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1.
Phytophthora fruit rot of watermelon, caused by Phytophthora capsici, is an important and emerging disease in Southeastern U.S.A. The effects of two cultural practices (raised bare ground and raised plastic mulched beds) used for growing watermelon and different fungicide treatments on development of Phytophthora fruit rot were evaluated. The experiments were conducted over three years (2005-2008) at research stations in North Carolina and South Carolina, U.S.A. Fungicides were applied at weekly intervals on the diploid cv. Mickey Lee for an average of five applications. Fruit rot incidence was recorded at the end of each experiment. Fruit rot incidence in the non-treated plots was 66% across two states and six trials. Overall, the levels of fruit rot on the raised bare ground and raised plastic mulched beds were not significantly different. Based on percent disease reduction relative to the non-treated check plots, the fungicide Captan was the most effective across years and locations (range = 23-70%, mean = 57%), followed by mandipropamid (25-65%, mean = 50%), fluopicolide (24-65%, mean = 43%) and cyazofamid (0-48%, mean = 31%). Mefenoxam, the current standard treatment reduced fruit rot by 8-28% (mean = 18%). The addition of copper hydroxide to the spray mix did not significantly enhance effectiveness of Captan or mandipropamid. The variability in fungicide efficacy observed in these experiments across locations and years demonstrates the importance of environmental conditions in disease development and management. Even when the most effective fungicides are used, heavy losses may occur when conditions are highly favorable for disease development. Ultimately, effective control of Phytophthora fruit rot of watermelon will require an integrated management strategy that includes well-drained fields, water management and crop rotation in addition to fungicides.  相似文献   

2.
In 2010 and 2011 an initial set of trials were carried out in order to evaluate the susceptibility of rootstocks used for grafting bell pepper (Capsicum annuum L.) in Italy to Phytophthora capsici, in comparison with widely used cultivars of pepper. In a second set of trials carried out in 2011 and 2012, grafting bell pepper onto resistant or partially resistant rootstock was combined with the use of compost-amended soil, to control Phytophthora blight. Trials were carried out in artificially or naturally infested soil, using five bell pepper cultivars (Fenice, Sienor, San Marco, Fiume, Cuneo) as susceptible not-grafted controls. In three trials, carried out in the presence of soil artificially infested with P. capsici, disease incidence in control plots ranged from 73 to 100% for the cvs. Cuneo and Fiume. Both cvs. Cuneo and Kaiman grafted on “Tecnico F1” rootstock provided complete control of P. capsici. A lower disease control, on the same cultivar, was provided by “Robusto” and “Capsifort”. On the cv. Fiume, “Terrano” provided complete control of the disease. By grafting all cultivars on “Robusto”, “Brutus”, “Snooker” and “Capsifort” a disease reduction by 68%–93%, 86%–100%, 67%–100% and 55%–78%, respectively, was provided. The general linear model analysis showed that for trials carried out under natural infestation the addition of compost to the soil, as well as the interaction of compost-amended soil with grafting, were significant factors influencing disease incidence reduction. The effect of grafting was a significant factor in reducing the percentage of diseased plants in all the trials. The addition of compost to the soil resulted in an effective and low-cost disease management solution, particularly when combined with susceptible not-grafted hybrids of bell pepper or when partially resistant rootstocks were used.  相似文献   

