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

2011 ◽  
Vol 12 (1) ◽  
pp. 16 ◽  
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.

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.

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 Accelerated Degradation of Metam-Sodium in Soil and Consequences for Root-Disease Management

2009 ◽  
Vol 99 (4) ◽  
pp. 362-368 ◽  
Author(s):  
Shachaf Triky-Dotan ◽  
Miriam Austerweil ◽  
Bracha Steiner ◽  
Yitzhak Peretz-Alon ◽  
Jaacov Katan ◽  
...  
Keyword(s):  
Verticillium Wilt ◽  
Field Experiments ◽  
Parent Compound ◽  
Agricultural Practices ◽  
Single Application ◽  
Metam Sodium ◽  
Accelerated Degradation ◽  
Controlled Conditions ◽  
Pod Quality ◽  
Repeated Applications

We studied the development of accelerated degradation (AD) of methyl isothiocyanate (MITC) following repeated applications of its parent compound, metam-sodium (MS). Laboratory studies and four sets of field experiments were conducted during 2002–04 in three commercial fields in Israel. Repeated applications of MS to the three soils in the laboratory under controlled conditions demonstrated AD of MITC in some soils. In a peanut field, MS significantly reduced the incidence of Pythium pod rot and improved pod quality after a single application but its effectiveness was greatly reduced after two applications. In a second experiment, MS was significantly effective after a single application in controlling Verticillium wilt in potato but its efficacy diminished after three consecutive applications. In an additional experiment, fumigation with MS following single or double applications was more effective in reducing Verticillium wilt severity of potato compared with triple applications. Soils which did not develop AD of MITC were also recorded. Preplant MS fumigation of melon fields was effective at reducing sudden wilt following a single and two consecutive applications. Our study shows that development of AD of MITC might occur following repeated applications of MS in commercial fields. The data on MITC dissipation in soil following repeated MS applications under controlled conditions indicate the chemical's potential loss of activity under regular agricultural practices and the need for a management strategy to prevent such a development.

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

Plant Disease ◽  
2007 ◽  
Vol 91 (11) ◽  
pp. 1372-1378 ◽  
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.

scholarly journals Relationships Between Verticillium dahliae Inoculum Density and Wilt Incidence, Severity, and Growth of Cauliflower

1998 ◽  
Vol 88 (10) ◽  
pp. 1108-1115 ◽  
Author(s):  
C. L. Xiao ◽  
K. V. Subbarao
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Field Experiments ◽  
Block Design ◽  
Disease Onset ◽  
Stomatal Resistance ◽  
Inoculum Density ◽  
Number Of Leaves ◽  
Leaves And Roots ◽  
Wilt Incidence

Microplot and field experiments were conducted to evaluate the effects of inoculum density on Verticillium wilt and cauliflower growth. Soil containing Verticillium dahliae microsclerotia was mixed with various proportions of fumigated soil to establish different inoculum densities (fumigated soil was used as the noninfested control). Seven inoculum density treatments replicated four times were established, and the treatments were arranged in a randomized complete block design. Soil was collected from each microplot immediately after soil infestation for V. dahliae assay by plating onto sodium polypectate agar (NP-10) selective medium using the Anderson sampler technique. Five-week-old cauliflower was transplanted into two beds within each 1.2- by 1.2-m microplot. At the same time, several extra plants were also transplanted at the edge of each bed for destructive sampling to examine the disease onset (vascular discoloration) after planting. Cauliflower plants were monitored for Verticillium wilt development. Stomatal resistance in two visually healthy upper and two lower, diseased leaves in each microplot was measured three times at weekly intervals after initial wilt symptoms occurred. At maturity, all plants were uprooted, washed free of soil, and wilt incidence and severity, plant height, number of leaves, and dry weights of leaves and roots were determined. The higher the inoculum density, the earlier was disease onset. A density of 4 microsclerotia per g of dry soil caused 16% wilt incidence, but about 10 microsclerotia per g of soil caused 50% wilt incidence. Both wilt incidence and severity increased with increasing inoculum density up to about 20 microsclerotia per g of soil, and additional inoculum did not result in significantly higher disease incidence and severity. A negative exponential model described the disease relationships to inoculum levels under both microplot and field conditions. Stomatal resistance of diseased leaves was significantly higher at higher inoculum densities; in healthy leaves, however, no treatment differences occurred. The height, number of leaves, and dry weights of leaves and roots of plants in the fumigated control were significantly higher than in infested treatments, but the effects of inoculum density treatments were variable between years. Timing of cauliflower infection, crop physiological processes related to hydraulic conductance, and wilt intensity (incidence and severity) were thus affected by the inoculum density. Verticillium wilt management methods used in cauliflower should reduce inoculum density to less than four micro-sclerotia per g of soil to produce crops with the fewest number of infected plants.

