 ◽  
Vol 90 (6) ◽  
pp. 771-776 ◽  
Author(s):  
J. K. Pataky ◽  
Tatjana Ledencan
Keyword(s):  
Sweet Corn ◽  
The United States ◽  
Exserohilum Turcicum ◽  
Corn Hybrids ◽  
General Resistance ◽  
Initial Inoculum ◽  
Field Corn ◽  
Race 1 ◽  
The 1960S ◽  
Corn Leaf Blight

The Ht1 gene conveys a chlorotic-lesion resistant reaction in corn infected by avirulent races of Exserohilum turcicum, the causal agent of northern corn leaf blight (NCLB). The widespread deployment of the Ht1 gene in field corn grown in North America since the 1960s resulted in an increased frequency of E. turcicum race 1, which is virulent against the Ht1 gene. The objective of this study was to assess the value of resistance conveyed by the Ht1 gene when initial inoculum consisted of different ratios of virulent and avirulent E. turcicum. Forty-two sweet corn hybrids with the Ht1 gene and 42 sweet corn hybrids without Ht1 were grown in five trials each in 2003 and 2004. In each trial, plants were inoculated with culture suspensions consisting of different percentages of E. turcicum race 0 and race 1, including: 100:0, 90:10, 75:25, 50:50, and 0:100. Severity of NCLB was rated visually from 0 to 100% leaf area infected when plants were about 3 to 4 weeks past the mid-silk growth stage. The Ht1 gene reduced severity of NCLB by as much as one-third when virulent isolates comprised 25% or less of the initial inoculum. Reduction in NCLB severity due to the Ht1 gene was more substantial on hybrids with susceptible backgrounds than on those with general resistance. When virulent isolates comprised 50% of the initial inoculum, NCLB severity was similar for hybrids with and without the Ht1 gene if hybrids had equivalent levels of general resistance (measured as NCLB severity from trials inoculated entirely with race 1). To accurately classify NCLB reactions of maize lines relative to their most probable performance in the United States, inoculum should consist of at least 50% E. turcicum race 1.

scholarly journals Evolution of Physiologic Races and Virulence of Puccinia striiformis on Wheat in Syria and Lebanon

Plant Disease ◽  
2002 ◽  
Vol 86 (5) ◽  
pp. 499-504 ◽  
Author(s):  
A. H. Yahyaoui ◽  
M. S. Hakim ◽  
M. El Naimi ◽  
N. Rbeiz
Keyword(s):  
Resistance Genes ◽  
Puccinia Striiformis ◽  
Yellow Rust ◽  
Wheat Breeding ◽  
Natural Conditions ◽  
Breeding Programs ◽  
Land Race ◽  
Physiologic Races ◽  
Resistant Genotypes

Virulence-avirulence phenotypes of Puccinia striiformis isolates collected in Lebanon and Syria were determined on seedlings of the wheat-yellow rust differential genotypes. We found 25 and 11 physiologic races over 6 years (1994 to 1999) in Syria and Lebanon, respectively. The composition of physiologic races found in Syria and Lebanon differed greatly between 1994 and 1999. Races identified in 1999, such as 230E150 and 230E134, have wider spectra of virulence on resistant genotypes than races collected in 1994. In Lebanon, three races were found in 1994 compared with six races in 1999. Yellow rust differential genotypes were used in a trap nursery to monitor yellow rust populations under natural conditions. Races identified from cultivars in the trap nursery in Syria and Lebanon, and from land race cultivars in Iraq, were recovered among the races identified from farm fields. Yellow rust samples were collected from Yemen, and none of the races identified from Yemen samples were identical to those in Syria and Lebanon. Virulence frequencies in the yellow rust population on the differential genotypes tested in the trap nurseries were above 70% for some resistance genes. Yellow rust populations in Syria and Lebanon have diverse virulence phenotypes. P. striiformis populations appear to be changing over, and this would be an important consideration for wheat breeding programs in the region.

scholarly journals Resistance of Eucalyptus pellita to rust (Puccinia psidii)

2014 ◽  
Vol 14 (4) ◽  
pp. 244-250 ◽  
Author(s):  
Marisângela Rodrigues Santos ◽  
Lúcio Mauro da Silva Guimarães ◽  
Marcos Deon Vilela de Resende ◽  
Leonardo Novaes Rosse ◽  
Karina Carnielli Zamprogno ◽  
...  
Keyword(s):  
Rust Resistance ◽  
Minor Effect ◽  
Primary Method ◽  
Narrow Sense Heritability ◽  
Puccinia Psidii ◽  
Eucalyptus Pellita ◽  
Eucalypt Plantations ◽  
Race 1 ◽  
Promising Source ◽  
Resistant Genotypes

