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1.
K.P. Hebbar M.H. Martel T. Heulin 《European journal of plant pathology / European Foundation for Plant Pathology》1998,104(1):29-36
Burkholderia cepacia (syn. Pseudomonas cepacia) strain PHQM100 applied as a seed coating was tested in growth chamber experiments for its ability to suppress preemergence damping-off, and postemergence damping-off in corn induced by Pythium and Fusarium spp. The symptoms observed in bioassays with soils naturally infested with the fungal pathogens were seed rot with Pythium spp. and mesocotyl and root tissue necrosis in the presence of Fusarium spp. Three corn cultivars that differed in their susceptibility to damping-off pathogens were used. Cultivar L was susceptible to pre- and postemergence damping-off, whereas cv. LPDP and cv. LG11 were moderately resistant and resistant to the damping-off diseases respectively. In the presence of Pythium spp., seed treatment with B. cepacia reduced seed rot, as compared to the untreated seeds, and this reduction was more consistent in the cv. LPDP than in the resistant cv. LG11 or the susceptible cv. L. In soils infested with Fusarium spp., seed treatment significantly reduced root and mesocotyl necrosis as compared to the untreated seeds, and this reduction was more consistent in the resistant cultivars LG11 and LPDP than in the susceptible cv. L. Root colonization levels by B. cepacia were similar in the three corn cultivars tested. Biocontrol efficiency of B. cepacia varied among cultivars mainly due to the differences in their susceptibility to the fungal pathogens. In spite of variability and also irrespective of the soil characteristics, B. cepacia increased seedling emergence and decreased mesocotyl and root necrosis when used as a seed coating. 相似文献
2.
从水稻旱育秧病苗上分离到67个菌株 ,经鉴定分属于镰刀菌58个、腐霉菌7个、丝核菌2个。经回接测定其致病性 ,结果表明致病的镰刀菌主要是串珠镰刀菌 (Fusarium moniliforme) ;腐霉菌中主要是盐腐霉 (Pythium salinum)、间生腐霉 (P .interedium)和顶生腐霉 (P .acrogenum) ;丝核菌为立枯丝核菌 (Rhizoctonia solani)。接种试验表明串珠镰刀菌在6～8d龄幼苗的根中部侵染发病率最高 ,腐霉菌和丝核菌在一叶一心期茎基部侵染发病率最高。药剂试验表明以浸种灵(二硫氰基甲烷)、土菌消(hymexazol)、甲霜灵(metalaxyl)等种子处理加土壤处理 ,防效优于单独种子处理或土壤处理。 相似文献
3.
Xue AG 《Phytopathology》2003,93(3):329-335
ABSTRACT Pea root rot complex (PRRC), caused by Alternaria alternata, Aphanomyces euteiches, Fusarium oxysporum f. sp. pisi, F. solani f. sp. pisi, Mycosphaerella pinodes, Pythium spp., Rhizoctonia solani, and Sclerotinia sclerotiorum, is a major yield-limiting factor for field pea production in Canada. A strain of Clonostachys rosea (syn. Gliocladium roseum), ACM941 (ATCC 74447), was identified as a mycoparasite against these pathogens. When grown near the pathogen, ACM941 often was stimulated to produce lateral branches that grew directly toward the pathogen mycelium, typically entwining around the pathogen mycelium. When applied to the seed, ACM941 propagated in the rhizosphere and colonized the seed coat, hypocotyl, and roots as the plant developed and grew. ACM941 significantly reduced the recovery of all fungal pathogens from infected seed, increased in vitro seed germination by 44% and seedling emergence by 22%, and reduced root rot severity by 76%. The effects were similar to those of thiram fungicide, which increased germination and emergence by 33 and 29%, respectively, and reduced root rot severity by 65%. When soil was inoculated with selected PRRC pathogens in a controlled environment, seed treatment with ACM941 significantly increased emergence by 26, 38, 28, 13, and 21% for F. oxysporum f. sp. pisi, F. solani f. sp. pisi, M. pinodes, R. solani, and S. sclerotiorum, respectively. Under field conditions from 1995 to 1997, ACM941 increased emergence by 17, 23, 22, 13, and 18% and yield by 15, 6, 28, 6, and 19% for the five respective pathogens. The seed treatment effects of ACM941 on these PRRC pathogens were greater or statistically equivalent to those achieved with thiram. Results of this study suggest that ACM941 is an effective bioagent in controlling PRRC and is an alternative to existing chemical products. 相似文献
4.
