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1.
ABSTRACT The effect of the fungal mycoparasite Coniothyrium minitans applied as a spray to crops infected with Sclerotinia sclerotiorum (causal agent of white mold) on contamination of soil with S. sclerotiorum sclerotia was studied in a 5-year field experiment. Sclerotial survival also was monitored during two subsequent years, when the field was returned to commercial agriculture. In a randomized block design, factorial combinations of four crops and three treatments were repeated 10 times. Potato (Solanum tuberosum), bean (Phaseolus vulgaris), carrot (Daucus carota), and chicory (Cichorium intybus), which are all susceptible to S. sclerotiorum, were grown in rotation. Plots were treated with C. minitans or Trichoderma spp. or were nontreated (control). Crops were rotated in each plot, but treatments were applied to the same plot every year. After 3 years during which it showed no effect on sclerotial survival, the Trichoderma spp. treatment was replaced by a single spray with C. minitans during the fourth and fifth years of the trial. The effect of treatments was monitored in subsequent seasons by counting apothecia as a measure of surviving S. sclerotiorum sclerotia and scoring disease incidence. Trichoderma spp. did not suppress S. sclerotiorum, but C. minitans infected at least 90% of S. sclerotiorum sclerotia on treated crops by the end of the each season. C. minitans lowered the number of apothecia compared with the other treatments during the second year after the bean crop. C. minitans reduced the number of apothecia by approximately 90% when compared with the control and Trichoderma spp. treatments and reduced disease incidence in the bean crop by 50% during the fifth year of the trial, resulting in a slightly higher yield. In 1993, but not 1994, a single spray with C. minitans was nearly as effective at reducing apothecia as three sprays (monitored in 1995). The final population size of sclerotia in soil at the end of the 7-year period was lower in all C. minitans plots than at the beginning of the trial, even in plots where two highly susceptible bean crops were grown during the period. The results indicate that the mycoparasite C. minitans has the potential to keep contamination of soil with sclerotia low in crop rotations with a high number of crops susceptible to S. sclerotiorum.  相似文献   

2.
The effects of Coniothyrium minitans inoculum quality and an 8-week interval between inoculum application and crop planting on sclerotinia ( Sclerotinia sclerotiorum ) disease in three successive lettuce crops were investigated in a glasshouse trial. Spore suspensions of three isolates of C. minitans (Conio, IVT1 and Contans) applied at 108 CFU m−2 and a standard Conio maizemeal–perlite application (06 L m−2, 1011 CFU m−2) were assessed for their ability to control S. sclerotiorum . Only the maizemeal–perlite inoculum (isolate Conio) consistently reduced sclerotinia disease. In the third lettuce crop only, isolates IVT1 and Contans formulated by Prophyta and isolate IVT as an oil–water formulation, all applied as spore suspensions, reduced disease at harvest compared with the untreated control. Recovery, viability and C. minitans infection of sclerotia buried during the 8-week period prior to each of the three lettuce crops, and of sclerotia formed on the crop, were tested. Only the maizemeal–perlite inoculum (isolate Conio) reduced the recovery of sclerotia buried in soil for weeks between inoculum application and crop planting, reducing their viability and increasing infection by C. minitans . Eight weeks was sufficient to enable C. minitans to infect sclerotia of S. sclerotiorum , and may account for disease control. After harvest of the second and third crops, maizemeal–perlite treatment (isolate Conio) reduced the number and viability of sclerotia recovered on the soil surface and increased infection by C. minitans compared with spore-suspension treatments. The effect of inoculum concentration and the influence of soil temperature (varying with time of year) on infection of sclerotia by C. minitans are discussed.  相似文献   

