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1.
Water hyacinth poses serious socio-economic and environmental problems in Ethiopia. To integrate fungal pathogens into water hyacinth management, a survey was conducted in the Rift Valley of Ethiopia. Based on morphological characterization and DNA sequencing, 25 fungal species were identified that belong to nine genera. Alternaria tenuissima, A. alternata, Aspergillus niger, Phoma sp., Curvularia trifolii, Mucor fragilis, M. racemosus, A. fumigatus, Fusarium oxysporum, and F. equiseti were the most common fungi detected. However, their occurrence was influenced by water wave action, temperature, season, and altitude. Among the fungal pathogens, A. alternata, A. tenuissima, F. oxysporum, F. equiseti, and Neofisicoccum parvum were highly pathogenic to water hyacinth. Alternaria alternata and A. tenuissima did not cause disease symptoms on ecologically important plant species (e.g. Noug, Tef, and Coffee). Application of the fungal pathogens on water hyacinth plants also showed 11%–67%, 22%–72%, 15%–55%, and 12%–50% reduction in fresh weight, dry weight, plant height, and root length of water hyacinth, respectively. This study suggests that fungal species have the potential to control water hyacinth biologically and provides baseline data for biological control efforts in the future.  相似文献   

2.
In 2004, a damping-off symptom was found on southern star, Oxypetalum caeruleum, in Kochi Prefecture, Japan. Two Phytophthora strains with different colony patterns on potato dextrose agar were isolated, and their pathogenicity was confirmed by inoculation of southern star plants and their reisolation from symptomatic plants. Both fungi were identified as Phytophthora palmivora based on morphology, physiology, and sequence analysis of the internal transcribed spacers of nuclear ribosomal DNA. This is the first report of Phytophthora blight of southern star in the world.  相似文献   

3.
The type virus of the family Hypoviridae, Cryphonectria hypovirus 1 strain EP713 (CHV1-EP713), infects Cryphonectria parasitica, the filamentous causal fungus of chestnut blight, and reduces its virulence. This pathosystem serves as a model to study fungus-mycovirus interactions. We previously developed a genetic screening protocol for host factors associated with symptom induction by CHV1-EP713 and its mutants. In the procedure the standard field fungal isolate EP155 was transformed by cDNA from a mild hypovirus mutant Cys(72), launching virus infection, and mutagenized by random plasmid insertion with pHygR conferring hygromycin resistance. We now report an extension of the study to characterize different mutant strains, with different phenotypes than their parental strain TCys(72)-1. TCys(72)-1 is moderately reduced in pigmentation and sporulation compared to the uninfected wild-type strain EP155. Mutants sfb1, sfb2 and k202 were characterized biologically and molecularly in comparison to the previously isolated mutant (namA) and the parental strain. These mutants harbored one (sfb1) or more copies (sfb2 and k202) of the mutagenic plasmid, pHygR. The three mutants had similar biological attributes; that is, vegetative growth rate, conidiation and virulence (assay on apples) was reduced on potato dextrose agar media, relative to the parental strain and pigmentation was the same or slightly increased. Interestingly, viral dsRNA accumulation levels were apparently unaltered in these mutants. The screening method was efficient for mining fungal mutants with unusual hypovirus symptoms. Further, characterization of the mutants provides interesting insights into symptom induction by the hypovirus.  相似文献   

4.
Anthracnose disease was found on centipede grass [Eremochloa ophiuroides (Munro) Hack.] planted as a ground cover on paddy field levees in Shiga Prefecture in 2004. The symptoms were ear blight, stalk blight, and leaf spots. The causal fungus was morphologically identified as Colletotrichum caudatum (Sacc.) Peck. This is the first report of centipede grass anthracnose caused by C. caudatum.  相似文献   