ABSTRACT The effect of seed meals derived from Brassica juncea, B. napus, or Sinapis alba on suppression of soilborne pathogens inciting replant disease of apple was evaluated in greenhouse trials. Regardless of plant source, seed meal amendment significantly improved apple growth in all orchard soils; however, relative differences in pathogen suppression were observed. All seed meals suppressed root infection by native Rhizoctonia spp. and an introduced isolate of Rhizoctonia solani AG-5, though B. juncea seed meal often generated a lower level of disease control relative to other seed meal types. When introduction of the pathogen was delayed until 4 to 8 weeks post seed meal amendment, disease suppression was associated with proliferation of resident Streptomyces spp. and not qualitative or quantitative attributes of seed meal glucosinolate content. Using the same experimental system, when soils were pasteurized prior to pathogen infestation, control of R. solani was eliminated regardless of seed meal type. In the case of B. juncea seed meal amendment, the mechanism of R. solani suppression varied in a temporal manner, which initially was associated with the generation of allylisothiocyanate and was not affected by soil pasteurization. Among those tested, only B. juncea seed meal did not stimulate orchard soil populations of Pythium spp. and infection of apple roots by these oomycetes. Although application of B. napus seed meal alone consistently induced an increase in Pythium spp. populations, no significant increase in Pythium spp. populations was observed in response to a composite B. juncea and B. napus seed meal amendment. Suppression of soil populations and root infestation by Pratylenchus spp. was dependent upon seed meal type, with only B. juncea providing sustained nematode control. Collectively, these studies suggest that use of a composite B. juncea and B. napus seed meal mixture can provide superior control of the pathogen complex inciting apple replant disease relative to either seed meal used alone. 相似文献
5.
江苏省玉米茎腐病菌种类鉴定 总被引：8，自引：0，他引：8
作者于1992～1995年,从江苏省玉米主产区采集的玉米茎腐病标样中分离获得105个菌株,经鉴定,致病菌种类有肿囊腐霉(Pythium inflatum)、禾生腐霉(P.graminicola)、串珠镰孢浙江变种(Fusarium moniliforme var.zhejiangensis)、串珠镰孢中间变种(F.moniliforme var.intermedium)、串珠镰孢胶孢变种(F.moniliforme var.subglutinans)、禾谷镰孢(F.graminearum)、拟枝孢镰孢厚膜变种(F.sporotrichioides var.chlamydosporum)、尖孢镰孢芬芳变种(F.oxysporum var.redolens)、接骨木镰孢(F.sambucinum)、茄病镰孢(F.solani)、半裸镰孢(F.semitectum)等11个种或变种。其中串珠镰孢浙江变种出现频率最高,占44.8％,肿囊腐霉和禾生腐霉致病力最强,这两类菌是江苏玉米茎腐病主要病原。 相似文献
6.
播前施用氟乐灵对棉花苗期病害及蕾期枯萎病的影响 总被引：2，自引：0，他引：2
田间试验在棉花苗病和枯萎病常年发病田进行。以１７５ｍｌ４８％氟乐灵乳油／６６６．７ｍ＾２的剂量处理苗床地表土，播种棉籽后以含氟乐灵（１．０－１．５ｍｇ有效成分／ｋｇ土）的土壤覆盖。以清水处理为对照，。结果表明Ｌ氟乐灵处理组的出苗率高于对照，苗前残废对比照降低，５２．９１％－７９．８０％。处理组苗床期立枯病和侄蛱贩发病率及死苗率显著降低，分别下降３０％和４２％左右；棉苗枯萎病的发病率及病情指明显低于 相似文献
7.