3.
The efficacy of a new fungicide fluopicolide in suppression of Phytophthora blight caused by Phytophthora capsici was evaluated under laboratory and field conditions. Studies with 51 P. capsici isolates from vegetable crops in Georgia, USA, indicated that 5.9% of the isolates were resistant, 19.6% were intermediately sensitive, and 74.5% were sensitive to 100 μg ml−1 of mefenoxam based on in vitro mycelial growth. EC50 values of fluopicolide in inhibiting mycelial growth of 25 isolates, representing resistant, intermediately sensitive, and sensitive to mefenoxam, ranged from 0.05 to 0.35 μg ml−1 with an average of 0.2 μg ml−1 EC50 values of fluopicolide in suppressing zoospore germination and sporangium production of the 25 isolates ranged from 1.1 to 4.5 μg ml−1 and 0.3–9.0 μg ml−1, respectively. Evaluation of a collection of 150 P. capsici isolates from vegetables and irrigation ponds found none of the isolates were resistant to 10 μg ml−1 of fluopicolide. Field experiments were conducted to determine the efficacy and application methods of fluopicolide for control of P. capsici on squash in spring 2007 and 2009. Fluopicolide applied through drip irrigation or as a foliar spray at 86.6 or 115.4 g ha−1 consistently provided significant disease reduction and increased squash yield. Results with fluopicolide were similar or slightly superior to mefenoxam applied at recommended rate. Fluopicolide applied at 57.7 g ha−1 did not provide consistent satisfactory disease suppression. The results indicated that fluopicolide was effective in suppression of different stages of the life cycle of P. capsici and could be a viable alternative to mefenoxam for managing Phytophthora blight in squash production.  相似文献   

4.
西瓜嫁接苗的植物保护酶同工酶与亲和力分析   总被引：6，自引：0，他引：6  
采用6种不同瓜类的砧木分别与西瓜(Citrulluslanatusvar.)西农8号进行嫁接,研究其对接穗过氧化物(POD)和超氧物歧化酶(SOD)同工酶及其接穗生长的影响。结果表明:接穗断根前西瓜实生苗与接穗苗同工酶的带型及其活性强度差异较小;断根后西瓜实生苗与不同砧木的嫁接苗生长及其叶片POD和SOD同工酶相似性变化较大。同工酶相似系数与嫁接苗的长势存在正相关,其中冬瓜、瓠子和葫芦砧木上接穗与实生苗的POD和SOD同工酶相似性最高,与西瓜的嫁接亲和性最强;丝瓜砧木上的接穗与实生苗的叶片POD和SOD同工酶相似性最低,与西瓜的嫁接亲和性最弱。  相似文献   

5.
Damping-off and vine decline diseases affect most greenhouse cucumber crops in Oman, with losses frequently exceeding 25% of seedlings and adult plants. As a consequence of some recent reports that disease control using metalaxyl fungicides were ineffective, seven local and introduced rootstocks were assessed for their response to Pythium aphanidermatum. The rootstocks were also tested for grafting compatibility and production potential under greenhouse conditions. During artificial inoculation trials, no damping-off symptoms were observed in the Hercules and Titan varieties, ridge gourd or sponge gourd. In three separate greenhouse trials, Titan, Hercules and squash var. Magda showed no damping-off or vine decline symptoms up to 45 days after transplanting. When cucumber was grafted onto the seven rootstocks, no symptoms were observed in the cucumber plants grafted onto Titan and Hercules rootstocks, whereas the cucumber grafted onto the other rootstocks showed varying levels of damping-off and vine decline diseases (10–40%). The Titan and Hercules rootstocks significantly increased the vegetative growth and the fruit number, weight and length compared to the self-grafted cucumbers, non-grafted cucumbers and cucumbers that were grafted onto the other rootstocks (P < 0.05). To the best of our knowledge, this study is the first to examine the influence of grafting on the resistance to Pythium and on the vegetative growth and yield of greenhouse cucumbers.  相似文献   

6.
Phytophthora cinnamomi is a major pathogen of cultivated macadamia (Macadamia integrifolia, Macadamia tetraphylla and their hybrids) worldwide. The susceptibility of the two non-edible Macadamia species (Macadamia ternifolia and Macadamia jansenii) to P. cinnamomi is not well-understood. Commercial macadamia trees are established on grafted seedling (seed propagation) or own-rooted cutting (vegetative propagation) rootstocks of hybrids of the cultivated species. There is little information to support the preferential use of rootstock propagated by either seedling or own-rooted cutting methods in macadamia. In this study we assessed roots of macadamia plants of the four species and their hybrids, derived from the two methods of propagation, for their susceptibility to P. cinnamomi infection. The roots of inoculated plant from which P. cinnamomi was recovered showed blackening symptoms. The non-cultivated species, M. ternifolia and M. jansenii and their hybrids were the most susceptible germplasm compared with M. tetraphylla and M. integrifolia. Of these two species, M. tetraphylla was less susceptible than M. integrifolia. Significant differences were observed among the accessions of their hybrids. A strong association (R2 > 0.75) was recorded between symptomatic roots and disease severity. Root density reduced with increasing disease severity rating in both own-rooted cuttings (R2 = 0.65) and germinated seedlings (R2 = 0.55). P. cinnamomi severity data were not significantly (P > 0.05) different between the two methods of plant propagation. The significance of this study to macadamia breeding and selection of disease resistant rootstocks is discussed.  相似文献   