5.
Gnomonia fragariae has been occasionally listed among the fungi associated with diseased strawberry plants. However its pathogenicity has not been established. During the investigation on strawberry decline in Latvia and Sweden, a fungus was repeatedly recovered from discoloured root and crown tissues of severely stunted plants. Attempts to induce sporulation of the isolates grown on several agar media resulted in the formation of mature ascomata only on potato carrot agar and oatmeal agar. On morphological grounds and comparisons with reference herbarium specimens these isolates were identified as Gnomonia fragariae. The pathogenicity of the fungus was evaluated initially in the detached leaf assay and subsequently in three bioassays on strawberry plants. All the bioassays showed that G. fragariae was pathogenic on strawberry and capable of causing severe root rot and petiole blight. The symptoms that developed in the greenhouse experiments closely resembled those observed in the fields. The fungus did not cause rapid plant death but growth and development of inoculated strawberry plants was severely affected. To our knowledge this is the first time when pathogenicity of G. fragariae as a root rot pathogen has been clearly established. Our study shows that G. fragariae is one of the serious pathogens involved in the root rot complex of strawberry in Latvia and Sweden.  相似文献   

6.
Laboratory and nursery experiments were conducted to identify the causal agent of a needle blight of Pinus wallichiana, a species native to the Western Himalayas. The pathogen was identified as Myrothecium verrucaria, on the basis of morphological, cultural and molecular characterization. BLAST analysis of ITS sequences of the pathogen revealed maximum sequence identity of 99% with M. verrucaria. The sequence is the first of this fungus from P. wallichiana. Phylogenetic analysis grouped all M. verrucaria isolates in a single clade; M. roridum and M. inundatum clustered in separate clades. The pathogen grew optimally at 25 ± 1 °C on oat meal agar, pH 5.5. Inoculation experiments with M. verrucaria demonstrated pathogenicity on Pinus halepensis, Cedrus deodara and Cryptomeria japonica, in addition to Pinus wallichiana.  相似文献   

7.
Phoma koolunga is a recently recognized pathogen in the ascochyta blight complex of field pea (Pisum sativum). Unlike the other three ascochyta blight pathogens, survival of P. koolunga is poorly understood. Survival of this fungus was examined on field pea stubble and as pseudosclerotia on the surface of, and buried in, field soil. Pseudosclerotia were formed in plates containing potato dextrose agar (PDA) mixed with sand or amended with fluorocytocin. After 1 month, P. koolunga was recovered on amended PDA from 93% of stubble sections retrieved from the soil surface, 36% of buried stubble sections and 100% of pseudosclerotia buried in field soil, pasteurized or not. The frequency of recovery of P. koolunga decreased over time and the fungus was not recovered from stubble on the soil surface at 15 months, nor was it recovered from stubble buried in soil at 11 months or later, or from pseudosclerotia buried for 18 months. In a pot bioassay, most ascochyta blight lesions developed on plants inoculated with stubble retrieved from the soil surface after 1 month. Infectivity of the inoculum decreased over time. Disease on plants inoculated with stubble that had been buried or left on the soil surface for up to 6 and 5 months, respectively, and pseudosclerotia retrieved at 14 months and later from field soil did not differ from the non‐inoculated control. These results suggest that field pea stubble may play a role in survival of P. koolunga, especially if it remains on the soil surface. In addition, pseudosclerotia were able to persist in soil and infect field pea plants into the next season.  相似文献   

8.
Studies were made in the Sudan for microorganisms pathogenic to water hyacinth (Etchhornia crassipes Solms) for biological control purposes. Many fungi and bacteria were isolated from plant parts showing disease symptoms. Pathogenicity tests revealed that only five out of the twenty-five fungal and bacterial isolates were damaging to the weed plant. These included Acremonium zonatum, Drechslera specifera and Fusarium equiseti. Phoma sorghina and a bacterium Bacillus sp. are reported for the first time as potential pathogens of water hyacinth. Pathogenic isolates were also found to produce toxic metabolites in liquid cultures.  相似文献   

9.
The effect of a granular formulation of sodium azide, applied annually to pine nursery beds at rates of 0, 67.2, and 134.5 kg a. i. ha?1 under water seal or plastic seal, on soil fungal populations was determined over a 3-year period. Populations of fungi in the soil decreased following application of the sodium azide each year; the greatest decrease occurred at the highest rate of application. Populations of fungi in soil treated with the azide generally remained lower than in the controls throughout each of the 3 years; however, the population disparity between treated and control plots decreased in magnitude with each succeeding year. Populations of Trichoderma spp., in plots treated with 134.5 kg sodium azide ha?1, increased 2 weeks after treatment each year, and the population peaks increased in magnitude each year. In addition the effect of sodium azide (technical grade > 99%) at concentrations of 0, 2, 5, 10, 20 and 50 μg ml?1 in potato dextrose agar and blackstrap molasses agar media was determined in vitro for 14 isolates of Trichoderma harzianum. Growth and sporulation differed among the isolates and between the two media tested. Generally, the azide temporarily inhibited growth of the fungi, but the majority of the isolates were able to grow on either medium containing 50 μg sodium azide ml?1, although sporulation was more profuse on the molasses than on the potato dextrose agar medium.  相似文献   

