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1.
The effects of removing or flaming potato vines and soil fumigation on population density ofVerticillium dahliae in soil, severity of Verticillium wilt, and tuber yield were studied in a field near Alliston, Ontario, between 1993 and 1996. Vines were physically removed or flamed using a propane flamer in September just before harvest and soil was fumigated with metam-sodium (Vapam) at 550 L/ha in October after harvest. Vine removal had no effect on soil populations ofV. dahliae, area under the disease progress curve (AUDPC), or tuber yield. Flaming once (1993), twice (1993 and 1994), or three (1993,1994, and 1995) times reduced the soil population density ofV. dahliae, and flaming twice (1993 and 1994) reduced AUDPC compared to the nontreated control, but had no effect on tuber yield. Fumigation once (1993) or twice (1993 and 1994) reduced pathogen density in soil and AUDPC, but did not increase tuber yield. Fumigation once (1993) or twice (1993 and 1994), in combination with flaming twice (1993 and 1994), was equally and significantly effective in reducing both population density ofV. dahliae in soil and AUDPC values and in increasing tuber yield in 1995. Annual flaming of vines in combination with soil fumigation once (1993) or twice (1993 and 1994) in the fall improved the control of Verticillium wilt of potato and realised the greatest profits.  相似文献   

2.
K. Scholte 《Potato Research》1989,32(3):377-385
Summary The incidence ofVerticillium dahliae andColletotrichum coccodes was studied in a crop rotation experiment on sandy soil from 1983 to 1986. Early in the growing season the percentage of stems infected byV. dahliae increased with increasing cropping frequency of potato, depending on the cropping sequence, and decreased with the application of granular nematicides. However, later in the growing season the initial differences decreased.C. coccodes infections of stems were not affected by these factors. The percentage of plants infected byV. dahliae closely correlated with the percentage of plants with wilt symptoms but this relationship was absent forC. coccodes. Early in the growing season, the more vigorous the plants, the greater the level ofV. dahliae infection. Soil infestation withV. dahliae increased with increasing cropping frequency of potato but was not affected by annual applications of granular nematicides.  相似文献   

3.
In 1994 and 1995, the effect of Verticillium wilt, caused byVerticillium dahliae andV. albo-atrum, on tuber yields, number and weight of U.S. No. 1 and B size tubers, and specific gravity was studied in northern Maine, an area with a short growing season. Seven clones (four resistant and three susceptible) were evaluated in a split-plot design with three replications. Clones were the whole-plot factor, and seed pieces in sub-plots were either uninoculated or inoculated with 50 ml of 4 × 104 cfu/mlVerticillium spp. at planting. Individual plants were scored for Verticillium wilt symptoms before harvest on a 1= <3% wilt to 10= >97% wilt. Differences among clones for wilting and specific gravity were significant. The inoculation treatment had no effect on any of the tuber traits measured. However, there were significant clone x inoculation interactions for most tuber traits. Reductions in yield, weight and number of U.S. No. 1 potatoes, and specific gravity were greater in the Verticillium wilt susceptible clones than in the resistant clones. These results suggest that breeding clones with resistance toVerticillium spp. will reduce yield losses, while maintaining tuber size and specific gravity under disease pressure.  相似文献   

4.
Potato breeding selections A66107-51 and A68113-4 (Solanum tuberosum gptuberosum) are being released as germplasm that is highly resistant to Verticillium wilt (Verticillium dahliae Kleb.) These selections have been extensively evaluated for resistance to Verticillium as measured by symptom severity and degree of colonization byV. dahliae. They combine outstanding wilt resistance with good tuber maturity characteristics, high yield, and french fry processing tuber type. A66107-51 has long-oblong, russeted tubers, with high yield and variable processing quality. A68113-4 has long-oblong, partially russeted tubers with high yield and good processing quality. Both selections are fertile as female parents, and A66107-51 is occasionally pollen fertile. The Verticillium resistance of these two clones has been transmitted to progeny. These selections were developed by USDA-ARS in cooperation with the Idaho Agricultural Experiment Station. Seed is available from USDA-ARS, Aberdeen, Idaho.  相似文献   

