First record of bacillary rickettsia-like organisms in European tick Dermacentor marginatus (Sulzer).

Bacillary rickettsia-like organisms (BRLO) were found in the tick Dermacentor marginatus. They are gram-negative and differ from common bacteria and reckettsiae both in the cultivation conditions and morphology. BRLO are non-pathogenic for ticks and guinea pigs. In our studies they were isolated on half-engorged females of D. marginatus, on which they are still maintained.     

Bartonella infections in fleas (Siphonaptera: Pulicidae) and lack of bartonellae in ticks (Acari: Ixodidae) from Hungary

Fleas (95 Pulex irritans, 50 Ctenocephalides felis, 45 Ctenocephalides canis) and ixodid ticks (223 ixodes ricinus, 231 Dermacentor reticulatus, 204 Haemaphysalis concinna) were collected in Hungary and tested, in assays based on PCR, for Bartonella infection. Low percentages of P. irritans (4.2%) and C. felis (4.0%) were found to be infected. The groEL sequences of the four isolates from P. irritans were different from all the homologous sequences for bartonellae previously stored in GenBank but closest to those of Bartonella sp. SE-Bart-B (sharing 96% identities). The groEL sequences of the two isolates from C. felis were identical with those of the causative agents of cat scratch disease, Bartonella henselae and Bartonella clarridgeiae, respectively. The pap31 sequences of B. henselae amplified from Hungarian fleas were identical with that of Marseille strain. No Bartonella-specific amplification products were detected in C. canis, I. ricinus, D. reticulatus and H. concinna pools.     

Susceptibility of some species of rodents to rickettsiae.

The present study was designed to test the susceptibility of free-living rodents, viz Apodemus flavicollis, Microtus arvalis, Clethrionomys glareolus, Mus musculus, and outbred white mice from Dobrá Voda farm, CSFR, to Coxiella burnetii, rickettsiae of the spotted fever group (Rickettsia sibirica, R. conorii, R. slovaca and R. akari) and rickettsiae of typhus group (R. typhi and R. prowazekii) by various routes of administration. The highest levels of antibodies to C. burnetii were found in A. flavicollis and M. arvalis inoculated intraperitoneally and intracerebrally. Antibodies to C. burnetii exerted peak levels between days 13 and 16 in contrast to white mice which showed maximum levels on day 28. When 10(0.5) and 10(0.05) EID50/0.25 ml of C. burnetii was administered intraperitoneally to A. flavicollis, M. arvalis and white mice, the agent was detected only in organs of wild animals. In addition to spleen, the bone marrow appeared as a predilective tissue for the detection of this agent. R. akari at a dose of 10(4.5) EID50/0.25 ml caused overt illness and death in rodents. Antibody levels to R. sibirica and R. conorii were dependent on dosage, route of inoculation and duration of infection, but were not dependent on animal species. Antibodies to R. slovaca and R. akari were dependent on dosage, infection duration and animal species but were not dependent on the route of infection. For R. conorii, R. sibirica and R. slovaca a sharp increase of antibody levels with high titres on days 4-6 and peak levels about day 11 post intraperitoneal infection was characteristic. Antibody level to R. akari increased up to day 21. Spotted fever group rickettsiae in rodents inoculated intraperitoneally were observed in various organs, particularly in tunica vaginalis and spleen at days 2-8 post infection. R. typhi at a dose of 10(4.3) EID50/0.25 ml inoculated intracerebrally or intraperitoneally killed white mice and inoculated intraperitoneally killed C. glareolus and M. musculus. The antibody response of white mice to intraperitoneal, subcutaneous or intranasal inoculation of this rickettsia was low and no antibody was detected following peroral administration. M. musculus did not develop antibodies after intracerebral, intranasal, subcutaneous or peroral inoculation of R. typhi. The target organs for this rickettsia were the spleen and tunica vaginalis. R. prowazekii inoculated intraperitoneally into white mice at a dose of 10(6.5) EID50/0.25 ml and at a dose of 10(4.5) EID50 into C. glareolus was fatal for these rodents.(ABSTRACT TRUNCATED AT 400 WORDS)     

Francisella tularensis from ixodid ticks in Czechoslovakia

A total of 26,478 ixodid ticks (935 pools) were examined by intracerebral inoculation of suckling mice. Six species of ticks were tested: Ixodes ricinus (23,470 individuals), I. trianguliceps (12), Haemaphysalis punctata (831), H. concinna (39), Dermacentor reticulatus (69) and D. marginatus (2,057). The ticks were collected largely by flagging vegetation, a substantial minority (4%) from animals. Three strains of Francisella tularensis were isolated, one each from I. ricinus (males, district Breclav, southern Moravia), D. reticulatus (males, district Breclav) and D. marginatus (engorged females collected from sheep in Roznava district, eastern Slovakia). D. marginatus and D. reticulatus represent new vector species for Czechoslovakia.     

