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1.
    
Phytophthora capsici is an oomycete known as the causal agent of wilting disease in Capsicum spp., which causes rotting of roots, crowns, stems, leaves and fruits. To date, little is known about the production of phytotoxic metabolites by P. capsici or their role in the infection process. As part of a project directed towards the isolation and identification of phytotoxins produced by a strain of P. capsici pathogenic to habanero pepper (Capsicum chinense), we have evaluated the effect of factors such as aeration, light and culture medium on the production of mycelium and phytotoxic metabolites by P. capsici. The results showed that culturing P. capsici in potato dextrose broth (PDB) containing habanero pepper leaf infusion, in the dark and under still conditions, results in a high production of mycelium and a high phytotoxicity of the culture filtrate, in the shortest period of time.  相似文献   

2.
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This study examined the effect of ASD strain (Aspergillus flavipes), isolated from continuous cropping soil for pepper and named by the sampling position, on soil microflora and soil enzymes in rooting zone soil of healthy and diseased (Phytophthora capsici) pepper plants. Results showed that the ASD strain could significantly reduce the number of bacteria and actinomycetes, with a significant increase in fungi in the rhizosphere soil of both healthy and diseased plants. With increasing colonization time of the ASD strain, the number of bacteria and actinomycetes decreased initially and then increased gradually, while the number of fungi was first increased significantly and later decreased slowly. The soil enzyme activities of urease, acid phosphatase, invertase and dehydrogenase were significantly increased by the ASD strain, while the activity of catalase was not significantly increased. As time from inoculation with the ASD strain increased, the activities of various enzymes were higher than controls. Maximum enzyme activities were found on the tenth day after ADS inoculation. The response of soil enzyme activities affected by the ASD strain was as follows: urease > dehydrogenase > invertase > acid phosphatase > catalase. These results suggest that the biocontrol of ASD strain could improve the micro ecology of rhizosphere soil.  相似文献   

3.
    
In this study, 76 bacterial strains were isolated from the rhizosphere soil of pepper. Of these, 23 bacterial isolates capable of inhibiting Phytophthora capsici growth were selected. Among the antagonistic bacteria, one strain, IBFCBF‐1 showed the strongest antagonistic activity, and was identified as Bacillus amyloliquefaciens based on the results of 16S rRNA gene sequence analysis, physiological and biochemical testing, and morphological characteristics. When tested with a dual‐culture method and with laboratory greenhouse studies, the strain IBFCBF‐1 was found to be a potential biocontrol agent for controlling the plant pathogen, P. capsici. Moreover, it showed high efficiency and broad‐spectrum antifungal properties in vitro. Under greenhouse conditions, IBFCBF‐1 could significantly promote the growth of pepper seedlings, and was able to solubilize phosphate, and produce indole acetic acid (IAA) and ammonia. This study clearly demonstrated that IBFCBF‐1 is a potential candidate exhibiting phytophthora blight‐suppressive and plant growth‐promoting effects on pepper.  相似文献   

4.
    
Phytophthora capsici inflicts damage on numerous crop plants by secreting a series of pectinase including pectate lyase (PEL). Here, we report a pectate lyase gene (Pcpel1) from a genomic library of a highly virulent P. capsici strain SD33. Pcpel1 was identified as an open reading frame of 1233 bp encoding a protein of 410 amino acids with a predicted amino‐terminal signal sequence of 21 amino acids. The predicted protein of Pcpel1 has a calculated molecular mass of 43.8 kDa and a pI value of 6.8. Analysis of the amino acid sequence suggested that it was a member of the polysaccharide lyase family 1 that shows pectate lyase activity. Moreover, heterologous expression of Pcpel1 in Pichia pastoris produced proteins with molecular mass 66 kDa, very likely due to differential glycosylation by the yeast. By western blotting and northern blotting analysis, Pcpel1 was strongly expressed during interaction of P. capsici with the host plant, suggesting its involvement in the process of host infection. The role of Pcpel1 in cell wall disassembly and host/parasite interaction is discussed.  相似文献   

5.
    
