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1.
Gene S31pg1, which encodes a polygalacturonase (PG), was previously isolated from citrus race S31 of Geotrichum candidum, the causal agent of citrus sour rot. We have now isolated and sequenced an additional PG gene, S31pg2, with 95% identity to S31pg1 in the mature proteins. To evaluate the contribution of the two PG genes in the development of citrus sour rot, each gene was expressed in the fission yeast Schizosaccharomyces pombe. Both genes conferred PG activity to the yeast. Crude enzyme solutions containing S31PG1 severely degraded the albedo tissue of lemon peel, but those containing S31PG2 did not. Concentrated crude S31PG1 solutions also caused soft rot on lemon fruit, indicating that not S31PG2 but S31PG1 is an important pathogenicity factor in citrus sour rot. Next, the protopectinase (PP) activity of each PG was measured. Although S31PG1 and S31PG2 are highly homologous, S31PG1 had high PP activity, whereas S31PG2 had much lower activity. PG from G. candidum noncitrus race S63 (nonpathogenic to citrus fruits) was also assayed but did not have any PP activity at all. These results suggest that the different PP activities of the PGs are a key to the pathogenicity of G. candidum to lemon fruit.  相似文献   

2.
The sweet potato (Ipomoea batatas) is characterized by the production of tuberous roots rich in starch and is one of the most produced and consumed vegetables in Brazil. Botryosphaeriaceae, among other fungi, are known to cause root and stem rot of sweet potato. However, no representative and accurate study has been performed for the correct identification of these fungal species in sweet potato in Brazil. Therefore, this study aimed to identify the Botryosphaeriaceae species associated with root and stem rot of sweet potato and confirm their pathogenicity. Tuberous roots and stems of sweet potato with rot symptoms were collected in production fields and markets and used for fungal isolations. The identification of fungi was based on the morphology of reproductive structures and phylogenetic analyses of the gene regions ITS, tef1-α, and rpb2. The following species were identified: Lasiodiplodia theobromae, L. hormozganensis, Macrophomina phaseolina, M. euphorbiicola, M. pseudophaseolina, and Neoscytalidium dimidiatum. For the pathogenicity test, one representative isolate for each species was inoculated in healthy tuberous roots and in 30-day-old healthy seedlings. Black and necrotic lesions on tuberous roots and stems were observed in all replications and resulted in the death of some seedlings. This is the first report of L. hormozganensis, M. pseudophaseolina, and M. euphorbiicola, as causal agents of the stem and root rot of sweet potato and N. dimidiatum as a causal agent of stem rot worldwide.  相似文献   

3.
We isolated 629 fungi from 1296 berry seeds of solanaceous plants, including tomato (Lycopersicon esculentum), eggplant (Solanum melongena), bell pepper (Capsicum annuum), and red pepper (Capsicum annuum var. annuum) preserved for long and short terms. The isolates were classified into 22 genera excluding unidentified fungi, and the fungal floras were divided into two types: the tomato–eggplant and pepper groups. The results of cluster analysis with unweighted pair-group method with arithmetic average also supported these groups. Most tomato seeds infested with Geotrichum candidum germinated and grew the same as uninfested seeds. Cladosporium sphaerospermum and Arthrinium sp. isolated from eggplant seeds strongly suppressed germination, and Penicillium variabile suppressed seminal root elongation on eggplant. Alternaria alternata, Botrytis cinerea, and Myrothecium verrucaria detected from red pepper or bell pepper seeds were pathogenic to the fruits and the seedlings after artificial inoculation.  相似文献   

4.
Fusarium rot on melon fruits is a postharvest disease and its importance in Brazil is increasing since its first report in 1999. Initially this disease was attributed to the fungus Fusarium semitectum based on pathogen morphology. However, there is controversy regarding the aetiology of this disease because, in the current species concept based on phylogenetic analysis, F. semitectum is regarded as a synonym to different Fusarium species. With the objective of elucidating the disease aetiology in Northeast Brazil, Fusarium isolates were obtained from melon fruits showing rot symptoms in the main producing areas of the country. From the phylogenetic analyses of TEF1 and RPB2 gene sequences, the isolates were identified as belonging to two phylogenetic species of the Fusarium incarnatum-equiseti species complex (FIESC), one in the Incarnatum clade (Fusarium sulawense) and the other in the Equiseti clade, which corresponds to a new lineage. The newly identified lineage is close to Fusarium lacertarum. Isolates from the two species showed morphological characteristics typical of the Incarnatum and Equiseti clades, agreeing with the molecular identification, and were pathogenic when inoculated on melon fruits. This is the first report of F. sulawense on melon fruits. The data generated in this study are potentially useful for a better management of the fusarium rot on melon.  相似文献   