7.
Macrophomina phaseolina is the causal agent of charcoal rot disease, which attacks many plant species, including those in the Cucurbitaceae. The fungus is frequently isolated from wilted melon and watermelon plants in Israel. Nevertheless, the role of M. phaseolina in disease progress and induction of wilting or yield reduction in watermelons and melons is not clear and not similar. Precise disease identification is important in order to suggest effective control measures. The objective of the current study was therefore to investigate disease progress and document its damage in watermelon and melon. Watermelons and melons were seeded in a field naturally infested with M. phaseolina and in the greenhouse in 10-L pots containing dune sand. Plants were inoculated at 35 days of age using two methods: drenching with macerated fungus around the crown area or stabbing the lower stem with an M. phaseolina-infested toothpick. Disease progress was documented in the field and in the greenhouse. Plant colonization and symptom development were more pronounced in melon than in watermelon. Large lesions and significant internal rotting developed in melon plants inoculated by the two methods in both field and greenhouse. In watermelon, however, no lesions or internal rotting were observed. Disease effect on melons and watermelons was observed only in the field, a short time before harvest, and was expressed as partial wilting and significant loss of shoot and fruit fresh weight similarly to disease appearance under natural infection. No wilting of melons or watermelons was observed in the greenhouse experiment.  相似文献   

8.
In North Carolina (NC), USA, Pythium stem rot on tobacco is caused by Pythium aphanidermatum. During the past 10 years, Pythium stem rot incidence has been reported more frequently in tobacco fields than before. Since 1997, tobacco flue-cured cultivars carrying the Ph gene that confers immunity to race 0 of Phytophthora parasitica var. nicotianae (Ppn) have also been deployed in NC. It has been questioned whether the introduction of cultivars carrying this resistance gene contributes to the increased incidence of Pythium stem rot. We used a strain of P. aphanidermatum expressing the β-glucuronidase (GUS) reporter gene to investigate the susceptibility of stem and root tissues of four flue-cured tobacco cultivars to Pythium stem rot. Cultivars NC71 (carries the Ph gene) and RJR15 (no Ph gene, but highly resistant to Ppn) were less susceptible (P < 0.05) to P. aphanidermatum than K326 and K346 cultivars that do not carry the Ph gene. Furthermore, different parts of the plant demonstrated significant differences (P < 0.0001) to P. aphanidermatum infection although the significance depended on the cultivar. That is, in K326 and NC71 the highest percent infection was in the adventitious roots, followed by the stems and lastly the true roots, whereas in K346 and RJR15 the highest percent infection was in the adventitious roots, then the true roots and last in the stems. These results do not support the hypothesis that cultivars carrying the Ph gene may be more susceptible to Pythium stem rot than cultivars without the gene. It is likely that other reasons such as the reduction or absence of mefenoxam application in fields where cultivars carrying the Ph gene are planted or reduction in competition for infection cites with Ppn have contributed to the increase of Pythium stem rot incidence in tobacco fields in NC.  相似文献   

