scholarly journals Selection for Resistance to Verticillium Wilt Caused by Race 2 Isolates of Verticillium dahliae in Accessions of Lettuce (Lactuca sativa L.)

HortScience ◽  
2011 ◽  
Vol 46 (2) ◽  
pp. 201-206 ◽  
Author(s):  
Ryan J. Hayes ◽  
Karunakaran Maruthachalam ◽  
Gary E. Vallad ◽  
Steven J. Klosterman ◽  
Krishna V. Subbarao
Keyword(s):  
Genetic Variation ◽  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Partial Resistance ◽  
Disease Incidence ◽  
Greenhouse Experiments ◽  
Complete Resistance ◽  
Race 1 ◽  
Selection For ◽  
Race 2

Verticillium wilt of lettuce caused by Verticillium dahliae can cause severe economic damage to lettuce producers. The pathogen exists as two races (Races 1 and 2) in lettuce, and complete resistance to Race 1 is known. Resistance to Race 2 isolates has not been reported, and production of Race 1-resistant cultivars will likely increase the frequency of Race 2 strains. The objective of this research was to select lettuce accessions for resistance to Race 2 isolates of V. dahliae. Two independent populations totaling 314 randomly sampled PIs were evaluated for Verticillium wilt disease incidence (DI) caused by V. dahliae isolate VdLs17 in one unreplicated and two replicated greenhouse experiments. Selection for PIs with reduced DI was conducted between each experiment and plant stems were plated on semiselective media to identify colonized plants that remained non-symptomatic. No accession with complete resistance was identified, although accessions with partial resistance were selected. Genetic variation for the frequency of V. dahliae-colonized plants that remain symptomless was detected. Four PIs (169511, 171674, 204707, and 226641) were selected for further testing in three replicated greenhouse experiments and demonstrated significantly lower disease incidence than the susceptible control cultivars. The results indicate that lettuce has genetic variation for partial resistance to a Race 2 isolate of V. dahliae. The resistant PIs selected in this research are morphologically diverse, and no dependence between rate of bolting and resistance was found. PIs with partial resistance may be useful for breeding lettuce cultivars with resistance to Race 2 isolates of V. dahliae.

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 Managing the Race Structure of Phytophthora parasitica var. nicotianae with Cultivar Rotation

Plant Disease ◽  
2005 ◽  
Vol 89 (12) ◽  
pp. 1285-1294 ◽  
Author(s):  
M. J. Sullivan ◽  
T. A. Melton ◽  
H. D. Shew
Keyword(s):  
Partial Resistance ◽  
Disease Incidence ◽  
Single Gene ◽  
Growing Season ◽  
Phytophthora Parasitica ◽  
Black Shank ◽  
Complete Resistance ◽  
Race 1 ◽  
High Level ◽  
Different Levels

Deployment of tobacco cultivars with single-gene, complete resistance to race 0 of the tobacco black shank pathogen, Phytophthora parasitica var. nicotianae, has resulted in a rapid increase in the occurrence of race 1 of the pathogen in North Carolina. Cultivar-rotation studies were conducted in three fields to assess how different levels and types of resistance affected the race structure and population dynamics of the pathogen when deployed in fields initially containing single or mixed races of the pathogen. In a field with both races present, a high level of partial resistance in cv. K 346 was most effective in reducing disease and decreasing the proportion of race 1 in the pathogen population. The deployment of complete resistance in cv. NC 71 resulted in intermediate levels of disease control and race 1 became the predominate race. The cv. K 326, with a low level of partial resistance, had the highest levels of disease, and race 0 was the dominant race recovered. In a field where no race 1 was detected initially, disease incidence was high with the use of partial resistance. Complete resistance was very effective in suppressing disease, but race 1 was recovered after only one growing season. By the end of the third growing season, race 1 was recovered from most treatments where single-gene resistance was deployed. A high level of partial resistance was most effective in suppressing disease in a field where race 1 initially was the predominant race. A rotation between cultivars with single-gene resistance and cultivars with a high level of partial resistance should provide the most effective approach to black shank management. This rotation will reduce disease incidence and minimize race shifts in the pathogen and, over time, should prolong the usefulness of the Ph gene for black shank control in commercial production of tobacco.

scholarly journals SOIL-BORNE FUNGAL RESISTANCE IN LYCOPERSICON PENNELLII ACCESSIONS.

