Verticillium Wilt Of Cotton Research Articles

Comparative effect of root-knot nematode on severity of verticillium and fusarium wilt in cotton

The effect of root-knot nematode (RKN) (Meloidogyne incognita) onVerticillium dahliae andFusarium oxysporum f.sp.vasinfectum in cotton (Gossypium hirsutum) was investigated. Two different inoculation methods were used, one in which inoculum was added to the soil, so that nematode and fungal inoculum were in close proximity; the other, inoculation into the stem, whereby the two inocula were spatially separated. Invasion of the roots by RKN enhanced disease severity, as measured by the height of vascular browning in the stem, following inoculation with either wilt pathogen. The effect of RKN on Fusarium wilt was more pronounced than that on Verticillium wilt. Nematode-enhanced infection byF. oxysporum is a well known effect but there are few reports of enhanced infection byVerticillium due to RKN. Relative resistance of a number of cotton cultivars to both wilt diseases, as measured by height of vascular browning, was similar to the known field performance of the cultivars. The use of vascular browning as an estimate of disease severity was therefore validated.

Sensitivity of Verticillium dahliae to prochloraz and prochloraz–manganese complex and control of Verticillium wilt of cotton in the field

Twenty-eight isolates of Verticillium dahliae from the cotton growing areas of Cukurova and Amik plains of Turkey were evaluated in vitro for their sensitivities to prochloraz and prochloraz–manganese complex. The fungicide sensitivity was determined by measuring mycelial growth on agar medium amended with prochloraz and prochloraz–manganese complex at dosages up to 100 μg ml −1. The mean ED 50 values for both locations ranged from 0.2590 to 0.3574 μg ml −1 for prochloraz and 0.5239–0.8409 μg ml −1 for prochloraz–manganese complex. The resistance factors for both fungicides were greater for the Cukurova than the Amik isolates. In field trials, the higher concentration of prochloraz (506 g a.i. ha −1) gave a slight reduction in disease severity. However, the higher concentration (1250 g a.i. ha −1) of prochloraz–manganese complex resulted in a significant effect ( P=0.05) on disease control.

Differential expression of induced resistance by an aqueous extract of killed Penicillium chrysogenum against Verticillium wilt of cotton

Dry mycelium of Penicillium chrysogenum (PEN), a waste product of the pharmaceutical industry, was extracted with water and applied to the roots of two Gossypium hirsutum cultivars (H552 and Vered) and two G. barbadense cultivars (PF15 and P906) to examine its efficacy in controlling Verticillium dahliae Kleb. Soil application of 5% PEN provided significant protection against Verticillium wilt in all the tested cultivars, although PF15 and P906 were genetically more resistant to the wilt disease than H552 and Vered. As PEN did not inhibit mycelial growth of V. dahliae in vitro, it is inferred that the disease controlling effects of PEN are attributed to induced resistance. Percentage protection induced by PEN in H552 and Vered was significantly higher than that of PF15 and P906, and the older seedlings of H552 showed a relatively higher percentage of protection than younger seedlings of the same cultivar, suggesting that the expression of induced resistance was somewhat cultivar-dependent and seedling age-dependent. Treatment with 5% PEN increased peroxidase (POX) activity and lignin deposition in hypocotyls at 16–48 and 24–48 h after PEN treatment, respectively. We assume that POX might result in lignification and thus be associated with the defense against Verticillium wilt. It is concluded that dry mycelium of PEN may be used to induce resistance against V. dahliae in cotton.

Dry mycelium ofPenicillium chrysogenum induces resistance against verticillium wilt and enhances growth of cotton plants