Peculiarities of behaviour of taiga (Ixodes persulcatus) and sheep (Ixodes ricinus) ticks (Acarina: Ixodidae) determined by different methods

A comparison of the behavioural peculiarities of Ixodes persulcatus Schulze, 1930 (north-western population, Russia) and Ixodes ricinus (L., 1758) from western Russia and Denmark was determined by using two methods. Method 1 involved a sojourn of ticks on vertical plastic sticks and showed that the questing behaviour of I. ricinus nymphs was dependent on temperature and relative humidity (RH). A significantly greater number of nymphs quested at 22 degrees C and 100% RH than at 18 degrees C. When the humidity was reduced to 30% all of the nymphs departed. In the second method, the activity of ticks on an inclined "ticksdrome" was estimated. The activity of I. ricinus adults from the Danish population was 1.2 times greater than that of ticks from Russia. Females of the species studied and specimens from all study areas were more active than all other stages of development. The locomotor activity of both adult and immature I. ricinus that were infected with Borrelia burgdorferi sensu lato was suppressed when compared with uninfected specimens. The locomotor activity of I. persulcatus females infected by borreliae with exoskeleton anomalies was 1.3 times greater (P<0.05) than that of infected ticks without anomalies. Our data showed that infected females with exoskeleton anomalies could crawl faster on a human and reach uncovered parts of the body that are vulnerable for attachment and feeding. A study of locomotor activity and questing behaviour may be useful for comparing the risk for different tick species and populations to transmit tick-borne pathogens.     

Comparison of the protein profiles of salivary gland extracts derived from three species of unfed and partially fed ixodid ticks analysed by SDS-PAGE

Salivary gland extracts (SGE) from unfed and 5 days fed adult female Ixodes ricinus (Linnaeus, 1758); Haemaphysalis inermis (Birula, 1895) and Dermacentor reticulatus (Fabricius, 1794) ticks were prepared. The protein content after feeding increased by 10.6, 8.7 and 6.8 times, respectively. Extracts were equilibrated to the same protein content and submitted to SDS-polyacrylamide gel electrophoresis followed by computer analysis of the scanned gels. Relative differences in protein profiles of extracts obtained from unfed and partially fed ticks were found in all species and some of them were similar in all three species used in the study. Results demonstrate that the increase of the protein content in salivary glands during the feeding does not occur proportionally. Some proteins are synthesised preferentially (67.1 kDa, 13.5 kDa) but other bands (in range of 15-16 kDa) present in the SGE derived from unfed ticks are less discernible in that of fed ticks.     

Laboratory evaluation of temperature effects on the germination and growth of entomopathogenic fungi and on their pathogenicity to two aphid species

As part of an approach to select potential mycoinsecticides for aphid biocontrol, we investigated the effects of temperature on the growth, germination and pathogenicity of some hyphomycete fungi. Commercially available mycoinsecticides (based on Beauveria bassiana (Balsamo) Vuillemin and Verticillium lecanii (Zimmermann) Viegas) and other isolates of B bassiana, V lecanii, Metarhizium anisopliae (Metschnikoff) Sorokin and Paecilomyces fumosoroseus (Wize) Brown & Smith were evaluated. The rate of in vitro conidial germination of all isolates was slower at 10 and 15 degrees C than at 20 and 25 degrees C. Similarly, in vitro growth of most isolates was adversely affected at 10 and 15 degrees C. The greatest reduction at 10 degrees C in rates of conidial germination and colony growth, compared with other temperatures, was for M anisopliae isolates. Germination of V lecanii (isolate HRI 1.72) was fastest at 10 degrees C compared with the other fungi. It was also the most pathogenic of three isolates tested against Aphis fabae Scopoli and Myzus persicae Sulzer at 10, 18 and 23 degrees C. Generally, A fabae was more susceptible than M persicae to infection by the fungal isolates tested. A significant interaction between aphid species and temperature indicated that the pathogenic nature of an isolate was dependent not only on the target aphid species but also the temperature conditions of the bioassay. The series of studies, detailed above, allowed a temperature profile to be formed for the different isolates. Verticillium lecanii isolate HRI 1.72 (commercialised as Vertalec) was the most promising isolate selected from results of the series of experiments. Temperature profiles in conjunction with infectivity assays can be useful in selecting appropriate isolates for a particular thermal environment.     