HortScience ◽  
1990 ◽  
Vol 25 (9) ◽  
pp. 1068f-1068 ◽  
Author(s):  
J.W. Scott ◽  
J.P. Jones
Keyword(s):  
Fusarium Wilt ◽  
Verticillium Wilt ◽  
Disease Incidence ◽  
Crown Rot ◽  
Fungal Resistance ◽  
Lycopersicon Pennellii ◽  
Cotyledon Stage ◽  
Race 1 ◽  
Fusarium Sp ◽  
Race 2

Forty-two Lycopersicon pennellii Corr. D'Arcy accessions, from the Tomato Genetics Stock Center, were inoculated for resistance to Fusarium wilt race 3 at the 3-leaf and cotyledon stage. All were over 90% healthy when inoculated at the 3-leaf stage but had greater disease incidence at the cotyledon stage. Crosses were made between healthy plants within each accession. Using this seed, 39 accessions were 100% healthy and 3 were over 96% healthy when inoculated at either stage. Seventeen F1's with susceptible parents were tested for race 3 and all had over 80% healthy plants. Twenty-two accessions were tested for Fusarium wilt race 1 and race 2. For race 1, 21 were 100% healthy and 1 was 91% healthy, For race 2, 20 were 100% healthy, 1 was 96% healthy, and 1 was 75% healthy. Forty accessions were screened for Fusarium crown rot and Verticillium wilt. For crown rot, LA 1277, LA 1367, and LA 1657 were over 95% healthy, 6 other accessions were over 68% healthy and several others had over 50% healthy plants, All 40 were susceptible to Verticillium wilt race 1. L. pennellii appears to be a good source of resistance to Fusarium sp. but not to Verticillium wilt.

scholarly journals Characterization of Verticillium dahliae Isolates and Wilt Epidemics of Pepper

Plant Disease ◽  
2003 ◽  
Vol 87 (7) ◽  
pp. 789-797 ◽  
Author(s):  
R. G. Bhat ◽  
R. F. Smith ◽  
S. T. Koike ◽  
B. M. Wu ◽  
K. V. Subbarao
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Random Amplified Polymorphic Dna ◽  
Disease Incidence ◽  
Bell Pepper ◽  
Central Coast ◽  
Minor Variation ◽  
Bell Peppers ◽  
Compatibility Group

Epidemics of Verticillium wilt in pepper fields of the central coast of California and isolates of Verticillium dahliae associated with these epidemics were characterized. The mean incidence of wilted plants per field ranged from 6.3 to 97.8% in fields with Anaheim, jalapeno, paprika, or bell peppers. In general, incidence of wilt in jalapeno and bell pepper crops was lower than in crops of other types of pepper. Inoculum density of V. dahliae in the surveyed pepper fields ranged from 2.7 to 66.6 microsclerotia g-1 dry soil, and the correlation between disease incidence and density of microsclerotia was high (r = 0.81, P < 0.01). Distribution of Verticillium wilt was aggregated in a majority of the pepper fields surveyed, but the degree of aggregation varied. Vegetative compatibility group (VCG) characterization of 67 isolates of V. dahliae indicated that 67% belonged to VCG 2, 22% to VCG 4, and 11% to a new group, designated VCG 6. The pathogenicity of isolates of V. dahliae from bell pepper and tomato plants was tested by inoculating 1-month-old bell pepper (cv. Cal Wonder) and tomato (cv. EP 7) seedlings and incubating the inoculated plants in the greenhouse. Seedlings of bell pepper were susceptible only to the isolates of V. dahliae from pepper, whereas seedlings of tomato were susceptible to both pepper and tomato isolates. Pepper isolates belonging to VCG 2, VCG 4, and VCG 6 were highly pathogenic to bell pepper and chili pepper. Temperatures between 15 and 25°C were optimal for mycelial growth of a majority of isolates of V. dahliae. Molecular characterization of pepper isolates of V. dahliae using a polymerase chain reaction (PCR)-based random amplified polymorphic DNA (RAPD) technique revealed minor variation among these isolates, but unique polymorphic banding patterns were observed for isolates belonging to VCG 6. Verticillium wilt of pepper is a major production constraint in the central coast of California. More aggressive isolates of V. dahliae may have been selected in this region as a result of intensive cropping practices.