ABSTRACT Late blight (Phytophthora infestans), pink rot (Phytophthora erythroseptica), leak (Pythium ultimum), dry rot (Fusarium sambucinum), and soft rot (Erwinia carotovora subsp. carotovora and subsp. atroseptica) are particularly damaging diseases of stored potato tubers worldwide. In this study, we present a methodology to detect and quantify the causal agents of the five aforementioned diseases from whole potato tubers, using real-time quantitative-polymerase chain reaction. Six primer pairs were designed to amplify targets smaller than 150-bp DNA in single copy protein-coding gene targets of each of the pathogens and the potato host. Using a large collection of pure culture DNA samples, all primer pairs specifically detected the DNA target in the intended pathogenic species. Amplification efficiencies over a five-log dilution series ranged between 95 and 100% and were unaffected by the presence of large amounts of host DNA. The detection level of the primers reached 0.5 pg of target DNA. Pathogens were detected in 100 pg of total DNA extracted from 170 to 250 g of tubers, 4 days after inoculation, regardless of the presence of symptoms. The presence of P. erythroseptica, Pythium ultimum, or E. carotovora was also detected in 1 ng of DNA extracted from potato tubers collected from a commercial storage facility. This study provides the first step in a methodology to predict the storability of potato tubers following harvest. 相似文献
8.
ABSTRACT Specific and sensitive quantitative diagnostics, based on real-time (TaqMan) polymerase chain reaction (PCR) and PCR enzyme-linked immunosorbent assay, were developed to detect dry-rot-causing Fusarium spp. (F. avenaceum, F. coeruleum, F. culmorum, and F. sulphureum). Each assay detected Fusarium spp. on potato seed stocks with equal efficiency. Four potato stocks, sampled over two seed generations from Scottish stores, were contaminated with F. avenaceum, F. sulphureum, F. culmorum, F. coeruleum or a combination of species, and there was a general trend towards increased Fusarium spp. contamination in the second generation of seed sampled. F. sulphureum and F. coeruleum caused significantly (P < 0.05) more disease in storage than the other species when disease-free tubers of potato cvs. Spunta and Morene were inoculated at a range of inoculum concentrations (0, 10(4), 10(5), and 10(6) conidia/ml). Increased DNA levels were correlated with increased disease severity between 8 and 12 weeks of storage. The threshold inoculum levels resulting in significant disease development on both cultivars were estimated to be 10(4) conidia/ml for F. sulphureum and 10(5) conidia/ml for F. coeruleum. To study the effect of soil infestation and harvest date on disease incidence, seed tubers of cvs. Morene and Spunta were planted in a field plot artificially infested with the four Fusarium spp. F. culmorum and F. sulphureum were detected in soil taken from these plots at harvest, and F. sulphureum DNA levels increased significantly (P < 0.05) at the final harvest. All four Fusarium spp. were detected in progeny tubers. There was a trend toward higher levels of F. culmorum detected in progeny tubers at the earliest harvest date, and higher levels of F. sulphureum at the final harvest. The use of diagnostic assays to detect fungal storage rot pathogens and implications for disease control strategies are discussed. 相似文献
9.
ABSTRACT Strain L324-92 is a novel Bacillus sp. with biological activity against three root diseases of wheat, namely take-all caused by Gaeumannomyces graminis var. tritici, Rhizoctonia root rot caused by Rhizoctonia solani AG8, and Pythium root rot caused mainly by Pythium irregulare and P. ultimum, that exhibits broad-spectrum inhibitory activity and grows at temperatures from 4 to 40 degrees C. These three root diseases are major yieldlimiting factors for wheat in the U.S. Inland Pacific Northwest, especially wheat direct-drilled into the residue of a previous cereal crop. Strain L324-92 was selected from among approximately 2,000 rhizosphere/rhizoplane isolates of Bacillus species isolated from roots of wheat collected from two eastern Washington wheat fields that had long histories of wheat. Roots were washed, heat-treated (80 degrees C for 30 min), macerated, and dilution-plated on (1)/(10)-strength tryptic soy agar. Strain L324-92 inhibited all isolates of G. graminis var. tritici, Rhizoctonia species and anastomosis groups, and Pythium species tested on agar at 15 degrees C; provided significant suppression of all three root diseases at 15 degrees C in growth chamber assays; controlled either Rhizoctonia root rot, takeall, or both; and increased yields in field tests in which one or more of the three root diseases of wheats were yield-limiting factors. The ability of L324-92 to grow at 4 degrees C probably contributes to its biocontrol activity on direct-drilled winter and spring wheat because, under Inland Northwest conditions, leaving harvest residues of the previous crop on the soil surface keeps soils cooler compared with tilled soils. These results suggest that Bacillus species with desired traits for biological control of wheat root diseases are present within the community of wheat rhizosphere microorganisms and can be recovered by protocols developed earlier for isolation of fluorescent Pseudomonas species effective against take-all. 相似文献
10.