10.
Foot rot is the most important disease in citrus in Spain. Phytophthora nicotianae var. parasitica is the major cause of this disease. Field treatments with classic contact fungicides have been extensively used for many years to combat stem and trunk Phytophthora diseases in citrus, while, more recently, foliar application of the systemic fungicide fosetyl-A1 has been used with great success. It is now also possible to use a biological control method for foot rot disease. Myrothecium roridum, a cosmopolitan soil hyphomycete with high cellulolytic activity, produces toxins which are very active against Phytophthora fungi. Culture filtrates of M. roridum cultured in liquid medium with low sugar content strongly inhibit in vitro development of P.n. parasitica, P. syringae and P. capsici. In glasshouse trials employingcross inoculations of M. roridum and P.n. parasitica in stems of sweet orange and willowleaf mandarin seedlings, the bark lesions produced by Phytophthora were clearly stopped at 7 or 10 days after inoculation and the cankers subsequently did not show evident activity. In field trials, M. roridum inoculated into the roots of several citrus species limited development of cankers due to P.n. parasitica (artificial or natural infection). The good results open a new way for control of Phytophthora diseases in citrus.  相似文献   

11.
Early blight, caused by Alternaria solani and A. grandis, severely affects potato crops around the world, and few management options apart from intensive fungicide use are available. In this work, we tested whether biocontrol treatments with different species of the mycoparasitic fungus Clonostachys could reduce early blight severity on the foliage of pot-grown potatoes of cultivar Ágata, and affect the survival and sporulation of the causal pathogen A. grandis. Twenty isolates from five Clonostachys species were screened in a preliminary biocontrol trial, and nine of them were selected and tested further in two confirmation trials. Treatments with three isolates from three species (C. chloroleuca, C. pseudochroleuca, C. rhizophaga) resulted in a significant reduction in disease severity in both confirmation trials, with control efficacy ranging from 88.7% to 92.9% in the first trial, and from 83.1% to 84.7% in the second trial. All Clonostachys isolates used in the confirmation trials survived on potato leaf tissues for at least 15 days, and resumed growth when subjected to high humidity, resulting in mycoparasitic overgrowth and significant reduction of the pathogen sporulation. Our results provide evidence that different species of Clonostachys, not only the ubiquitous C. rosea, are sources of useful candidates for the biocontrol of potato early blight and possibly other plant diseases caused by fungal pathogens.  相似文献   

12.
Burkholderia plantarii , the pathogen of bacterial seedling blight of rice, was detected in paddy water. Its concentration rose in July and August. The bacterial concentration in the paddy water was always higher along levees than at distances more than 5 m from levees. Confirmed to be released into water when graminaceous weeds were immersed, B. plantarii survived for at least 4 days at 30°C. B. plantarii was splashed at least 30 cm upward by rain splash in the field. Harvested seeds, which had been sprayed with B. plantarii released from graminaceous weeds at the flowering stage, retained the bacteria. Bacterial seedling blight occurred when the seeds were then sown in nursery boxes. These results indicated that graminaceous weeds growing on levees of paddy fields are a source of infection of the disease and that rice seeds are infected through the paddy water. Received 23 May 2002/ Accepted in revised form 1 September 2002  相似文献   

13.
Colletotrichum gloeosporioides and C. acutatum are causal agents of grape ripe rot, but with available methods, sporulation of C. gloeosporioides on plate media has been unstable and inferior to that of C. acutatum. To facilitate studies on C. gloeosporioides, I developed an improved method to induce conidiation of this fungus. Isolates of C. gloeosporioides were pre-cultured in potato dextrose broth for 1 week, then pulverized in whole broth. The homogenate was then spread on diluted oatmeal agar (15–20% commercial oatmeal agar medium, 1.5% agar) plates. After the plates were cultured at 25°C under continuous light for another week, the C. gloeosporioides isolates sporulated stably on the plate medium.  相似文献   