Resistance to race 1 of Kabatiella caulivora in subterranean clover (Trifolium subterraneum L.) cultivars and breeding lines

2008 ◽  
Vol 59 (6) ◽  
pp. 561 ◽  
Author(s):  
P. G. H. Nichols ◽  
M. P. You ◽  
M. J. Barbetti
Keyword(s):  
Subterranean Clover ◽  
Trifolium Subterraneum ◽  
Breeding Lines ◽  
Race 1 ◽  
Kabatiella Caulivora ◽  
Selection For ◽  
Race 2 ◽  
Resistant Progeny ◽  
Clover Scorch

Twenty-eight cultivars and 106 F6-derived breeding lines of subterranean clover (Trifolium subterraneum) were screened in the field for their response to clover scorch disease caused by race 1 of Kabatiella caulivora. Eleven of the cultivars, including Denmark and Goulburn, were classified as resistant. Breeding lines with Denmark parentage had 55% of progeny with resistance, while those of Goulburn had only 19% of resistant progeny, suggesting different modes of inheritance. Selection for resistance to race 2 of K. caulivora in the F4 generation markedly increased the probability of selecting F6-derived lines with resistance to race 1, suggesting linkage between genes for resistance to both races.

scholarly journals Host Range of Verticillium isaacii and Verticillium klebahnii from Artichoke, Spinach, and Lettuce

Plant Disease ◽  
2015 ◽  
Vol 99 (7) ◽  
pp. 933-938 ◽  
Author(s):  
Suraj Gurung ◽  
Dylan P. G. Short ◽  
Xiaoping Hu ◽  
German V. Sandoya ◽  
Ryan J. Hayes ◽  
...  
Keyword(s):  
New Species ◽  
Host Range ◽  
Disease Severity ◽  
Verticillium Wilt ◽  
Agricultural Soils ◽  
Phylogenetic Analyses ◽  
Greenhouse Experiment ◽  
Vascular Wilt ◽  
Race 1 ◽  
Race 2

Verticillium is a genus that includes major vascular wilt pathogens. Recently, multilocus phylogenetic analyses of the genus identified five new species, including Verticillium isaacii and V. klebahnii, both of which occur in agricultural soils in coastal California and have been isolated from asymptomatic and diseased spinach and lettuce plants. Little data are available regarding their pathogenicity and virulence on a broader range of crops important to the region. Four isolates each of V. isaacii and V. klebahnii along with two reference isolates of V. dahliae races 1 and 2 were inoculated on eight crops (artichoke, cauliflower, eggplant, lettuce, pepper, tomato, spinach, and strawberry) in a greenhouse experiment. After 8 weeks, plants were assessed for disease severity to determine the relative host ranges of Verticillium isolates. Additionally, 13 lettuce lines resistant to race 1 and partially resistant to race 2 of V. dahliae were screened against V. isaacii and V. klebahnii to evaluate their responses. Three of four V. isaacii and four of four V. klebahnii isolates tested were nonpathogenic on all crops tested except those indicated below. One V. isaacii isolate caused wilt on artichoke and ‘Salinas’ lettuce and most isolates of both species caused varying degrees of Verticillium wilt on strawberry. Lettuce lines resistant to V. dahliae race 1 and partially resistant to V. dahliae race 2 also exhibited resistance to all of the isolates of V. isaacii and V. klebahnii. Thus, at least some isolates in the populations of V. isaacii and V. klebahnii have the potential to become significant pathogens of coastal California crops. However, resistance developed against V. dahliae also offers resistance to the pathogenic isolates of both species, at least in lettuce.