Temperature Effects on Developmental Stages of Isolates from Three Clonal Lineages of Phytophthora infestans

ABSTRACT Sporangia germination of Phytophthora infestans isolates belonging to three clonal lineages (US-1, -7, and -8) was assessed at temperatures ranging from 10 to 25 degrees C. At 10 degrees C there were no significant differences in germination percents among US-1, -7, and -8. At 18 or 20 degrees C US-7 and -8 had significantly lower germination percents than US-1. At 21, 24, or 25 degrees C all clonal lineages had low germination percents. Sporangia of the US-7 and -8 lineages germinated more quickly at 15 degrees C (P = 0.001) during the first 2 h than did the US-1 lineage. The incubation period (IP), lesion area (LA), and sporulation per unit of lesion area (SPU) of the isolates were assessed on inoculated detached leaflets of susceptible potato cv. Norchip kept at 10, 15, 20, or 25 degrees C. In general, IP declined exponentially and LA increased exponentially with increasing temperatures. SPU had a quadratic shape, with the maximum at 15 degrees C. Averaged over all temperatures, the US-7 lineage had the shortest IP (59.3 h compared to 66.4 h for US-1 [P = 0.012] and 71.7 h for US-8 [P = 0.026]). Again, averaged over all temperatures, the US-8 lineage had a larger LA (P = 0.030) than US-1. There was no significant difference between US-7 and -1 for LA. There were no significant differences among lineages in terms of SPU. These results indicate that clonal lineages differ from each other in epidemiological attributes, but the differences can be complex.     

Growth and pathogenicity of isolates of the fungus Metarhizium anisopliae against the parasitic mite, Psoroptes ovis: effects of temperature and formulation

Psoroptes mites (Acari: Psoroptidae) are important ectoparasites of mammals, and are of particular economic significance as the agents of mange in sheep. To be effective against mites, putative fungal biocontrol agents must be able to operate at the relatively high temperatures and humidities found at the sheep skin surface. To consider this, the growth rates of different isolates of the entomopathogenic fungus Metarhizium anisopliae (Metschnikoff) Sorokin (Deuteromycotina: Hyphomycetes) were compared and the pathogenicity of these isolates against Psoroptes derived from rabbits (Psoroptes ovis Hering, syn P cuniculi) were evaluated at temperatures between 28 degrees C and 40 degrees C, and when formulated in either Tween 80 or silicone oil. For this study four multi-conidia, arthropod-derived, isolates of M anisopliae were used: from the USA, France, Denmark and Brazil. One single-conidia culture derived from the US isolate was also included in the investigation. Fungal growth was higher at the lower temperatures and none of the isolates grew at 40 degrees C. The growth of the US and single-conidia isolate declined markedly with temperature. In contrast, the Danish, French and Brazilian isolates grew almost as well at 32 degrees C and 35 degrees C as at 28 degrees C and 30 degrees C. The French and Brazilian isolates showed some growth at 37.5 degrees C but the Danish and US isolates did not. The number of fatal infections which resulted from exposure of mites to the fungal isolates was also strongly influenced by temperature. At 30 degrees C all isolates gave between 70 and 90% infection. The number of infections declined with increasing temperature and no infections were seen at 40 degrees C. However, the French and Danish isolates of M anisopliae gave higher numbers of infections than the other isolates at elevated temperatures. When formulated in silicone oil, significantly higher levels of infection were obtained than when formulated in Tween 80, even at the relatively high temperature of 37.5 degrees C. It is suggested that high-temperature adapted isolates of M anisopliae formulated in silicone oil offer good candidates as control agents under the conditions found at the sheep skin surface.     

