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Background: Rusted root rot is one of the most common root diseases in Panax ginseng, and Cylindrocarpon destructans is one of the main pathogenic fungus. The objective of this study was to screen and explore the extracts of biocontrol bacteria isolated from ginseng rhizosphere soil against Cylindrocarpon destructans. Results: Bacterial strains Bacillus amyloliquefaciens YY8 and Enterobacteriacea YY115 were isolated and found to exhibit in vitro antifungal activity against C. destructans. A combination of crude protein extract from B. amyloliquefaciens YY8 and ethyl acetate extract from Enterobacteriacea YY115 in a 6:4 ratio exhibited the strongest antifungal activity against C. destructans. Measurements of electrical conductivity, protein content, and nucleic acid content in suspension cultures of C. destructans treated with a mixture extracts indicated that the extracts disrupted the cell membranes of rusted root rot mycelia, resulting in the leakage of electrolytes, proteins, and nucleic acids from the cells, and ultimately inhibiting the growth of C. destructans. The combined extracts suppressed the infection of ginseng roots discs by C. destructans effectively. Conclusion: The extracts obtained from the two bacterial strains effectively inhibited C. destructans in P. ginseng. It can provide scientific basis for the development of new biological control pesticides, reduce the use of chemical pesticides, and promote the sustainable development of agriculture. [ABSTRACT FROM AUTHOR]

Abstract Background Rusted root rot is one of the most common root diseases in Panax ginseng, and Cylindrocarpon destructans is one of the main pathogenic fungus. The objective of this study was to screen and explore the extracts of biocontrol bacteria isolated from ginseng rhizosphere soil against Cylindrocarpon destructans. Results Bacterial strains Bacillus amyloliquefaciens YY8 and Enterobacteriacea YY115 were isolated and found to exhibit in vitro antifungal activity against C. destructans. A combination of crude protein extract from B. amyloliquefaciens YY8 and ethyl acetate extract from Enterobacteriacea YY115 in a 6:4 ratio exhibited the strongest antifungal activity against C. destructans. Measurements of electrical conductivity, protein content, and nucleic acid content in suspension cultures of C. destructans treated with a mixture extracts indicated that the extracts disrupted the cell membranes of rusted root rot mycelia, resulting in the leakage of electrolytes, proteins, and nucleic acids from the cells, and ultimately inhibiting the growth of C. destructans. The combined extracts suppressed the infection of ginseng roots discs by C. destructans effectively. Conclusion The extracts obtained from the two bacterial strains effectively inhibited C. destructans in P. ginseng. It can provide scientific basis for the development of new biological control pesticides, reduce the use of chemical pesticides, and promote the sustainable development of agriculture.

In the UK, strawberry is mostly grown in coconut coir substrate under protection. Coir substrate is usually used only for one or two cropping seasons because the continuous reuse of coir without any treatment leads to yield decline. In this study, we investigated the changes in bacterial and fungal communities in strawberry roots and bulk coir in relation to (i) the coir substrate age (cropping seasons) and (ii) oak or beech biochar amendment at planting. Coir age did not affect fungal/bacterial alpha (within-sample) diversity but affected beta (between-sample) diversity. Amendment with either oak or beech biochar did not lead to significant changes in either alpha or beta diversity for both fungi and bacteria, but it did alter the relative abundance of 13 fungal ASVs. This study identified six bacterial and 20 fungal ASVs with a significant positive linear relationship with coir age and also eight bacterial and 22 fungal ASVs with a significant negative linear relationship with coir age. Notably, the observed strawberry yield decline in reused coir substrate could be associated with a generalist root pathogen, Ilyonectria destructans (ex. Cylindrocarpon destructans), of which the abundance increased annually by 225% and 426% in strawberry root and bulk coir, respectively. Future research is needed to confirmthe role of I. destructans in reused coir on strawberry plant health and fruit productivity and then to identify management strategies for yield decline mitigation. [ABSTRACT FROM AUTHOR]

Hydrogen peroxide is an eco-friendly oxidizing agent, which has exhibited a broad spectrum of antimicrobial activity without adverse environmental impact. This study was conducted to investigate the antifungal Effect of hydrogen peroxide treatment against Cylindrocarpon destructans, and consequently to evaluate its control efficacy against root rot disease of 2-year-old ginseng plants. Hydrogen peroxide treatment strongly inhibited the viability of C. destructans conidia in vitro. The hydrogen peroxide at a concentration of 300 mg/l significantly reduced disease infection of the ginseng root when treated to spore suspension (107 conidia/ml). Spraying with 300 mg/l of hydrogen peroxide reduced the root rot disease of the ginseng sprouts by 15% compared to the untreated control at 14 days after the inoculation. However, 300 mg/l of hydrogen peroxide delayed the emergence of ginseng plants during sprouting under aeroponic conditions. Further works need to be done to provide an acceptable control efficacy of hydrogen peroxide against the disease and its good safety to ginseng plants.

