scholarly journals Characterization of Race-Specific Interactions Among Isolates of Verticillium dahliae Pathogenic on Lettuce

2006 ◽  
Vol 96 (12) ◽  
pp. 1380-1387 ◽  
Author(s):  
Gary E. Vallad ◽  
Qing-Ming Qin ◽  
Rebecca Grube ◽  
Ryan J. Hayes ◽  
Krishna V. Subbarao
Keyword(s):  
Verticillium Dahliae ◽  
Field Experiments ◽  
Sequence Data ◽  
Intergenic Spacer ◽  
Distinct Subgroup ◽  
Race 1 ◽  
Race 2 ◽  
The 1960S ◽  
Significant Disease

Verticillium wilt, caused by Verticillium dahliae, poses a major threat to lettuce (Lactuca sativa) production in California. Incorporation of resistance into commercial lettuce cultivars offers the least expensive technique of sustaining production in infested areas. To test the breadth of the resistance identified in field experiments, a pair of susceptible (‘Salinas’ and ‘Sniper’) and resistant (‘La Brillante’ and ‘Little Gem’) lettuce cultivars were used as differentials and individually inoculated with 29 isolates of V. dahliae and two isolates of V. albo-atrum from several hosts, including lettuce, in replicated greenhouse experiments. The reactions of the four cultivars were determined based on the disease severity at maturity. None of the V. albo-atrum isolates or V. dahliae isolates from cruciferous hosts caused significant disease on lettuce. Both Salinas and Sniper were susceptible to many isolates of V. dahliae (21 of 23) from noncruciferous hosts, and the isolates varied in their overall virulence. However, of these, only three isolates caused significant disease on the resistant cvs. La Brillante and Little Gem. These three isolates also were distinct from the other V. dahliae isolates based on sequence data from the intergenic spacer (IGS) region of the nuclear ribosomal RNA gene, suggesting that they form a phylogenetically distinct subgroup that differs in virulence toward specific lettuce genotypes. Accordingly, isolates of V. dahliae virulent on all tested cultivars, including the resistant La Brillante and Little Gem, were designated as race 2, whereas those virulent only on the susceptible Salinas and Sniper were designated as race 1. Although a range of virulence among isolates has been described in other hosts, this is the first description of distinct virulence phenotypes in V. dahliae since a similar race structure was described in tomato in the 1960s.

scholarly journals Delayed Foliar Symptoms Caused by Verticillium dahliae as an Alternative Resistance Trait in Iceberg Lettuce

HortScience ◽  
2017 ◽  
Vol 52 (4) ◽  
pp. 513-519
Author(s):  
Germán V. Sandoya ◽  
Krishna Subbarao ◽  
Ryan Hayes
Keyword(s):  
Verticillium Dahliae ◽  
Field Experiments ◽  
Economic Losses ◽  
Central Coast ◽  
Delayed Onset ◽  
Iceberg Lettuce ◽  
Foliar Symptoms ◽  
Race 1 ◽  
Resistance Trait ◽  
Race 2

Verticillium wilt caused by Verticillium dahliae Kleb. is an economically damaging disease of iceberg lettuce on the Central Coast of California. Foliar wilting symptoms that manifest near or at peak market maturity (MM) lead to collapse of the head, making it unmarketable. Complete resistance to race 1 of the pathogen is known, but adequate levels of resistance are not available against race 2. Additional mechanisms or traits that reduce foliar symptoms (FS) are needed to lessen economic losses from this disease. Since the disease affects leaves, the harvested product, identification of iceberg cultivars that delay the onset of FS past peak MM could reduce yield loss from the disease. The goal of this research was to identify iceberg lettuce germplasm with delayed onset of FS. Diverse iceberg cultivars were evaluated in replicated field experiments for MM, FS severity, and adaptation. A few winter-adapted cultivars showed fewer FS past MM and seem to be promising candidates for breeding. These cultivars are not adapted to the California Central Coast where the disease currently predominates. Further studies will determine the usefulness of this trait for breeding improved cultivars for use in V. dahliae–infested fields. Developing new cultivars that combine currently available sources of partial resistance against race 2 with delayed onset of FS could lead to reduced crop losses should race 2 of V. dahliae become widespread.

scholarly journals Analysis of Verticillium dahliae Suggests a Lack of Correlation Between Genotypic Diversity and Virulence Phenotypes