Eucalypts rust (Puccinia psidii) is currently one of the major diseases in commercial eucalypt plantations in Brazil. The primary method of disease control is the use of resistant genotypes, and, among the different species of Eucalyptus, E. pellita is indicated as a promising source of resistance. In this work, the genetic control of rust resistance in E. pellita through inoculations under controlled conditions of 441 plants from four full-sibling families was studied. Inoculations were performed using the monopostular isolate UFV-2, race 1. All families tested segregated for rust resistance, and the number of resistant plants was higher than susceptible in all crosses. Inheritance models based on few genes did not fully explain the observed segregation patterns, and the narrow-sense heritability of rust resistance was estimated between 32.7% and 37.3%. The results suggested that rust resistance in E. pellita is complex and is controlled by major- and minor-effect genes.

Genetic diversity and population structure of Algerian chickpea (Cicer arietinum) genotypes: use of agro-morphological traits and molecular markers linked or not linked to the gene or QTL of interest

2020 ◽  
Vol 71 (2) ◽  
pp. 155
Author(s):  
Djihad Bellemou ◽  
Teresa Millàn ◽  
Juan Gil ◽  
Aissa Abdelguerfi ◽  
Meriem Laouar
Keyword(s):  
Genetic Diversity ◽  
Molecular Markers ◽  
Cicer Arietinum ◽  
Morphological Traits ◽  
Ascochyta Blight ◽  
Principal Component ◽  
Breeding Programs ◽  
Average Value ◽  
Conservation Of Genetic Resources ◽  
Resistant Genotypes

Assessment of genetic diversity among chickpea (Cicer arietinum L.) germplasm at the morphological and molecular levels is fundamental for chickpea breeding and conservation of genetic resources. Genetic variability of 46 chickpea genotypes including 42 Algerian genotypes and four control varieties was evaluated by using 15 agro-morphological traits. Eleven molecular markers including nine simple sequence repeats, one sequence characterised amplified region (SCY17) and one gene-specific (CaETR4) were used to characterise the 46 genotypes and eight references varieties added for disease resistance or susceptibility. Genotypes resistant to ascochyta blight were identified by the markers SCY17 and CaETR4 present together. High diversity was observed for all measured morphological traits between genotypes. Yield components, plant height, phenological traits and growth habit were the traits most involved in variation among genotypes and were partitioned into four groups by using principal component analysis. All molecular markers were polymorphic. In total, 91 alleles were obtained ranging from 2 to 21 per locus with average of 8.27 alleles per marker. Polymorphism information content ranged from 0.58 to 0.99 with an average value of 0.87. UPGMA clustering and Bayesian-based model structure analysis grouped genotypes into two clusters, but the distribution of the genotypes by cluster was not the same for the two analyses. According to the presence of markers indicating resistance to ascochyta blight (SCY17 and CaETR4), three resistant genotypes (FLIP 82-C92, ILC 6909, ILC 7241) were selected and should be tested in controlled conditions for confirmation. Considering the narrow diversity of cultivated chickpea, the Algerian genotypes can be considered as interesting for future breeding programs.

scholarly journals Distinct and Combined Roles of the MAP Kinases of Cochliobolus heterostrophus in Virulence and Stress Responses

2008 ◽  
Vol 21 (6) ◽  
pp. 769-780 ◽  
Author(s):  
Aeid Igbaria ◽  
Sophie Lev ◽  
Mark S. Rose ◽  
Bee Na Lee ◽  
Ruthi Hadar ◽  
...  
Keyword(s):  
Stress Responses ◽  
Map Kinases ◽  
Cochliobolus Heterostrophus ◽  
Wild Type ◽  
Necrotrophic Pathogen ◽  
Disease Symptoms ◽  
Monosaccharide Transporter ◽  
Maize Leaves ◽  
Mitogen Activated Protein ◽  
Corn Leaf Blight

