Identified Resistance in Lettuce Germplasm to Verticillium Wilt Caused by Verticillium dahliae

Since its appearance in 1995, Verticillium wilt of lettuce has spread through the Salinas River Valley, where nearly 60% of California's lettuce acreage is located. A replicated field trial was conducted to assess various modern and heirloom lettuce (Lactuca sativa) cultivars, plant introductions, and L. virosa lines for resistance to Verticillium wilt. Based on horticultural type, lettuce plants were destructively sampled at harvest maturity and assessed for the incidence of Verticillium wilt. Of the L. sativa cultivars, only the iceberg type displayed pronounced foliar symptoms of stunting and wilting. Disease incidence based on root symptoms ranged from 0% to 100%, with continuous variation found across and within lettuce types. Most cos, crisphead, and leaf cultivars exhibited 20% or greater disease incidence. Butter cultivars exhibited the lowest disease incidence among the major lettuce types examined, and Latin and Batavia type cultivars exhibited the lowest disease incidence overall. Disease progression was further monitored for 10 select lettuce cultivars for 2 weeks past harvest maturity. Disease intensity increased over the 2-week period for some cultivars, demonstrating the need to assess plants for Verticillium wilt past harvest maturity to avoid misclassifying plants. The L. sativa plant introduction lines tested, predominantly stem and oil-seed horticultural types, were quite susceptible and exhibited distinct symptoms of wilt and defoliation, possibly due to their elongated growth habit. The variation in disease incidence among the L. virosa lines tested was discontinuous, with discrete differences in susceptibility. Overall, the results reflected trends found in previous greenhouse and field trials.

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Characterization of Verticillium dahliae Isolates and Wilt Epidemics of Pepper

Plant Disease ◽

10.1094/pdis.2003.87.7.789 ◽

2003 ◽

Vol 87 (7) ◽

pp. 789-797 ◽

Cited By ~ 81

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.

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

Phytopathology ◽

10.1094/phyto.1997.87.3.325 ◽

1997 ◽

Vol 87 (3) ◽

pp. 325-331 ◽

Cited By ~ 40

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.

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Screening for Resistance to Verticillium Wilt in Spinach and Isolation of Verticillium dahliae from Seed of Spinach Accessions

HortScience ◽

10.21273/hortsci.47.9.1297 ◽

2012 ◽

Vol 47 (9) ◽

pp. 1297-1303 ◽

Cited By ~ 7

Author(s):

Maria I. Villarroel-Zeballos ◽

Chunda Feng ◽

Angela Iglesias ◽

Lindsey J. du Toit ◽

James C. Correll

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Crop Production ◽

Spinacia Oleracea ◽

Quantitative Resistance ◽

Germplasm Collection ◽

Plant Introduction ◽

Infested Soil ◽

Wide Range ◽

North Central Regional

Verticillium dahliae is a pathogen of spinach (Spinacia oleracea) during spinach seed crop production but not in vegetative leafy spinach crops, because plants remain asymptomatic until bolting has been initiated (conversion from vegetative to reproductive growth). The objectives of this research were to evaluate a set of USDA spinach germplasm accessions for resistance to Verticillium wilt and to determine the range in incidence of natural seed infection/infestation in a subset of the USDA spinach accessions screened for resistance. A total of 120 Spinacia spp. accessions from the USDA North Central Regional Plant Introduction Station spinach germplasm collection and 10 commercial S. oleracea hybrids were screened for resistance to V. dahliae in Trials 1, 2, and 3 in 2006, 2007, and 2008, respectively, in greenhouse evaluations. Each accession was grown in either V. dahliae-infested or non-infested potting mix and rated weekly on a seven-step scale from 1 week before bolting to 4 weeks after bolting. A wide range of disease severity ratings was observed among the accessions evaluated. Most of the accessions were highly susceptible. There was no evidence of qualitative resistance but some showed greater levels of quantitative resistance than others. Plants in soil infested with V. dahliae senesced faster and had significantly reduced biomass compared with plants in non-infested soil of the same accession. In addition, in Trial 2 (2007), 34% (20 of 59) of the seed samples assayed of the accessions were infested or infected with V. dahliae; and in Trial 3, (2008) 16% (21 of 130) of the seed samples of the USDA accessions evaluated were infested or infected with V. dahliae, V. tricorpus, or Gibellulopsis nigrescens (formerly known as V. nigrescens). These results are valuable for characterizing potential genetic variability within spinach germplasm for resistance to V. dahliae.

