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1.
Metam sodium is a widely used soil fumigant for Verticillium wilt management in most potato production regions of the United States. Environmental concerns regarding volatilization losses have led to restrictions on the use of metam sodium. The potato industry adapted to these restrictions by replacing metam sodium applications through sprinkler irrigation with shank injection applications of the fumigant. Previous research established parameters for effective shank application of metam sodium based on soil temperature, injection depth and rate of fumigation. However, these recommendations were based on research conducted under coarse-textured soil conditions with a low organic matter (OM) content (<1.3%). However, many potato production soils in North Dakota and Minnesota have a finer silt loam texture and OM contents of >2.5%. Therefore, it is important to know whether metam sodium fumigation recommendations for coarse-textured soils can be adapted to fine-textured soils. Two field trials were conducted using a split strip-block design for studying metam sodium efficacy in managing wilt. In both years, metam sodium injection depth and soil temperature at the time of injection did not result in significant differences in any study variable evaluated. All metam sodium fumigation rates significantly (P?<?0.05), lowered Verticillium microsclerotia, reduced wilt severity, and improved tuber yield compared to non-treated plots. However, significant differences among fumigation rates were not observed across any variable evaluated. A relatively low rate of 373 l/ha is as effective as higher metam sodium rates for effective control of Verticillium wilt. Results presented here suggest that current metam sodium recommendations for shank injection applications in coarse-textured soils can be implemented in field soils with a fine texture and higher OM content.  相似文献   

2.
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   

3.
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   

4.
The effect of plowing and deep-rip tillage, in combination with chemigation or shank injection of metam sodium, onVerticillium dahliae populations and disease development was assessed in two fields with differing soil types and potato rotations. Soil samples were collected on a geo-referenced basis at depths of 0 to 10 cm and 10 to 20 cm before tillage, after tillage, after chemical application, and before planting and assayed for the presence of the pathogen. Propagules ofV. dahliae were detected at 140 of 141 sites sampled prior to tillage. Most (74.4% in heavy, sandy loam; 63.1% in light, loamy sand) were concentrated in upper 10 cm of the soil profile. Plowing redistributed inoculum vertically while deep-rip tillage did not. In the non-chemical treated areas of both fields, theVerticillium population reached a maximum between 25 July and 8 August before declining to near pre-tillage levels. Overall, the population generally was lower in the field with heavy soil, higher organic matter content, and a 3-year crop rotation. Metam sodium appeared to be most effective when shank injected, as the levels of inoculum in both fields declined by 60% to 80% following this application method. Chemigation was ineffective in the lighter soil, but the inoculum density in the deep-rip tillage area of the field with the heavier soil declined by nearly 20% in the upper and 60% in the lower strata following this treatment. The number ofV. dahliae propagules at the 10- to 20-cm depth in the plowed area of the same field was reduced by 25% following chemigation, but remained unchanged in the upper strata. Wilt was reduced in both fields by as much as 50% with shank injection of metam sodium with concomitant increases in total yield, marketable yield and gross income. Increases in total yield were significant (P<0.05) for the main effect of chemical, in the plowed area of the field with the heavier soil type following shank injection. These data suggest that growers might benefit from altering their tillage and chemical application practices as part of an integrated approach to managing Verticillium wilt.  相似文献   

5.
In three years (1994, 1995, and 1996), a total of 100 commercial potato fields in southeastern Idaho were surveyed for soil variables, severity of Verticillium wilt, soil inoculum density ofVerticillium dahliae andColletotrichum coccodes, colonization of stems, root, and tubers byV. dahliae andC. coccodes, and tuber yield, size, and quality. As a generalization, factors related to soil integrity (organic matter, organic nitrogen, and increased nutrient availability) were most closely related to wilt suppression and higher tuber yields, whereas factors related to loss of soil integrity (sodium and reduced nutrient availability) were related to increased wilt and lower tuber yields. In a multiple regression analysis, three independent variables, feeder-root infections byV. dahliae, sodium content in soil, and soil organic content, were significant predictors of tuber yield. With these three factors, this model accounted for 49%, 53%, and 62% of the field variability related to total yield in 1994, 1995, and 1996, respectively. Throughout this investigation,V. dahliae root infections had the most direct effect on tuber yield, which emphasizes the importance of quantifying root infections in epidemiological studies of Verticillium wilt. Based on these results, organic matter may be one factor that can be manipulated for suppression of Verticillium wilt without reducing soil populations of the pathogen.  相似文献   