5.
Effect of nitrogen and phosphorus fertilization rates on the incidence of Verticillium wilt caused byVerticillium albo-atrum orV. dahliae and tuber yield in potato cv Yukon Gold was evaluated in field plots. In three years of study,V. albo-atrum caused a higher incidence of wilt symptoms (74%–100%) thanV. dahliae (5%–81%) resulting in lower marketable tuber yield. In plots infested withV. albo-atrum, tuber yield ranged from 12.3-22.8 T ha1 compared to 18.1– 31.5 T ha-1 in plots infested withV. dahliae. Application of nitrogen above (280 kg ha-1) or below (70 kg ha-1) the recommended rate of 140 kg ha-1 at planting did not suppress foliar symptoms or protect against yield loss caused by eitherV. albo-atrum orV. dahliae. Similarly, phosphorus rate adjustments did not consistently affect disease incidence regardless of the pathogen. Management of nitrogen or phosphorus fertility rates at planting does not appear to be a viable approach for suppressing Verticillium wilt in the determinant, wiltsusceptible cultivar Yukon Gold.  相似文献   

6.
Management practices for the suppression of Verticillium wilt of Russet Burbank potato include sanitation, use of optimum sprinkler-irrigation practices, soil solarization, and an adequate soil fertility program. Among all cultural factors considered, nitrogen (N) deficiency in potato tissue was most commonly associated with the severity of Verticiilium wilt in Russet Burbank potato. Field studies have shown that increased N availability suppresses Verticiilium incidence on cv Russet Burbank while having no effect on cv Norgold Russet. Studies from both greenhouse and field show that the colonization ofV dahliae in potato stem tissue is suppressed in cv Russet Burbank when the availability of Phosphorous (P) is increased to the optimum. Following one season of cropping with Russet Burbank potato, the treatment providing the optimal N availability also suppressed the increases ofV dahliae populations in the soil during the following year of consecutive cropping. Similarly, after two seasons of continuous potato cropping, treatments with optimal P had lower soil populations ofV. dahliae in soil. Results show the suppression of Verticiilium wilt with optimal fertility. Verticiilium wilt [caused by eitherVerticiilium dahliae Kleb, (microsclerotial form) orVerticiilium albo- atrum Reinke and Berthold (dark mycelial form)] is one of the most severe diseases of potato in the United States. Potato yields, tuber size, and specific gravity may be substantially reduced by this disease, depending on severity, time of occurrence, and growing season. In Idaho and other arid growing regions of the United States, Verticiilium wilt is caused byVerticillium dahliae Kleb. Idaho field studies involving cropping practices, soil fumigation treatments, solarization, and Verticillium-resistant potato clones all support the importance ofV dahliae upon potato yield. Data from these studies show that yield losses due toV. dahliae commonly approximate 5 to 12 metric T/ha (5, 6). Table 1 illustrates the effect of several cropping practices upon relativeV dahliae populations in soil with the effects upon both disease severity and potato yield. With continuous cropping of Russet Burbank,V dahliae populations in soil increased, and yields were reduced by 18 to 19 metric Tlha when compared to locations that had been allowed to remain either weed-free and fallow or where corn had been previously cropped. It was estimated thatV dahliae was influencing yield by about 10 to 12 metric Tlha based on a regression analysis of yield as a function ofV dahliae populations in soil. Similarly, whenV dahliae was suppressed by fumigation treatments involving mixtures of dichloropropene and picfume, yields more significantly increased by 6.5 to 12 metric T/ha (5). Although many factors may influence yields, clones with higher Verticillium resistance than Russet Burbank generally out-yield Russet Burbank. Figure 1 demonstrates the effect of solarization (a technique involving the laying of clear plastic on soil for the purpose of elevating soil temperatures to killV dahliae). When Verticillium was controlled in this manner (lo), there was no significant yield difference between the Russet Burbank potato and the highly resistant A68113-4 clone. The A68113-4 clone grown in non-solarized soil out-yielded the Russet Burbank in non-solarized soil by 31 percent while the solarization treatment significantly increased yield for the Russet Burbank and A68113-4 clones by 46 and 18 percent, respectively. These yield responses were observed in a field where inoculum levels ofV dahliae were relatively low (2.10 cfulgrn of soil). With these losses, the need to develop control procedures is great and to achieve this control the need also exists to accurately evaluate the effect of treatments uponV dahliae. Our Idaho studies have routinely utilized such a procedure (9) in combination with comparisons of both disease severity and yield.  相似文献   