5.
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6.
Fusarium rot of melon, caused by species of the genus Fusarium, has become an important postharvest disease for many Brazilian producers. Due to the delayed onset of symptoms, this disease is often only detected when fruits arrive at the importing country, thus generating economic loss for the exportation of the fruit. This study was developed with the aim of investigating which Fusarium species cause fruit rot in melon and to evaluate any differences in aggressiveness and development of symptoms. Species were identified through phylogenetic analysis of two loci and morphological markers. The 28 isolates obtained from diseased melon fruits of different commercial cultivars were identified as Fusarium falciforme (FSSC), F. sulawesiense, F. pernambucanum (FIESC), and F. kalimantanense (FOSC). Three isolates belong to a new phylogenetic lineage within the F. fujikuroi species complex (FFSC). All isolates were tested for pathogenicity, and first symptoms of rot in Canary melon were observed 2 days after inoculation. Isolates of F. falciforme and F. sulawesiense were shown to be more aggressive. Our results extend information on Fusarium species that cause fruit rot in melon and support the development of management strategies, as there is currently no efficient control for this disease. To our knowledge, this is the first report of the occurrence of species of the FSSC, FOSC, and FFSC from muskmelon fruits in Brazil.  相似文献   

7.
Previously, we established an expression system of polygalacturonase (PG) S31PG1 and S31PG2 from Geotrichum candidum pathogenic isolate S31 using the fission yeast Shizosaccharomyces pombe and clarified the importance of S31PG1 in the pathogenicity of G. candidum S31 on lemon fruit. In the present study, we established an expression system for S63PG1 from the nonpathogenic isolate S63. When S63PG1 was expressed, only PG activity was detected, whereas both PG and protopectinase (PP) were active when S31PG1 was expressed. Furthermore, S63PG1 had no ability to cause soft rot, while S31PG1 did. These results indicate that the PP activity of PG is a key to the pathogenicity of the fungus.  相似文献   

8.
Tomatoes grown in soilless systems can be seriously damaged byFusarium oxysporum Schlect f.sp.radicis lycopersici (Forl) causing Fusarium crown and root rot (FCRR). FCRR suppression can be achieved through the use of chemicals, selected substrates, composts and artificially introduced antagonistic microorganisms. This study evaluated the natural capacity of a used rockwool to suppress FCRR infections. New and used rockwool, sampled from closed soilless systems, was either autoclaved or not, either artificially inoculated withForl or not and, finally, sown with tomato seeds cv. ‘Cuore di Bue’. The effects of autoclaved/non-autoclaved and used/new rockwool on FCRR incidence were assessed by evaluating the symptoms of crown rot on the root — shoot transition zone of tomato seedlings. Non-autoclaved and inoculated used rockwool significantly reduced FCRR incidence when compared with non-autoclaved and inoculated new rockwool. Autoclaved and inoculated used rockwool did not suppress FCRR, similarly to new and inoculated rockwool. These findings are in accordance with other research that, on a cucumber/Pythium host/pathogen complex in a closed rockwool soilless system, demonstrated the key role of resident microflora in suppressing the root rot disease. http://www.phytoparasitica.org posting Dec. 8, 2006.  相似文献   

9.
Soil samples from 99 sites in four geographic regions of Israel were examined for the presence ofGeotrichum citri-aurantii, the sour-rot pathogen of citrus fruit. The soil at each site was sampled from three locations: the center of, the margin of, and 100 m distant from a citrus grove.Geotrichum spp. were present in all geographic regions, but could be detected in only 183 of 297 locations. Sixty to 80% of the soil samples in the center and margin of the groves containedG. citri-aurantii, whereas only less than 21% of the soil samples outside the citrus grove contained this pathogen. Of the total soil samples, only 10% contained avirulent strains (i.e., G. candidum). Outside the citrus grove, 100 m from the margin,Geotrichum spp. could not be detected at most locations (75–100%). Results indicated a possible association between the sour-rot pathogen and the grove environment in Israel.  相似文献   

10.

