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1.
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2.
The utilization of phosphites (Phi) could be considered as another strategy to be included in integrated disease management programmes to reduce the intensive use of fungicides and production costs. The aim of the present work was to analyze whether the beneficial effects of phosphite treatment previously observed in potato plants grown under greenhouse conditions, were reflected after harvest of field grown potatoes, both in disease protection and in yield. In addition, biochemical compounds possibly involved in induced defence responses by Phi, like phytoalexins, pathogenesis related proteins and oxidative stress enzymes were measured. Foliar applications of KPhi to field grown crops resulted in post-harvest tubers with a reduced susceptibility to Phytophthora infestans, Fusarium solani and Erwinia carotovora infections, suggesting that this compound induced a systemic defence response. An increase in phytoalexin content in P. infestans inoculated tubers obtained from Phi-treated plants suggests their participation in the defence response. Chitinase content increased 72 h after wounding or inoculation with P. infestans in tubers from KPhi-treated plants compared to wounded or infected tubers from non-treated plants. Contrary to this, the isoforms of β-1,3-glucanases analyzed did not increase in the tubers of Phi-treated plants. The increment in peroxidase and polyphenol oxidase activities indicated that these enzymes could be part of the Phi defence mechanism. No negative effects were observed in potato yield at harvest, measured as total tuber weight and dry matter, after foliar KPhi treatment. This suggests that the energetic cost involved in the defence response activation would not be detrimental to plant growth.  相似文献   

3.
The root lesion nematode Pratylenchus penetrans parasitizes a wide range of economically important crops, including potato (Solanum tuberosum). Damage by P. penetrans impacts not only the potato yield but can also reduce the tuber quality. Detailed information on tuber infection by P. penetrans is scarce for most cultivars and molecular detection of nematodes from infected tubers is needed. The objective of this study was to assess tuber symptomatology due to P. penetrans infection in 10 potato cultivars and to provide an accurate molecular methodology for nematode detection using tuber peels. Sprouts of certified potato seed from cultivars Agata, Agria, Camel, Désirée, Dirosso, Kennebec, Laura, Picasso, Royata, and Stemster were planted in 2 L pots, and soil was inoculated with 4 P. penetrans/g of soil. Sixty days after inoculation, tubers were harvested, inspected for lesions, and the number of nematodes/g of potato peel assessed. Observations of tubers with symptoms showed the presence of P. penetrans in superficial layers of peels around the lenticels and injured necrotic tissue. Different nematode stages were detected in tubers of all inoculated cultivars, varying from 4 to 46 nematodes/g of potato peel. Species-specific primers showed suitable sensitivity and reproducibility for the detection of P. penetrans in tuber potato peel samples. The molecular detection of P. penetrans directly from tuber peels can facilitate routine nematode inspections of potato seed tubers or cull potatoes for nematode detection, and prevent further dissemination of this species.  相似文献   

4.
Pectolytic bacteria were isolated from potato tubers and stems showing tuber soft rot and blackleg symptoms. Approximately half (52 %) of the isolates could grow at both 27 and 37 °C while another half (48 %) failed to grow at 37 °C. All isolates could be amplified with primers specific to the pectate lyase (pel) gene. Carbon utilisation profiles could not conclusively identify these isolates. PCR amplification using primers specific for Pectobacterium carotovorum subsp. brasiliensis was positive for all isolates that grew at 37 °C. However, the group that did not grow at 37 °C failed to amplify with P. atrosepticum specific primers. To characterise this group of isolates, the intergenic transcribed spacer region (ITS) was amplified and PCR products digested with two restriction enzymes (RsaI and CfoI) to generate ITS-PCR-RFLP profiles. The profiles of these new isolates were compared to those of the type strains of other pectolytic bacteria. Profiles of five of the selected atypical strains generated with the enzyme CfoI appeared to be most similar to those of P. wasabiae type strain. Phylogenetic analysis using concatenated partial gene sequences of housekeeping genes mdh and gapA clustered these isolates together with those of P. wasabiae reference strains thus confirming their identity. These strains were virulent on potato tubers and stems but did not elicit hypersensitive response on tobacco plants. This is the first report of P. wasabiae causing soft rot and blackleg of potatoes in South Africa.  相似文献   