Based on previous cloning of VpRPW8‐e, we obtained a 1,126 bp VpRPW8‐e promoter sequence in this study. A large number of TATA‐boxes, CAAT‐boxes, and other cis‐acting elements were predicted including light‐responsive elements, hormone‐responsive elements, stress‐responsive elements, and growth‐ and development‐associated elements within the promoter sequence. To further investigate the function of this promoter, we examined its activity in response to biotic and abiotic stress. The VpRPW8‐e promoter was strongly activated by Plasmopara viticola infection, and activation also occurred when the orientation of the promoter was reversed, although to a lesser extent. Deletion analysis showed that the ?1,126 to ?475 bp region of VpRPW8‐e promoter had high activity. A promoter fragment 5′ deleted to ?475 bp (P?475) was activated in response to heat and cold stress, and even more strongly in response to Phytophthora capsici and salicylic acid (SA). Furthermore, Transgenic Nicotiana benthamiana were generated, VpRPW8‐e driven by P?475 enhanced resistance to Ph. capsici in N. benthamiana. Based on these results, the ?475 bp region was deduced to be an indispensable part of the VpRPW8‐e promoter. VpRPW8‐e promoter is involved in pathogen‐ and stress‐inducible expression.  相似文献   

6.
    
Grafting is an alternative method of plant propagation used to prevent soil‐borne diseases. This technique can improve the development of plants and therefore improve fruit yield and quality; however, several studies report that when a plant is grafted, there may be compatibility problems and changes in the phenological pattern of the crop and fruit yield and quality with respect to non‐grafted plants. There are no reports in the literature on the behaviour of serrano chilli grafted on varieties resistant to Phytophthora capsici. In this study, we evaluated the phenological behaviour and response to inoculation with P. capsici in commercial serrano chilli (Camino Real, Harris Moran) grafted or not on CM‐334 as a strategy to explore the possibility of incorporating the use of grafts in the production systems of serrano chilli. The plants were grafted at 55–60 days and maintained for 13 days in a curing chamber for the acclimatization process. At 36 and 43 days after transplantation, they were inoculated with the pathogen (300,000 zoospores/plant). None of plants grafted and inoculated with the pathogen showed wilt symptoms. All plants not grafted and inoculated with P. capsici died. There was a significant reduction in the production of leaves and flowers in the grafted plants, in relation to the non‐inoculated and non‐grafted plants, as well as a temporary delay in the beginning of fruit production with respect to the non‐grafted plants, but this delay did not affect the overall yield of the crop.  相似文献   

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8.
    
The oomycete Phytophthora capsici causes wilting disease in chilli pepper and another solanaceous plants, with important economic consequences. Although much investigation has been conducted about this pathogen, little is still known about which of its proteins are involved in the infection process. In this study, the bioassay‐guided fractionation of the secretome of P. capsici resulted in the purification of a phytotoxic protein fraction designated as p47f, capable of inducing wilting and necrosis on leaves of Capsicum chinense Jacq, and having a 47 kDa polypeptide with proteolytic activity as the major component. The isolated p47f fraction induced DNA degradation and decreased cell survival of C. chinense cell suspension culture. Sequencing of p47f indicated the presence of 15 proteins, which could be grouped into seven classes including a protease group, cell wall remodelling proteins and the transglutaminase elicitor M81D, among others. This is the first report of P. capsici secreting proteins that modulate cell responses mediated by ROS in the host.  相似文献   

9.
    
Walnut decline caused by Phytophthora sp. occurred in an orchard in Sakarya province in Turkey. Affected young trees showed poor growth, leaf discolouration, root and crown rot and eventual death. A Phytophthora sp. isolated from necrotic taproots and crown tissues. The causal agent of the disease was identified as Phytophthora cinnamomi by morphological characteristics and comparing sequences of internal transcribed spacer (ITS) region. Upon conducting pathogenicity test, averaging 7.8‐cm‐long canker developed on basal stem within 2 weeks, while no cankers developed in the control plants.  相似文献   

10.
    