7.
Collectotrichum coccodes, the pathogen causing black dot disease of potato, was investigated to determine its potential for causing symptoms on the aerial parts of potato plant, premature vine death, and reduction in yield under greenhouse and field conditions. Spray inoculations with conidial suspensions (106 colony forming units/ml) ofC. coccodes caused sunken, dark, necrotic lesions on stems, leaves and petioles, vein and leaf necrosis, dieback and premature vine death under growth chamber and greenhouse conditions. Field inoculations in 1986 and 1987 provided evidence for an increased incidence of premature vine death in seven potato genotypes (Russet Burbank, Norgold Russet, Superior, Butte, NDA 8694-3, A68113-4 and A66107-51). Late season application of metribuzin at 0.84 kg/ha significantly increased the incidence of stems with black dot symptoms in cv. Russet Burbank at one location. Field inoculations in 1987 at two locations resulted in yield reduction in the late-maturing cv. Russet Burbank (6.3 and 6.5 t/ha) and clone A68113-4 (5.0 t/ha), but not in the early maturing cv. Norgold Russet. Similar results were obtained in greenhouse studies following soil inoculations withC. coccodes: yield reduction was observed in cv. Russet Burbank but not in cvs. Norgold Russet, Superior and Katahdin. Colonization of stem ends of tubers byC. coccodes from spray inoculated field plots was higher than in tubers from uninoculated plots at one of the two locations. These results point to a much broader potential ofC. coccodes as a potato pathogen, than hitherto documented. Colletotrichum coccodes (Wallr.) Hughes (syn.C. atramentarium (Berk. & Br. Taub.) was described in 1825 (21) and has a wide host range (5). Potato and tomato are the more economically important hosts. This fungus has been variously referred to as an unspecialized, minor pathogen or secondary invader (18), weak pathogen (22), specialized parasite (5), or superficial colonizer and widespread epiphyte (19). The symptoms produced by this pathogen on potato have been described as black dot (10, 14) on stems, stolons, tubers and roots, sometimes associated with leaf scorch or wilt (24), rubbery tuber wilt (1), and tuber skin necrosis (17). The fungus is commonly associated with senescent, decaying root and stem tissue, especially at the end of the season. In Idaho, instances of premature death of potato without typical symptoms of Verticillium wilt, but accompanied by a high incidence of stems with black dot symptoms, have been observed in potato crops grown on fields fumigated with metam sodium. Additional observations by growers have also implicated the possible interaction of the herbicide metribuzin with the incidence of black dot. Although it was observed by some workers to accelerate leaf senescence (12, 22), Schmiedeknecht (21) concluded thatC. coccodes was unable to infect the green leaves of potato plant. Even thoughVerticillium dahliae is generally considered the major factor in potato early dying (20), several workers (7, 11, 13, 19, 22) have investigated the possible role ofC. coccodes in causing premature death of potato (8). However, these studies examinedC. coccodes only as a soilborne, root and tuber pathogen of potato; its effects on shoot portions (aerial parts) of the plant were not considered. In addition to causing anthracnose of fruits of tomato, pepper and squash (18), recent reports indicate thatC. coccodes causes foliage blights on eastern black nightshade (2) and velvetleaf (25). The objectives of this study were: (1) to examine the potential ofC. coccodes to cause symptoms on aerial parts of potato plant, (2) to investigate the effect of spray inoculation in the field withC. coccodes on incidence of premature vine death, tuber colonization and yield of potato, and (3) to document the effect of soil inoculation withC. coccodes alone or in combination withV. dahliae on potato varieties under greenhouse conditions.  相似文献   