3.
Budge SP  Whipps JM 《Phytopathology》2001,91(2):221-227
ABSTRACT All pesticides used in United Kingdom glasshouse lettuce production (six fungicides, four insecticides, and one herbicide) were evaluated for their effects on Coniothyrium minitans mycelial growth and spore germination in vitro agar plate tests. Only the fungicides had a significant effect with all three strains of C. minitans tested, being highly sensitive to iprodione (50% effective concentration [EC(50)] 7 to 18 mug a.i. ml(-1)), moderately sensitive to thiram (EC(50) 52 to 106 mug a.i. ml(-1)), but less sensitive to the remaining fungicides (EC(50) over 200 mug a.i. ml(-1)). Subsequently, all pesticides were assessed for their effect on the ability of C. minitans applied as a solid substrate inoculum to infect sclerotia of Sclerotinia sclerotiorum in soil tray tests. Despite weekly applications of pesticides at twice their recommended concentrations, C. minitans survived in the soil and infected sclerotia equally in all pesticide-treated and untreated control soil trays. This demonstrated the importance of assessing pesticide compatibility in environmentally relevant tests. Based on these results, solid substrate inoculum of a standard and an iprodione-tolerant strain of C. minitans were applied individually to S. sclerotiorum-infested soil in a glasshouse before planting lettuce crops. The effect of a single spray application of iprodione on disease control in the C. minitans treatments was assessed. Disease caused by S. sclerotiorum was significantly reduced by C. minitans and was enhanced by a single application of iprodione, regardless of whether the biocontrol agent was iprodione-tolerant. In a second experiment, disease control achieved by a combination of C. minitans and a single application of iprodione was shown to be equivalent to that of prophylactic sprays with iprodione every 2 weeks. The fungicide did not affect the ability of C. minitans to spread into plots where only the fungicide was applied and to infect sclerotia. These results indicate that integrated control of S. sclerotiorum with soil applications of C. minitans and reduced foliar iprodione applications was feasible, did not require a fungicide tolerant isolate, and that suppression of Sclerotinia disease by C. minitans under existing chemical control regimes has credence.  相似文献   

4.
Coniothyrium minitans, marketed as Contans, has become a standard management tool against Sclerotinia sclerotiorum in a variety of crops, including winter lettuce. However, it has been ineffective against lettuce drop caused by S. minor. The interactions between C. minitans and S minor were investigated to determine the most susceptible stage in culture to attack by C. minitans, and to determine its consistency on S minor isolates belonging to four major mycelial compatibility groups (MCGs). Four isolates of S. minor MCG 1 and 5 each from MCGs 2 and 3 and one from MCG 4 were treated in culture at purely mycelial, a few immature sclerotial, and fully mature sclerotial phases with a conidial suspension of C. minitans. Sclerotia from all treatments were harvested after 4 weeks, air dried, weighed, and plated on potato dextrose agar for recovery of C. minitans. S. minor formed the fewest sclerotia in plates that received C. minitans at the mycelial stage; C. minitans was recovered from nearly all sclerotia from this treatment and sclerotial mortality was total. However, the response of MCGs was inconsistent and variable. Field experiments to determine the efficacy of C. minitans relative to the registered fungicide, Endura, on lettuce drop incidence and soil inoculum dynamics were conducted from 2006 to 2009. All Contans treatments had significantly lower numbers of sclerotia than Endura and unsprayed control treatments, and drop incidence was as low as in Endura-treated plots (P > 0.05). Although the lower levels of lettuce drop in Contans treatments were correlated with significantly lower levels of sclerotia, the lower levels of lettuce drop, despite the presence of higher inoculum in the Endura treatment, was attributable to the prevention of infection by S. minor. A useful approach to sustained lettuce drop management is to employ Contans to lower the number of sclerotia in soil and to apply Endura to prevent S. minor infection within a cropping season.  相似文献   

5.
In two field trials with oilseed rape, Coniothyrium minitans was applied to soil as a maizemeal-perlite preparation in order to determine its effect on sclerotial survival and apothecial production of Sclerotinia selerotiorum. The mycoparasite infected sclerotia and decreased sclerotial survival, carpogenic germination and production of apothecia. Effects were greatest when inoculum of C. minitans was applied in autumn, at the time of sowing, rather than when it was applied in spring. C. minitans survived in soil for 2 years and spread to adjacent control plots and infected sclerotia within those plots. However, despite the fact that the inoculum potential of S. selerotiorum was reduced by C. minitans treatment, no disease control was obtained either in trial 1, where disease levels were low (0-20% of plant stems affected), or in trial 2, where disease levels were high (up to 70% of plant stems affected). Possible reasons for this failure of C minitans to control sclerotinia disease in oilseed rape, and strategies to improve its efficacy in the field, are discussed.  相似文献   