Plant Disease ◽  
2011 ◽  
Vol 95 (10) ◽  
pp. 1224-1232 ◽  
Author(s):  
Zahi K. Atallah ◽  
Karunakaran Maruthachalam ◽  
Gary E. Vallad ◽  
R. Michael Davis ◽  
Steven J. Klosterman ◽  
...  
Keyword(s):  
Verticillium Dahliae ◽  
Intergenic Spacer ◽  
Genotypic Diversity ◽  
Sources Of Resistance ◽  
Race 1 ◽  
Geographic Regions ◽  
Race 2 ◽  
Ve Resistance Gene ◽  
Unknown Sequence

Verticillium dahliae causes severe wilt and recurring losses in numerous agricultural and ornamental hosts worldwide. Two virulence phenotypes (races) have been identified based on the Ve resistance gene and its homologs but their distribution and evolutionary history are unknown. Sequence analyses of the intergenic spacer of the ribosomal DNA and amplified fragment length polymorphism markers suggested an absence of correlation between genotypic diversity and virulence phenotypes. Additionally, both race 1 and 2 phenotypes were isolated in various geographic regions and hosts. Sustained levels of migration of both virulence phenotypes among various geographic regions were evident, and the study also suggested that both virulence phenotypes infect a variety of hosts, regardless of the availability of resistant cultivars. Given the high genotypic diversity observed in V. dahliae, more than the two known virulence phenotypes may be present in nature but not yet identified because of the current lack of sources of resistance other than the Ve gene and its homologs. The inclusion of various genotypes exhibiting the same virulence phenotype may greatly improve the long-term effectiveness of resistance to race 2 of V. dahliae regardless of the host. This study also confirms the transcontinental gene flow and high genotypic diversity of V. dahliae affecting lettuce in coastal California regardless of the molecular markers employed.

scholarly journals Characterization of a Regional Population of Fusarium oxysporum f. sp. niveum by Race, Cross Pathogenicity, and Vegetative Compatibility

2007 ◽  
Vol 97 (4) ◽  
pp. 461-469 ◽  
Author(s):  
X. G. Zhou ◽  
K. L. Everts
Keyword(s):  
Fusarium Oxysporum ◽  
Vegetative Compatibility ◽  
Infested Soil ◽  
Vegetative Compatibility Group ◽  
Atlantic Region ◽  
Compatibility Group ◽  
Race 1 ◽  
Regional Population ◽  
Race 2

Eighty-eight isolates of Fusarium oxysporum f. sp. niveum, collected from wilted watermelon plants and infested soil in Maryland and Dela-ware, were characterized by cross pathogenicity to muskmelon, race, and vegetative compatibility. Four isolates (4.5%) were moderately pathogenic to ≥2 of 18 muskmelon cultivars in a greenhouse test, and one representative isolate also was slightly pathogenic in field microplots. The four isolates all were designated as race 2, and were in vegetative compatibility group (VCG) 0082. Of the 74 isolates to which a VCG could be assigned, 41 were in VCG 0080, the VCG distributed most widely; 27 were in VCG 0082, and were distributed in half of the 20 watermelon fields surveyed; and 6 were in the newly described VCG 0083, and were restricted to three fields. Among the isolates in VCG 0080, 8 were designated as race 0, 21 as race 1, and 12 as race 2. Of the isolates in VCG 0082, 6 were designated as race 0, 11 as race 1, and 10 as race 2. All isolates in VCG 0083 were designated as race 2. Isolates from more than one race within the same VCG or isolates from more than one VCG were recovered from single plants and fields. No differences in aggressiveness on differential watermelon cultivars were observed among isolates from different VCGs of the same race. A diverse association between virulence and VCG throughout the Mid-Atlantic region suggests that the pathotypes of F. oxysporum f. sp. niveum may be of local origin or at least long existent in the region.

scholarly journals Nondefoliating and Defoliating Strains from Cotton Correlate with Races 1 and 2 of Verticillium dahliae