8.
For three years, potato yields, tuber quality, and incidence ofVerticillium dahliae were measured in field plots previously cropped for one year to the following nonhosts: sudan grass, green peas followed by sudan grass (same year), spring wheat, spring wheat followed by sudan grass (same year), sweet corn and field corn. One year rotation to nonhosts did not reduce the population ofV. dahliae propagules in the soil and in only one of the three years wereV. dahliae propagule numbers in potato stems significantly reduced in plots following nonhost crops, compared with plots following potatoes. Verticillium wilt symptoms in potatoes were not reduced by one year rotation to any of these crops and only in one year in three was yield significantly increased. In two of three years, percent U.S. No. 1 tubers was increased following one-year rotation with green peas plus sudan grass, and in one of the two years, specific gravity was increased by rotation. Rotational cropping to nonhosts for two years between potatoes significantly reduced preplant soil populations ofV. dahliae propagules in the soil and in potato stems the following fall. However, soil populations in these two year rotational plots the spring following potato were not reduced compared to plots previously cropped to potatoes two consecutive years. Cropping to nonhosts for two years had no consistent effect on incidence of Verticillium wilt in subsequent potato crops. Two years’ rotation to nonhosts increased plant height and yield compared to continuous cropping to potato but not percent U.S. No. 1 tubers. The various nonhost crops all had about the same non-significant effect on yield. In two out of three years’ trials, fumigation significantly reduced both the incidence of Verticillium wilt and number ofV. dahliae propagules in stems in plots compared to plots non-fumigated. In only one trial, fumigation significantly increased tuber yields and percent U.S. No. 1 tubers.  相似文献   

9.
Summary The effect ofStreptomyces spp. (netted scab) on the growth of potato was investigated in three pot experiments, in two of which the effect ofVerticillium dahliae was also assessed. The netted scab organisms attacked all underground plant parts of susceptible potato cultivars early in the growing season; the roots were especially seriously attacked, markedly reducing tuber yield and number but prolonging the duration of the growing season. The nematicide oxamyl had little effect on the incidence of netted scab. Repeated growing of the susceptible cv. Bintje greatly increased soil contamination with the netted scab pathogens. V. dahliae reduced haulm growth before wilt symptoms were evident and it reduced tuber yield but not number. Oxamyl delayed infection byV. dahliae by controlling parasiticPratylenchus nematodes (mainlyP. thornei).  相似文献   

10.
Summary The interaction betweenErwinia carotovora subsp.atroseptica (Eca) andVerticillium dahliae and its effect on symptom development in potato cultivars showing different degrees of resistance to them was examined over two seasons in irrigated fields in a hot, dry climate. Four cultivars were used: Cara, highly resistant to blackleg and tolerant to Verticillium wilt; Pentland Crown also resistant to blackleg but susceptible to Verticillium wilt; Désirée, moderately susceptible to blackleg but tolerant to Verticillium wilt; and Maris Bard, susceptible to both diseases. Seed tubers were inoculated with Eca immediately after harvest in Scotland, to simulate natural infection, and then planted in Israel in soil naturally infested byV. dahliae. In Verticillium tolerant cultivars, Eca infection increased the rate of colonization byV. dahliae and significantly enhanced symptom development, as assessed by suppression of plant height and wilt symptoms. This report is a portion of the Ph.D. thesis of the senior author in Ben-Gurion University of the Negev.  相似文献   