6.
Coniothyrium minitans grew on all ten solid-substrates (barley, barley-rye-sunflower, bran-vermiculite, bran-sand, maizemed-perlite, millet, oats, peat-bran, rice and wheat) tested, producing high numbers of germinable pycnidiospores (1.9–9.3×108 g–1 air dry inocula). All solid substrate inocula survived better in the laboratory at 5 and 15 °C than at 30 °C for at least 64 weeks.In pot bioassays carried out in the glasshouse and field, soil incorporations of each inoculum almost completely inhibited carpogenic germination ofS. sclerotiorum. In the field bioassay, no sclerotia were recovered after 38 weeks fromC. minitans-treated pots compared to 56% from control pots. In the glasshouse bioassay, 9–30% of sclerotia were recovered after 20 weeks fromC. minitans-treated pots, but 88–100% of these were infected by the antagonist. The antagonist also spread to infect sclerotia in control pots.In larger scale glasshouse trials, single preplanting soil-incorporations of five inocula (barley-ryesunflower, maizemeal-perlite, peat-bran, rice and wheat) controlled Sclerotinia disease in a sequence of lettuce crops, with only small differences between the types of inocula tested. At harvest,C. minitans reduced sclerotial populations on the soil surface and over 74% of sclerotia recovered fromC. minitans-treated plots were infected by the antagonist.C. minitans survived in soil in all solid-substrate inocula-treated plots for at least 39 weeks at levels of 104–105 colony forming units cm–3 soil and spread to infect over 36% of sclerotia recovered from control plots.  相似文献   

7.
The effects of different inocula of the mycoparasite Coniothyrium minitans on carpogenic germination of sclerotia of Sclerotinia sclerotiorum at different times of year were assessed. A series of three glasshouse box bioassays was used to compare the effect of five spore-suspension inocula of C. minitans , including three different isolates (Conio, IVT1 and Contans), with a standard maizemeal–perlite inoculum. Apothecial production, as well as viability and C. minitans infection of S. sclerotiorum sclerotia buried in treated soil, were assessed. Maizemeal–perlite inoculum at 107 CFU per cm3 soil reduced sclerotial germination and apothecial production in all three box bioassays, decreasing sclerotial recovery and viability in the second bioassay and increasing C. minitans infection of sclerotia in the first bioassay. Spore-suspension inocula applied at a lower concentration (104 CFU per cm3 soil) were inconsistent in their effects on sclerotial germination in the three box bioassays. Temperature was an important factor influencing apothecial production. Sclerotial germination was delayed or inhibited when bioassays were made in the summer. High temperatures also inhibited infection of sclerotia by C. minitans . Coniothyrium minitans survived these high temperatures, however, and infected the sclerotia once the temperature decreased to a lower level. Inoculum level of C. minitans was an important factor in reducing apothecial production by sclerotia. The effects of temperature on both carpogenic germination of sclerotia and parasitism of sclerotia by C. minitans are discussed.  相似文献   