Characterization and PCR-based detection of benzimidazole-resistant isolates of Monilinia laxa in California

Monilinia laxa is a pathogen of brown rot of stone fruit and almond in California, causing blossom blights and fruit rots. In this study, low-level resistance to the benzimidazole fungicides benomyl and thiophanate-methyl was detected in field isolates of M laxa collected from stone fruits and almonds in California. Low-resistant (LR) isolates grew in potato dextrose agar (PDA) plates amended with benomyl and thiophanate-methyl at 1 and 5 microg ml(-1), respectively, but not in plates amended with benomyl at 5 microg ml(-1) or thiophanate-methyl at 50 microg ml(-1). The benzimidazole LR isolates were characterized by temperature sensitivity and the DNA sequence of the beta-tubulin gene. The LR isolates showed high-temperature sensitivity, being sensitive to 1 microg ml(-1) of benomyl at 28 degrees C but resistant at 8-24 degrees C. Analysis of the DNA sequence of the beta-tubulin gene showed that the LR isolates had a point mutation at the amino-acid position 240, causing substitution of leucine by phenylalanine. Based on the point mutation, a pair of allele-specific PCR primers was developed for rapid detection of LR isolates of M laxa. In addition, a pair of PCR primers specific to M laxa was developed on the basis of the differences in the DNA sequence of the intron 6 of beta-tubulin gene from M laxa, M fructicola and other fungal species. The primer pair amplified the expected 376-bp DNA fragment from all M laxa isolates tested, but not from 14 other fungal species isolated from stone fruit and almond crops. The restriction endonuclease BsmA I recognized the sequence GTCTCC in the PCR products from sensitive (S) isolates only, but not the GTTTCC sequence in the PCR products from LR isolates. The endonuclease digested the 376-bp PCR products from S isolates to produce two bands (111 and 265 bp) on agarose gels. Thus, both allele-specific PCR and the PCR-restriction fragment length polymorphism (PCR-RFLP) methods could be useful for rapidly detecting benzimidazole-resistant isolates of M laxa from stone fruit and almond crops in California.     

The influence of temperature on the development of Moniezia expansa (Rudolphi, 1810) in oribatid mites

The life cycle of Moniezia expansa was studied experimentally using 10 species of oribatid mites as intermediate hosts. Four of them became infected, namely Scheloribates laevigatus (76.2%), Sch. latipes (70.8%), Liacarus coracinus (20%) and Platynothrus peltifer (1.1%). The last was found for the first time to serve as intermediate host of M. expansa in Czechoslovakia. The development of the cysticercoid of M. expansa in the oribatid mites at 28 degrees C and 85% relative humidity is completed within 27 days. At 18-20 degrees C and the same relative humidity the development lasts even 97 days.     

Tick salivary gland extract-activated transmission of Borrelia afzelii spirochaetes

Saliva-activated transmission of Borrelia afzelii Canica, Nato, du Merle, Mazie, Baranton et Postic, 1993 was demonstrated using salivary gland extract (SGE) from Ixodes ricinus (L., 1758) ticks and C3H mice. Injection of Borrelia spirochaetes together with SGE increased the level of bacteraemia and accelerated the appearance of bacteria in the urinary bladder, compared with the injection of spirochaetes alone. More I. ricinus nymphs became infected when feeding on mice inoculated with B. afzelii plus SGE. Analysis of cytokines produced by cells of draining lymph nodes from SGE-treated mice showed a suppression of proinflammatory cytokines IFN-gamma, IL-6 and GM-CSF following a transient upregulation in comparison with the control mice infected without SGE.     

Fungicide seed treatment efficacy against Microdochium nivale and M. majus in vitro and in vivo

BACKGROUND: Seed-borne Microdochium majus (Wollenweber) and M. nivale Fries are the primary pathogens responsible for Fusarium seedling blight in the UK. The two species show differences in pathogenicity, host preference and sensitivities to temperature, but their relative sensitivities to fungicide seed treatments are unknown. The aim was firstly to determine the efficacy of fungicide seed treatments towards single-spore isolates of M. majus and M. nivale using in vitro experiments, and subsequently to determine efficacy in vivo over a range of temperatures. RESULTS: Differences in EC(50) values between all seed treatments were evident from the in vitro experiments and ranged from 0.028 mg L(-1) for fludioxonil to 22.8 mg L(-1) for carboxin + thiram. The two seed treatments that showed best performance in vitro were used to examine efficacy towards seed-borne infection in vivo at 4, 8, 12 and 16 degrees C. Generally, seedling emergence improved and the severity of stem-base disease symptoms on emerged seedlings was reduced for both species through the use of the fungicides. The combination of fludioxonil + difenconazole showed improved performance compared with fludioxonil alone. Significantly less severe symptoms were observed through the use of fludioxonil and fludioxonil + difenconazole compared with bitertanol + fuberidazole at 12 degrees C and for all except one M. nivale infected seed lot at 8 degrees C. CONCLUSIONS: Differences in fungicide sensitivity between the two species in vitro were not evident in vivo. This is the first report of the effect of fungicide seed treatments on the control of seedling blight caused by M. majus and M. nivale.     