Dry mycelium (DM) ofPenicillium chrysogenum and its water extract (DME) were examined for their effects on induced resistance against Verticillium wilt and plant growth of cotton in the greenhouse. Soil application of 0.1–5% DM or 0.5–5% DME provided significant protection against the wilt, relative to the control. As neither DM nor DME inhibited mycelial growth ofVerticillium dahliae in vitro, it is suggested that the disease-controlling effects of DM or DME are attributed to induced resistance. DME (5%), as well as DME treated with chloroform or cold acetone, were as effective as 2% DM in reducing disease severity of Verticillium wilt, implying that the resistance-inducing substance(s) in DM are mostly water-soluble, with neither proteins nor lipids likely to be responsible for the induction of resistance. No significant difference in root colonization withV. dahliae was found between control-inoculated and 2% DM- or 5% DME-inoculated plants. However, colonization of hypocotyls and epicotyls was drastically suppressed by either 2% DM or 5% DME relative to the control. Treatments with 2% DM or 5% DME significantly increased ionically-bound peroxidase (POX) activity in roots, hypocotyls and the second leaf of cotton plants, with the hypocotyls expressing the highest increase. Soil application of DM or DME increased plant height, fresh and dry weight of inoculated and non-inoculated cotton plants, relative to their corresponding controls. It is concluded that DM may be used in cotton crops to promote plant growth and to induce resistance againstV. dahliae. POX might be associated with the defense against Verticillium wilt.

Effect of 2,6-dichloroisonicotinic acid or benzothiadiazole on Alternaria leaf spot, bacterial blight and Verticillium wilt in cotton under field conditions

In field experiments, cotton (Gossypium hirsutum/G. barbadense) plants were treated with foliar applications of the synthetic activators 2, 6-dichloroisonicotinic acid (INA) or benzo [1, 2, 3] thiadiazole-7-carbothioic acid S-methyl ester (BTH) and the severity of natural infection with Alternaria macrospora, Xanthomonas campestris pv. malvacearum and Verticillium dahliae was assessed. Percentage leaf area infected with A. macrospora was significantly (P=0.05) lower in plants following one application of INA or BTH in the 95/96 and 97/98 seasons, respectively, compared with untreated plants. There was also significantly (P=0.05) less defoliation in the treated plants. Plants treated with one application of BTH had significantly (P=0.05) lower leaf areas infected with X. campestris pv. malvacearum and decreased defoliation compared with untreated plants in the 97/98 season. The severity of foliar symptoms of Verticillium wilt was significantly (P=0.05) decreased in plants treated with one application of INA or multiple applications of BTH compared with untreated plants in four experiments conducted over four field seasons. The reduced susceptibility of the cotton plants to Alternaria leaf spot, bacterial blight and Verticillium wilt is attributed to systemic acquired resistance following application of INA or BTH.

Differentiation of cotton-defoliating and nondefoliating pathotypes of Verticillium dahliae by RAPD and specific PCR analyses

Severe Verticillium wilt of cotton in southern Spain is associated with the spread of a highly virulent, defoliating (D) pathotype of Verticillium dahliae. Eleven of the D and 15 of a mildly virulent, nondefoliating (ND) pathotype were analyzed by random amplified polymorphic DNA (RAPD) using the polymerase chain reaction (PCR). Six of 21 primers tested generated pathotype-associated RAPD bands. Another 21 V. dahliae isolates were compared in blind trials both by RAPD-PCR using the six selected primers and pathogenicity tests on cotton cultivars. There was a 100% correlation between pathotype characterization by each method. Unweighted paired group method with arithmetic averages cluster analysis was used to divide the 47 V. dahliae isolates into two clusters that correlated with the D or ND pathotypes. There was more diversity among ND isolates than among D isolates, these latter isolates being almost identical. ND- and D-associated RAPD bands of 2.0 and 1.0 kb, respectively, were cloned, sequenced, and used to design specific primers for the D and ND pathotypes. These pathotype-associated RAPD bands were present only in the genome of the pathotype from which they were amplified, as shown by Southern hybridization. The specific primers amplified only one DNA band of the expected size, and in the correct pathotype, when used for PCR with high annealing temperature. These specific primers successfully characterized V. dahliae cotton isolates from China and California as to D or ND pathotypes, thus demonstrating the validity and wide applicability of the results.