Plant Disease ◽  
2015 ◽  
Vol 99 (12) ◽  
pp. 1713-1720 ◽  
Author(s):  
Xiao-Ping Hu ◽  
Suraj Gurung ◽  
Dylan P. G. Short ◽  
German V. Sandoya ◽  
Wen-Jing Shang ◽  
...  
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Reference Strain ◽  
The United States ◽  
Specific Primers ◽  
Differential Cultivars ◽  
Race 1 ◽  
Polymerase Chain ◽  
Race 2 ◽  
Important Disease

Verticillium wilt, caused by Verticillium dahliae, is an important disease of cotton worldwide. Isolates of V. dahliae can be characterized as race 1 or race 2 based on the responses of differential cultivars of tomato and lettuce, or as defoliating or nondefoliating based on symptom expression in cotton. To investigate the frequency and distribution of races and defoliation phenotypes of cotton-associated V. dahliae, 317 isolates from China, Israel, Turkey, and the United States were tested by polymerase chain reaction (PCR) using defoliating, nondefoliating, and race 1- and race 2-specific primers DF/DR, NDF/NDR, VdAve1F/VdAve1R, and VdR2F/VdR2R, respectively. Of the total, 97.2% of isolates genotyped as defoliating were also characterized as race 2, while 90.8% of isolates genotyped as nondefoliating were also genotyped as race 1. To verify these results, three cotton cultivars—‘FM 2484B2F’ (highly resistant), ‘98M-2983’ (highly susceptible), and ‘CA4002’ (partially resistant)—used as differentials were each inoculated with 10 isolates characterized by PCR: six defoliating/race 2 strains (GH1005, GH1021, HN, XJ2008, XJ592, and reference strain Ls17) and four nondefoliating/race 1 strains (GH1015, GH1016, GH1020, and reference strain Ls16). All defoliating/race 2 isolates except for Ls17 caused defoliation on 98M-2983 and CA4002. Isolate Ls17 caused defoliation on 98M-2983 only. The nondefoliating/race 1 isolates caused Verticillium wilt symptoms devoid of defoliation on 98M-2983. The greenhouse assays confirmed the molecular identification of race and defoliation phenotype. Although the existence of races has not been previously established among V. dahliae isolates from cotton, the long-established nondefoliating and defoliating population structure corresponded with V. dahliae races 1 and 2, respectively.

scholarly journals Phenotypic and molecular characterization of the causal agent of chafer beetle mortality in the wheat fields of the Kurdistan province, Iran

2015 ◽  
Vol 55 (3) ◽  
pp. 227-234 ◽  
Author(s):  
Keivan Karimi ◽  
Mahdi Arzanlou ◽  
Asadollah Babai Ahari ◽  
Mostafa Mansour Ghazi
Keyword(s):  
Field Experiments ◽  
Biocontrol Agent ◽  
Galleria Mellonella ◽  
Sequence Data ◽  
Biological Control Agent ◽  
Control Agent ◽  
Internal Transcribed Spacer Region ◽  
First Case ◽  
Potential Biocontrol Agent

AbstractWe report the first case of chafer beetle [Anisoplia austriaca(Herbst 1783)] mortality caused byActinomucor elegansvar.elegansin wheat fields of the Kurdistan province, Iran. For three years, dead larvae ofAnisoplia austriacawere collected from wheat fields of the Kurdistan province. Similar isolates of a fast-growing fungus were recovered from all samples. The fungal isolates were identified asA. elegansvar.elegansbased on morphological and cultural characteristics. The identity of the species was further confirmed using sequence data of the ITS (Internal Transcribed Spacer) region of ribosomal DNA. Koch’s postulates were fulfilled by the inoculation of the larvae ofA. austriacaandGalleria mellonella(Linnaeus, 1758) (as the model insect) using the spore suspension ofA. elegansvar.elegans. The viability of sporangiospores was evaluated using a spore dilution technique on germination medium. The results on the pathogenicity (100% mortality inA. austriacalarvae) and viability tests (germination: 95.45%) demonstrated thatA. elegansvar.eleganscan be considered as a potential biocontrol agent against the chafer beetle. Field experiments are still required to evaluate the capacity ofA. elegansas a biological control agent.

scholarly journals CHARACTERIZATION OF RESISTANCE TO ROOT-KNOT NEMATODES IN SWEETPOTATO