Heterokaryon compatibility and genetic recombination within a host plant between hop wilt isolates of Verticillium albo–atrum

Heterokaryon compatibility was tested by pairing complementary auxotrophic mutants of three fluctuating (M18, M33 and M50) and three progressive (PV1, PV2 and PV3) hop wilt isolates of Verticillitim albo–atrum . The criteria of compatibility adopted were prototrophic growth on a glucose minimal medium at 26°C and the presence of diploid conidia. Most pairings produced at least some heterozygous diploids, showing there was no complete incompatibility barrier to hyphal and nuclear fusion on an agar medium. The incidence of prototrophic diploidy was greater within paired mutants of progressive isolates, and between PV1 and the three fluctuating isolates. A recombinant haploid prototroph was re–isolated following inoculation of Antirrhinum plants with a pair of complementary auxotrophs (M18 nic -4 cob -26 and PV3 arg -8 pyr -2). In hop, this recombinant was of intermediate pathogenicity compared with the two parental wild–type isolates. Four large–spored, diploid isolates were obtained from Antirrhinum following inoculation with heterozygous diploid conidia (M18 nic -4 cob -26/PV3 arg -8 pyr -2) from diploids synthesized on agar. All four diploids remained stable on agar and one showed moderately high pathogenicity in hop, from which it was re–isolated as a stable diploid 10 weeks later.     

Experimental verification of the effect of constant and changing water temperature on the micropopulation growth in Gyrodactylus gobiensis Gl?ser, 1974 (Monogenea) parasitizing gudgeon (Gobio gobio L.)

It has been verified under laboratory conditions that constant and changing water temperature markedly affects the micropopulation growth in Gyrodactylus gobiensis parasite on the body surface of gudgeons (Gobio gobio L.). At a water temperature of 12 degrees C, the number of gyrodactylids gradually increased up to the mean value of 63 specimens per host, which was reached on days 27-28 after experimental infection. At a constant temperature of 18 degrees C, the parasites completely disappeared from the bodies of infected fishes on days 15-20 p.i. A similar effect was produced by gradually increasing temperature from 12 to 18 degrees C, while the decrease in water temperature from 18 to 12 degrees C resulted in an increase in the parasite number.     

Pathogenicity and colonization studies on wild–type and auxotrophic isolates of Verticillium albo–atrum from hop

Three fluctuating (M18, M33 and M50) and three progressive (PVl, PV2 and PV3) hop wilt isolates of Verticillium albo–atrum Reinke and Berthold were tested against the hop ( Humulus lupulus L.) cultivars, Fuggle, Wye Challenger and Wye Target. Significant differences in pathogenicity were observed between progressive and fluctuating isolates and although wilt symptoms varied in intensity from season to season, the relative order of pathogenicity and host resistance usually remained the same. Using a detached leaf procedure, differences were observed in the frequency of successful re–isolations of Vertieillium from hop plants infected with wild–type isolates. This procedure is discussed as a possible additional method for distinguishing between progressive and fluctuating hop wilt isolates. Auxotrophic and morphological mutants derived from these six wild–type isolates were tested under glasshouse conditions against hop and the non–selective alternative host Antirrhinum majus L. (cv. Maximum). Although auxotrophic mutants generally showed a reduction in pathogenicity to, and ability to colonize, both hop and Antirrhinum , certain auxotrophs retained near–parental levels of colonization and were therefore suitable for studies on possible parasexual recombination in these hosts.     

Ticks of small mammals from the Hindu Kush (Afghanistan).

During the First Czechoslovak expedition to the East Hindu Kush in June-September 1965 a total of 193 hosts belonging to 12 species was examined on the presence of ticks. Specimens of the genera Ixodes, Haemaphysalis, Dermacentor and Rhipicephalus were found. Data and comments are given for the species collected.     