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Relationship Between the Inoculum Density of Verticillium dahliae and the Progress of Verticillium Wilt of Olive

Plant Disease ◽

10.1094/pdis-91-11-1372 ◽

2007 ◽

Vol 91 (11) ◽

pp. 1372-1378 ◽

Cited By ~ 41

Author(s):

F. J. López-Escudero ◽

M. A. Blanco-López

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Disease Incidence ◽

Olive Tree ◽

Temporal Variations ◽

Inoculum Density ◽

Infested Soil ◽

Initial Inoculum ◽

Progress Curve ◽

Olive Trees

An experiment was conducted in microplots which were artificially infested with a defoliating isolate of Verticillium dahliae using seven different treatments of inoculum densities ranging from 0 to 10 microsclerotia per gram of soil (ppg). The experiment was conducted in Andalucía (southern Spain), and the susceptible Spanish olive cv. Picual was used to determine the relationship between pathogen inoculum density and the progress of Verticillium wilt of olive (VWO). The inoculum, produced on a sodium pectate cellophane medium, was found to efficiently infect olive trees. Symptoms first appeared 30 weeks after the trees were transplanted into infested soil. Periods of increasing disease incidence in the following seasons and years were mainly during spring and autumn, particularly in the second year after planting. Olive trees exhibited a high susceptibility to the defoliating pathotype of the pathogen, even at very low inoculum levels; in fact, diseased plants were encountered throughout the experiment regardless of the inoculum density treatment. Inoculum densities greater than 3 ppg in the soil resulted in final disease incidence greater than 50% for the trees after 2.5 years. Therefore, these inoculum densities must be considered very high for olive trees. There were no differences in final disease incidence, mean symptom severity, or area under the disease progress curve between plots infested with 10 or 3.33 ppg, whereas other treatments exhibited lower values for each of these disease parameters. The temporal variations of disease incidence and severity were highly correlated for the higher inoculum density treatments, with r2 values ranging from 0.92 to 0.84 for disease incidence and from 0.93 to 0.88 for severity. However, r2 was slightly lower for the treatments involving lower inoculum densities of the pathogen in microplots. The slopes of the linear regression curves were statistically different for nearly all the inoculum density treatments. Positive correlation was found between the initial inoculum density and final disease incidence values after the study period that was accurately explained by mathematical models. The results suggest that susceptible olive cultivars should not be planted in soils infested with virulent defoliating pathotypes of V. dahliae. Results also clarify that inoculum density levels obtained from field soil analyses can be used for establishing a risk prediction system with a view to controlling VWO in olive tree plantations.

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Verticillium Wilt Incited by Verticillium dahliae in Eggplant Grafted on Solanum torvum in Italy

Plant Disease ◽

10.1094/pd-89-0777b ◽

2005 ◽

Vol 89 (7) ◽

pp. 777-777 ◽

Cited By ~ 5

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Vascular Tissue ◽

Disease Incidence ◽

Conidial Suspension ◽

Root Knot Nematode ◽

Solanum Torvum ◽

Meloidogyne Spp ◽

Resistant Rootstock ◽

Low Incidence

Eggplant cultivars grafted on rootstocks resistant to root-knot nematodes (Meloidogyne spp.) are increasingly grown in Italy to reduce nematode infection. During the winter of 2003-2004, eggplants (cv Black Bell and Mirabell) grafted on the nematode-resistant rootstock Solanum torvum were observed with symptoms of a wilt disease in several greenhouses in Sicily (southern Italy). The vascular tissue in stems of affected plants appeared brown. These plants were stunted and developed yellow leaves with brown or black streaks in the vascular tissue. The wilt appeared in several greenhouses at a very low incidence (0.01 to 0.05%). Later, during the fall of 2004, disease incidence was approximately ten times greater in the same greenhouses on new crops. Verticillium dahliae was consistently and readily isolated from symptomatic vascular tissue of the rootstock (S. torvum) and the scion (cv Black bell) when cultured on potato dextrose agar (PDA) (1). Healthy, 50-day-old plants of S. torvum and eggplant (cv. Black Bell) were separately inoculated by root dip with a conidial suspension (1 × 107 CFU/ml) of two isolates of V. dahliae obtained from the rootstock and the scion of the infected grafted plants and with a known pathogenic isolate of V. dahliae from nongrafted eggplant. Noninoculated S. torvum and eggplant served as control treatments. Plants (30 per treatment) were grown in a glasshouse at temperatures ranging between 12 and 41°C (weekly average 15 to 36°C) and relative humidity ranging between 36 and 99% (weekly average 54 to 95%). The first wilt symptoms and vascular discoloration in the roots, crowns, and veins developed 26 and 21 days after inoculation on S. torvum and eggplant, respectively. Seventy-two days after inoculation, 20, 26, and 27% of S. torvum plants and 97, 100, and 87% of the eggplants showed symptoms caused by V. dahliae isolates obtained from the scion of diseased grafted plants, the rootstock of diseased grafted plants, and nongrafted eggplants, respectively. Noninoculated plants remained healthy. To our knowledge, this is the first report in Italy of Verticillium wilt on eggplant grafted on S. torvum rootstocks under commercial conditions. Use of eggplant grafted on the nematode-resistant rootstock of S. torvum presents an interesting opportunity to control the root-knot nematode but has to be carefully considered when dealing with soils severely infested by V. dahliae. Reference: (1) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002.