9.
茎基腐病是我国小麦生产上一种新的土传病害,近年在黄淮麦区发生日益加重,成为影响小麦安全生产的新问题。为给该病的防治和抗病育种工作提供依据,本研究以国内新发现的小麦茎基腐病优势病原菌假禾谷镰刀菌(Fusarium pseudograminearum)Wz2-8A菌株为接种物,分别以国外抗病材料SUNCO和国内高度感病品种国麦301为抗性对照和感病对照,对黄淮麦区主推小麦品种进行了苗期盆栽接种和田间成株期接种抗性鉴定,并采用病情指数法进行了抗性评价。结果表明,供试品种在室内苗期及田间成株期均无免疫品种和高抗品种,其中室内苗期接种所有品种均表现感病或高度感病;田间病圃成株期抗性鉴定发现兰考198、许科718等10个黄淮麦区主推小麦品种表现为中抗,占供试品种总数的11.36%;焦麦266、郑麦004、郑麦0856等41个品种表现感病,占供试品种总数的46.59%;其余品种表现为高感,平均病情指数最高可达57.97,占供试品种总数的42.05%。本研究发现我国黄淮麦区主推小麦品种对茎基腐病优势病原菌假禾谷镰刀菌抗性整体较差,需要进一步加强抗病资源筛选,创制新的抗病材料,并充分利用中抗材料进行抗病育种。  相似文献   

10.
1,3-dichloropropene (1,3-D, C3H4Cl2) is one of the potential candidates as soil disinfectant since the restriction of methyl bromide (MeBr) in soil fumigation due to its ecological risk. Its nematode, soil-borne pathogen and weed control efficacies were evaluated in a laboratory dose-response study and in two commercial tomato fields. Laboratory studies found that the seeds of Digitaria chinensis Hornem. were the most sensitive to soil fumigation with 1,3-D, followed by Eleusina indica (Linn.) Gaertn., Echinochloa crusgalli (L.) Beauv. and Amaranthus retroflexus L. with the LC90 values between 14.23 and 73.59 mg kg−1 soil. Among the pathogens, Phytophthora capsici Leonian was the most sensitive and Fusarium oxysporum f. sp. fragariae was the least sensitive to 1,3-D fumigation with the LC50 values were 0.24 and 1.55 g m−2. Rhizoctonia solani Kühn., Phytophthora nicotianae var. nicotianae and Botrytis cinerea Persoon exhibited intermediate susceptibility. Field trials revealed that 1,3-D applied to the field at 180, 120 and 80 L ha−1 could suppress Meloidogyne incognita root galling while maintaining high tomato marketable yields, better than Dazomet at the concentration of 400 kg ha−1. Our results indicated that 1,3-D was an excellent nematicide and could provide good to moderate weed and pathogen control. Based on our results, 1,3-D, in combination with other alternatives to MeBr is recommended to reach an integrated pest management.  相似文献   

11.
Paradox (Juglans hindsii × J. regia), the dominant rootstock used in the California walnut industry, is susceptible to crown gall caused by Agrobacterium tumefaciens. In practice, soil fumigation has been a common pre-plant management strategy for crown gall, but even the industry standard, methyl bromide (MeBr), results in inconsistent disease control. To examine MeBr efficacy and identify potential alternatives, combinations of 1,3-dichloropropene (1,3-D), chloropicrin, iodomethane, dazomet, and metam-sodium were examined. Except for 1,3-D alone, all treatments reduced A. tumefaciens and Phytophthora cactorum populations below detection limits. MeBr eliminated A. tumefaciens populations in buried gall tissue, but a combination of 1,3-D and chloropicrin (TC35) did not. An additional 280 kg/ha of chloropicrin in addition to TC35 eliminated A. tumefaciens populations in buried gall tissue. Of the treatments tested, TC35 was the best alternative to MeBr given its efficacy on soil populations of A. tumefaciens and P. cactorum and potential suppressiveness to soil recolonization by A. tumefaciens. MeBr reduced general aerobic bacterial populations below detection limits producing a temporary biological vacuum. A. tumefaciens reintroduced in soils treated with MeBr and TC35 reached significantly higher populations than in non-fumigated soil. However, A. tumefaciens populations in TC35-treated soil were 100-fold lower than MeBr-treated soil 110 d after reintroduction. Increased recolonization rates resulting in higher subsequent soil populations could be a mechanism underlying the observed inconsistent crown gall control after MeBr application.  相似文献   