Local germplasm may be the basis for genetic improvement for sustainability and resilience, yet little is known about Greek peach [Prunus persica (L.) Batsch] local genetic resources. The aims of the present study were to entail a prospection in the mainland and islands of Greece for local traditional and underutilized germplasm and study their genetic and morphological variation and susceptibility to shoot blight from Cylindrocarpon destructans and Monilinia laxa. A total of 32 peach cultivars/accessions were prospected from the mainland (Imathia and Magnesia) and islands (Andros, Ikaria, Kythira, Lesvos and Samos) of Greece. Leaf and fruit morphological characterization was made in situ and ex situ using 42 qualitative and quantitative morphological descriptors. Nine clones of 'Lemonato', isolated in Magnesia, with differing ripening times, were found to vary in leaf and fruit phenotypic traits. The local peach genotypes were separated from 12 old foreign cultivars, in 8 out of the 42 leaf and fruit phenotypic traits studied. We observed greater lesion damages from C. destructans than M. laxa. Local cultivars had greater resistance to Cylindrocarpon destructans than foreign cultivars, with 'Lemonato Andrea', 'Daggalakou' and 'Papagianni' exhibiting the greatest resistance. Genetic characterization was performed in the studied local and foreign peach cultivars/accessions, using eight Inter Simple Sequence Repeats (ISSRs), resulting in a total of 404 bands. Analysis of molecular variance and principal coordinates analysis revealed moderate to low genetic diversity among the peach cultivars, and three distinct clusters were formed. Furthermore, multiple regression analysis was implemented for the association study between morphological traits and the ISSR markers, revealing several markers that are statistically and significantly correlated with fruits' traits. The obtained results could be valuable for breeding programs and future research on peach. [ABSTRACT FROM AUTHOR]

Ginseng is an important medicinal plant cultivated in East Asia for thousands of years. It is typically cultivated in the same field for 4 to 6 years and is exposed to a variety of pathogens. Among them, ginseng root rot is the main reason that leads to the most severe losses. In this study, endophytic bacteria were isolated from healthy ginseng, and endophytes with antagonistic effect against ginseng root rot pathogens were screened out. Among the 17 strains, three carried antagonistic effect, and were resistant to radicicol that is a mycotoxin produced by ginseng root rot pathogens. Finally, Bacillus velezensis CH-15 was selected due to excellent antagonistic effect and radicicol resistance. When CH-15 was inoculated on ginseng root, it not only inhibited the mycelial growth of the pathogen, but also inhibited the progression of disease. CH-15 also carried biosynthetic genes for bacillomycin D, iturin A, bacilysin, and surfactin. In addition, CH-15 culture filtrate significantly inhibited the growth and conidial germination of pathogens. This study shows that endophytic bacterium CH-15 had antagonistic effect on ginseng root rot pathogens and inhibited the progression of ginseng root rot. We expected that this strain can be a microbial agent to suppress ginseng root rot.

Local germplasm may be the basis for genetic improvement for sustainability and resilience, yet little is known about Greek peach [Prunus persica (L.) Batsch] local genetic resources. The aims of the present study were to entail a prospection in the mainland and islands of Greece for local traditional and underutilized germplasm and study their genetic and morphological variation and susceptibility to shoot blight from Cylindrocarpon destructans and Monilinia laxa. A total of 32 peach cultivars/accessions were prospected from the mainland (Imathia and Magnesia) and islands (Andros, Ikaria, Kythira, Lesvos and Samos) of Greece. Leaf and fruit morphological characterization was made in situ and ex situ using 42 qualitative and quantitative morphological descriptors. Nine clones of ‘Lemonato’, isolated in Magnesia, with differing ripening times, were found to vary in leaf and fruit phenotypic traits. The local peach genotypes were separated from 12 old foreign cultivars, in 8 out of the 42 leaf and fruit phenotypic traits studied. We observed greater lesion damages from C. destructans than M. laxa. Local cultivars had greater resistance to Cylindrocarpon destructans than foreign cultivars, with ‘Lemonato Andrea’, ‘Daggalakou’ and ‘Papagianni’ exhibiting the greatest resistance. Genetic characterization was performed in the studied local and foreign peach cultivars/accessions, using eight Inter Simple Sequence Repeats (ISSRs), resulting in a total of 404 bands. Analysis of molecular variance and principal coordinates analysis revealed moderate to low genetic diversity among the peach cultivars, and three distinct clusters were formed. Furthermore, multiple regression analysis was implemented for the association study between morphological traits and the ISSR markers, revealing several markers that are statistically and significantly correlated with fruits’ traits. The obtained results could be valuable for breeding programs and future research on peach.