14.
Parthenium hysterophorus (Asteraceae) is known as one of the most aggressive invasive weeds, causing severe economic, environmental, human and animal health problems in India and around the world. During a series of extensive surveys for natural enemies of P. hysterophorus, a leaf spot pathogen was isolated from the affected parts of the parthenium following the standard isolation techniques using potato dextrose agar (PDA) and parthenium dextrose agar (PeDA) media. Koch's postulates were performed and found satisfactory for the isolate and proved to be pathogenic to this weed. On the basis of cultural, morphological and molecular characteristics, the pathogen was identified as Alternaria sp. PMK2. The growth of the pathogen was studied on eight selected media and it exhibited varying degrees of growth on different media. Phytotoxicity of fungal cultural filtrates was also confirmed on parthenium leaves in laboratory conditions. Due to the virulent nature of the isolated pathogen, it may be selected for further studies to develop mycoherbicide for control of this devastating weed.  相似文献   

15.
A study was conducted to investigate production of antifungal substances (AFS) by Coniothyrium minitans (Cm), a mycoparasite of Sclerotinia sclerotiorum (Ss), in modified Czapek-Dox (MCD) broth and potato dextrose broth (PDB), and effects of AFS of Cm on mycelial growth and germination of sclerotia and ascospores of Ss and incidence of leaf blight of oilseed rape caused by Ss. Results showed that mycelial growth of Ss was reduced by 41.6 and 84.5% on 3 day-old cultures grown on potato dextrose agar (PDA) amended with 10% (v v−1) of cultural filtrates of Cm grown in MCD (MCDcm) after incubation for 6 and 15 days, respectively, and by 2.7 and 15.7% on PDA amended with 10% (v v−1) of cultural filtrates of Cm grown in PDB for 6 and 15 days, respectively. In addition to retardation of mycelial growth, morphological abnormality of Ss such as hyphal swellings and cytoplasm granulation were also observed in colonies grown on PDA amended with cultural filtrates of MCDcm. Sclerotia of Ss soaked in the filtrates of MCDcm for 24 h remained viable, but their ability to undergo myceliogenic germination on PDA was delayed, compared to sclerotia treated with MCD. Germination of ascospores of Ss was unaffected on PDA amended with 10% of the filtrates of MCDcm. However, germ tubes of Ss were shortened and deformed by the formation of hyphal swellings in the treatment of MCDcm. Treatment of leaves of oilseed rape with cultural filtrates of MCDcm reduced incidence of leaf blight caused by Ss, compared to the controls (water or MCD). This study suggests that AFS produced by Cm plays an important role in the suppression of mycelial growth and germ-tube development of ascospores of Ss and that there is potential for using AFS of Cm to control leaf blight of oilseed rape caused by ascospores of Ss.  相似文献   

16.

Development of late blight of potatoes caused by Phytophthora infestans (US 8 fungal genotype, A2 mating type) was monitored in two Russet Norkotah commercial fields at Fort Fairfield in 1996 and Duncan Farm in 1997. Experimental plots representing various disease treatments (low, moderate, high and random late blight severity levels) were established in two fields in 1996. In 1997, only low and high disease treatments were established. The application of fungicides for late blight control was conducted in both years. Late blight incidence and severity were assessed in each plot of each treatment. Components of late blight disease development, tuber blight incidence and tuber yields were determined from each plot. Progress of late blight disease was rapid in 1996 but not in 1997. During the 1996 cropping season, mean disease incidence and severity in the random disease treatment plots were 84 and 21% respectively within 10 days of disease detection. In 1997, low levels of late blight severity were detected in the field plots. Average numbers of late blight leaf and stem lesions on infected plant and fungal sporangia on the diseased leaf were not significantly affected by disease treatment. Late blight foliar severity significantly affected potato tuber yields. Lowest tuber yield was obtained in plots with high disease levels and highest yields were recorded in plots with low late blight severity in 1996. Late blight severity was significantly correlated with tuber yield but not with per cent tuber blight.  相似文献   