Vine decline of kiwifruit was observed in an orchard in Bart?n province of Turkey. Affected vines exhibited poor terminal growth, leaf discoloration and various degrees of dieback, including complete vine death. Symptoms were observed in the field on roots, crowns and stems. Two Phytophthora species were isolated from decayed cortical roots and lower stems of kiwifruits. They were identified as Phytophthora cryptogea and Phytophthora megasperma by their morphological characteristics and the analysis of sequences of the internal transcribed spacer (ITS) region of the rDNA. Pathogenicity of the isolates was tested by stem inoculation on kiwifruit seedlings. After 4 weeks, cankers developed in the plants inoculated with P. cryptogea, while no cankers formed in those inoculated with P. megasperma and in control plants. This is the first report of P. cryptogea causing root and stem rot of kiwifruit in Turkey.  相似文献   

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12.
    
Forty‐nine Phytophthora isolates were obtained from roots and crown of apricot trees with symptoms of decline grown in commercial orchards in Malatya, Elaz?? and Diyarbak?r provinces, Turkey, in 2011 and 2013. All of the recovered isolates were identified as Phytophthora palmivora on the basis of morphological characteristics. Blast analysis of ITS region sequences of rDNA of 5 isolates revealed 100% identity with a reference isolates of P. palmivora from GenBank. Isolates of P. palmivora were pathogenic on 12‐month‐old wild apricot rootstock ‘Zerdali’ plants that were wound inoculated on the roots and on the crown. This study demonstrated that P. palmivora is the cause of the crown and root rot found on apricot in Turkey. To our knowledge, this is the first report of P. palmivora on this host plant.  相似文献   

13.
    
Pepper Phytophthora blight (PPB), caused by Phytophthora capsici, is an important disease of pepper in China. The extensive application of metalaxyl has resulted in widespread resistance to this fungicide in field. This study has evaluated the activities of several fungicides against the mycelial growth and sporangium germination of metalaxyl‐sensitive and metalaxyl‐resistant P. capsici isolates by determination of EC50 values. The results showed that the novel carboxylic acid amide (CAA) fungicide mandipropamid exhibited excellent inhibitory activity against PPB both in vitro and in vivo, with averagely EC50 values of 0.075 and 0.004 μg/ml in mycelial growth and sporangium germination, respectively, and over 88% efficacy in controlling PPB. The other three CAA fungicides also provided over 70% efficacy in controlling PPB. The mycelial growth was less sensitive to quinone outside inhibitor (QoI) fungicides azoxystrobin and trifloxystrobin than that of sporangium germination in P. capsici isolates. However, azoxystrobin and trifloxystrobin provided over 80% efficacy in controlling PPB. It was noted that propamocarb and cymoxanil did not exhibit activity against the mycelial growth or sporangium germination of P. capsici isolates in the in vitro tests, with over 70% efficacy in controlling PPB. The new fungicide mixture 62.5 g/l fluopicolide + 625 g/l propamocarb (trade name infinito, 687.5 g/l suspension concentrate (SC)) produced over 88% efficacy in controlling PPB caused by both metalaxyl‐sensitive and metalaxyl‐resistant isolates. The data of this study also proved that there was obviously no cross‐resistance between metalaxyl and the other tested fungicides. Therefore, these fungicides should be good alternatives to metalaxyl for the control of PPB and management of metalaxyl resistance.  相似文献   

14.
    
Oomycetes are one type of the most highly destructive of the diseases that cause damage to some important crop plants, such as potato late blight, cucumber downy mildew, and grape downy mildew. As main approach of the ongoing search for new botanical fungicide from plant, the secondary metabolites of D. aspersa were investigated. Through efficient bioassay‐guided isolation, two new ( 1 and 2 ) and 12 known compounds ( 3  –  14 ) were isolated, and their structures were determined via extensive NMR, HR‐ESI‐MS, and IR. They were isolated from this genus for the first time except for compounds 11 and 12 . The biological properties of 1  –  14 were evaluated against Pseudoperonospora cubensis and Phytophthora infestans. Compounds 1  –  8 showed potent antifungal activity in vitro. Additionally, compound 3 has preferable control effect on cucumber downy mildew, showing dual effect of protection and treatment in vivo.  相似文献   

15.
    