6.
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   

7.
Verticillium wilt is a fungal disease of potato caused by two species of Verticillium, V. dahliae and V. albo atrum. The pathogen infects the vascular tissue of potato plants through roots, interfering with the transport of water and nutrition, and reducing both the yield and quality of tubers. We have evaluated the reaction of 283 potato clones (274 cultivars and nine breeding selections) to inoculation with V. dahliae under greenhouse conditions. A significant linear correlation (r = 0.4, p < 0.0001) was detected between plant maturity and partial resistance to the pathogen, with late maturing clones being generally more resistant. Maturity-adjusted resistance, that takes into consideration both plant maturity and resistance, was calculated from residuals of the linear regression between the two traits. Even after adjusting for maturity, the difference in the resistance of clones was still highly significant, indicating that a substantial part of resistance cannot be explained by the effect of maturity. The highest maturity-adjusted resistance was found in the cv. Navajo, while the most susceptible clone was the cv. Pungo. We hope that the present abundance of data about the resistance and maturity of 283 clones will help potato breeders to develop cultivars with improved resistance to V. dahliae.  相似文献   

8.
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   

9.
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   

10.
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   

11.
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   

12.
Verticillium dahliae Kleb. is a soilborne fungal pathogen of many crops. In potato, it is the major causal agent of Early Dying. In Manitoba, potato fields planted with cv. Russet Burbank are infested with highly pathogenic V. dahliae isolates, which can produce up to 90 % disease severity. The objective of the study was to evaluate selected compost, green manure, and seed-meal treatments, in comparison with the soil fumigant Vapam, for their ability to reduce propagule density of V. dahliae in soil and decrease disease, and to enhance potato yield. Select green manure crops (oriental and white mustard, Canada milk vetch, sorghum-sudangrass, rye, alfalfa, oat/pea mixture), organic amendments (composted cattle manure and mustard seed-meal), and Vapam, and crop sequences that contribute to the suppression of Verticillium, or the improvement of potato yield were used in a 3-year field study initiated in 2006. Survival in soil of microsclerotia was evaluated as a measure of treatments’ success in potentially reducing Early Dying. Compost and seed-meal treatments, compared to an untreated control, reduced incidence to 30 and 40 %, respectively, but only seed-meal reduced V. dahliae propagule density. Overall, green manures over 1 or 2-years were ineffective in reducing propagule density or improving potato yield. Vapam was partially effective in reducing the propagule density only at the beginning of the potato season, but it did not reduce disease incidence compared to the control. Compost and seed-meal are promising as alternative control of V. dahliae. Only compost reduced disease and increased potato yield, which was associated with improved nutrient availability (phosphorus and sulfate) in soil.  相似文献   

13.
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   

14.
Field studies involving the effects of growing sweet corn (Zea mays var. Jubilee sweet corn and var. Jubilee super-sweet corn) as a green manure for 2 or 3 seasons demonstrated both suppression of verticillium wilt by 60–70% (Verticillium dahliae Kleb.) and increased potato yields. Although these treatments showed no direct effect on V. dahliae soil populations, the colonization of V. dahliae on potato feeder-roots and in potato tissue of stem apices were reduced. Feeder-root colonization by V. dahliae was positively correlated with verticillium wilt incidence (P?≤?0.05 to P?≤?0.01) and negatively correlated with yield (P?≤?0.05). Corn green manures additionally increased populations of several soilborne fungi which included Ulocladium, and Fusarium equiseti. Specific nutritional and microbial effects were secondary to the effects of cropping practices. When compared with the fallow treatments for 1994, 1995, and 1997, the percentage yield increases for 1994 were: +34% for total yield, +57% for U.S. #1’s, and +127% for tubers >280 g; for 1995 (a year of reduced degree-days and decreased verticillium incidence): +14% for total yields, +15% for U.S. #1 yields, and +21% for tubers >280 g; for 1997: +24% for yield totals, +74% for U.S. #1’s and +179% for tubers >280 g. For establishing these yield benefits, stalks with and without ears of corn were used as green manures. Corn varieties differed for effectiveness as a green manure, which could be accounted for by differences of biomass. When compared with the super-sweet corn, the sweet corn produced an increase (>2-fold) of biomass with less than half of the resulting wilt incidence. When potato was grown consecutively for 2 years, the benefits from green manures became mostly eliminated. However, following 2 consecutive years of potato, a single green manure of sweet corn was sufficient to return the potato crop to the original benefits of verticillium suppression and increased yields. This occurred even though soilborne V. dahliae inoculum levels had increased by >4-fold from 45 to 182 cfu g?1 of soil. Results of this study demonstrate the importance of green manures and soil-ecology to the management of the Russet Burbank potato.  相似文献   