5.
The seed potatoes used in these experiments had been grown in a slightly acid pleistocene sandy soil or in a marine, holocene sandy loam. They were free of sclerotia ofR. solani or lightly or moderately speckled with them. Seed potatoes from the sandy soil produced plants that suffered less fromRhizoctonia than plants from seed potatoes that had been grown on the marine sandy loam. Similarly harvested tubers had, in a non-conducive soil and in conducive soils with a (very) low inoculum density ofR. solani, fewer sclerotia when they came from seed potatoes grown in an acid sand. In each soil, the degree of infestation of the crop not only depended on the severity of infection of the seed potatoes, but also on their origin. With regard to sclerotia production on tubers, three types of soil were distinguished: suppressive, conducive with a high, and conducive with a very low inoculum density ofR. solani. The differences in infestation and in the amounts of sclerotia on tubers between the crop grown from seed potatoes from the sandy soil and that from seed potatoes from the marine sandy loam soil, is attributed to a richer load of antagonists on the former and possibly to a larger proportion of saprophyticRhizoctonia strains among their sclerotia. The antagonists seem to be inhabitants of the subterranean parts of the plant and to function independently of the soil. This implies possibilities for their use in biological control.  相似文献   

6.
Contamination of potatoes by Erwinia carotovora during grading   总被引：1，自引：1，他引：0  
Considerable tuber contamination by soft rot erwinias in rotting tubers can occur when grading potato stocks. Erwinia carotovora pv. carotovora , from a single rotting tuber, contaminated c. 100 kg of potatoes during mechanical grading, c. 50% being contaminated with 104–105 bacteria per tuber. Survival of the bacteria during storage was related to the degree of damage sustained by the tubers during grading which in turn depended on the model of oscillating riddle grader used and the cultivar of potato. Chemical disinfection of the grader immediately before use and of tubers immediately after grading reduced contamination.  相似文献   

7.
An improved method for detection, quantification and classification of soft rot bacteria associated with potato seed tubers, plant material, soil and water has been developed. The method is based on the use of a modified version of the crystal violet pectate selective medium (CVP), enrichment cultures under anaerobic conditions using pectate as the sole carbon source for recovery improvement, and the quantitative estimation ofErwinia spp. by employing a new solid medium - most probable number (MPN) method. The use of this method enabled an improvement in the recovery and identification of specificErwinia spp. in mixed populations. This was done by incubating CVP plates — used for the MPN counting — at three different temperatures (15, 28 and 39°C). These combined techniques were used for estimating low level populations at less than one cell per gram or ml tested ofErwinia carotovora subsp.carotovora, E. carotovora subsp.atroseptica, andE. chrysanthemi.  相似文献   

8.
Wheat plants rapidly recognize pathogenic and non-pathogenic conidia of the powdery mildew fungusBlumeria (syn. Erysiphe)graminis on their leaf surfaces. This suggests that a chemical signal emanates from conidia at the pre-penetration stage of infection. Conidia of B. graminis f. sp. tritici were found to contain an elicitor that was easily washed off their surface. The elicitor activity is heat stable and could not be removed by phenol extraction. By contrast, elicitor activity is sensitive to periodate oxidation and partial acid hydrolysis suggesting that the elicitor activity resides in a carbohydrate moiety. Analysis of carbohydrates revealed mostly glucose, with smaller amounts of xylose and mannose. The glucosyl residues of the B. graminis elicitor were found to be linked (1 → 2)-, (1 → 4), and (1 → 6)-, with (1 → 4, 1 → 6)- branch point residues, and no 3-linked glucose residues were detected. As treatment with β -mannanase significantly reduced elicitor activity, mixed-linkage (1 → 4), (1 → 6)-mannosyl residues appeared to be important for elicitor activity. The B. graminis elicitor induced the expression of all defence-related genes tested in wheat and also induced resistance to subsequent attack by B. graminis f. sp. tritici. In contrast, a hypersensitive response was not induced by the elicitor in the absence or the presence of a challenging inoculum of B. graminis f. sp. tritici. The elicitor also induced the accumulation of thaumatin-like proteins in barley, oat, rye, rice and maize, but did not induce necrosis in any of these species. This suggests that the B. graminis elicitor represents a host non-specific determinant of non-self recognition in cereals activating general defence responses other than the hypersensitive reaction.  相似文献   