HortScience ◽  
2005 ◽  
Vol 40 (3) ◽  
pp. 868e-869
Author(s):  
J.A. Thies
Keyword(s):  
Meloidogyne Incognita ◽  
Ipomoea Batatas ◽  
Nematode Species ◽  
Plant Introduction ◽  
Root Knot Nematode ◽  
Race 1 ◽  
Race 2 ◽  
The U.S ◽  
Greenhouse Tests

Thirteen sweetpotato (Ipomoea batatas) genotypes were characterized for resistance to Meloidogyne incognita, M. javanica, M. hapla, and M. arenaria races 1 and 2 in greenhouse tests. The following sweetpotato genotypes representing a range of reactions to M. incognita were evaluated: U.S. Plant Introduction (PI) 399163 (highly resistant = HR), Sumor (HR), Nemagold (HR), Excel (HR), Tinian (HR), Hernandez (resistant = R), Jewel (R), Regal (R), Porto Rico (intermediate = I), Centennial (susceptible = S), Georgia Jet (S), Sulfur (S), and Beauregard (S). Meloidogyne incognita was most pathogenic to sweetpotato of the four Meloidogyne spp. evaluated in these studies. The U.S. Plant Introduction (PI) 399163 and Sumor were resistant to M. incognita in all tests. Only two genotypes, Beauregard and Porto Rico, were susceptible to M. javanica. All genotypes evaluated were resistant to M. hapla, M. arenaria race 1, and M. arenaria race 2. Sumor, U.S. PI 399163, and Nemagold appear to provide the highest levels of resistance against the four Meloidogyne spp. used in these studies. Since M. incognita is the most commonly occurring root-knot nematode species in sweetpotato growing areas of the southern U.S. and is pathogenic to most of the commonly grown sweetpotato cultivars, efforts to develop resistant cultivars that have desirable horticultural characteristics for the U.S. market should be directed toward this root-knot nematode species.

scholarly journals Characterization of Capsicum chinense Cultigens for Resistance to Meloidogyne arenaria, M. hapla, and M. javanica

Plant Disease ◽  
2001 ◽  
Vol 85 (3) ◽  
pp. 267-270 ◽  
Author(s):  
Judy A. Thies ◽  
Richard L. Fery
Keyword(s):  
High Resistance ◽  
Meloidogyne Incognita ◽  
Capsicum Chinense ◽  
Sources Of Resistance ◽  
Alternative Source ◽  
Highly Pathogenic ◽  
Habanero Pepper ◽  
Race 1 ◽  
Race 2

Four Capsicum chinense cultigens with known reactions to Meloidogyne incognita were characterized for resistance to M. arenaria races 1 and 2, M. hapla, and M. javanica, in greenhouse and growth-chamber tests. The M. incognita-resistant cultigens PA-353, PA-398, and PA-426 exhibited high resistance to M. arenaria race 1; the M. incognita-susceptible PA-350 was susceptible to M. arenaria race 1. M. arenaria race 2 and M. javanica were not highly pathogenic to any of the C. chinense cultigens. PA-353, PA-398, and PA-426, however, supported an average of 98.1 and 94.8% fewer (P < 0.05) M. arenaria race 2 and M. javanica eggs per gram fresh root, respectively, than PA-350. M. hapla was pathogenic to all four C. chinense cultigens. PA-353, PA-398, and PA-426 will be useful sources of resistance to M. arenaria races 1 and 2, M. javanica, and M. incognita, for developing resistant habanero pepper cultivars; however, an alternative source of resistance must be identified for M. hapla.

scholarly journals Distribution and Pathogenic Characterization of Pyrenophora tritici-repentis and Stagonospora nodorum in Ohio

2006 ◽  
Vol 96 (12) ◽  
pp. 1355-1362 ◽  
Author(s):  
Jessica S. Engle ◽  
Laurence V. Madden ◽  
Patrick E. Lipps
Keyword(s):  
Linear Analysis ◽  
The Other ◽  
Stagonospora Nodorum ◽  
Pyrenophora Tritici Repentis ◽  
Logistic Analysis ◽  
Wheat Leaf ◽  
Race 1 ◽  
Race 2 ◽  
Log Linear