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Effects of Crop Rotation and Irrigation on Verticillium dahliae Microsclerotia in Soil and Wilt in Cauliflower

Phytopathology ◽

10.1094/phyto.1998.88.10.1046 ◽

1998 ◽

Vol 88 (10) ◽

pp. 1046-1055 ◽

Cited By ~ 87

Author(s):

C. L. Xiao ◽

K. V. Subbarao ◽

K. F. Schulbach ◽

S. T. Koike

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Drip Irrigation ◽

Disease Incidence ◽

Subsurface Drip Irrigation ◽

Irrigation Methods ◽

Irrigation Regimes ◽

Subsurface Drip ◽

Field Plots ◽

Plot Design

Experiments were conducted in field plots to evaluate the effects of broccoli residue on population dynamics of Verticillium dahliae in soil and on Verticillium wilt development on cauliflower under furrow and subsurface-drip irrigation and three irrigation regimes in 1994 and 1995. Treatments were a factorial combination of three main plots (broccoli crop grown, harvested, and residue incorporated in V.dahliae-infested plots; no broccoli crop or residue in infested plots; and fumigated control plots), two subplots (furrow and subsurface-drip irrigation), and three sub-subplots (deficit, moderate, and excessive irrigation regimes) arranged in a split-split-plot design with three replications. Soil samples collected at various times were assayed for V. dahliae propagules using the modified Anderson sampler technique. Incidence and severity of Verticillium wilt on cauliflower were assessed at 7- to 10-day intervals beginning a month after cauliflower transplanting and continuing until harvest. Number of propagules in all broccoli plots declined significantly (P < 0.05) after residue incorporation and continued to decline throughout the cauliflower season. The overall reduction in the number of propagules after two broccoli crops was approximately 94%, in contrast to the fivefold increase in the number of propagules in infested main plots without broccoli after two cauliflower crops. Disease incidence and severity were both reduced approximately 50% (P < 0.05) in broccoli treatments compared with no broccoli treatments. Differences between furrow and subsurface-drip irrigation were not significant, but incidence and severity were significantly (P < 0.05) lower in the deficit irrigation regime compared with the other two regimes. Abundance of microsclerotia of V. dahliae on cauliflower roots about 8 weeks after cauliflower harvest was significantly (P < 0.05) lower in treatments with broccoli compared with treatments without broccoli. Rotating broccoli with cauliflower and incorporating broccoli residues into the soils is a novel means of managing Verticillium wilt on cauliflower and perhaps on other susceptible crops. This practice would be successful regardless of the irrigation methods or regimes followed on the susceptible crops.

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Evaluation of Soil Fumigants for Management of Verticillium Wilt of Peanut in Texas

Plant Health Progress ◽

10.1094/php-2011-0323-02-rs ◽

2011 ◽

Vol 12 (1) ◽

pp. 16 ◽

Cited By ~ 7

Author(s):

J. E. Woodward ◽

T. A. Wheeler ◽

M. G. Cattaneo ◽

S. A. Russell ◽

T. A. Baughman

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Production System ◽

Field Experiments ◽

Disease Incidence ◽

Minor Effect ◽

Metam Sodium ◽

Effect On Yield ◽

Soil Fumigants ◽

A Minor

Field experiments were conducted to evaluate the effect of the fumigants chloropicrin and metam sodium on soil populations of Verticillium dahliae, disease incidence, and peanut yield and grade. Chloropicrin was ineffective at reducing soil populations of V. dahliae. The application of chloropicrin provided a 7 to 10% reduction in incidence of Verticillium wilt; however, there was no effect on yield or grade. Applications of metam sodium reduced soil populations of V. dahliae, but did not impact disease incidence, yield, or grade. Although fumigants had a minor effect on V. dahliae and disease incidence, the lack of a response in yield or quality limits the use of these chemicals in a production system. Accepted for publication 13 January 2011. Published 23 March 2011.