17.
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18.
In experiments in vitro at 20 and 30°C the fungiPhytophthora palmivora, Aspergillus melleus, Thielaviopsis paradoxa, Pestalotiopsis versicolor andCurvularia pallescens showed a better mycelial growth on cassava dextrose agar than on potato dextrose agar and yam dextrose agar. This also applied to sporulation, except for the last two fungi at 20°C, which sporulated best on potato dextrose agar.Samenvatting Bij verggeljking van de invloed van aardappelglucose-agar (PDA), cassaveglucoseagar (CaDA) en yamglucose-agar (YDA) op de mycelium groei en sporulatie vanCurvularia pallescens, Phythophthora palmivora, Aspergillus melleus, Pestalotiopsis versicolor enThielaviopsis paradoxa, bleek CaDa in het algemeen de beste groei (Tabel 1) en sporulatie (Tabel 2) te geven. Cassaveglucose-agar kan beschouwd worden als een goede algemene voedingsboden voor het kweken van schimmels. Vooral in de tropische landen kan men hiervan een nuttig gebruik maken. De geschiktste cassavevariëteit moet langs empirische weg geselekteerd worden.  相似文献   

19.

BACKGROUND

The fungus Diaporthe eres was isolated from a fungal pathogen‐infected leaf of Hedera helix (English ivy) exhibiting necrosis. It is hypothesized that the causative fungus produces phytotoxins as evidenced by necrotic lesions on the leaves.

RESULTS

The fungus was isolated and grown in Czapek Dox broth culture medium and potato dextrose broth culture medium and identified as Diaporthe eres. The ethyl acetate extracts of the culture broths were phytotoxic to lettuce (Lactuca sativa) and bentgrass (Agrostis stolonifera). 3,4‐Dihydro‐8‐hydroxy‐3,5‐dimethylisocoumarin ( 1 ) and tyrosol ( 2 ) were isolated and identified as the phytotoxic constituents. Six analogs of 3,4‐dihydro‐isocoumarin were synthesized and shown to be phytotoxic. The synthesized 3,4‐dihydro‐8‐hydroxy‐3,7‐dimethylisocoumarin and 3,4‐dihydro‐8‐hydroxy‐3,3,7‐trimethylisocoumarin were two‐ to three‐fold more phytotoxic than the naturally occurring 1 in a Lemna paucicostata growth bioassay.

CONCLUSION

Synthesis and herbicidal activities of the several new analogs of 1 are reported for the first time. These promising molecules should be used as templates for synthesis and testing of more analogs. © 2017 Society of Chemical Industry  相似文献   

20.
胡蓉  郑露  刘浩  黄俊斌 《植物保护学报》2020,47(6):1261-1269
为探究稻麦轮作模式下秸秆还田对水稻根际微生物多样性与水稻纹枯病发生的影响,本研究采用Illumina测序技术结合生物信息学比较分析了秸秆还田与不还田处理的水稻根际微生物群落多样性差异,并采用实时荧光定量PCR （real-time fluorescent quantitative PCR,RT-qPCR）对这2种稻田土壤中水稻纹枯病菌Rhizoctonia solani含量进行测定,并采用随机五点取样法调查稻田中水稻纹枯病发病率和病情指数。结果表明,秸秆还田后水稻根际细菌群落Chao1丰富度指数和Shannon多样性指数均有所增加,分别增加14.42%和4.39%,其中前者增幅显著;根际真菌群落Chao1丰富度指数降低29.60%,而Shannon多样性指数略有增加,增加5.96%;在门水平上,秸秆还田和不还田处理的水稻根际土壤优势细菌门均为变形菌门、放线菌门、绿弯菌门和酸杆菌门,优势真菌门均为子囊菌门、接合菌门和担子菌门;在属水平上,秸秆还田处理的硝化螺旋菌属和芽胞杆菌属相对丰度分别比不还田处理的显著增加96.11%和106.19%;在水稻孕穗期秸秆还田土壤中水稻纹枯病菌含量比不还田处理的显著增加120.20%;秸秆还田后水稻纹枯病发生加重,病情指数比不还田处理的增加18.10%~45.41%。  相似文献   

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