8.
Wu BM  Subbarao KV 《Phytopathology》2003,93(12):1572-1580
ABSTRACT The temporal and spatial dynamics of Sclerotinia minor sclerotia and the resulting incidence of lettuce drop were studied under furrow irrigation with conventional tillage and subsurface-drip irrigation with minimum tillage during 1993-95. Lettuce crops were grown each year during the spring and fall seasons. All plants were inoculated immediately after thinning in the spring of 1993. Grids of 24 contiguous quadrats (1 by 1 m(2)) were demarcated in the centers of each 150-m(2) plot. Lettuce drop incidence in each quadrat was evaluated each season prior to harvest. One soil sample (100 cm(3)) was collected from each quadrat at harvest and after tillage prior to planting of the next crop for both spring and fall crops and assayed for S. minor sclerotia using wet sieving. Lloyd's index of patchiness, the beta-binomial distribution, and variance of moving window averages were used to evaluate the spatial patterns of sclerotia and lettuce drop incidence under the two irrigation systems and associated tillage treatments. Disease incidence remained significantly higher under furrow irrigation than under subsurface-drip irrigation throughout the study period, and was significantly higher on fall crops than on spring crops. Under furrow irrigation, the number of sclerotia at the end of a crop season increased significantly over that at the beginning of the season, but no significant changes were detected over years. In contrast, the number of sclerotia within a single season did not increase significantly under subsurface drip irrigation, nor was year-to-year accumulation of sclerotia statistically significant. The degree of aggregation of sclerotia increased significantly during a cropping season under furrow irrigation, but not under subsurface drip irrigation. The conventional tillage after harvest under furrow irrigation decreased the degree of aggregation of sclerotia after each season, but the distribution pattern of sclerotia under subsurface-drip irrigation changed little by the associated minimum tillage. Spatial pattern analyses suggested that the aggregation of S. minor sclerotia occurred at a scale of no more than 1 m, and distribution of diseased lettuce plants was random at a scale larger than 1 m. The combination of fewer sclerotia produced by each crop and its unaltered distribution under subsurface drip irrigation and associated minimum tillage makes it a valuable cultural practice for lettuce drop management.  相似文献   

9.
盾壳霉是一种重要的生防菌,其在土壤中的存活数量直接关系到防治病害的效果。然而目前没有对土壤中盾壳霉直接计数的方法,构建一种简单易行的土壤中盾壳霉计数方法对研究盾壳霉在土壤中的存活动态具有重要意义。本研究利用农杆菌转化法构建了潮霉素基因和绿色荧光蛋白基因标记的双标记盾壳霉菌株,并测定转化子的生长速度、产孢量和菌核致腐能力,初步分析了该方法计数土壤盾壳霉的有效性和可行性。结果显示,潮霉素基因和绿色荧光蛋白基因可以稳定地遗传和表达,并且部分转化子生长速度、产孢量和菌核致腐能力与出发盾壳霉菌株JNCM没有显著差异。加入土壤中的盾壳霉转化子可以在含潮霉素(50μg/mL)、氯霉素(100μg/mL)和链霉素(100μg/mL)的PDA平板培养,杂菌得到充分抑制,呈现绿色荧光的盾壳霉转化子被有效检出,检出限达到2×103个/g土。本研究所构建的计数方法能有效检出施入土壤中的盾壳霉并进行活菌计数,可以用于盾壳霉JN-CM产品在土壤中的定殖、生长、繁殖和存活情况的研究。应用双标记平板计数法研究了不同温度、湿度、接种量和添加菌核等条件下盾壳霉JN-CM在土壤中的存活规律。结果显示,在含有核盘菌菌核的土壤中,盾壳霉JN-CM可以通过重寄生维持一段时间(12周)的数量增长,在长达半年左右(24周)的时间里其存活率仍然可以维持在65%左右。在不含菌核的土壤中,在一般土壤温度(10~20℃)范围内,无论土壤水分含量高低,其半年存活率也可以维持在50%左右。因此,可以预测,连续施用盾壳霉JN-CM生防制剂,可以使其数量在土壤中长期维持在一定的水平范围,达到长效防治效果。  相似文献   

10.
Neck rot ( Botrytis allii ) affected bulbs of onions for 2 successive years when these were grown either in the field in soil from which an infected crop had been cleared 6 months previously or when infected debris was incorporated into field soil 6 months before the first crop was sown. These sources did not continue to cause infection of onion crops grown on the contaminated areas in the four succeeding years.
The white storage tissue of onion bulbs (healthy or infected) persisted for less than 6 months in unsterile field soil contained in pots while sclerotia present in similar soil varied in their rate of decay but lost their capacity to produce conidiophores of B. allii after 6 months. In one sample, sclerotia were not recovered after 5 months; Gliocladium roseum , a mycoparasite, was present in this sample and may have affected survival.  相似文献   