12.
A greenhouse experiment was performed to study the effectiveness of the application of organic amendments followed by soil plastic mulching for control of Phytophthora capsici in temperate climate regions. The organic amendments were i) a non-composted mixture of sheep manure and chicken litter; ii) a semicomposted mixture of horse manure and chicken litter, and iii) Brassica carinata pellets + Sinapis alba as fresh green manure. In particular, we studied the effect of treatments on P. capsici oospore survival, disease incidence and soil properties. The treatment with B. carinata + S. alba resulted in a 93% reduction in disease incidence. The application of the semicomposted and non-composted mixture followed by soil plastic mulching caused 86 and 65% reduction, respectively, in disease incidence due, at least partially, to a decrease in oospore viability, the production of NH3 and an increase in soil microbial activity. Significantly higher values of dehydrogenase, β-glucosidase, urease and acid and alkaline phosphatase activities were detected in treated soils, possibly resulting in pathogen suppression. The application of organic amendments followed by soil plastic mulching can be a good option for control of P. capsici in protected pepper crops under temperate climate.  相似文献   

13.
The Mainestay potato variety is high-yielding and late-maturing producing attractive, round, white-skinned, white-fleshed tubers with medium-shallow eyes. Its major use is expected to be as a maincrop tablestock variety. Mainestay appearance ratings are similar to those of Katahdin, and greening in Mainestay tubers is less than in Kennebec. Most boil and bake qualities were rated equal to Katahdin in at least half of the tests, and Mainestay usually has a low incidence of internal defects. However, purple streak, heat necrosis, vascular discoloration, and heat sprouts have been seen on occasion. Mainestay tubers do not show the net necrosis caused by potato leafroll virus, and have shown very little hollow heart or blackspot bruising. Mainestay is susceptible to common scab and acid scab, but moderately resistant to verticillium wilt (Verticillium, albo-atrum andV. dahliae), early blight (Alternaria solani), rhizoctonia (Rhizoctonia solani), dry rot (Fusarium sambucinum), and pink rot (Phytophthora erythroseptica). It is moderately susceptible to the common race of late blight (Phytophthora infestans). Mainestay tubers are slow to mature after vine kill, and additional time is required prior to harvest in order to allow for proper periderm development and to reduce storage losses.  相似文献   

14.
Rhizoctonia solani causes economically important root and hypocotyl diseases in common bean throughout the world. Root health is a vital factor in plant development and root diseases would negatively influence water and nutrient uptake as well as cause direct stand reduction and root rot damage to the crop. An efficient common bean screening method to evaluate damping-off and early root/hypocotyl damage from R. solani was developed and used to identify dry bean lines with levels of resistance to this disease. Two sets of 163 and 111 lines previously evaluated for drought tolerance in Nebraska and Puerto Rico were evaluated for damping-off resistance and early root/hypocotyl damage under greenhouse conditions. Disease severity on plants was identified based on above-ground symptoms, seedling survival and root lesions using a rating scale of 1 (resistant) to 9 (susceptible). In the first set of lines representing commonly grown dry bean cultivars, germplasm and sources of damping-off resistance, the Rhizoctonia mean rating ranged from 1.7 to 3.9; Phaseolus vulgaris lines PI 310668 and PI 533249 had the highest damping-off resistance. In the second set of the best lines from a drought tolerance shuttle breeding program the Rhizoctonia mean rating was between 2.6 and 5.7. The availability of drought tolerant dry bean lines allowed the testing of the hypothesis that there was a correlation between selecting for drought tolerance and R. solani damping-off resistance. No correlation between mean disease rating and drought tolerance was found, but adapted dry bean lines such as NE14-08-176 released as SB-DT1, and NE14-08-225 were identified with moderate damping-off resistance and drought tolerance. Lines with both traits and other attributes will facilitate development of resistant bean cultivars to manage damping-off caused by R. solani.  相似文献   