11.
Changes in potato production over the past 10 to 20 years, have resulted in increased emphasis being placed on breeding for resistance to Verticillium wilt, caused by Verticillium dahliae Kleb. While many russet-skinned cultivars recently have been released with reported resistance to Verticillium wilt, information is lacking on the level of pathogen colonization, and therefore, the level of true genetic resistance is not known. Eight russet-skinned cultivars were grown in field trials with low and high levels of V. dahliae in the soil, and evaluated for wilt, stem colonization, yield, and tuber vascular discoloration. A recently developed QPCR assay was validated, with strong relationships to culture plating assays over three stem sampling dates. Additionally, stem colonization levels, as determined by QPCR, were related to wilt and tuber vascular discoloration. However, total yield did not exhibit a strong relationship to any other parameter evaluated in this study. Results from these studies indicate that varying levels of true resistance are present in the russet-skinned cultivars evaluated, and that the QPCR assay can be reliable in rapidly evaluating resistance to V. dahliae under field conditions. Based on pathogen quantification using stem colonization derived from traditional plating assays and QPCR, the resistance level of several cultivars is more clearly defined and discussed.  相似文献   

12.
A three-year field study was conducted during 1984–1986 to determine the interactive effects of nitrogen and phosphorus fertilization on Verticillium wilt, and yield and quality of continuously-cropped Russet Burbank potato. The experiment was conducted on a calcareous, silt loam soil with low initial levels of NO3-N (0.9 mg/kg), P (3.5 mg/kg), andVerticillium dahliae (9 cfu/g of soil). The experimental design consisted of a factorial combination of three N treatments (unfertilized check, preplant N or split N) and three P treatments (0,120, or 240 kg P/ha) applied to the same plots during the three-year study. Nitrogen was applied at 0 or 300 kg N/ha in 1984 and 0 or 240 kg N/ha in 1985 and 1986. By the spring of 1986, soil P concentrations for the 0,120, and 240 kg P/ha treatments had increased to 7, 25, and 50 mg/kg and no additional P was applied. In addition to suppressing Verticillium wilt by as much as 95%, N & P treatments also reduced the rate of increase of soilborne inoculum ofV. dahliae. After one season of cropping, the N treatment providing the most efficient N fertilization (300 kg N/ha, split-application) resulted in significantly (p=0.01) lowerV. dahliae counts in soil than the other N treatments. After two seasons of continuous cropping, applying 120 to 240 kg P/ha produced lower populations ofV. dahliae in soil compared to the treatment with no added P. Generally, as N and P treatments approached the highest levels, both wilt incidence andV. dahliae colonization values were reduced. There was a progressive reduction in total yield in nearly all treatments during each year of continuous cropping. Reduction of yield and increased Verticillium wilt incidence was generally greater with N or P deficient plants than with optimally fertilized plants. The highest total and U.S. No. 1 yields and least Verticillium wilt were obtained each year by applying split N and 240 kg P/ha. Results show that optimal N and P can minimize both Verticillium wilt and yield losses that normally occur with intensive potato cropping.  相似文献   

13.
Summary The reaction of 40 potato clones and six accessions ofSolanum spp. to wilt caused byVerticillium dahliae and to the acetone precipitate (AP) of the toxin produced by the pathogen in vitro was studied. There was a highly significant correlation between the wilt reaction of the clones in the glasshouse, the incidence and progress of wilt and severe wilt in the field, and the degree of colonization of stem apices byV. dahliae. Of the clones and accessions evaluated, NDA8694-3, Norgold Russet, BelRus, Superior, Russet Norkotah, Norland andS. demissum were the most susceptible, while A66107-51, A68113-4, Targhee, NDA843-3, Alpha, A7805-8, A7816-14, Russet Nugget,S. chacoense, S. sparsipilum, andS. tarijense were the most resistant to wilt. The reaction of genotypes to the AP ofV. dahliae toxin in an excised leaf bioassay was not correlated with their reaction to Verticillium wilt in the field or glasshouse. Idaho Agricultural Experiment Station Article No. 89741.  相似文献   