11.
Coniothyrium minitans isolate Conio grew on both maizemeal-perlite and ground maizemeal-perlite, producing high numbers (1.6×107 conidiag–1 inoculum) of germinable conidia. Coniothyrium minitans isolate Conio applied as a preplanting soil incorporation of maizemeal-perlite inoculum at full application rate (0.6lm–2; 1011 colony forming units (cfu)m–2) significantly reduced Sclerotinia disease in a sequence of three lettuce crops grown in a glasshouse. No reduction in disease was achieved with any of the reduced rate treatments (108cfum–2) of a range of C. minitans isolates (Conio ground maizemeal-perlite at reduced rate, Conio and IVT1 spore suspensions derived from maizemeal-perlite, IVT1 spore suspension derived from oats and Contans® WG spore suspension). After harvest of the second and third crops, C. minitans maizemeal-perlite at full rate reduced the number and viability of sclerotia recovered on the soil surface and increased infection by C. minitans compared with spore suspension and reduced rate maizemeal-perlite inocula. Coniothyrium minitans was recovered from the soil throughout the trial, between 105 and 107cfucm–3 in maizemeal-perlite inoculum full rate treated plots and 101–104cfu cm–3 in all other inoculum treated plots.Pot bioassays were set up corresponding to the inoculum used in the glasshouse, with the addition of Conio ground maizemeal-perlite at a rate corresponding to the full rate maizemeal-perlite. Coniothyrium minitans maizemeal-perlite and ground maizemeal-perlite at full rate significantly decreased carpogenic germination, recovery and viability of sclerotia and increased infection of sclerotia by C. minitans in comparison with spore suspension treatments, reflecting results of the glasshouse trials. Additionally, reduced maizemeal-perlite treatment also decreased apothecial production, recovery and viability of sclerotia compared with the spore suspension treatment, despite being applied at similar rates. Simultaneous infection of sclerotia by several isolates of C. minitans was demonstrated. Inoculum level in terms of colony forming unitscm–3 of soil appears to be a key factor in both control of Sclerotinia disease and in reducing apothecial production by sclerotia.  相似文献   

12.
Carry-over of inoculum of X.c. pv. campestris in the soil from one cropping season to the next was studied in field experiments over three years. These studies were supported by laboratory and greenhouse experiments on quantitative assessment of bacteria by bioassay using the Most Probable Number technique, and on recovery rates of bacteria from the soil. The mean recovery rate from artificially infested soil was 58%. Extinction of X.c. pv. campestris in soil infested with infected plant debris proceeded exponentially and extinction rates depended on temperature, as did the decomposition of plant debris. In replicated field plots, over three years, infection foci of black rot disease were established. At harvest time, all plants were chopped and resulting plant debris was rotovated into the soil. The resulting soil infestation was sampled and showed clear infestation foci reflecting the original infection foci of the crop. These infestation foci decreased with time and disappeared after the winter. Follow-up crops remained virtually uninfected. The results show that in The Netherlands good crop and soil management impedes survival of inoculum from one year to the next, so that cabbage can be grown continuously. Polyetic carry-over of inoculum by debris in the soil can be avoided in The Netherlands.  相似文献   

13.
Crop rotation is the oldest, and perhaps the best cultural practice for reducing the risk of take-all. The effects of crops sown before wheat in a rotation are known in detail, but we know little about the opportunities for reducing take-all risk by planting certain crops in the summer period between wheat harvest and the planting of a subsequent winter wheat crop. We investigated the effects on take-all of five summer fallow crops, two soil tillage treatments and a fungicide seed treatment, in a five site-year experiment. We tested the effects of oats, oilseed rape, mustard, ryegrass and volunteer wheat crops. Bare-soil plots were also included. Take-all epidemics varied with year and site. Summer fallow crops had a greater effect on tilled plots. The incidence and severity of take-all were significantly higher in the wheat volunteer plots, whereas maintaining bare soil provided the lowest level of disease. Oilseed rape had no significant effect on take-all incidence in our experiment. The best candidates for reducing take-all risk appeared to be oats, mustard and ryegrass. These summer fallow crops decreased disease levels only when associated with conventional tillage. Summer fallow crops did not alter take-all decline in the same way as a break crop after a wheat monoculture.  相似文献   