Cylindrocarpon destructans causes ginseng root rot and produces radicicol that has an antifungal effect. In this study, we developed a method to detect this fungus using enzyme-linked immunosorbent assay (ELISA). Secreted proteins of C. destructans were used as antigens to obtain C. destructans-specific IgG from mouse. Out of 318 monoclonal antibodies generated from mouse, two antibodies (Cd7-2-2 and Cd7-2-10) showed highest specificity and sensitivity. Indirect ELISA using both antigens successfully detected C. destructans in soils, but direct ELISA using IgG conjugated with horseradish peroxidase failed to detect antigens in soils. The indirect ELISA developed here can efficiently detect the fungus and help manage ginseng root rot disease in fields.

Cylindrocarpon destructans/Ilyonectria radicicola is thought to cause both rusty symptom and root-rot disease of American and Korean ginseng. Root-rot disease poses a more serious threat to ginseng roots than rusty symptoms, which we argue result from the plant defense response to pathogen attack. Therefore, strains causing rotten root are characterized as more aggressive than strains causing rusty symptoms. In this review, we state 1- the molecular evidence indicating that the root-rot causing strains are genetically distinct considering them as a separate species of Ilyonectria, namely I. mors-panacis and 2- the physiological and biochemical differences between the weakly and highly aggressive species as well as those between rusty and rotten ginseng plants. Eventually, we postulated that rusty symptom occurs on ginseng roots due to incompatible interactions with the weakly aggressive species of Ilyonectria, by the established iron-phenolic compound complexes while root-rot is developed by I. mors-panacis infection due to the production of high quantities of hydrolytic and oxidative fungal enzymes which destroy the plant defensive barriers, in parallel with the pathogen growth stimulation by utilizing the available iron. Furthermore, we highlight future areas for study that will help elucidate the complete mechanism of root-rot disease development.

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Phytochemical investigation on pathogenic fungus Cylindrocarpon destructans isolated form Meconopsisgrandis plant led to the isolation of two new isochromene derivatives namely, 6,8-dimethoxy-3-methyl- 3,4-dihydrobenzoisochromene-4,9,10-triol (1) and 3,5,6-trihydroxy-4-methylbenzoisochromene-9,11-dione (2) along with four known compounds (3-6). The structures of these compounds were elucidated by 1D and 2D NMR and mass spectroscopic data analysis. The isolated compounds were evaluated for cytotoxic activity. The compounds 1-4 showed good inhibition against the growth of cell lines MCF-7 and PC-3. Compounds 5-6 showed minimum inhibitory effect of cancerous cell lines growth. [ABSTRACT FROM AUTHOR]

Black foot disease of grapevines is a major economic issue for the viticulture industry, with several Dactylonectria and Ilyonectria species identified as causal agents worldwide. This study aimed to confirm the pathogenicity of an Ilyonectria pseudodestructans isolate recovered from a symptomatic grapevine in a nationwide survey. An initial pot experiment inoculated callused and root-wounded grapevine propagation material of varieties '101- 14' and '5C' with I. pseudodestructans conidia. The second pot experiment compared the pathogenicity of I. pseudodestructans conidial, chlamydospore and mycelial inocula. Disease incidence, severity and root and shoot dry weights were determined after 4-5 months of growth. Ilyonectria pseudodestructans was recovered from inoculated plants resulting in higher disease incidence and severity compared with the uninoculated control. Disease severity and incidence was higher for callused compared to rooted propagation material, but did not differ between grapevine varieties. Conidial inoculum caused greater disease incidence and severity compared with chlamydospore and mycelial inocula. Ilyonectria pseudodestructans propagules infected grapevine plant material via the callused basal ends or wounded roots, indicating this species is a potentially important pathogen of grapevines both in nurseries and vineyards. [ABSTRACT FROM AUTHOR]