木霉对土传病原真菌的拮抗作用 总被引：100，自引：2，他引：100
分别在体外及温室测定了筛选菌株哈茨木霉Trichoderma harzianum(T82)和Tricho-derma sp.(NF9)对土传病原真菌的拮抗作用。体外测定表明,木霉菌株T82和NF9对白绢病菌Sclerotium rolfsii,立枯丝核菌Rhizoctonia solani,瓜果腐霉Pythium aphanidermatum刺腐霉P.spinosum和尖镰孢Fusarium oxysporum在对崎培养中的拮抗系数分别为2或2~3和2。温室测定表明,用0、6%(W/W)T82麸皮培养物(107cfu/g)处理土壤。在人工接种白绢病菌,立枯丝核菌及瓜果腐霉20天后,黄瓜发病率分别比未用木霉处理的对照减少46、5%,28.4%和81。2%;用T82和NF9木霉孢子悬浮液(108cfu/ml)处理黄瓜种子,人工接种白绢病菌11天后,黄瓜成苗率分别比未用木霉处理的对照增加14%的20%。分别在光学显微镜和扫描电镜下观察到木霉T82对白绢病菌菌丝和菌核的重寄生以及木霉T82和NF9对立枯丝核菌菌丝的缠绕。穿入及寄生。作者认为重寄生可能是试验木霉菌株T82和NF9对白绢病菌和立枯丝核菌的主要拮抗机制。 相似文献
11.
由Dickeya spp.引起的细菌性软腐病在多种作物和花卉上常造成严重的经济损失,尤其近年来由D.zeae引起的水稻细菌性基腐病和香蕉软腐病,以及由D.solani引起的马铃薯软腐病均造成重大的农业失收,这些问题促进了对该属细菌致病机理的重视和深入研究。同时,Dickeya属细菌基因组序列的发表将进一步加速对这些重要病原微生物的研究。本文旨在对Dickeya属细菌的寄主范围、主要致病因子及其调控系统的研究进展作详细的梳理分析,以明确这一重要领域的研究现状并为从分子水平上阐明Dickeya属病原细菌的致病机理和寄主专化性提供依据。 相似文献
12.
The effectiveness of various methods for detecting three fungal potato pathogens was compared with artificially infested soil, naturally infested tuber-borne soil and field soil. In the spring of 1985 and 1986 field soils from 30 farms in north-east Scotland were sampled just before planting a seed potato crop and 6 months after harvesting such a crop. The minimum statutory gap between crops is 5 years. Polyscytalum pustulans was recovered from 32 out of 60 field soil samples taken 6 months after harvest while from fields sampled in the spring before a potato crop was planted the fungus was isolated from 10 out of 30 soils in 1985 and five out of 30 in 1986. Phoma foveata was isolated from only one out of 60 pre-planting soil samples but Fusarium solani var. coeruleum was recovered from eight of these soils.
Microplant bait plants were grown over 3 years at an experimental farm near Edinburgh in various fields at different intervals after a previous potato crop. Contamination by P . pustulans was not related to interval after potatoes between 1 - 7 years. No contamination was recorded in fields where potatoes had not been grown for more than 30 years. 相似文献
Microplant bait plants were grown over 3 years at an experimental farm near Edinburgh in various fields at different intervals after a previous potato crop. Contamination by P . pustulans was not related to interval after potatoes between 1 - 7 years. No contamination was recorded in fields where potatoes had not been grown for more than 30 years. 相似文献
13.