During 2019, fruit blight and rot symptoms were observed on olive (O. europaea L.) fruits on trees grown in the Experimental Farm, Faculty of Agriculture, Sohag University, Egypt. Fungal isolates recovered from symptomatic fruits were identified as Curvularia lunata (Walker) Boedijn (two isolates) and A. alternata (Fr.) Keissl. (one isolate). Koch’s postulates were fulfilled by a pathogenicity test conducted in vitro on olive fruits wounded before inoculation with fungal isolates and incubation at 25?±?0.2 °C in a moist chamber for a week. During incubation, we observed the development of blight and rot symptoms on fruits inoculated with both isolates of C. lunata, similar to the natural symptoms described. Conversely, A. alternata was nonpathogenic to olive fruits. PCR amplification using the specific P1 and P2 primers to C. lunata based on the Clg2p Ras protein gene sequences resulted in approx. 870 base pairs for all DNA of C. lunata analyzed, confirming the identification of C. lunata. In vitro, both chitosan nano and non-nano scale effectively inhibited mycelial growth by reducing linear mycelium and biomass and sporulation of C. lunata. In vivo, chitosan nanoscale at 2.0 mg mL?1 greatly reduced the infection and the lesion diameter of C. lunata inoculated fruits after a week and effectively induced defense-related enzyme activity of PO, PPO, and PAL. This report is the first recording of fruit blight and rots on olive caused by C. lunata, as a new disease. Also, we report the in vitro and vivo toxicity of nanoparticles of chitosan as a natural elicitor, effectively inducing defense-related enzymes against C. lunata.

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11.
Trichoderma harzianum isolate T39 and T. virens isolate DAR 74290 were evaluated as potential biological agents for control of pink rot of potato and root and stem rot of tomato caused by Phytophthora erythroseptica. Cell-free metabolites of T. virens DAR 74290 completely inhibited growth of P. erythroseptica in vitro and appeared to be fungicidal. T. virens DAR 74290 and Trichodex, a commercial formulation of T. harzianum T39, were tested for their ability to protect potato and tomato plants from disease caused by P. erythroseptica in glasshouse experiments. Trichodex and T. virens DAR 74290, alone and combined, reduced disease severity in shoots and roots of potatoes 10 weeks after inoculation with the pathogen. The yield of potatoes from plants treated with P. erythroseptica and T. virens DAR 74290 (mean of 12.9g fresh weight/pot) was significantly greater than in controls inoculated with the pathogen alone (mean of 2.1g/pot). Treatment with Trichodex alone increased the yield of tubers compared to the uninoculated controls. T. virens DAR 74290 increased the survival of tomato seedlings inoculated with the pathogen, and both this isolate and Trichodex decreased the severity of disease on tomato.  相似文献   

12.
Fungi isolated in Brazil, from lettuce, broccoli, spinach, melon and tomato, were identified as Rhizoctonia solani. All lettuce isolates anastomosed with both AG 1-IA and IB subgroups and all isolates from broccoli, spinach, melon and tomato anastomosed with AG 4 subgroup HG-I, as well as with subgroups HG-II and HG-III. DNA sequence analyses of ribosomal internal transcribed spacers showed that isolates from lettuce were AG 1-IB, isolates from tomato and melon were AG 4 HG-I, and isolates from broccoli and spinach were AG 4 HG-III. The tomato isolates caused stem rot symptoms, the spinach, broccoli and melon isolates caused hypocotyl and root rot symptoms on the respective host plants and the lettuce isolates caused bottom rot. This is the first report on the occurrence in Brazil of R. solani AG 4 HG-I in tomato and melon, of AG 4 HG-III in broccoli and spinach and of AG 1-IB in lettuce.  相似文献   

13.
Brown rot is the main disease of stone fruits in Brazil, but the susceptibility of peaches to brown rot at different stages of development in the field has not been studied under subtropical conditions. This information is relevant to guide the management of the disease. The objective of this research was to determine the influence of inoculating peaches with Monilinia fructicola at different stages of development on the infection and progress of brown rot at postharvest. Two experiments were carried out: one ex vivo with two cultivars and the other in the field for two seasons. Peaches were inoculated at different sizes for both experiments. In the field, peaches were bagged to avoid natural infection, and M. fructicola inoculum was monitored. The ex vivo incidence of the disease was lower at pit hardening than at other fruit stages for both cultivars. The incidence of brown rot for peaches attached to the trees increased with fruit ripening. Conversely, the time for symptom expression was reduced according to peach diameter. Peaches inoculated with a diameter smaller than 2 cm showed a lower incidence of brown rot and longer periods for disease expression than fruit inoculated near harvest. In conclusion, in areas with high inoculum in the orchard, a common condition in the subtropics, the grower must prevent infection at all stages of fruit development, thus avoiding losses during marketing.  相似文献   