Isolation, Characterization, and Distribution of a Biocontrol Fungus from Cysts of Heterodera glycines

ABSTRACT Seventy-six populations of Heterodera glycines were collected from 33 counties in 10 states of the United States along the Mississippi and Missouri Rivers in 1992 and 1993. A sterile hyphomycete fungus of an unnamed taxon, designated ARF18 and shown to be a parasite of eggs of H. glycines, was isolated from eggs and cysts of 10 of the populations from Kentucky, Louisiana, Mississippi, and Tennessee. Ten isolates of ARF18 obtained in this study and seven isolates obtained in earlier studies were characterized for cultural morphology on several growth media, the ability to produce sclerotium-like structures (SLS) on cornmeal agar, growth rates, pathogenicity to eggs of H. glycines in vitro, and mitochondrial (mt) DNA restriction fragment length polymorphisms (RFLPs). All 17 isolates of ARF18 readily grew on potato dextrose agar, cornmeal agar, and nutrient agar. Based on colony morphology and SLS appearance on cornmeal agar, the isolates could be grouped into two morphological phenotypes. Isolates that produced SLS that were composed of a compact mass of hyphae were designated ARF18-C, whereas isolates that produced SLS composed of a mass of loosely clumped hyphae were designated ARF18-L. Only minor differences in growth rates were detected among the ARF18-C and ARF18-L isolates. All 10 ARF18-C isolates, which were from Arkansas, Louisiana, Mississippi, and Tennessee, belonged to a single mtDNA RFLP haplotype. The seven ARF18-L isolates shared many comigrating mtDNA restriction fragments with one another, but belonged to three distinct mtDNA RFLP haplotypes. Ability to infect eggs of H. glycines in vitro varied considerably among the various isolates of ARF18. In particular, several of the ARF18-C isolates were consistently able to infect over 50% (mean = 70.0%, standard deviation = 16%) of the eggs of H. glycines, whereas ARF18-L infected eggs to a lesser degree (mean = 25%, standard deviation = 27%). ARF18-C was isolated only from H. glycines populations from below 37 degrees N latitude. The presence of ARF18 was associated with soils with Mg levels <314 kg/ha, cyst numbers >4.5 per 100 cm(3), and iron levels >203.5 kg/ha; or with Mg levels >314 kg/ha and Na levels <121 kg/ha. The widespread distribution of ARF18 and the ability of some isolates to aggressively colonize eggs of H. glycines are indications that it has potential as a biological control agent for H. glycines.     

Two ways of experimental infection of Ixodes ricinus ticks (Acari: Ixodidae) with spirochetes of Borrelia burgdorferi sensu lato complex

A previously reported procedure for the introduction of Borrelia spirochetes into tick larvae by immersion in a suspension of spirochetes was tested on Ixodes ricinus (L.) ticks and three of the most medically important European Borrelia genomic species, B. burgdorferi sensu stricto, B. garinii and B. afzelii. The procedure was compared with "classical" infection of nymphs by feeding on infected mice. Both methods yielded comparable results (infection rate 44-65%) with the exception of B. afzelii, which produced better results using the immersion method (44%) compared with feeding on infected mice (16%). Nymphs infected by the immersion method at the larval stage were able to transmit the infection to na?ve mice as shown by serology and PCR detection of spirochetal DNA in organs. The immersion method is faster than feeding on infected mice and provides more reproducible conditions for infection. It can be exploited for studies on both pathogen transmission and Borrelia-vector interactions.     

Factors Influencing Development of Root Rot on Ginseng Caused by Cylindrocarpon destructans

ABSTRACT The fungus Cylindrocarpon destructans (Zins) Scholten is the cause of root rot (disappearing root rot) in many ginseng production areas in Canada. A total of 80 isolates of C. destructans were recovered from diseased roots in a survey of ginseng gardens in British Columbia from 2002-2004. Among these isolates, 49% were classified as highly virulent (causing lesions on unwounded mature roots) and 51% were weakly virulent (causing lesions only on previously wounded roots). Pectinase and polyphenoloxidase enzymes were produced in vitro by C. destructans isolates when they were grown on pectin and phenol as a substrate, respectively. However, highly virulent isolates produced significantly (P < 0.001) higher enzyme levels compared with weakly virulent isolates. Histopathological studies of ginseng roots inoculated with a highly virulent isolate revealed direct hyphal penetration through the epidermis, followed by intracellular hyphal growth in the cortex. Subsequent cell disintegration and accumulation of phenolic compounds was observed. Radial growth of highly and weakly virulent isolates on potato dextrose agar was highest at 18 and 21 degrees C, respectively and there was no growth at 35 degrees C. Mycelial mass production was significantly (P 相似文献