15.
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   

16.
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   

17.
A procedure was developed and tested to evaluate potato germ plasm for relative rates of vascular colonization byVerticillium dahliae. The number of colony forming units (CFU) per ml of plant sap, extracted from stems and plated on a medium, was used to assess vascular colonization from plants grown for 100 days in a field plot infested withV. dahliae. Sap extracted from main stem tissue at the ground line gave more CFU ofV. dahliae than tissue at the mid and apical region of the main stem. Aliquots of 0.05, 0.1 and 0.2 ml of plant sap were equally efficient in measuring vascular colonization. Thirty-three clones were evaluated for amount of vascular colonization in field and greenhouse tests with the former giving the best results. Cultivars and clones resistant to Verticillium wilt in Idaho, Maine, Minnesota, North Dakota and New York each had a low index of wilt and a low number of CFU/ml ofV. dahliae in plant sap in these tests. Clones intermediate in both wilt index and vascular colonization as well as selections with a high wilt index and extensive vascular colonization were found using the fresh sap assay method. Correlation values of, r = 0.92, r = 0.91 and r = 0.86 were observed between CFU/ml and percentage of foliar wilt for 11 clones/cultivars in 1986, 1987 and 1988, respectively. The correlation between CFU/ml and both moisture and temperature for the cultivars Kennebec and Russet Burbank, during a 6-yr period was r = 0.83.  相似文献   

18.
Two strawberry nursery field trials comparing soil disinfection with different fumigants (metam sodium, dazomet, chloropicrin, chloropicrin +1,3D) and a steaming system exploiting the exothermic reaction between steam and CaO (Bioflash System™) were conducted in 2010–2012 to evaluate the effect of treatments on Verticillium dahliae Kleb. inhabiting the soil, and on plant health, growth and yield of strawberry daughter plants. Chemical fumigants and the Bioflash System™ decreased the number of V. dahliae colonies in the soil, which corresponded to reduced incidence of Verticillium wilt (efficacy about 80%). The use of chemical fumigants had a positive impact on the size of the mother plants. The surface area covered by plants grown on the treated plots was 1.1–1.7 times larger than plants grown on non-fumigated control plots. The number of runners, as well as daughter plants, produced from plants grown on plots treated with all chemical fumigants was significantly higher than in the non-fumigated control or in the plots treated with the Bioflash System™. The disinfection treatments significantly increased the yield of marketable daughter plants, approximately 1.5–3 times higher in comparison to plants grown on control plots. Steam disinfection with the Bioflash System™ was the least effective treatment in this respect. The differences in marketable plants yield among the chemical fumigants significantly affected the net marginal return and the return on investment of the crop. In this respect, the steam disinfection was economically efficient only in one season. The efficacy in controlling Verticillium wilt even with low doses of metam sodium and dazomet and their influence on yield and quality of daughter plants is confirming the feasibility of these fumigants for strawberry nursery management.  相似文献   

19.
Nine potato clones/cultivars selected for varying degrees of Verticillium wilt (VW) resistance based on degree of vascular colonization, were intercrossed and outcrossed to 13 uncharacterized clones. Based on growth characteristics of 3,535 seedling transplants and an assay quantifyingV. dahliae in potato vascular tissue, 404 clones were selected for further tests. The average number ofVerticillium dahliae colony forming units (CFU) expressed as Log10(CFU + l)/0.1 ml of plant sap for the 404 clones was 2.3, and 1.3 and 3.7 for resistant Reddale and susceptible Kennebec checks, respectively. Thirty-five clones (8.66%) had CFU values equal to or less than Reddale suggesting that VW resistance is a readily transmitted trait.  相似文献   

20.
Viable propagules ofVerticillium albo-atrum andV. dahliae were recovered from potato stems before and after burial in the field during 1968–1971. Of 14 cultivars tested: Red Pontiac and Superior ranked highest in numbers of propagules ofV. albo-atrum. Russet Burbank, Kennebec, and Irish Cobbler ranked highest withV. dahliae, respectively. Survival ofV. albo-atrum in infected stems was evident (5 ? 34 × 103 ppg) even after burial in field soil for 17 months. In general, survival ofV. albo-atrum (47–69%) was higher thanV. dahliae (23 – 61%) following field burial of infected stems for 7 months.  相似文献   

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