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

HortScience ◽  
2005 ◽  
Vol 40 (4) ◽  
pp. 1109B-1109
Author(s):  
G.E. Vallad ◽  
Q.M. Qin ◽  
R. Grube ◽  
R.J. Hayes ◽  
E. Ryder ◽  
...  
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Growth Habit ◽  
Disease Incidence ◽  
Plant Introduction ◽  
Field Trials ◽  
Plant Introductions ◽  
Foliar Symptoms ◽  
Harvest Maturity ◽  
Salinas River

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.

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

Plant Disease ◽  
2005 ◽  
Vol 89 (7) ◽  
pp. 777-777 ◽  
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.

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

1998 ◽  
Vol 88 (10) ◽  
pp. 1046-1055 ◽  
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.

scholarly journals First Report of Verticillium Wilt Caused by Verticillium dahliae on Avocado Trees in Greece

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1584-1584 ◽  
Author(s):  
E. A. Markakis ◽  
N. Kavroulakis ◽  
G. C. Koubouris
Keyword(s):  
Verticillium Wilt ◽  
Verticillium Dahliae ◽  
Vascular Tissue ◽  
Disease Incidence ◽  
Natural Infection ◽  
The United States ◽  
Persea Americana ◽  
Artificial Inoculation ◽  
Pathogenicity Test ◽  
First Report

Avocado (Persea americana) is an important crop for Chania, Crete, Greece, and is grown on more than 800 ha. In November 2013, 4-year-old trees in a new avocado grove of cv. Hass grafted onto the rootstock ‘Bacon,’ previously planted in citrus trees, showed symptoms of yellowing, leaf fall, twig and branch dieback and vascular tissue discoloration. Disease incidence was estimated at 2.3% (12 out of 530 trees affected). A fungus was consistently and readily isolated from symptomatic vascular tissue, previously surface-disinfested with 95% ethanol, on acidified potato dextrose agar (APDA). After 7 days, slow-growing colonies were transferred to PDA and the growth rate of the fungus was 2.9 mm/day at 24°C in the dark. Microscopic observations revealed hyaline hyphae with many irregular, dark microsclerotia measuring 40 to 200 × 30 to 75 μm (average 94.5 × 50.3 μm) developing after 21 days of growth. Hyaline, elliptical, single-celled conidia measuring 2.8 to 7.5 × 2.5 to 4.3 μm (average 4.8 × 3.1 μm) developed on verticillate conidiophores. For molecular characterization, Verticillium dahliae specific primer pair ITS1-F/ITS2-R that amplifies the rRNA internal transcribed spacer (ITS) region was used (2). Band of expected size was amplified, sequenced, and deposited in GenBank (Accession No. KJ818294). On the basis of morphological characteristics (3) and a BLAST search with 100% identity to the published ITS sequence of a V. dahliae isolate in GenBank (KC834733.1), the fungus was identified as V. dahliae. Five 1-year-old avocado plants of cv. Hass, grafted onto the rootstock ‘Bacon,’ were used for pathogenicity tests. Artificial inoculation was performed by making a 5.0 × 3.5 mm hole in the rootstock trunk, injecting approximately 40 μl of a 2.8 × 107 conidia/ml suspension into the vessels (spores were introduced passively), sealing with Vaseline, and covering with adhesive paper tape. Five control plants were mock inoculated with sterilized distilled water. Disease symptoms that appeared 18 days post artificial inoculation were similar to those observed under natural infection conditions. Thirty-five days post artificial inoculation, disease incidence was 80%, whereas the percentage of positive V. dahliae re-isolations from infected tissues was 95% (96.7 and 93.3% from rootstock and graft, respectively). The extent of vascular tissue discoloration from the point of inoculation ranged from 11 to 62 cm, whereas V. dahliae was successfully re-isolated even from the end of the graft (approximately 60 cm above the initial inoculation point), thus confirming Koch's postulates. Neither symptoms nor positive isolations were observed in control plants. The pathogenicity test was repeated twice with similar results. Verticillium wilt of avocado has been observed in several countries including Argentina, Chile, Ecuador, Israel, Mexico, Morocco, Spain, and the United States (1). To the best of our knowledge, this is the first report of Verticillium wilt on avocado in Greece. This disease could potentially be an increasing problem in areas where young avocado trees are established on land previously planted in vegetable crops. References: (1) J. C. Goud and J. A. Hiemstra. Chapter 3 in: A Compendium of Verticillium Wilt in Trees Species, 1998. (2) E. A. Markakis et al. Eur. J. Plant Pathol. 124:603, 2009. (3) G. F. Pegg and B. L. Brady. Verticillium Wilts. CABI Publishing, Wallingford, UK, 2002.