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Evaluation of Inoculation Methods for Screening Horseradish Cultivars for Resistance to Verticillium dahliae

Plant Disease ◽

10.1094/pdis.1997.81.4.356 ◽

1997 ◽

Vol 81 (4) ◽

pp. 356-362 ◽

Cited By ~ 12

Author(s):

N. Atibalentja ◽

D. M. Eastburn

Keyword(s):

Least Squares ◽

Total Variation ◽

Verticillium Wilt ◽

Verticillium Dahliae ◽

Coefficient Of Variation ◽

Good Predictor ◽

Infested Soil ◽

Inoculation Methods ◽

Foliar Symptoms ◽

Incubation Periods

Four inoculation methods—colonized oatseed, root dip, infested soil, and set dip—were tested in the greenhouse for their effectiveness in identifying horseradish cultivars that are resistant to Verticillium wilt of horseradish. Examination of the inoculum density-disease relationships derived with each of these methods on susceptible (647A) and resistant (769A) cultivars showed that all were effective, though at varying degrees, in differentiating between susceptible and resistant reactions. Results were more consistent with the root dip method as it produced the largest least-squares means difference in wilt index between the two cultivars, the highest r 2, the lowest coefficient of variation, the shortest incubation periods, and the highest incidence of foliar symptoms. Overall, inoculum concentrations accounted for only a small amount of the total variation in wilt index (0.14 ≤ r 2 ≤ 0.73). This observation, in accord with previous reports on other hosts of Verticillium dahliae, would suggest that inoculum densities may not be a good predictor of the severity of Verticillium wilt of horseradish.

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Screening the Peanut Core Collection for Resistance to Tomato Spotted Wilt Virus

Peanut Science ◽

10.3146/i0095-3679-23-1-11 ◽

1996 ◽

Vol 23 (1) ◽

pp. 57-61 ◽

Cited By ~ 37

Author(s):

W. F. Anderson ◽

C. C. Holbrook ◽

A. K. Culbreath

Keyword(s):

Core Collection ◽

Tomato Spotted Wilt Virus ◽

Disease Incidence ◽

Field Trials ◽

Stepwise Multiple Regression ◽

Sources Of Resistance ◽

Plant Introductions ◽

Resistant Cultivars ◽

Tomato Spotted Wilt ◽

Wilt Virus

Abstract Tomato spotted wilt virus (TSWV) is among the greatest yield-reducing viruses affecting peanut (Arachis hypogaea L.). The best known method of control of TSWV is through the use of resistant cultivars. Unfortunately, only a few peanut genotypes with moderate levels of resistance are known. The objectives of this study were to identify additional sources of resistance to TSWV and to determine whether plant descriptor information is associated with reaction to TSWV in the field. Peanut plant introductions from a core collection were evaluated for resistance to TSWV in field trials from 1991 to 1993. Great variability was found among PIs for reaction to natural TSWV epidemics at Attapulgus, GA. Accessions which exhibited potential resistance in 1991 or 1992 were reevaluated in subsequent years. Disease pressure was high in 1993 and 27 accessions exhibited significantly greater resistance than Florunner, and one (PI 262049) had lower disease incidence than Southern Runner. Only minor relationships existed between TSWV incidence and plant descriptor traits (growth habit and maturity) using the stepwise multiple regression procedure. Peanut accessions with resistance to TSWV were found among all maturity levels and growth habits. These accessions provide additional parents and may provide additional genes for resistance that may be useful in developing resistant cultivars.

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Cryptic Infection and Systemic Colonization of Leguminous Crops by Verticillium dahliae, the Cause of Verticillium Wilt

Plant Disease ◽

10.1094/pdis-04-19-0850-re ◽

2019 ◽

Vol 103 (12) ◽

pp. 3166-3171 ◽

Cited By ~ 1

Author(s):

M. G. Lloyd ◽

N. McRoberts ◽

T. R. Gordon

Keyword(s):

Verticillium Wilt ◽

Verticillium Dahliae ◽

Warm Season ◽

Field Trials ◽

Cool Season ◽

Common Vetch ◽

Rotation Scheme ◽

Sunn Hemp ◽

Leguminous Crops ◽

Rotation Crop

Verticillium dahliae, the cause of Verticillium wilt, is a widespread pathogen that affects many crops in California and throughout the world. Cover cropping with leguminous species is often integrated into a rotation scheme for its contribution to soil nitrogen, and can contribute to management of Verticillium wilt provided the chosen crop does not support development of V. dahliae. Seven cool season legumes (faba bean, bell bean, field pea, hairy vetch, common vetch, purple vetch, and woollypod vetch), and three warm season legumes (sesbania, sunn hemp, and black-eyed pea) were evaluated as hosts for reproductive growth of V. dahliae. All 10 legumes were colonized by V. dahliae, while remaining symptomless, when subjected to a root-dip inoculation. Similar results were obtained when plants were grown in infested potting soil, albeit with a lower frequency of infection than in root-dip assays. All tested legumes were also infected in field trials, with the exception of bell bean. Overall, warm season legumes sustained higher rates of infection than cool season legumes. Common vetch was the most extensively colonized of the cool season legumes. Based on the results of this study, legumes may not be an appropriate rotation crop in fields where Verticillium wilt is a problem.

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