14.
J.G. WHITE 《Plant pathology》1983,32(2):151-157
Lettuce seedlings raised in peat blocks placed on contaminated soil subsequently developed lettuce big-vein disease symptoms when grown in pots of sterilized compost. Incorporation of 0.01 g carbendazim per 4.3 cm3 peat block reduced the number of plants with disease symptoms but did not prevent root infection by Olpidium brassicae , the vector of the big-vein agent. Similar results were obtained when seedlings propagated in the absence of big-vein disease were grown in pots of contaminated soil but carbendazim was less effective when the treated blocks were planted in contaminated field plots. Methyl bromide applied at 500, 750 or 1000 kg/ha temporarily controlled the disease but re-contamination occurred and was complete after three consecutive crops.
Bromide residues in lettuce heads reached 9240 μg/g dry tissue in the first crop but fell to a maximum 772 μg/g by the third crop. Bromide residues in soil fell to natural levels over this period.  相似文献   

15.
The soilborne fungus Sclerotinia sclerotiorum infects many important crop plants. Central to the success of this pathogen is the production of sclerotia, which enables survival in soil and constitutes the primary inoculum. This study aimed to determine how crop plant type and S. sclerotiorum isolate impact sclerotial production and germination and hence inoculum potential. Three S. sclerotiorum isolates (L6, L17, L44) were used to inoculate plants of bean, carrot, lettuce, oilseed rape (OSR) and potato, and the number and weight of sclerotia per plant quantified. Carpogenic germination of sclerotia collected from different hosts was also assessed for L6. Production of sclerotia was dependent on both crop plant type and S. sclerotiorum isolate, with OSR and lettuce supporting the greatest number (42–122) and weight (1.6–3.0 g) of sclerotia per plant. The largest sclerotia were produced on OSR (33–66 mg). The three S. sclerotiorum isolates exhibited a consistent pattern of sclerotial production irrespective of crop type; L6 produced large numbers of small sclerotia while L44 produced smaller numbers of large sclerotia, with L17 intermediate between the two. Germination rate and percentage was greatest for larger sclerotia (4.0–6.7 mm) and also varied between host plants. Combining sclerotial production data and typical field crop densities suggested that infected carrot and OSR could produce the greatest number (3944 m?2) and weight (73 g m?2) of S. sclerotiorum sclerotia, respectively, suggesting these crops potentially contribute a greater increase in inoculum. This information, once further validated in field trials, could be used to inform future crop rotation decisions.  相似文献   

16.
The effects of metham-sodium (MES) soil treatment, a varying number of benomyl foliar sprays (two, three and six) and combined treatments on control of lettuce drop disease were studied at two sites in Israel naturally infested with the pathogen Sclerotinia sclerotiorum. MES killed 85% of the S. sclerotiorum sclerotia in the top 10 cm of soil where initial populations were 0.6 and 1.6 viable sclerotia per kg soil at the two sites. Of the remaining viable sclerotia. only 30% produced apothecia. MES treatment alone reduced numbers of apothecia to 5% of those counted in the unsprayed control treatment. Numbers of ascospores deposited on the crop in the MES-treated plots were 7-20% of those deposited on control plots. Lettuce drop decreased the total yield by 30% in unsprayed control plots; MES application reduced the loss to 4% and also increased the number of marketable plants. Benomyl sprays alone also significantly reduced numbers of apothecia and disease development and consequently increased yield, although not to the extent observed with the MES treatment alone. Combined treatments produced the best disease control, but this improvement was not accompanied by any major increase in yield compared to that with MES treatment alone.  相似文献   