Etiology, Importance, and Distribution of Verticillium Wilt of Cotton in Southern Spain

Surveys for Verticillium wilt in 142 cotton fields in 1981 to 1983 and 1985 indicated that the disease is widespread in the Guadalquivir Valley, southern Spain, where it occurs in 80.0 to 82.5% of the fields. Verticillium wilt was most prevalent in the upper valley in the 1981 to 1983 surveys and in the lower valley in the 1985 survey. Analyses of dry soil samples collected in spring 1985 by means of an Andersen sampler detected Verticillium dahliae propagules in 35.1% of the fields surveyed. Inoculum density in soil was much higher in the lower valley (average 37.1 CFU/g) than in the upper and central areas of the valley (average 4.7 CFU/g). The increasing importance of the disease in the lower valley corresponds to the spread of a defoliating pathotype of V. dahliae in this area during the early 1980s. Two groups of isolates, including 100 mild nondefoliating and 90 severe defoliating, were distinguished among 191 isolates by means of morphological, physiological, and pathogenicity tests. The remaining isolate was identified as nondefoliating with intermediate virulence. All defoliating isolates were obtained from the lower valley, while nondefoliating isolates were widespread. Isolates of the defoliating pathotype produced elongated and rounded microsclerotia on water agar, were able to grow on sanguinarine-amended potato dextrose agar, and fluoresced under UV light. Isolates of the nondefoliating pathotype formed only rounded microsclerotia on water agar, were inhibited greatly on sanguinarine-amended PDA, and did not fluoresce under UV light. Furthermore, the defoliating isolates had an optimum temperature for in vitro growth of 24 to 27°C compared with 21 to 24°C for the nondefoliating isolates.

Effect of vesicular-arbuscular mycorrhizal fungi on verticillium wilt of cotton

The development of vesicular-arbuscular mycorrhizal fungi (VAMF): Glomus mosseae (Nicol and Gerd.) Gerdemann and Trappe, Glomus versiforme (Karsten) Berch, Sclerocystis sinuosa Gerdemann and Bakhi and Verticillium dahliae and the effects of the VAMF on the verticillium wilt of cotton (Gossypium hirsutum L. and Gossypium barbadense L.) were studied with paper pots, black plastic tubes and clay pots under natural growth conditions. All of the tested VAMF were able to infect all the cotton varieties used in the present experiment and typical vesicles and arbuscules were formed in the cortical cells of the cotton roots after inoculation. The cap cells, meristem, differentiating and elongating zones of the root tip were found to be colonized by the VAMF. In the case of most V. dahliae infection, the colonization occurred mostly from the root tip up to 2 cm. VAMF and V. dahliae mutually reduced their percentage of infection when inoculated simultaneously. VAMF inoculation reduced the numbers of germinable microsclerotia in the soil of the mycorrhizosphere, while the quantity of VAM fungal spores in the soil was not influenced by infection of with V. dahliae. The % of arbuscule colonization in roots was negatively correlated with the disease grades, while the numbers of vesicles in roots were not. These results suggest that certain vital competition and antagonistic reactions exist between VAMF and V. dahliae. VAMF reduced the incidence and disease indices of verticillium wilt of cotton during the whole growth phase. It is evident that cotton seedling growth was promoted, flowering was advanced, the numbers of flowers and bolls were increased, and this resulted in an increase in the yield of seed cotton. Among the VAMF species, Glomus versiforme was the most effective, and Sclerocystis sinuosa was inferior. So far as the author is aware, such an effect of VAMF on the increase of cotton wilt tolerance/resistance is reported here far the first time.

Control of Verticillium wilt of cotton by means of soil solarization and tolerant cultivars in southern Spain