Black foot disease of grapevines causes significant economic loss to the viticulture industry worldwide. A novel method was developed to investigate the fate of propagules of three species associated with black foot disease in New Zealand, Dactylonectria macrodidyma, Ilyonectria europaea and I. liriodendri, in soil. Conidia or mycelium of one isolate each of the three species were buried in soil in nylon mesh bags, and conidia/chlamydospore numbers were determined microscopically after 2 and 3 weeks. Conidia and chlamydospores were produced by mycelial inocula of all isolates, with greater numbers of chlamydospores after 3 weeks. Conidial inocula of all isolates also produced chlamydospores. Chlamydospores were formed at either the terminus or side of a hypha, and single and multiple conidia formed chlamydospores by combining their cellular protoplasm. Chlamydospores were produced from conidia, and conidia from mycelium faster for the I. europaea isolate than the D. macrodidyma and I. liriodendri isolates. The rapid formation of chlamydospores as survival propagules will facilitate the ability of these pathogens to persist in soil in the absence of a host. [ABSTRACT FROM AUTHOR]

Ginseng (Panax ginseng C.A. Meyer) is a medicinal crop that requires a long culture time before it is ready to harvest, thus generating high economic and environmental costs. Symbiotic bacteria that live within the plant provide the host plant with many advantages in terms of metabolism and disease resistance. Here, we isolated endophytic bacteria from various tissues of P. ginseng seedlings using a culture-dependent method and we compared their tissue distribution. In addition, their antimicrobial activity against two fungal pathogens was investigated. Based on 16S rRNA sequencing, we identified 21 bacterial strains from ginseng seedlings. Leaves and rhizomes showed higher bacterial species diversity than root bodies and tails. While Bacillus strains were detected in all tissues, Xanthomonas and Micrococcaceae strains were specifically isolated from rhizome and leaf tissues, respectively. Fourteen bacterial strains showed antimicrobial activities against Cylindrocarpon destructans and/or Botrytis cinerea, with different activities. Among them, two strains (PgKB29 and PgKB35) showed strong antimicrobial activities against both fungi. Taken together, these results provide a better understanding of endophytic bacteria in P. ginseng seedlings and suggest the possibility of biological control of fungal pathogens using endophytic bacteria. [ABSTRACT FROM AUTHOR]

The soil-borne ascomycete fungus Cylindrocarpon destructans causes ginseng root rot disease and produces various secondary metabolites such as brefeldin A and radicicol. The slow growth of this fungus compared with other plant pathogenic and saprophytic fungi in soil disturbs isolation of this fungus from soil and infected ginseng. In this study, we developed a selective medium for C. destructans using radicicol produced by this fungus. Supplementing 50 mg/L of radicicol to medium inhibited the mycelia growth of other fungi including Botrytis cinerea, Rhizoctonia solani and Alternaria panax, but did not affect the growth of C. destructans. In addition, conidia germination of other fungal species except for C. destructans was inhibited in submerged culture supplemented with radicicol. This medium provides a very efficient tool for isolating C. destructans and also can be used as an enrichment medium for this fungus.

This study investigated the effects of rice husk and rice husk biochar on root rot (caused byCylindrocarpon destructansandFusarium solani) of ginseng (Panax ginseng) and on soil organisms. The effects were compared between paddy-converted and upland soils characterised by high and low nutrient content, respectively. The prevalence of root rot disease in the upland soil decreased in plots treated with rice husk at 5.2 Mg ha−1compared to the untreated control. Small differences in soil chemical properties between different treatments suggested the role of biotic factors in the suppression of the disease. In both soils, the lowest hyphal growth ofFusarium solaniwas observed in soil collected from plots treated with rice husk at 5.2 Mg ha−1. The results suggested that the low incidence of root rot disease was due to the suppressive effect of soil on pathogenic fungi in the treated upland soil. Principal component analysis of phospholipid fatty acid results suggested that changes in microbial community structure contributed to soil suppressiveness in the paddy-converted soil. The highest density of fungivorous nematodes was observed with rice husk at 5.2 Mg ha−1in the paddy-converted soil, andAphelenchussp. collected from the plots were successfully cultured onF. solaniandC. destructans. This observation showed that the fungivorous nematodes have potential to suppress pathogenic fungi by feeding on them. It was shown that rice husk can be used in control of root rot disease while promoting the growth of beneficial organisms suppressing pathogenic fungi and that the effect may differ by soil type. [ABSTRACT FROM PUBLISHER]