ABSTRACT Suppression of seedling damping-off disease caused by Pythium spp. and Rhizoctonia solani is a potential benefit of formulating soilless container media with compost. Thirty-six compost samples from Pacific Northwest commercial composting facilities were analyzed for a number of physical, chemical, and biological properties, including suppression of damping-off caused by Pythium ultimum, P. irregulare, and R. solani. The samples were produced from diverse feedstocks and composting technol ogies; this was reflected in a large degree of variability in the measured properties. When mixed with sphagnum peat moss and inorganic aggregates, 67% of the compost samples significantly suppressed P. irregulare damping-off of cucumber, 64% suppressed P. ultimum damping-off of cucumber, and 17% suppressed damping-off of cabbage caused by R. solani. Suppression of Pythium damping-off was related to the potential of compost to support microbial activity and a qualitative index of ammonia volatilization. Suppression of Rhizoctonia damping-off was not related to any one compost factor. Currently available compost products potentially could provide commercially acceptable control of damping-off caused by Pythium spp., but it is necessary to fortify composts with microbial antagonists for the control of R. solani. 相似文献
14.
灰黄青霉CF3对马铃薯土传病原真菌的拮抗性及其促生作用 总被引：2，自引：0，他引：2
为探索灰黄青霉Penicillium griseofulvum CF3对马铃薯土传病害病原真菌立枯丝核菌Rhizoctonia solani、茄病镰刀菌Fusariumsolani、硫色镰刀菌F.sulphureum及大丽轮枝菌Verticillium dahliae的拮抗性及对马铃薯的促生作用,采用菌丝生长速率法和甜瓜种子发芽法分别研究了CF3发酵液对病原菌菌丝的抑制作用、对立枯丝核菌微菌核形成的影响及其发酵液的促生作用,并采用盆栽试验法研究了CF3孢子粉对马铃薯植株的促生作用及对抗逆性的影响.CF3发酵滤液对4株病原真菌菌丝生长的抑菌率达53％～72.1％,对立枯丝核菌微菌核的抑制率达36.8％～100％,并显著促进甜瓜种子胚根、胚轴生长.灰黄青霉孢子粉拌土和包衣接种均能促进马铃薯植株生长并增强植株的抗逆性.其中,拌土接种使马铃薯地上植株鲜重和多酚氧化酶活性较对照分别增加38.3％和9％,丙二醛含量降低28.8％.研究表明灰黄青霉CF3对连作马铃薯常见土传真菌病害有较强的生防潜力,对马铃薯具有良好的促生作用. 相似文献
15.
Control of damping-off in cress and sugar-beet by commercial seed-coating with Pythium oligandrum 总被引：2，自引：1，他引：2
Seeds of cress and sugar-beet were coated with oospores of Pythium oligandrum using commercial seed-pelleting or film-coating procedures. Following either procedure approximately 104 oospores were recovered from both seed types, achieving 75.94% of the targeted dose. Oospore germination (9.19%) was unaffected by the coating treatments. Both types of treatment reduced damping-off of cress caused by P. ultimum in artificially infested sand and potting compost and by Rhizoctonia solani in artificially infested sand. In some cases, the level of control was equivalent to fungicide drenches. In general, pelleting of P. oligandrum on cress gave better control than film-coating treatments. P. oligandrum also reduced damping-off of sugar-beet in soil naturally infested with Aphanomyces cochlioides and Pythium spp. Control was equivalent to that achieved with hymexazol fungicide seed-coating treatments and was related to the inoculum potential of A. cochlioides in the soil; neither standard hymexazol coatings nor P. oligandrum treatments gave control at high inoculum potentials. P. oligandrum was not rhizosphere competent on cress or sugar-beet. 相似文献
16.