Spatial Patterns of Microsclerotia of Verticillium dahliae in Soil and Verticillium Wilt of Cauliflower

1997 ◽  
Vol 87 (3) ◽  
pp. 325-331 ◽  
Author(s):  
C. L. Xiao ◽  
J. J. Hao ◽  
K. V. Subbarao
Keyword(s):  
Spatial Patterns ◽  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Binomial Distribution ◽  
Disease Incidence ◽  
Soil Samples ◽  
Random Pattern ◽  
Parameter Estimates ◽  
Regular Pattern ◽  
Vascular Discoloration

The spatial patterns of microsclerotia of Verticillium dahliae in soil and wilt symptoms on cauliflower were determined at three sites in each of two fields in 1994 and 1995. Each site was an 8 × 8 grid divided into 64 contiguous quadrats (2 by 2 m each). Soil samples were collected to a depth of 15 cm with a probe (2.5 cm in diameter), and samples from four sites in each quadrat were bulked. Plants in each quadrat were cut transversely, and the number of plants with vascular discoloration and the number without discoloration were recorded. The soil was assayed for microsclerotia by the modified Anderson sampler technique. Lloyd's index of patchiness (LIP) was used as an indicator to evaluate the aggregation of microsclerotia in the field. Spatial autocorrelation and geostatistical analyses were also used to assess the autocorrelation of microsclerotia among quadrats. The LIP for microsclerotia was greater than 1, indicating aggregation of propagules; however, the degree of aggregation at most sites was not high. Significant autocorrelation within or across rows was detected in some spatial autocorrelograms of propagules, and anisotropic patterns were also detected in some oriented semivariograms from geostatistical analyses for microsclerotia, indicating the influence of bed preparation in the fields on pathogen distribution. The parameter estimates p and θ in the beta-binomial distribution and the index of dispersion (D) associated with the distribution were used to assess the aggregation of diseased plants at each site. A random pattern of wilt incidence was detected at 7 of 12 sites, and an aggregated pattern was detected at 5 of 12 sites. The degree of aggregation was not high. A regular pattern of wilt severity was detected at all sites. The high disease incidence (77 to 98%) observed at 11 of the 12 sites could be explained by high inoculum density.

scholarly journals Suppression of Fusarium Wilt Caused by Fusarium oxysporum f. sp. niveum Race 2 on Grafted Triploid Watermelon

Plant Disease ◽  
2014 ◽  
Vol 98 (10) ◽  
pp. 1326-1332 ◽  
Author(s):  
Anthony P. Keinath ◽  
Richard L. Hassell
Keyword(s):  
Fusarium Oxysporum ◽  
Fusarium Wilt ◽  
Disease Incidence ◽  
The United States ◽  
Infested Soil ◽  
Marketable Yield ◽  
Race 1 ◽  
Susceptible Control ◽  
Triploid Watermelon ◽  
Race 2