14.
Nine soils collected in New Jersey and Maryland were infested with microsclerotia ofVerticillium dahliae and planted with potato cv. Superior for five successive crops in the greenhouse to induce suppressiveness to Verticillium wilt. Potatoes were harvested 9–12 wk after planting and disease incidence was determined by recovery ofV. dahliae from stem segments on selective medium. Six of the nine soils had high disease incidence during the first cropping and remained conducive to Verticillium wilt throughout the experiment. Disease incidence increased in soils 3 and 9 over time, while disease incidence decreased nonlinearly in soil 1. Viability of microsclerotia buried in soil 9 for 4 wks was reduced compared to the viability of microsclerotia buried in soils 1, 3, and 6. Addition of 50 or 100 g hydrated lime/10 kg soil to soil 9 eliminated its suppressiveness to Verticillium wilt. Repeated cropping of the same soil can induce suppressiveness to Verticillium wilt. Soils exhibiting induced suppressiveness may be a source of new antagonists againstV. dahliae.  相似文献   

15.
Verticillium wilt, caused by the soil-borne fungus Verticillium dahliae, is one of the most important diseases of potato in North America. Soil incorporation of alfalfa residues prior to planting potato could be a nonchemical Verticillium wilt management tactic by reducing the number of viable microsclerotia in field soil. Verticillium dahliae microsclerotia were quantified in field soils where organic material from alfalfa was incorporated, and numbers of microsclerotia were compared to fields where alfalfa residue was not incorporated. In addition, bacterial metagenomics was utilized to characterize soils where organic material from alfalfa was or was not incorporated to determine if alfalfa residue incorporation facilitates the formation of soils that suppress or kill V. dahliae microsclerotia. The number of V. dahliae microsclerotia in soil was greater (P = 0.0003) in fields where crop residue was incorporated than fields without incorporation when chloropicrin was used as a fumigant. Conversely, the number of V. dahliae microsclerotia observed in potato plants did not differ (P = 0.4020) between fields where residues were or were not incorporated if chloropicrin was used. Alfalfa residue incorporation did not significantly alter the soil bacterial metagenome compared to fields not subject to residue incorporation in both years of study. Despite these conclusions, the method can be employed to analyze the effect of grower practices with the intent of linking a field practice to increasing soil bacterial diversity and decreasing Verticillium wilt severity on potato.  相似文献   

16.
Verticillium spp. wilt pathogens enter the root and eventually penetrate xylem vessels of the plant where they can spread into the vascular tissue of the potato tuber. Infected tuber vessel elements often become discolored creating a serious internal tuber quality defect that prevents sale of raw product to its primary market. Despite the costly losses and disease issues created by these infections, the physiological responses to colonization of tuber vessel elements are poorly described, and a model system to study these responses in the laboratory has not been developed. The objectives of this research were to develop such a model system by determining if tuber vessel elements could be infiltrated withVerticillium spp. in a laboratory setting and if a detectable physiological response could be elicited and identified. Results demonstrated that tuber vessel elements in the model system could be infiltrated and that infiltration ofVerticillium dahliae Kleb. conidia into these vessel elements induced a suberization response on the walls of neighboring parenchyma cells. However, the walls of the infiltrated tuber vessel elements did not suberize. A similar suberization response was found in tubers that had been naturally infected byVerticillium dahliae in the field. The suberization response was histochemically determined by assessing the accumulation of suberin poly(aliphatics) and poly(phenolics). This process of internal suberization of tuber parenchyma cells occurred without induction by a wound signal. Consequently, the suberization signal was derived by introduction of the plant-pathogen into the tuber vessel elements. This simple model system provides a versatile tool to investigate the physiological responses of potato tuber to colonization of vessel elements. This is believed to be the first report for such a physiological response toVerticillium spp. in potato tuber.  相似文献   