Howell CR 《Phytopathology》2007,97(1):66-71
ABSTRACT Good quality seeds of cotton cultivars often escaped pre-emergence damping-off incited by Pythium spp. and Rhizopus oryzae, and they were resistant to postemergence damping-off incited by Rhizoctonia solani. Poor quality seeds, however, were highly susceptible to both phases of seedling disease and required seed treatment in order to survive. Pre-emergence damping-off incited by Pythium spp. and Rhizopus oryzae could be controlled by seed treatment with biocontrol preparations of a number of Trichoderma spp., but these treatments were much less effective in controlling postemergence disease incited by Rhizoctonia solani. Postemergence seedling disease can be controlled by fungicides, but they were much less effective in controlling the pre-emergence phase of the disease. Combination seed treatments of poor quality cotton seeds with fungicides and Trichoderma spp. preparations, followed by planting in pathogen-infested soil, indicated that this technique will control both phases of seedling disease. Seed treatment with either the fungicides or the biocontrol agents alone did not achieve this goal. The optimum combination treatment for disease control was that of chloroneb plus Trichoderma spp., followed by chloroneb plus metalaxyl (Deltacoat AD) plus T. virens strain G-6. 相似文献
17.
ABSTRACT Soil receptivity as a quantifiable characteristic ranging from conduciveness to suppressiveness to soilborne pea pathogens Thielaviopsis basicola and Aphanomyces euteiches was determined by analysis of differences in disease response curves obtained by artificial introduction of inoculum into natural field soil samples. Several parameters, including maximum root rot severity, the area under the health index curve, scores on the first axis of a principal component analysis (PCA) on dose responses, and Weibull model fitting were used to describe the disease responses. In all cases, the Weibull model gave satisfactory fits. PCA yielded a first axis that comprised 86% of the variance found when using Weibull predicted responses for T. basicola and 74% of the variance found for A. euteiches. This PCA axis essentially represented the average increase in disease severity due to the addition of increasing doses of inoculum to the soil. The Weibull scale parameter B, which represents the amount of inoculum necessary to increase root rot severity by 63% with respect to the level caused by pathogens naturally present in the soil, is another means of quantifying the receptivity of soils to these plant pathogens. Weibull parameter B, maximum root rot severity, the areaunder the health index curve, and the scores on the first PCA axis were strongly correlated for each of the pathogens tested individually. To compare the extent and behavior of soil receptivity responses to different pathogens, Weibull parameters B and C (slope at dose B) were chosen because of their universal definition, in contrast to PCA scores. Comparison of the average levels of Weibull parameters B and C indicated significant differences between the pathogens. Yet, no significant similarity in the ranking of the soils was found for the three pathogens, demonstrating that individual soils may interact with different pathogens in totally different ways. In general, soils were suppressive to T. basicola but conducive to A. euteiches, whereas their response to Fusarium solani f. sp. pisi ranged from conducive to suppressive. Therefore, risk assessment of soils prior to planting may require different strategies for each pathogen. Bioassays with soil samples taken before the last pea crop in 1987 and 1991 revealed a significant increase in the natural inoculum potential of soils that mainly was accounted for by A. euteiches and Pythium spp. These results strongly indicate that A. euteiches must be considered one of the most threatening pathogens to pea crops in the Netherlands. 相似文献
18.
A. Mulder L. J. Turkensteen A. Bouman 《European journal of plant pathology / European Foundation for Plant Pathology》1992,98(2):103-114
An overview is given on the history of vine killing meant to reduce virus transmission to potato seed tubers. With mechanical harvesting, problems arise with respect to skin damage and pathogens, which strongly develop on the decaying vines and roots, such asRhizoctonia solani, Phoma exigua var.foveata andErwinia spp. Green-crop-harvesting (GCH), a recently developed fully mechanical vine killing method, is marked by vine destruction, lifting tubers, placing them on a soil bed followed by covering them with soil and an in situ healing period of at least ten days in the newly formed ridges.GCH is characterized by a very low level of skin damage, excellent healing conditions and reduced development of above mentioned pathogens.By applying fungicides or antagonistic organisms with the first lifting, effective control was achieved of a number of important potato diseases. Late blight was controlled by fungicides. Control of black scurf and gangrene was improved by the application of either fungicides or antagonists. Erwinia spp. were found to be effectively controlled by antagonists. Perspectives of GCH to control these diseases and other important ones are discussed. 相似文献
19.