Cylindrocarpon destructans is an ascomycete soil-borne pathogen that causes ginseng root rot. To identify effective biocontrol agents, we isolated several bacteria from ginseng cultivation soil and evaluated their antifungal activity. Among the isolated bacteria, one isolate (named JH7) was selected for its high antibiotic activity and was further examined for antagonism against fungal pathogens. Strain JH7 was identified as a Chromobacterium sp. using phylogenetic analysis based on 16S rRNA gene sequences. This strain was shown to produce antimicrobial molecules, including chitinases and proteases, but not cellulases. Additionally, the ability of JH7 to produce siderophore and solubilize insoluble phosphate supports its antagonistic and beneficial traits for plant growth. The JH7 strain suppressed the conidiation, conidial germination, and chlamydospore formation of C. destructans. Furthermore, the JH7 strain inhibited other plant pathogenic fungi. Thus, it provides a basis for developing a biocontrol agent for ginseng cultivation. [ABSTRACT FROM AUTHOR]

The ornamental Tagetes minuta is a herbaceous plant of the Asteraceae family. T. minuta, a species native to southern South America, is used as a condiment, as a refreshing beverage, and for medicinal purposes. In 2011, disease symptoms of yellowing, root and foot rot, drying of leaves, and plant death were observed in an ornamental marigold (T. minuta) greenhouse in Fars province. The infected plants were collected and transferred to a laboratory. Samples were washed, cut into small pieces, surface disinfested with a 0.5% NaClO solution, and cultured on Potato Dextrose Agar (PDA) acidified to pH 4.5 with 0.5% lactic acid. Based on morphological characters, the causal agent was identified as Cylindrocarpon destructans. To confirm morphological identification, DNA was extracted from isolates using a genomic DNA purification Kit. The region of internal transcribed spacers 1, 2, and 5.8S genes of rDNA were amplified using the ITS4 and ITS1 universal primer set. Fragments of 600 bp were recovered from PCR, purified, sequenced, edited, and deposited in GenBank. The isolates had a 100% identity with all the compared C. destructans sequences. The pathogenicity tests were done with a suspension of 1 × 106 conidia per ml homogenised in sterile water. The symptoms on inoculated plants were similar to those previously observed and the fungus was reisolated from the inoculated plants. This is the first documented report of C. de-structans as a cause of root and foot rot disease on T. minuta in Iran.

Ginseng root rot caused by Cylindrocarpon destructans is the most destructive disease of ginseng. Six different fungicides (thiophanate-methyl, benomyl, prochloraz, mancozeb, azoxystrobin, and iprodione) were selected to evaluate the inhibitory effect on the mycelial growth and conidial germination of C. destructans isolates. Benomyl and prochloraz were found to be the most effective fungicides in inhibiting mycelial growth of all tested isolates, showing 64.7% to 100% inhibition at a concentration of 10 μg/mL, whereas thiophanate-methyl was the least effective fungicide, showing less than 50% inhibition even at a higher concentration of 100 μg/mL. The tested fungicides exhibited less than 20% inhibition of conidium germination at concentrations of 0.01, 0.1, and 1 μg/mL. However, the inhibition effect of mancozeb on condium germination of C. destructans was significantly increased to 92% to 99% at a higher concentration of 100 μg/mL, while the others still showed no higher than 30% inhibition. [ABSTRACT FROM AUTHOR]