Eight field experiments (I‐VIII) were conducted in clay soils naturally infested with a cotton‐defoliating pathotype of Verticillium dahliae in the lower Guadalquivir Valley of Andalucia, southern Spain, during the period 1986‐90. Experiments I‐VI aimed to determine the efficacy of soil solarization in reducing populations of the pathogen in soil and eventually contributing to the control of Verticillium wilt of cotton. The population of V. dahliae in the 0‐to 40‐cm soil layer was reduced to undetectable or very low levels after solarization for 6 to 10 weeks. The final incidence of Verticillium wilt in the cotton crop following solarization was reduced to 13% or less in solarized plots, compared to 55–90·5% in unsolarized controls. The onset of disease incidence in the solarized plots was delayed by 2–7 weeks, increased at a lower rate, and had a smaller area under the disease progress curve, compared to that in unsolarized plots. Seed cotton yields in solarized plots increased by 11·3‐130·9% depending upon experiments, cultivars and years. Experiments VII and VIII aimed to determine the use of the highly wilt‐tolerant cotton cv. Acala GC 510 for control of the disease that had been cropped to susceptible cotton cultivars the year before in solarized soils. Solarized or unsolarized plots were first sown to susceptible cotton cvs Acala SJ2 and Coker 310, and the following year were sown to cv. Acala GC 510. The inoculum density of V. dahliae at the time of sowing cv. Acala GC 510 in previously solarized plots had increased to moderate levels, but remained considerably lower than that in unsolarized plots. The final disease incidence in cv. Acala GC 510 grown in unsolarized plots was lower than that in susceptible cultivars grown in the same plots the year before. Furthermore, the disease incidence in cv. Acala GC 510 grown in solarized plots was as high as that in susceptible cultivars grown the year before with much less initial inoculum.

Influence of Inoculum Density of Defoliating and Nondefoliating Pathotypes ofVerticillium dahliaeon Epidemics of Verticillium Wilt of Cotton in Southern Spain

Linear regression analysis of data transformed according to several mathematical models showed no significant correlation between the inoculum density of Verticillium dahliae determined at sowing time in randomly chosen cotton fields and the incidence of plants with vascular discoloration, the incidence of plants with foliar symptoms, or a disease intensity index for Verticillium wilt of cotton calculated at the end of the crop season. Epidemic development of Verticillium wilt in cotton was investigated in field plots naturally infested with different inoculum densities of the defoliating and nondefoliating pathotypes of V. dahliae in 1986 and 1987. The straight line model adequately described the increase in the incidence of plants showing foliar symptoms and the disease intensity index over the accumulated physiological time from sowing. For similar levels of initial inoculum, the defoliating pathotype of V dahliae caused an earlier epidemic onset, a higher rate of increase in the incidence of foliar symptoms and the disease intensity index over physiological time, and a higher final amount of both disease measurements than the nondefoliating pathotype. Also, for the two disease measurements, the rate of progress increased with the initial inoculum density of the defoliating pathotype up to a threshold of 24 to 44 CFU/g of dry soil in 1986 and 44 to 75 CFU/g of dry soil in 1987. Differences in severity among Verticillium wilt epidemics were described more appropriately by the descriptive parameters of the increase in the disease intensity index over physiological time than by the corresponding parameters of the increase in the incidence of foliar symptoms.

Potassium and Aldicarb‐Disulfoton Effects on Verticillium Wilt, Yield, and Quality of Cotton

Optimum cotton (Gossypium hirsutum L.) yield with good fiber quality requires healthy vigorous plants throughout the season. Recently, verticillinm wilt (Verticilllum dahllae Kleb.) and K deficiency symptoms occurred during August and September in cotton grown on sandy loam soils of the Mississippi Delta. Symptoms developed earlier and faster in some caitivars compared with others. In a field study, applications of K and pesticides on verticillium wilt‐K deftciency symptoms, yield and fiber quality of ‘DES 119’ and ‘Stoneville 825’ cottons were evaluated. Broadcast application and topsoil incorporation of 112 kg K ha‐1 yr‐1 reduced verticillium wilt‐K deficiency symptoms from 12 to 7%, averaged across both cultivars, but did not affect lint yield. The root‐gall [caused by Meloidogyne incognita (Kofoid & White) Chitwood] index was reduced from 2.7 to 2.5 and from 2.7 to 2.4 by K and aldicarb‐PCNB‐ETMT [5% 2‐methyl‐2‐(methylthio)propionaidehyde‐O‐(methylcarbamoyl)oxime + 10% pentachloronitrobenzene + 2.5% 5‐ethoxy‐3‐(trichloromethyi)‐l,2,4‐thiodiazole; 0.56 + 1.12 + 0.28 kg a.i. ha‐1], respectively. Fiber strength (kN m kg‐1) was increased from 20.4 to 20.9 by K and micronaire reading was increased from 3.99 to 4.13 by aldicarb treatment. Yield, fiber quality, verticillinm wilt‐K deftciency symptoms, and root‐gall index differed between euitivars. In soil infested with V. dahliae and M. incognita, K could be used to reduce verticillium wilt‐K deficiency symptoms and root‐gall index and to increase fiber strength of cotton. Aldicarb also can be used to reduce root‐gall index. Knowing the reaction of cotton cultivars to K and to pesticides should help cotton breeders develop better adapted cultivars.