To determine the distribution of Stagonospora nodorum and Pyrenophora tritici-repentis on wheat in Ohio, flag leaves with lesions were collected from wheat-producing counties in 2002 and 2003. Counties were arbitrarily grouped into seven regions. Log-linear analysis of pathogen presence within regions indicated that the presence of S. nodorum was independent of the presence of P. tritici-repentis. A logistic analysis revealed that the occurrence of both pathogens varied by region in one or both years. The aggressiveness of S. nodorum isolates was determined by inoculating two susceptible genotypes with a subsample of isolates from each region from both years. S. nodorum isolates obtained from northeast Ohio, with fewer wheat fields, were less aggressive than those from other regions. Isolates obtained from west-central Ohio, surrounded by regions with high wheat production annually, were significantly more aggressive than those obtained in the remaining five regions. Isolates from the five other regions did not differ significantly (P > 0.05) in aggressiveness. Races 1 and 2, and a few race 3 isolates, of P. tritici-repentis were detected in Ohio. The distribution of P. tritici-repentis races 1 and 2 was not associated with any region, although the prevalence of race 1 was three times greater than race 2. The rarer race 3 was associated with three dispersed regions. Results indicate that S. nodorum was the major wheat leaf-blotching pathogen. There were no positive or negative associations of S. nodorum and P. tritici-repentis or individual races of P. tritici-repentis in any of the tested regions, which indicates that neither pathogen can be used to predict the presence of the other. The isolated northeastern corner of Ohio appeared to contain isolates of S. nodorum with unique characteristics and potentially only one race of P. tritici-repentis, indicating that this area may be genetically isolated from the remaining tested areas of the state.

scholarly journals Genome Sequence of Verticillium dahliae Race 1 Isolate VdLs.16 From Lettuce

2020 ◽  
Vol 33 (11) ◽  
pp. 1265-1269
Author(s):  
Jie-Yin Chen ◽  
Dan-Dan Zhang ◽  
Jin-Qun Huang ◽  
Dan Wang ◽  
Shi-Jun Hao ◽  
...  
Keyword(s):  
Verticillium Dahliae ◽  
Genetic Basis ◽  
Reference Genome ◽  
Genomic Diversity ◽  
Host Responses ◽  
Ongoing Research ◽  
Differential Host ◽  
Population Genomic ◽  
Race 1 ◽  
Race 2

Verticillium dahliae is a widespread fungal pathogen that causes Verticillium wilt on many economically important crops and ornamentals worldwide. Populations of V. dahliae have been divided into two distinct races based upon differential host responses in tomato and lettuce. Recently, the contemporary race 2 isolates were further divided into an additional race in tomato. Herein, we provide a high-quality reference genome for the race 1 strain VdLs.16 isolated from lettuce in California, U.S.A. This resource will contribute to ongoing research that aims to elucidate the genetic basis of V. dahliae pathogenicity and population genomic diversity.

Colonization of tomatoes by Verticillium dahliae: determinative phase II

1996 ◽  
Vol 74 (8) ◽  
pp. 1279-1288 ◽  
Author(s):  
Julie Gold ◽  
Barbara Lee ◽  
J. Robb
Keyword(s):  
Verticillium Dahliae ◽  
Wilt Disease ◽  
Symptom Expression ◽  
Race 1 ◽  
Race 2 ◽  
The Relationship ◽  
Ve Gene ◽  
Defensive Mechanism ◽  
Colonizing Ability

To investigate the relationship between stem colonizing ability of Verticillium and wilt disease development, the colonization capacities of Verticillium dahliae, race 1 or race 2, were compared in near-isolines of the cultivar Craigella, with (Ve+) and without (Ve−) Ve-gene resistance, and in the cultivar IRAT-L3, which also lacks the Ve-gene. Only the Ve+/V.d.1 interaction was resistant to disease. Lateral and vertical invasiveness of the pathogen were assessed cytologically and fungal biomass was monitored by PCR-based diagnostics. The pathogen was most aggressive in the Ve−/V.d.1 interaction; colonization capacity was reduced in the other five combinations, but most severely, and equivalently, in Ve+/V.d.1, IRAT/V.d.1, and IRAT/V.d.2. Further study of the development and role of the vascular coating response in IRAT-L3 indicated a pattern of expression similar to that observed in other susceptible plants, and it was concluded that the reduced colonization of this cultivar by V. dahliae resulted from another unknown defensive mechanism. Stem colonizing ability that is compatible with resistance in one cultivar and race combination may promote symptom expression and even death in another. Keywords: tomato, Verticillium dahliae, vascular coating, resistance.

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