Ginseng (Panax ginseng) is a traditional medicinal plant in China, and the dried root is highly valued for its medicinal properties and is widely used in Chinese traditional medicine. Cylindrocarpon root rot of ginseng caused by Cylindrocarpon destructans is the main disease, which is difficult to be eliminated from soil, leading to serious crop yield losses and limited the re-use of fields for successive ginseng crops. Methyl jasmonate (MeJA), which is one of the plant lipid derivatives, considered as a signaling substance during plant-microbe interactions. It is related to plant resistance to biotic and abiotic stress, can be involved in plant response to pathogens and other adversity stress and signal transmission, and can be used to induce plant disease resistance reaction. The objective of this study was to test the effects of MeJA on C. destructans and to find the possible relationships between MeJA and pathogenic factors of C. destructans. To assess the influence of MeJA on soil pathogens, the direct effects of artificially applied MeJA on C. destructans were evaluated, including the effects on colony growth, spore germination, biomass and phytopathogenic enzyme activities of this pathogen. The results showed that MeJA strongly inhibited its growth and spore germination, whereas it stimulated phytopathogenic enzyme activities. The colony diameter of C. destructans on PDA decreased from(8.23±0.15)cm(control)to(0.71±0.00)cm(800 μg · mL-1). At the highest concentration(800 μg · mL-1)of MeJA, the colony diameter of C. destructans had almost totally inhibited, but the diameter had no difference compared with the untreated control at lower concentrations(1-50 μg · mL-1 MeJA). The biomass reduced by 65.3%-100% and the percent of spore germination decreased by 100% at concentrations higher than 400 μg · mL-1. Potent suppression of the growth of germ-tubes was observed at different concentrations, especially at(400-800)μg · mL-1, where the growth of germ-tubes was inhibited completely. However, activities of phytopathogenic enzymes(pectinase, cellulase, amylase, and protease)were greatly stimulated by MeJA at higher concentrations(MeJA>200 μg · mL-1), while the activity of protease was little changed. The activity of pectinase was high up to(0.61±0.05)U·mL-1·min-1 at the concentration of 800 μg · mL-1. The activity of cellulase was stimulated at high concentrations of MeJA in liquid culture, while it was suppressed at low concentrations(1-50 μg · mL-1). The activity of cellulase was(0.31±0.02)μmol·min-1 at 800 μg · mL-1 of MeJA. Amylase activity substantial increased at concentrations of(200-800)μg · mL-1, which was(0.45±0.02)μmol·min-1 at the concentration of 800 μg · mL-1. It was concluded that MeJA greatly inhibited C. destructans growth and spore germination, but stimulated activities of hydrolytic enzymes of C. destructans at higher doses. There might be different mechanisms presented for the effects of MeJA on hyphal growth and virulence factors of C. destructans. The critical concentration of MeJA inhibitory effects on C. destructans was 200 μg · mL-1. The research lays a foundation for the subsequent experiment using MeJA to induct disease resistance. This is of help to understand the mechanism of Cylindrocarpon root rot of ginseng and to control pathogen in practice. [ABSTRACT FROM AUTHOR]

Double-stranded RNAs (dsRNAs) are widespread in plant pathogenic fungi, but their functions in fungal hosts remain mostly unclear, with a few exceptions. We analyzed dsRNAs from Nectria radicicola, the causal fungus of ginseng root rot. Four distinct sizes of dsRNAs, 6.0, 5.0, 2.5, and 1.5 kbp, were detected in 24 out of the 81 strains tested. Curing tests of individual dsRNAs suggested that the presence of 6.0-kbp dsRNA was associated with high levels of virulence, sporulation, laccase activity, and pigmentation in this fungus. The 6.0-kbp dsRNA-cured strains completely lost virulence-related phenotypes. This 6.0-kbp dsRNA was reintroduced by hyphal anastomosis to a dsRNA-cured strain marked with hygromycin resistance, which resulted in the restoration of virulence-related phenotypes. These results strongly suggest that 6.0-kbp dsRNA up regulates fungal virulence in N. radicicola. Sequencing of several cDNA clones derived from 6.0-kbp dsRNA revealed the presence of a RNA-dependent RNA polymerase (RDRP) gene. Phylogenetic analysis showed that this gene is closely related to those of plant cryptic viruses. Biochemical analyses suggested that the 6.0-kbp dsRNA may regulate fungal virulence through signal-transduction pathways involving cyclic AMP-dependent protein kinase and protein kinase C.

We analyzed the genetic diversity of Cylindrocarpon destructans isolates obtained from Korean ginseng (i.e., Panax ginseng) roots by performing virulence tests and nuclear ribosomal gene internal transcribed spacer (ITS) and mitochondrial small subunit (mt SSU) rDNA sequence analysis. The phylogenetic relationship analysis performed using ITS DNA sequences and isolates from other hosts helped confirm that all the Korean C. destructans isolates belonged to Nectria/Neonectria radicicola complex. The results of in vivo and ex vivo virulence tests showed that the C. destructans isolates could be divided into two groups according to their distinctive difference in virulence and the genetic diversity. The highly virulent Korean isolates in pathogenicity group II (PC II), together with foreign isolates from P ginseng and R quinquefolius, formed a single group. The weakly virulent isolates in pathogenicity group I, together with the foreign isolates from other host plants, formed another group and exhibited a greater genetic diversity than the isolates of PC II, as confirmed by the mt SSU rDNA sequence analysis. In addition, as the weakly virulent Korean isolates were genetically very similar to the foreign isolates from other hosts, they were likely to originate from hosts other than the ginseng plants. [ABSTRACT FROM AUTHOR]

Highlights: [•] Our results show that organic amendments can alter the incidence of plant disease via a change in soil-borne fungal pathogens. [•] Incidence of root-rot disease in ginseng was increased by the application of manure composts. [•] Cylindrocarpon destructans and Fusarium solani are the main pathogens that caused the disease. [•] The hyphal growth of the two pathogenic soil-borne fungi was promoted in the soils in which manure composts were applied. [Copyright &y& Elsevier]