Inverse relationship between cotton plant density and verticillium wilt incidence and severity: evidence for an alternative hypothesis

The relationship between cotton plant density and verticillium wilt incidence and severity in a greenhouse study was investigated. A negative relationship between verticillium wilt ( Verticillium dahliae Kleb.) incidence and cotton ( Gossypium hirsulum L.) plant density has been observed by other investigators and in this study as well. However, previous authors attributed this negative relationship to the declining probability of infection with increasing plant density. In this study, each plant was inoculated through a severed root and thus did not have the potential to ‘escape’ infection; none the less, it was found that more crowded plants showed fewer disease symptoms. The observed result was therefore attributed to a decline in host suitability with increasing host density.

Integrated Control of Verticillium Wilt of Cotton

Integrated Control of Verticillium Wilt of Cotton

Effects of Seed Density on Stand, Verticillium Wilt, and Seed and Fiber Characters of Cotton1

Rapid germination and emergence and vigorous seedling growth enhance the opportunities for profitable production of cotton (Gossypium hirsutum L.). Within seed lot, the heavier, more dense seed are most likely to exhibit these traits. In 1976, acid‐delinted, gravity‐graded seed of ‘Paymaster 909’ and ‘Tamcot SP37’ were separated into four density classes by a liquid separation process. These classes were: D1 = very low density (floaters); D2 = low density; D3 = medium density; and D4 = high density. Seed with cracked coats were included in the D4 class. Commercially gravity‐graded (DG) seed of each cultivar were used as standards. All samples were treated with carboxin‐captafol {(5,6‐dihydro‐2‐methyl‐1, 4‐oxathiin‐ 3‐carboxanilide plus cis‐N‐[(l,l,2,2‐tetrachloroethyl) thio]‐4‐cyclohexene‐l,2‐dicarboximide)} 2‐2 F SP (2 lbs. of each fungicide as aflowable seed protectant) at g/kg of seed. Enough seeds of each class were obtained to conduct tests for 2 years. The Paymaster 909 select seed were representative of the type commonly planted by area farmers. Tamcot SP37 seed were obtained from a planting of registered seed that failed to mature properly and consequently failed to meet germination reqmrements for certification in Texas. Seed index, germination, and stand were highest and the prevalence of Verticillinm wilt (caused by Verticillium dahliae Kleb.) was lowest in plants from D3 seed, but plants from D2 seed performed almost as well. The poorest overall performance was shown by plants from D1 seed, whereas the performance of plants from D4 seed lots equaled or slightly exceeded that of plants from DG seed. The liquid seed‐separation process may enable seed proeessors to isolate seed for significantly improved germination, seedling survival, and lint yield, and reduced prevalence of Verticillium wilt. The liquid separation process may be used in breeding and seed‐increase programs to select high‐quallty planting seed for performance evaluations. The process also may be used to isolate seed of acceptable quality for planting from seed that fail to meet quality standards after commercial gravity grading. Seed index may be used to select density classes for planting seed.

Neutralizes and Pesticides and their Sequence of Application to Acid‐delinted Cottonseed: Effects on Germination, Stand, and Verticillium Wilt of Cotton1

Neutralizing acid residues on cottonseed after HCl delinting contributed to seedling emergence and survival in field plantings and emergence in greenhouse plantings, but not necessarily to survival in the greenhouse where seedling diseases were severe or to germination in the laboratory. Similar results were obtained with an experimental neutralizer (EN) and the standard neutralizer (NH3) used alone or in combination with fungicides and the insecticide, disulfoton. The percentage of plants with foliar symptoms of Verticillium wilt was reduced by the neutralizers and pesticides. Decrease in wilt symptoms was related to increased plant populations. Percentage germination, emergence and survival of seedlings and Verticillium wilt were similar when EN and pesticides were applied simultaneously or sequentially. Use of EN can eliminate ammonia and ammonium chloride pollutants currently associated with acid delinting of cottonseed.