M. J. CELETTI H. W. JOHNSTON J. KIMPINSKI H. W. PLATT R. A. MARTIN 《Plant pathology》1990,39(4):606-611
Barley and winter wheat were sampled over 3 years to characterize soil-borne organisms involved with cereal crown and root disease complexes. Winter wheat crowns were infected more often by Fusarium avenaceum and F. sambucinum than barley crowns. Bipolaris sorokiniana and F. graminearum were more common in crown tissue of barley underseeded with clover than in winter wheat crowns. In roots, the incidence of F. avenaceum was highest in winter wheat. In soil, populations of Rhizoctonia solani and F. sambucinum were higher in winter wheat than barley underseeded with ryegrass. Stunt nematodes (Tylenchorhynchus spp.) were greatest in winter wheat and barley underseeded with ryegrass. The incidence of F. avenaceum in roots of winter wheat correlated positively with the severity of crown and root rot symptoms. The severity of barley crown and root rot correlated positively with the incidence of R. solani in crowns, F. avenaceum in crowns and roots, B. sorokiniana in roots, and numbers of stunt nematodes in the soil. The incidence of soil-borne organisms was also recorded in annual ryegrass. soybean, potato, pea, and clover which were grown in rotation with barley and winter wheat. The incidence of R. solani and F. avenaceum was highest in clover crown tissue, and F. sambucinum was prevalent in soybean hypocotyls. Soil population levels of R. solani, F. avenaceum , and stunt nematodes were greatest in ryegrass and pea soil just prior to ploughing down or harvesting these crops, respectively. 相似文献
20.
Potato seed tubers are imported to Israel from northern Europe and planted in spring; tubers harvested early from the spring
crop are used as seed for the autumn crop. Although only seed lots registered as certified are imported, a previous survey
(1984–1994) indicated that most imported lots were affected by latent or active infections caused byErwinia carotovora,Streptomyces scabies, Rhizoctonia solani, Fusarium spp. andSpongospora subterranae. The survey was extended until 1998, and included additional pathogens:Ralstonia solanacearum,Helminthosporium solani, Colletotrichum coccodes andVerticillium dahliae. Most of these pathogens were also monitored in domestic seed tubers, and are reported for the first time. Brown rot was not
observed in any of the imported lots. Blackleg and soft rot caused byErwinia spp. were detected in most of the imported lots; however, less than 7% of the lots were contaminated at high levels, while
approximately 65% were contaminated at moderate levels. Common scab was detected in most of the imported lots; 51% of the
imported lots were contaminated at moderate or high levels, whereas only 6.5% of the domestic seed lots were contaminated
at these levels. Black scurf was detected in most of the imported lots; on average, 47.3%, 44.2% and 1.4% of the lots were
contaminated at low, moderate and high levels, respectively, and only 7.1% were disease-free. In contrast, most of the domestic
lots were either disease-free (45.4%) or had a low disease incidence (37.3%). Only 16.7% of the lots were moderately infected
and 0.2% were highly contaminated. Silver scurf was observed in most of the imported lots during all years of the survey,
with no differences among the producing countries; on average, 22.7%, 66.1% and 7.5% of the lots were contaminated at low,
moderate and high levels, respectively, and only 3.7% were disease-free. Most of the domestic lots (76%) were disease-free
and only 6.6% were infected at moderate or high levels. Black dot was observed in a considerable portion of the shipments
from Holland during all years of the survey, particularly in 1998, when 34% of the lots were infected. The shipments from
France and Germany were infected at low levels, except in 1998, when 19% and 11% of the lots, respectively, arrived infected.
In shipments from Scotland and Ireland low incidences of the disease were observed in 1994 and 1995. In the domestic lots,
black dot incidence was low (<2.4%) except in 1996, when 11% of the lots were infected.V. dahliae was monitored only in domestic seed tubers. The incidence of disease-free lots was 56–64%, whereas in 20–30% of the lots
the level of infection was <5%, and in 6–16% of the lots the level was >5%. The survey findings demonstrate transmission of
seedborne pathogens; most of these pathogens can become established in the soil and eventually cause severe outbreaks of disease
in potatoes grown in Israel.
http://www.phytoparasitica.org posting May 16, 1999. 相似文献