In a visit to an avocado plantation located in the department of Antioquia in Colombia, seedlings with less than one month of being transplanted to the field were observed with leaf yellowing, leaf flaccidity, growth delay and root rot, symptoms associated with avocado wilt. Based on a field diagnosis, the diseased plants were subjected to the habitual treatment for Phytophthora cinnamomi Rands, a pathogen commonly associated with the wilt, without a positive response. Samples were taken from these plants and transferred to the Plant Protection Laboratory of the National University of Colombia, headquarters Medellin, where they were processed and cultured on the semi-selective media for Phytophthora spp. V8-PARPH and V8-NARPH and acidified PDA (APDA) and V8 for fungi. Cylindrocarpon destructans (Zinss) Scholten was the fungus consistently isolated; in any case, P. cinnamomi was isolated. The isolate was inoculated in avocado plants, and they showed leaf yellowing, leaf flaccidity, growth delay and rotten roots, symptoms commonly observed in avocado wilt, and which, in addition, are similar to those reported for avocado black root rot disease. From the inoculated tissues, the same fungus could be re-isolated confirming Koch's postulates. The results observed in this work suggested the presence of this disease in Colombia for the first time. [ABSTRACT FROM AUTHOR]

Abstract: A ginseng pathogen, Cylindrocarpon destructans, and five nonpathogens were tested for their sensitivity to a total ginsenoside fraction (T-GF), a protopanaxadiol-type ginsenoside fraction (PPD-GF) and a protopanaxatriol-type ginsenoside fraction (PPT-GF) from the roots of Panax ginseng C.A. Meyer. The results showed that T-GF inhibited growth of the five ginseng nonpathogens, while it promoted growth of the ginseng pathogen C. destructans. PPT-GF and PPD-GF both inhibited the growth of the five ginseng nonpathogens, although the activity of PPT-GF was higher than that of PPD-GF. PPT-GF and PPD-GF exhibited different activities on C. destructans: PPT-GF inhibited its growth, whereas PPD-GF significantly enhanced its growth. The subsequent analysis of enzymatic degradation of ginsenosides by the test fungi showed that C. destructans can consecutively hydrolyze the terminal monosaccharide units from the sugar chains attached at C3 and C20 in PPD-type ginsenosides by extracellular glycosidase activity to yield four major products, gypenoside XVII (G-XVII), compound O, compound Mb and the ginsenoside F2. By contrast, the ginseng nonpathogens Aspergillus nidulans and Cladosporium fulvum have no extracellular glycosidase activity toward sugar chains attached to C3 in PPD-type ginsenosides. These results indicated that ginsenosides might act as host chemical defenses, while the ginseng root pathogenic fungi might counter their toxicity by converting PPD-type ginsenosides into growth or host recognition factors. The ability of ginseng root pathogens to deglycosylate PPD-type ginsenosides may be a pathogenicity factor. [Copyright &y& Elsevier]

Cylindrocarpon destructans causes root rot disease in ginseng and can survive for a long time, producing chlamydospores. We optimized conditions to induce chlamydospore production from the conidia of C. destructans, isolated from Korean ginseng. This will provide the basis for testing the efficacy of control agents targeting these chlamydospores. [ABSTRACT FROM AUTHOR]

Cylindrocarpon destructans (Zins.) Scholt. (C. radicicola Wr.) (Booth 1966) is known to be a common root surface inhabitant of many plants (Gerlach 1961, Matturi and Stenton 1964). This fungus has been isolated from the roots of both healthy and diseased plants. Because of its abundance on the root surface, it is considered to be a pioneer colonizer of this ecological niche (Stenton 1958, Matturi and Stenton 1964). According to Matturi and Stenton (1964) C. radicicola is not specialized in the direction of parasitism. On the other hand the pathogenicity of this fungus has been well documented by many investigators. A review of its phytopathological importance is given by Gerlach (1964) and Scholten (1964). Pathogenicity of C. radicicola for forest trees seedlings has been reported by Kluge (1966), Manka and Gierczak (1971), Kowalski (1980). According to Cartwright (cf. Evans et al. 1967) strains of this fungus can produce typical symptoms of disease, even without actively invading seedlings. This fact would suggest that they may affect the plant by their metabolites excreted into the root zone of plants. A toxic metabolite – nectrolide &nash; was detected in C. radicicola cultures by Evans et al. (1967). Analysis of nectrolide established the formula C&sub16;H&sub24;O&sub4; its physical and chemical properties were identical as the antibiotic Brefeldin "A" produced by Penicillin bn-fcldiamnn (cf. Evans et al. 1967). These authors suggest that if nectrolide is responsible for the stunting of seedlings, the compound must be produced at the surface of living roots. Many authors are of the opinion that because of the intimate contact of microorganisms with the plant cells in the root zone, microbial metabolites may directly affect development, growth and health of the plant (Hussain and Vancura 1970, Brown 1972, Barea and Brown 1974). Synthesis of plant growth regulators by microorganisms of the rhizosphere and rhizoplane of different plants has been well docum... [ABSTRACT FROM AUTHOR]