The Influence of Several Crop Sequences on the Incidence of Verticillium Wilt of Cotton and on the Population of Verticillium dahliae in Field Soil

The Influence of Several Crop Sequences on the Incidence of Verticillium Wilt of Cotton and on the Population of Verticillium dahliae in Field Soil

Use of enzyme-deficient mutants of Verticillium dahliae to assess the importance of pectolytic enzymes in symptom expression of Verticillium wilt of cotton

Mutants of Verticillium dahliae Kleb. deficient for one to four pectolytic enzymes were induced by u.v. irradiation and isolated from indicator plates designed to detect them. Loss of enzyme activity was confirmed by standard assays. The importance of these enzymes to disease expression was investigated by following disease development in cotton plants inoculated with enzyme-deficient mutants. These techniques showed that mutants deficient for endopolygalacturonase or pectin methylesterase or pectin transeliminase and pectic acid trans-eliminase or all of these enzymes except pectin methylesterase, induced apparently normal symptoms of Verticillium wilt in stem-inoculated cotton plants.

Significance of endo-polygalacturonase activity to symptom expression of verticillium wilt in cotton, assessed by the use of mutants of Verticillium dahliae Kleb

Conidia of three defoliating isolates of Verticillium dahliae Kleb. from cotton ( Gossypium hirsutum L.) were irradiated with ultraviolet light. Survivors showing no endo-polygalacturonase activity were detected on an indicator medium containing polygalacturonic acid. Loss of enzyme activity was confirmed by viscometric assay. These mutants induced the same disease symptoms as parent strains when they were inoculated into 6-week-old cotton plants. Mutant strains reisolated from infected tissue retained their endo-polygalacturonase deficiency. It is concluded that production of active endo-polygalacturonase by V. dahliae is not essential for symptom expression of verticillium wilt in cotton.

Potassium Uptake by Cotton in Relation to Verticillium Wilt1

AbstractIncreasing evidence of a close relationship between K‐nutrition of cotton plants (Gossypium hirsutum L.) and verticillium wilt (Verticillium dahliae Kelb) development was observed in certain K‐deficient soils in San Joaquin Valley, California. Therefore, a K uptake field experiment on verticillium‐infected K‐deficient soil with 270 kg K/ha fertilized and unfertilized plots were conducted on both (420 liter/ha) chloropicrin (trichloronitromethane) fumigated and non‐fumigated treatments. The uptake of fertilizer K was traced by the “reverse‐tagging” procedure in which the indigenous soil‐Rb was used as a tag for K. In this instance the fertilizer Rb/K ratio was about 0.01 of the Rb/K ratio of the labile K in the upper foot of the soil profile.Cotton plants grown on fumigated soil absorbed 62% of their leaf K from the fertilizer source versus 48% for the non‐fumigated soils. Also it was observed that in the unfertilized plots, fumigation induced shifts in Rb/K ratio in plant tissues, which is explained by the differences in the Rb/K ratios in the upper and lower soil horizons coupled with reduced uptake efficiencies when roots in the upper soil horizons are infected with verticillium wilt.K‐fertilization alone resulted in a significant decrease in verticillium wilt. In both fumigated and non‐fumigated plots, yields of cotton lint responded significantly to K‐fertilization. However, corrections of K deficiency symptoms of cotton leaves required a combination of soil fumigation with chloropicrin and K‐fertilization.

Characteristics and Concentration of Propagules of Verticillium dahliae in Air-Dried Field Soils in Relation to the Prevalence of Verticillium Wilt in Cotton

Characteristics and Concentration of Propagules of Verticillium dahliae in Air-Dried Field Soils in Relation to the Prevalence of Verticillium Wilt in Cotton