scholarly journals Grafting Eggplant onto Tomato Rootstock to Suppress Verticillium dahliae Infection: The Effect of Root Exudates

HortScience ◽  
2009 ◽  
Vol 44 (7) ◽  
pp. 2058-2062 ◽  
Author(s):  
Na Liu ◽  
Baoli Zhou ◽  
Xin Zhao ◽  
Bo Lu ◽  
Yixiu Li ◽  
...  
Keyword(s):  
Disease Severity ◽  
Verticillium Wilt ◽  
Root Exudates ◽  
Verticillium Dahliae ◽  
Disease Incidence ◽  
Total Yield ◽  
Mass Spectrometry Analysis ◽  
Gas Chromatography Mass Spectrometry ◽  
Mycelium Growth ◽  
Soilborne Disease

Verticillium wilt (caused by Verticillium dahliae), a soilborne disease, often causes significant reductions of yield in eggplant (Solanum melongena L.) production where crop rotation is limited. Rootstock replacement through grafting is considered an effective method to control this disease. This 2-year study investigated the eggplant yield, resistance to verticillium wilt, and allelochemicals in root exudates of eggplant grafted onto a tomato rootstock. Both disease incidence and disease severity on grafted eggplant were markedly lower than those of nongrafted eggplants. Fifteen days after V. dahliae inoculation, grafted eggplants did not exhibit any infection, whereas the disease incidence and disease severity index of the nongrafted eggplants were 68.3% and 37.8% in 2006 and 66.7% and 36.3% in 2007, respectively. Twenty-five days after inoculation, disease incidences on grafted eggplants were only 8.1% and 9.5% in 2006 and 2007, respectively, but those of the nongrafted eggplants increased to 100%. As a result, early yield, total yield, and average fruit weight were significantly increased by grafting when inoculated with V. dahliae in 2006 and 2007. Mycelium growth of V. dahliae was inhibited by the root exudates of grafted eggplants. In contrast, the root exudates of nongrafted eggplants enhanced the mycelium growth. The gas chromatography–mass spectrometry analysis revealed that the composition in the root exudates released by grafted eggplants differed not only from the nongrafted eggplants, but also from the tomato rootstock plants. Ten chemical classes were isolated and identified in root exudates of grafted eggplants. Carbazoles, amines, azulene, and fluorene were only detected in the grafted eggplants. The relative contents of ester compounds were the highest in the root exudates from the grafted eggplant followed by derivatives of benzene, whereas the relative contents of benzene derivatives were much higher than that of the ester compounds in the root exudates from the nongrafted eggplant and tomato rootstock.

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