In comparative studies on potyviruses from West African yams (Dioscorea spp.) the following isolates were used: Dioscorea greenbanding mosaic virus (DGMV) and a Nigerian yam virus (YV-N), both isolated from Dioscorea rotundata, and a beet mosaic virus isolate from D. alata (BtMV-Y) formerly designated Dioscorea alata ring mottle virus. Naturally infected D. alata containing very few particles of BtMV-Y, contained primarily particles of a second potyvirus (Dioscorea alata virus, DaV) which could not be transmitted but which was included in these studies wherever possible. The normal lengths of DGMV, YV-N, DaV, and BtMV-Y were 754, 772, 805, and 812 nm, respectively. All viruses induced cytplasmic inclusions of the pinwheel type and laminated aggregates. In addition, the nucleoli of BtMV-Y infected cells contained characteristic electron dense inclusions. The buoyant density of purified DGMV and BtMV-Y in CsCl was 1.336 g/cm3 and 1.321 g/cm3, respectively. The sedimention velocities (Srei) of DGMV, YV-N, and BtMV-Y were 156, 158, and 162 S, respectively. In SDS-polyacrylamide gel electrophoresis the coat protein of purified DGMV and YV-N all migrated as a single band with an apparent molecular weight of 36 kd. Coat protein of purified DaV showed up to 5 bands with molecular weights of 36 to 32 kd. Polypeptides of purified BtMV-Y had an estimated molecular weight of 35 kd but those from infected plant extracts had a molecular weight of 36 kd. DGMV, YV-N, and BtMV-Y particles contained a single nucleic acid with an apparent molecular weight of 3.2, 3.2, and 3.1 Md, respectively. Using X-DNA digested with Hind III as a marker, the molecular weight of DGMV and BtMV-Y nucleic acid was calculated to be 3.6 Md ±10%. The nucleic acid was determined to be single-stranded RNA by enzymatic digestion and by staining with acridine orange. [ABSTRACT FROM AUTHOR]

New plantations of olive tree in southern Spain are being severely affected by wilt or dieback and death, which has been locally called ‘Drying Syndrome’. To determine the etiology of this problem, a study was carried out in samples of affected young trees collected during a seven year period (1989–1995), and in two field surveys in 1994–95 and 1996. Besides some insect damage and agronomic problems, the ‘Drying Syndrome’ was associated with Verticillium wilt, winter frost and root rot fungi. Although ‘Drying Syndrome’ can be distinguished from Verticillium wilt, the latter was included in this study, since, frequently, Verticillium wilt symptoms were unspecific and Verticillium dahliae could not be always isolated in the diagnostic work that preceded this study. Early winter frost caused a vascular necrosis and wilt of the young olive trees. This unusual and severe damage was related with the lack of frost hardiness due to warm temperatures during the previous autumn. Root rot fungi were very frequent in the samples of diseased olive trees of field or nursery origin, and they were the main cause of ‘Drying Syndrome’ in the second field survey, when a heavy rainfall level occurred during winter. Pathogenicity tests showed that five fungal species (Cylindrocarpon destructans, Phytophthora megasperma, P. palmivora, Pythium irregulare and Sclerotium rolfsii) were pathogenic to olive trees and reproduced symptoms of ‘Drying syndrome’ in rooted cuttings of cultivar Picual. Other fungal species associated with root rot of olive trees in the field or in the nurseries, including Fusarium acuminatum, F. eumartii, F. oxysporum, F. solani, Macrophomina phaseolina and Rhizoctonia solani, were weakly or not pathogenic. Pathogenicity of P. megasperma, P. palmivora and P. irregulare depended on soil water content, since isolates tested caused extensive root rot and sudden plant death only when the soil was continuously waterlogged. The high frequency of P. megasperma in waterlogged field soils and its pathogenicity dependence on soil water content suggest that this pathogen may play an important role in the well known sensitivity of young olive trees to ‘root asphyxiation’. [ABSTRACT FROM AUTHOR]