17.
Fungi isolated from soils in central Italy by a baiting technique with sclerotia of Sclerotinia sclerotiorum were evaluated for their antagonism in vitro to this fungus using dual cultures and tests with sclerotia. Trichoderma spp., Coniothyrium minitans and species of Fusarium and Penicillium all showed strong antagonistic activity. Morphological alterations were observed in the mycelium of S. sclerotiorum. Trichoderma spp. and Gliocladium catenulatum killed a very high percentage (96–100%) of the sclerotia.  相似文献   

18.
The effect of four solarizing plastic materials on weed suppression and yield response of two lettuce cultivars (‘Bacio’ and ‘Moringa’) grown during two consecutive seasons was investigated at Metaponto (40°23′N; 16°47′E; 10 m a.s.l.), southern Italy. All solarization treatments suppressed winter and summer weeds with no significant difference among the plastic materials, although biodegradable film was less efficient in controlling common purslane and common amaranth. Weed infestation at the harvest of both lettuce cultivars was not affected by the solarizing material, whereas fewer weeds were found in the plots grown with ‘Bacio’ than with ‘Moringa’. Lettuce yield in two successive growing seasons was always significantly higher in solarized plots than in nontreated control, without any statistical difference among the plastic materials. Yield and head quality of cv. ‘Bacio’ were higher than ‘Moringa’ in the first growing season, but the opposite occurred in the second crop. Soil solarization was confirmed to be effective for weed management in field lettuce crops in the Mediterranean areas, although weed suppression may be affected also by the lettuce cultivar. Choice of solarizing materials, when similarly effective on weeds and crop yield, should take into account also their cost. Low density polyethylene plastics emerged as the best choice in conventional lettuce crops as highly effective as, and less expensive than the other materials, whereas the use of biodegradable films should be limited to organic lettuce systems.  相似文献   

19.
A combined baiting, double monoclonal antibody immunoassay was developed that allows specific and sensitive detection of the economically important soil-borne plant pathogen Rhizoctonia solani in naturally infested soils. The assay is quick, taking only three days to complete from receipt of soil samples and the immunoassay format allows recovery of Rhizoctonia isolates from colonized baits for determination of anastomosis group (AG) affiliation and pathogenicity. The assay was tested on naturally infested soils from commercial glasshouses used to grow lettuce. Using the immunoassay, conventional anastomosis tests against known AG isolates, and pathogenicity tests, it was shown that R. solani isolates recovered from soil samples were pathogenic towards lettuce and belonged to AG4. Furthermore, those isolates that exhibited strong pathogenicity towards lettuce were recovered from sites that had experienced severe Rhizoctonia damage in previous lettuce crops. The possibility of developing a preplanting test to predict damage to specific crop plants due to the presence of particular AGs in the soil is discussed.  相似文献   

20.
The effects of post‐harvest curing and storage temperature on severity of black dot, caused by Colletotrichum coccodes, were investigated for potato crops grown for different crop durations (days from 50% emergence to harvest) in soils that posed a low, medium and high risk of disease. In field trials over four growing seasons (2005–8), black dot severity at harvest increased with increasing crop duration, within the range 103–146 days from 50% emergence to harvest (P < 0.05). In field trials over three growing seasons (2006–8), black dot severity on tubers at harvest increased significantly with increasing soil inoculum in each year, within the range 43–4787 pg C. coccodes DNA/g soil (P < 0.05). Storage trials were conducted to measure the influence of accumulated post‐harvest temperature on black dot. In 2005, no difference in black dot severity was observed on tubers stored for 20 weeks at 2.5 and 3.5 °C. In 2006 (but not 2007), increasing the duration of curing after harvest from 4 to 14 days increased black dot severity on tubers from 8.9 to 11.2% (P < 0.01) in long duration crops (>131 days after 50% emergence) grown under high (>1000 pg C. coccodes DNA/g soil) soil inoculum. The number of days of curing did not affect disease severity for shorter duration crops grown at high soil inoculum, or on crops grown at medium or low (100–1000 and <100 pg C. coccodes DNA/g soil, respectively) soil inoculum concentrations. Soil inoculum and crop duration together provided a reasonable prediction of black dot severity at harvest and after a 20‐week storage period.  相似文献   

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