14.
Of the 44 currently accepted species of Phytophthora, 18 have been reported in the Mediterranean area. The status of each is briefly reviewed. On citrus, P. citrophthora and P. nicotianae var. parasitica are mainly responsible for foot rot and gummosis, and in addition P. hibernalis, P. syringae, P. cifricola and P. cactorum for brown rot of fruits. The incidence of these species is closely linked to their temperature requirements. The use of sour orange as a resistant rootstock has long provided satisfactory control of foot rot and gummosis, while chemical treatments are effective against brown rot. However, there are indications that, with changingcultural practices, the resistance of sour orange is less well expressed, and the species is incidentally also susceptible to citrus tristeza closterovirus. Alternative rootstocks are therefore being sought.  相似文献   

15.
Septoria leaf spot, caused by Septoria lycopersici, is considered one of the most important diseases of tomato in Brazil. Despite its importance, the disease agent is still poorly studied. Septoria isolates collected from different production regions of Brazil were characterized by molecular, morphological, and pathogenic methods. A set of 104 isolates was sequenced for the DNA Tub, Cal, and EF1-α loci. Ten isolates were selected, according to geographical region of origin and type of leaf lesion (typical or atypical), for morphological characterization and for evaluation of aggressiveness on tomato cultivar Santa Clara. To evaluate the pathogen host range, cultivated and wild Solanaceae plants were inoculated with four selected isolates. The results showed that all isolates grouped with the type isolate of S. lycopersici in maximum likelihood and Bayesian inference trees. The isolates were morphologically similar. All isolates selected for pathogenicity testing on tomato were able to induce typical symptoms of the disease, but differed in their aggressiveness. A total of eight species of Solanaceae were also identified as potential alternative hosts for S. lycopersici. This information will provide a more accurate assessment of the risks involved with the introduction of new crops, especially of the genus Solanum, in areas where the species is already present. In addition, it will provide the basis for the establishment of more efficient methods in the management of Septoria leaf spot of tomatoes in natural conditions and in the different production systems.  相似文献   

16.
Infection with Likubin bacterium (LB) followed by Phytophthora parasitica increased the mortality of sour orange and pummelo seedlings, and enhanced the P. parasitica-induced root rot in all the four types of citrus tested. The LB-induced enhancement of root infection by P. parasitica was apparent within 1h of exposure to zoospore suspension. The enhancement of P. parasitica-induced root rot was affected by the infection sequence. Inoculation of sour orange seedlings with LB before P. parasitica was more effective in increasing P. parasitica-induced root rot than LB and P. parasitica concomitantly or LB after P. parasitica. Grafting P. parasitica susceptible scions of ponkan (Citrus reticulata) onto P. parasitica-tolerant rootstocks of sour orange greatly increased the susceptibility of rootstocks to P. parasitica. Results also demonstrate the enhancement of LB-induced symptoms by P. parasitica in citrus plants.  相似文献   

17.
Recent data on the epidemiology of the common mycotoxigenic species of Fusarium, Alternaria, Aspergillus and Penicillium in infected or colonized plants, and in stored or processed plant products from the Mediterranean area are reviewed. Emphasis is placed on the toxigenicity of the causal fungal species and the natural occurrence of well known mycotoxins (aflatoxins, ochratoxins, fumonisins, trichothecenes, zearalenone, patulin, Alternaria-toxins and moniliformin), as well as some more recently described compounds (fusaproliferin, beauvericin) whose toxigenic potential is not yet well understood. Several Fusarium species reported from throughout the Mediterranean area are responsible of the formation of mycotoxins in infected plants and in plant products, including: Fusarium graminearum, F. culmorum, F. cerealis, F. avenaceum, F. sporotrichioides and F. poae, which produce deoxynivalenol, nivalenol, fusarenone, zearalenone, moniliformin, and T-2 toxin derivatives in wheat and other small grains affected by head blight or scab, and in maize affected by red ear rot. Moreover, strains of F. verticillioides, F. proliferatum, and F. subglutinans, that form fumonisins, beauvericin, fusaproliferin, and moniliformin, are commonly associated with maize affected by ear rot. Fumonisins, were also associated with Fusarium crown and root rot of asparagus and Fusarium endosepsis of figs, caused primarily by F. proliferatum. Toxigenic A. alternata strains and associated tenuazonic acid and alternariols were commonly found in black mould of tomato, black rot of olive and citrus, black point of small cereals, and black mould of several vegetables. Toxigenic strains of A. carbonarius and ochratoxin A were often found associated with black rot of grapes, whereas toxigenic strains of A. flavus and/or P. verrucosum, forming aflatoxins and ochratoxin A, respectively, were found in moulded plant products from small cereals, peanuts, figs, pea, oilseed rape, sunflower seeds, sesame seeds, pistachios, and almonds. Finally, toxigenic strains of P. expansum and patulin were frequently found in apple, pear and other fresh fruits affected by blue mould rot, as well as in derived juices and jams.  相似文献   