15.
Cuban citriculture has recently been affected by important pests and diseases including black citrus aphid Toxoptera citricida Kirkaldy, citrus leafminer Phyllocnistis citrella Stainton, Asiatic citrus psyllid Diaphorina citri Kuwayama, Citrus tristeza disease, and huanglongbing. This complex of ‘invasive species’ is thought to be contributing to the increasing decline of commercial citrus groves. During several surveys carried out in commercial citrus areas of several provinces in Cuba, symptoms of dieback, characterized by the presence of abundant dry branches and wood rot were detected on Criolla Valencia orange, Marsh grapefruit trees on sour orange, and Cleopatra mandarin rootstocks. Samples of branches and trunk wood were processed and a fungus was isolated from all samples. Morphological, physiological and molecular characterization demonstrated that the isolated agent is Fomitiporia maxonii Murrill. The incidence of affected trees was high in most surveyed groves, reaching 100% in old groves. Symptoms similar to the ones found in naturally infected trees were reproduced on trees inoculated with pure cultures of the fungus, and the fungus was recovered in culture from inoculated trees, thus fulfilling Koch's postulates. This is the first report of an association of F. maxonii with citrus wood rot in Cuba.  相似文献   

16.
Bioconverted eicosapentaenoic acid (bEPA), obtained from Pseudomonas aeruginosa PR3, was assessed for its in vitro and in vivo anti-fungal potential. Mycelial growth inhibition of the tested plant pathogens (Rhizoctonia solani, Botrytis cinerea, Fusarium oxysporum, Fusarium solani, Phyptophthora capsici, Sclerotinia sclerotiorum and Colletotrichum capsici) was measured in vitro. bEPA at the concentration of 5 μl/ml inhibited 52–60% fungal mycelial growth for all of the plant pathogens in vitro except S. sclerotiorum. Minimum inhibitory concentrations (MICs) of bEPA were found in the range of 250–500 μg/ml. Also, bEPA had a detrimental effect on spore germination for all the tested plant pathogens. Three plant pathogenic fungi (F. oxysporum, P. capsici and C. capsici) were subjected to an in vivo anti-fungal screening. bEPA at the initial concentration of 3000 μg/ml had a 100% anti-fungal effect against all of the tested plant pathogens. Concentrations of bEPA corresponding to 1500, 500 and 300 μg/ml were applied to the plants and revealed promising anti-fungal effects, supporting bEPA as a potential anti-fungal agent.  相似文献   

17.
Rhizoctonia solani Kühn is an important pathogen of sugar beet (Beta vulgaris L.) that can cause damping-off and crown and root rot. Commercial cultivars which are highly resistant to the pathogen are not as high yielding as susceptible cultivars under low or absent disease pressure. These resistant cultivars often do not have resistance to other common pathogens such as Aphanomyces cochlioides, Cercospora beticola, and Fusarium oxysporum. Fungicides, such as azoxystrobin which belongs to the quinone outside inhibitors (QoI) class, are necessary for controlling Rhizoctonia solani, but there are concerns about the buildup of fungicide-resistant strains in the targeted pathogen population. There is a need to find effective fungicides from different chemical groups so they can be rotated with the current widely-used azoxystrobin to manage R. solani. The objective of this greenhouse study was to evaluate the efficacy of penthiopyrad, a succinate dehydrogenase inhibitor (SDHI), in managing R. solani on sugar beet using three different application methodologies. Penthiopyrad effectively controlled R. solani on sugar beet when applied at 210, 280, 420, or 550 g a.i./ha in-furrow at planting and as a soil drench at the 4-leaf stage. However, foliar application of penthiopyrad failed to provide disease control. These trials indicated that penthiopyrad needs to be in close proximity or direct contact with R. solani in the soil to provide effective control. Penthiopyrad has the potential to be used as an effective alternate partner with azoxystrobin for controlling R. solani and to help in mitigating the development of fungicide resistant isolates of R. solani.  相似文献   