Pathogenicity mitogen-activated protein kinases (MAPKs), related to yeast FUS3/KSS1, are essential for virulence in fungi, including Cochliobolus heterostrophus, a necrotrophic pathogen causing Southern corn leaf blight. We compared the phenotypes of mutants in three MAPK genes: HOG1, MPS1, and CHK1. The chk1 and mps1 mutants show autolytic appearance, light pigmentation, and dramatic reduction in virulence and conidiation. Similarity of mps1 and chk1 mutants is reflected by coregulation by these two MAPKs of several genes. Unlike chk1, mps1 mutants are female-fertile and form normal-looking appressoria. HOG1 mediates resistance to hyperosmotic and, to a lesser extent, oxidative stress, and is required for stress upregulation of glycerol-3-phosphate phosphatase, transaldolase, and a monosaccharide transporter. Hog1, but not Mps1 or Chk1, was rapidly phosphorylated in response to increased osmolarity. The hog1 mutants have smaller appressoria and cause decreased disease symptoms on maize leaves. Surprisingly, loss of MPS1 in a wild-type or hog1 background improved resistance to some stresses. All three MAPKs contribute to the regulation of central developmental functions under normal and stress conditions, and full virulence cannot be achieved without appropriate input from all three pathways.

scholarly journals A decade of using small-to-medium throughput allele discrimination assay to determine prion protein gene (Prnp) genotypes in sheep in Slovenia

2017 ◽  
Vol 30 (1) ◽  
pp. 144-149 ◽  
Author(s):  
Jelka Zabavnik ◽  
Marko Cotman ◽  
Polona Juntes ◽  
Ivan Ambrozic
Keyword(s):  
Prion Protein ◽  
Protein Gene ◽  
Classical Scrapie ◽  
Prion Protein Gene ◽  
Atypical Scrapie ◽  
Susceptible Genotype ◽  
Pcr Assay ◽  
Breeding Programs ◽  
Resistant Genotypes ◽  
Selection Of

Sheep with valine (V) at codon 136 and glutamine (Q) at codon 171 of the prion protein gene ( Prnp) are highly susceptible to classical scrapie, whereas phenylalanine (F) at codon 141 and histidine (H) at codon 154 play a major role in the susceptibility to atypical scrapie. A TaqMan real-time PCR assay was developed to determine Prnp alleles at codons 136, 141, 154, and 171 and used in classical scrapie eradication and breeding programs adopted in Slovenia. The frequency of the most resistant genotypes ARR/ARR and ARR/ARQ increased significantly in tested animals ( n = 35,138) from 6.7 and 27.1% of the tested sheep in 2006 to 12.1 and 32.4%, respectively, in 2015. Frequencies of more susceptible genotypes ARQ/ARQ and ARQ/VRQ decreased significantly from 36.4 and 3.5% in 2006 to 31.1 and 1.8%, respectively, in 2015. The most susceptible genotype VRQ/VRQ was detected in <0.5% of tested sheep. Frequencies of alleles AFRQ and AHQ affecting the susceptibility to atypical scrapie did not change significantly. The developed assay was suitable for genotyping on a small-to-medium throughput scale and was successfully used in classical scrapie eradication, as well as for the selection of classical scrapie–resistant sheep within breeding programs in Slovenia.

RAPD markers for a sunflower rust resistance gene

1996 ◽  
Vol 47 (3) ◽  
pp. 395 ◽  
Author(s):  
WR Lawson ◽  
KC Goulter ◽  
RJ Henry ◽  
GA Kong ◽  
JK Kochman
Keyword(s):  
Resistance Gene ◽  
Rust Resistance ◽  
Durable Resistance ◽  
Dominant Gene ◽  
Rust Resistance Gene ◽  
Breeding Programs ◽  
Resistant Parent ◽  
F2 Population ◽  
Race 1 ◽  
Selection For

An F2 population of sunflower (Helianthus annuus L.) was tested for segregation of a gene conferring resistance to sunflower rust (Puccznia helzanthi) Australian Race 0 (North American Race 1). The resistant parent, RHA279, of this cross was thought to possess a single dominant resistance gene to this race. Genetic analysis confirmed that this population was segregating for a single dominant gene, the R1 gene, for resistance to this race of the pathogen. Using bulked segregant and RAPD analyses, two markers were identified which co-segregated with the rust resistance gene in the F2 population. These markers, designated OT06959 and 01\/112850, are linked to the rust resistance gene at a distance of 4.5 cM and 26 cM, respectively, with the markers situated one either side of the gene. The availability of markers closely linked to this gene will greatly enhance selection for the gene in future breeding programs, and especially assist efforts to pyramid the gene with other rust resistance genes to produce sunflower varieties with more durable resistance to rust.

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