18.
Red rot is an important disease of sugarcane, reported from the main producing countries of the crop. The main causal agent is Colletotrichum falcatum, which induces reddish internal stalk rot, resulting in loss of quality and quantity of sugars. While the occurrence of this disease has been reported in plantations in Brazil, the aetiology of the disease is not yet fully understood. We isolated and identified the fungi associated with sugarcane plants showing symptoms of red rot. Thirty isolates were recovered and grouped by morphology within the genera Colletotrichum and Fusarium. Based on phylogenetic analyses of DNA sequences from ITS, ACT, SOD, GAPDH, and EF-1α, eight isolates were identified as C. falcatum (n = 6) and C. plurivorum (n = 2). Twenty-two isolates belonged to the Fusarium fujikuroi species complex and were identified as F. sacchari (n = 8), F. proliferatum (n = 3), and F. madaense (n = 11). Coinfection with C. falcatum and Fusarium species were frequently observed. C. falcatum and Fusarium strains induced reddening of internal tissues and stalk rot in sugarcane plants, symptoms of red rot, while Fusarium species also induced symptoms of pokkah boeng. C. plurivorum, whose sexual stage was observed on the surface of stems, did not induce stalk rot or leaf symptoms. The results obtained in this study clarify the aetiological agents of red rot of sugarcane in Brazil. The conditions that lead to the development of specific symptoms of red rot or pokkah boeng are under investigation.  相似文献   

19.
Brown rot caused by fungi belonging to the genus Monilinia is one of the major limiting factors of sour and sweet cherry production. Up to now, three species, M. fructigena, M. laxa and M. fructicola, have been identified as causal agents of brown rot on cherries worldwide. From 2010 to 2013, during the monitoring of cherry orchards in different areas of Poland, a fourth species, M. polystroma, was isolated from brown rot symptoms on sour and sweet cherry fruits. To the best of the authors’ knowledge, this is the first time M. polystroma has been reported as the causal agent of brown rot on cherries. The genetic diversity of M. polystroma isolates from cherries and other hosts was analysed using PCR MP, ISSR and RAPD techniques and showed its clear distinctness from other Monilinia spp. tested. The cluster analysis of fingerprinting data revealed a high similarity of M. polystroma isolates from Poland and their close relationship with the reference strain from Japan, indicating that this species is a recently introduced pathogen. The highest genetic distance between the examined isolates and the highest number of different genotypes was observed in an ISSR assay. Detailed genetic diversity characteristics revealed that M. polystroma isolates from cherries did not create a distinct group but were intermingled with M. polystroma isolates from other hosts. The results of the pathogenicity test conducted on different fruit species indicated a lack of host specificity for M. polystroma isolates.  相似文献   

20.
In an attempt to find effective control measures againstColletotrichum coccodes, an emerging pathogen causing root rot on tomato in northern Italy, four experimental trials were carried out during the years 2005 and 2006 in Piedmont and Liguria in order to evaluate the effectiveness of the combination of different rootstocks (Beaufort F1, He Man F1, Maxifort) with various fumigants. In the presence of medium to high disease incidence, the best results were obtained by combining the use of a resistant tomato rootstock with soil fumigation with dimethyl disulfide at 40 or 80 gm−2 or metham sodium at 192 g m−2. Chloropicrin, applied at 20 g m−2, and the tested rootstocks alone, did not enable effective control of the pathogen. The need to monitor the appearance of new diseases and the resurgence of old ones is stressed.  相似文献   

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