Phytophthora root and crown rot (Phytophthora cryptogea) on gerbera is difficult to manage because most gerbera cultivars are susceptible to P. cryptogea. This study was conducted in order to determine the in vivo (pot experiment) efficacy of some fungicides and biofungicides. In pot experiments, fungicides were applied 7 days after inoculation with P. cryptogea, while biofungicide was applied 7 days before inoculation. In this study, soil drenches of five fungicides were tested. “Ametoctradin+dimethomorph (100 ml/day),” “mandipropamid+difenoconazole (60 ml/day),” “propamocarb+fosetyl‐Al (200 ml/day),” “mancozeb+metalaxyl‐M (250 g/day)” and “azoxystrobin+difenoconazole (100 ml/day)” active substances were used. Similarly, one biofungicide Bacillus amyloliquefaciens syn. MBI 600 (50 g/100 L) was applied by soil drenching. Efficacy of treatments was assessed according to the percentage of the root system which was visibly rotten at the end of the experiment. Root and crown rot severity was rated on a scale of 0 = 0% root system necrotic, 1 = 1%‐25% necrotic, 2 = 26%‐50% necrotic, 3 = 51%‐75% necrotic and 4 = 76%‐100% necrotic from 12 to 21 days. In this experiment, “azoxystrobin 200 g/L + difenoconazole 125 g/L” exhibited the highest efficacy against P. cryptogea with a ratio of 43.75%. The other fungicides and biofungicides ametoctradin 300 g/L + dimethomorph 225 g/L, mandipropamid 250 g/L + difenoconazole 250 g/L, propamocarb 530 g/L + fosety‐Al 310 g/L, mancozeb 64%+metalaxyl‐M 4% and Bacillus amyloliquefaciens syn. MBI 600 11% were ineffective. Importance should be given to management strategies of P. cryptogea of and more experiments should be carried out for a better understanding of the use of registered fungicides and biofungicides.  相似文献   

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17.
    
Capsaicinoids are pungent compounds found in pepper (Capsicum spp.) fruits. Capsaicin showed antimicrobial activity in plate assays against seven isolates of five species of fungi and nine isolates of two species of oomycetes. The general trend was that oomycetes were more inhibited than fungi. Assays of capsaicin biosynthetic precursors suggest that the lateral chain of capsaicinoids has more inhibitory activity than the phenolic part. In planta tests of capsaicinoids (capsaicin and N‐vanillylnonanamide) applied to the roots demonstrated that these compounds conferred protection against the pathogenic fungus Verticillium dahliae and induced both chitinase activity and expression of several defence‐related genes, such as CASC1, CACHI2 and CABGLU. N‐Vanillylnonanamide infiltrated into cotyledons confers systemic protection to the upper leaves of pepper against the fungal pathogen Botrytis cinerea. In wild‐type tomato plants such cotyledon infiltration has no protective effect, but is effective in the Never‐ripe tomato mutant impaired in ethylene response. A similar effect was observed in tomato after salicylic acid infiltration.  相似文献   

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20.
    
Controlling pests in pre‐ and postharvest crops using natural and low‐impact products is a major challenge. The lactoperoxidase system is an enzymatic system that exists in all external secretions in mammals and is part of the non‐immune system. We tested its efficacy in in vitro microplates on Phytophthora infestans, Penicillium digitatum, Penicillium italicum, Penicillium expansum and Botrytis cinerea to determine the most suitable concentrations for use. Then, we verified its efficacy in planta under controlled conditions. Solutions prepared with 5.4 mm iodide and 1.2 mm thiocyanate and diluted threefold inhibited pathogen growth in vitro by 63–100%. Twofold‐diluted solutions protected potato plants against P. infestans by 60–74% under controlled conditions. Undiluted solution inhibited orange's and apple's postharvest pathogens in curative application with efficacy levels ranging between 84 and 95% in orange and between 63 and 74% in apple. 1.5‐fold concentrated solutions inhibited postharvest pathogens of apple in curative application with efficacy levels ranging between 84 and 92%. Our results also show that the oxidative stress response of fruit following wounding could interfere with ion efficiency. Our tests demonstrate for the first time that this biochemical method is as efficient as a conventional synthetic chemical method under controlled conditions.  相似文献   

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