18.
Soil solarisation together with the application of animal manure has been described as an alternative process for control of Phytophthora capsici root rot in pepper crops. A mixture of fresh sheep manure and dry chicken litter (SCM) and a semi-composted mixture of horse manure and chicken litter (HCM) were applied at 5.1 kg m−2 (dry weight) under plastic sheets to reduce Phytophthora inoculum survival rate and disease incidence. Non-solarised (C) and solarised (S) soils were used as control treatments. Mean NH3 concentration increased in SCM during biodisinfestation process (14.8 mg NH3 m−3) compared with HCM (9.1 mg NH3 m−3), accounted for the higher organic N content and potential N mineralisation. The higher NH3 concentration in SCM could have contributed to reduce the inoculum survival rate (30.6% and 75.0% in SCM and HCM plots, respectively). Inoculum survival rate was not reduced in S (94.4%) as temperature was below 33 °C throughout the experimental period. After biodisinfestation treatment, N2O and CO2 emissions tended to be higher in SCM, despite high spatial variability. Cumulative N2O emissions were 1.31 and 0.42 g N2O-N m−2 in SCM and HCM after 43 days. The larger N application and organic N mineralisation rate on fresh manure amended soils might have contributed to higher N2O emissions during and after soil biodisinfestation by denitrification and nitrification, respectively. Cumulative CO2 emission averaged 211.0 and 159.9 g CO2-C m−2 in SCM and HCM, respectively. The soluble organic C, more abundant in fresh manure, might have favoured soil respiration in SCM. Disease incidence decreased in SCM and HCM plots (disease incidence, 2%-8%) in relation to solarised soils (42%) after 4 months. Microbial suppressiveness might have contributed to minimise Phytophthora disease incidence in SCM and HCM plots. Pepper fruit yield increased with manure amendment in SCM and HCM, which averaged 4.6 and 4.3 kg m−2, respectively. Further research will be necessary to guarantee an effective Phytophthora biodisinfestation by fitting manure N and organic matter applications, improving crop yield and reducing greenhouse gas pollution.  相似文献   

19.
Fusarium basal rot (FBR) caused by Fusarium oxysporum f. sp. cepae (Foc) is one of the most significant production constraint to shallot. Field experiment was conducted in a naturally Foc infested soil at Debre Zeit Agricultural Research Center during 2006 and 2007 cropping seasons to evaluate the level of resistance of sixteen shallot genotypes against FBR disease. Treatments were arranged in randomized complete block design with four replications. The genotypes significantly varied in their susceptibility to FBR and yield. They were grouped into tolerant, moderately and highly susceptible types. Five genotypes (DZ-Sht-168-1A, DZ-Sht-157-1B, Huruta, Negelle and DZ-Sht-169-1b) were identified to be tolerant as they had reduced disease severity levels from 26.8 to 32.5% and increased mean yield by more than 5 t ha−1 compared to highly susceptible genotypes (DZ-Sht-076-4, DZ-Sht-201-1C and DZ-Sht-054-3A). Among the tolerant genotypes, DZ-Sht-169-1b had greatly reduced bulb rot incidence by 48% in ground storage and 30% in wire mesh shelf as compared to highly susceptible genotype DZ-Sht-201-1C. The tolerant genotypes have high yielding characteristic, and farmers could adopt them for cultivation where FBR is a problem.  相似文献   

20.
Sensitivity to benzimidazoles in isolates of the brown rot pathogen (Monilinia laxa) collected from stone fruit in central and northern Greece was evaluated and the molecular basis for resistance was investigated. M. laxa isolates were classified as benzimidazole – sensitive (S) or highly resistant (HR) based on their sensitivity profiles to carbendazim. Thirty seven percent of the isolates belonged to the HR phenotype, carried no apparent fitness penalties and exhibited resistance factor values (based on EC50 values) greater than 500. Highly resistant isolates were also less sensitive to the benzimidazoles benomyl and thiophanate-methyl but more sensitive to the N-phenylcarbamate diethofencarb and the benzamide zoxamide compared to isolates belonging to the S phenotype. Fungitoxicity tests with fungicides belonging to other chemical classes revealed no cross resistance relationships between benzimidazoles and the dicarboximide iprodione, the phenylpyrrole fludioxonil, the hydroxyanilide fenhexamid, the carboxamide boscalid, the triazole tebuconazole and the strobilurin-type fungicide pyraclostrobin, indicating that a target site modification is probably responsible for the resistant phenotypes observed. Comparison of the β-tubulin gene DNA sequences between resistant and sensitive isolates revealed a point mutation resulting from the E198A substitution of the corresponding protein in all HR isolates tested. An Eco31I restriction site in the β-tubulin gene, which was destroyed in HR M. laxa isolates, allowed the development of a PCR-RFLP diagnostic for the detection of the E198A resistance mutation.  相似文献   

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