Fusarium wilt of watermelon, caused by the soilborne fungal pathogen Fusarium oxysporum f. sp. niveum race 2, is a serious, widespread disease present in major watermelon-growing regions of the United States and other countries. ‘Fascination,’ a high yielding triploid resistant to race 1, is grown in southeastern states in fields that contain a mixture of races 1 and 2. There is some benefit to using cultivars with race 1 resistance in such fields, even though Fascination is susceptible to Fusarium wilt caused by race 2. Experiments in 2012 and 2013 were done in fields infested primarily with race 2 and a mixture of races 1 and 2, respectively. Fascination was grafted onto four rootstock cultivars: bottle gourd (Lagenaria siceraria) ‘Macis’ and ‘Emphasis’ and interspecific hybrid squash (Cucurbita maxima× C. moschata) ‘Strong Tosa’ and ‘Carnivor.’ Nongrafted and self-grafted Fascination were used as susceptible control treatments. In both experiments, mean incidence of plants with symptoms of Fusarium wilt was ≥52% in the susceptible control treatments and ≤6% on the grafted rootstocks. Disease incidence did not differ between rootstock species or cultivars. In both years, Fascination grafted onto Strong Tosa and Macis produced more marketable-sized fruit than the susceptible control treatments. Grafted Emphasis and Carnivor also produced more fruit than the control treatments in 2012. The cucurbit rootstocks suppressed Fusarium wilt caused by race 2 and increased marketable yield of triploid watermelon grown in infested soil.

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 Control of Fusarium Wilt of Watermelon by Grafting onto Bottlegourd or Interspecific Hybrid Squash Despite Colonization of Rootstocks by Fusarium

Plant Disease ◽  
2014 ◽  
Vol 98 (2) ◽  
pp. 255-266 ◽  
Author(s):  
A. P. Keinath ◽  
R. L. Hassell
Keyword(s):  
Fusarium Wilt ◽  
Interspecific Hybrid ◽  
Citrullus Lanatus ◽  
Disease Incidence ◽  
Field Performance ◽  
Control Treatment ◽  
Infested Field ◽  
Race 1 ◽  
Seedless Watermelon ◽  
Race 2

Grafting watermelon (Citrullus lanatus var. lanatus) onto rootstocks of interspecific hybrid squash (Cucurbita moschata × C. maxima), bottle gourd (Lagenaria siceraria), or citron (Citrullus lanatus var. citroides) has been used in Asia and Israel to mange Fusarium wilt of watermelon caused by Fusarium oxysporum f. sp. niveum. The objectives of this study were to determine the frequency of infection of six rootstocks by F. oxysporum f. sp. niveum races 1 and 2 and the field performance of grafted rootstocks in Charleston, SC. Grafted and nongrafted watermelon and rootstock plants were inoculated in the greenhouse with race 1, race 2, or water (the control treatment). With both races, the frequency of recovery of F. oxysporum from scion and rootstock portions of inoculated watermelon plants grafted onto ‘Ojakkyo’ citron was greater than from watermelon plants grafted onto ‘Shintosa Camel’ and ‘Strong Tosa’ interspecific hybrid squash, and from plants grafted onto ‘Emphasis’, ‘Macis’, and ‘WMXP 3945’ bottlegourd. For nongrafted plants inoculated with race 1, percent recovery also was greater from Ojakkyo than from interspecific hybrid squash and bottlegourd. For nongrafted plants inoculated with race 2, F. oxysporum was recovered from the base of ≥79% of all inoculated plants. More than two-thirds (15) of 21 isolates recovered from the tops or scions of inoculated plants were pathogenic on watermelon. In spring 2010 and 2011, the six rootstocks were grafted with seedless watermelon ‘Tri-X 313’, which is susceptible to both races, and transplanted in a field infested with races 1 and 2 of F. oxysporum f. sp. niveum. Disease incidence for nongrafted and self-grafted Tri-X 313 (the control treatments) and Tri-X 313 grafted onto Ojakkyo citron did not differ significantly. Grafted watermelon plants produced greater weights and numbers of fruit than plants of the two control treatments. Nonpathogenic isolates of F. oxysporum and isolates of F. oxysporum f. sp. niveum colonized interspecific hybrid squash, bottlegourd, and grafted watermelon. The rootstocks evaluated, however, restricted movement of F. oxysporum f. sp. niveum into the watermelon scion, suppressed wilt symptoms, and increased fruit yields in an infested field.

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