17.
Verticillium wilt, caused by Verticillium dahliae Kleb., is a primary component of the early dying complex of potato (Solanum tuberosum L.) in the United States. Although genetic resistance to V. dahliae exists and has been incorporated into several potato cultivars, the commercial potato industry is still dominated by cultivars susceptible to the pathogen. As a result, soil fumigation with metam sodium remains an important means by which Verticillium wilt is controlled, despite its expense and potentially negative environmental impact. Recent restrictions on metam sodium use by the Environmental Protection Agency directed at reducing exposure to vapor emissions have increased the need to improve shank injection of the soil fumigant. In studies reported here, the application of metam sodium reduced the severity of Verticillium wilt, however, soil temperature at the time of injection, metam sodium injection depth, and application rate had little overall effect. In 2011, temperature at the time of metam sodium injection did not result in significant differences in any parameter evaluated. However, in 2012, soil populations of V. dahliae, wilt severity and host colonization were significantly reduced when metam sodium was applied at 4 °C compared to 13 or 15 °C. No significant differences were observed between a single or two metam sodium injection depths in any parameter evaluated across the 2 years the study was conducted. While all rates of metam sodium significantly reduced soil populations of V. dahliae compared to the non-treated control, significant differences across rates were rarely observed. Improved control of Verticillium wilt and increased yield can be achieved as a result of these studies. The effective control of Verticillium wilt can be obtained by using metam sodium at a comparatively low rate of 373 l/ha, particularly when applied at a relatively cold soil temperature of 4 °C using a single injection depth of 25 cm. The potential impact of these application modifications of metam sodium in reducing emissions and non-target exposure is discussed.  相似文献   

18.
Results of studies on survival of sclerotia of Sclerotinia and microsclerotia of Verticillium, demonstrated that soil flooding in western Washington is a possible alternative field rotation practice for S. sclerotiorum (white mold), but not for V. dahliae (Verticillium wilt). Cone-tainer experiments in the greenhouse showed that flooding at 16.5 °C caused S. sclerotiorium sclerotia to lose viability between 12 and 24 weeks while a growth chamber experiment revealed that flooding for 18 weeks at 11 °C or 20 °C was sufficient. V. dahliae microsclerotia appeared resistant to flooding under greenhouse and field settings; recovery ranged within 5 to 10 % of the initial soil population after 6 and 12 months. Potatoes planted into field microplots either flooded or fallowed the previous summer had similar Verticillium wilt ratings and potato yield. Lack of control of V. dahliae by flooding may be due partly to relatively low soil temperatures in a cool, marine climate.  相似文献   

19.
Summary Samples of a sandy soil and a marine clay soil sterilized by steam were put in 55-1 containers insulated with polystyrene and placed outdoors on a brick pavement. Sandy soil was infested singly or in all possible combinations with root-knot nematodes (Meloidogyne spp.) and the fungiRhizoctonia solani andVerticillium dahliae, and the marine clay soil was infested with the root-lesion nematodePratylenchus neglectus and the same fungi to evaluate the effects of these organisms on the yield of potato. The experiments were carried out from 1983 to 1986. Tuber yield was reduced by single infestations of theMeloidogyne spp. andV. dahliae but not significantly byR. solani orP. neglectus. A three-factor interaction: nematode ×R. solani × V. dahliae was found in both experiments.R. solani andV. dahliae showed significant synergistic effects when soil was infested with theMeloidogyne spp. orP. neglectus.  相似文献   

20.
Premature death of potato vines is widespread in irrigated potato fields of the Pacific Northwest.Verticillium dahliae is a major cause of early dying in fields with a history of potato production, but in fields new to potato production, or those that have been fumigated and have a lowV. dahliae population in the soil, premature death of vines can also occur.Erwinia carotovora pv.carotovora (Ecc) andE. carotovora pv.atroseptica (Eca) have been implicated in the early dying disease syndrome in these fields. Both bacterial pathogens are associated with symptoms similar to those caused byV. dahliae; i.e., a progressive chlorosis and necrosis of the foliage and vascular discoloration that may extend a short distance up the stem. Greenhouse pathogenicity studies on cv. Russet Burbank cuttings in which symptom development was identical to that produced byV. dahliae have verified thatEcc andEca can cause potato early dying.  相似文献   

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