9.
Very low numbers of Corynebacterium sepedonicum (Spiek. et Kotth.) Skapt et Burkh. in potato tubers can be detected by inoculating the bacterial fraction separated from cores (including the vascular tissue) taken from the heel end of tubers into young eggplants (Solanum melanogena). One tuber with simulated latent ring rot infection could be detected readily when mixed with 99 uninfected tubers.  相似文献   

10.
A total of 185 hexanic, dichloromethanic, ethanolic and hydroethanolic extracts from 24 species of Cerrado plants, were tested against Zabrotes subfasciatus, Acanthoscelides obtectus, and human saliva α-amylases. Twelve crude extracts presented inhibition rates greater than 80% against digestive α-amylases of the insect pest Z. subfasciatus, at a concentration of 1 mg mL−1. These extracts were also tested against A. obtectus and human saliva α-amylases to verify their affinity and specificity of action. The hydroethanolic Kielmeyera coriacea stem bark extract presented a strong inhibitory potential, with IC50 values of 110 μg mL−1 for Z. subfasciatus and 272.12 μg mL−1 for A. obtectus, in addition to a 97.09% reduction in enzyme activity of human saliva α-amylases at 125 μg mL−1. The hexanic Aspidosperma macrocarpon root wood extract totally inhibited the activity of Z. subfasciatus α-amylases, reduced the enzyme activity of A. obtectus by 14.69% at 1 mg mL−1, but did not alter the activity of human saliva α-amylases, thus characterizing greater inhibition affinity and specificity. The results suggest that the application of plant extracts against insect α-amylases represent a promising biotechnological tool for development of new insect pest control strategies, with noticeable affinity and specificity of action against different target enzymes.  相似文献   

11.
The pathogenicity of the bacteriumErwinia carotovorasubsp.atroseptica, which causes potato soft rot, is triggered by short oligogalacturonates released by enzymic degradation of plant cell wall pectin. In the first stage unsaturated digalacturonate (uDG), produced by the action of pectate lyases, is degraded by oligogalacturonide lyase (OGL) to keto-deoxyuronate (DKI). The OGL encoding gene fromE. carotovoraand the corresponding recombinant enzyme were characterized. Measuring the changes in plant cell viability and tissue maceration during soft rot pathogenesis in tissue slices of sprouting potato tubers, it was observed that exposure to uDG and DKI, produced by recombinant OGL, killed up to 30% of the plant cells over a period of 16h. This protected the tissue against maceration byE. carotovorasubsp.atroseptica. Endogenous OGL activity was detected in extracts from sprouting tubers where it may be involved in the conversion of uDG into cell toxic compounds. The results indicate that an additional function of small, diffusable digalacturonates is to induce plant cell death during the rotting process, thus contributing to defence reactions againstE. carotovorasubsp.atroseptica.  相似文献   

12.
Pectobacterium brasiliense (Pbr) infects a wide range of crops worldwide, causing potato blackleg and soft rot and vegetable soft rots. This study aimed to characterize the genetic diversity and virulence variability among 68 Pbr strains isolated from either symptomless potato progeny tubers, diseased potato plants, ware potatoes wash water, or vegetables grown in Israel, as well as strains isolated from symptomless seed tubers grown in Europe, or diseased potato plants grown in France. The collection was typed using PCR and TaqMan real-time PCR analyses, dnaX sequence analysis, pulsed-field gel electrophoresis (PFGE), and pectolytic activity. dnaX phylogeny grouped almost all strains in a common genetic clade related to Pbr, which was distinct from the other Pectobacterium species. PFGE analysis identified two main clusters, including one major group of 47 strains with 95%–100% similarity. Maceration assays on two potato cultivars showed significant differences between strains but with no correlations with the source of the strains nor the status of the host (with/without symptoms). Molecular (dnaX sequences and PFGE profiles) and phenotypic analyses (tuber maceration tests) showed that the tested Pbr strains are not a homogeneous group. Analysis of the tested Pbr strains isolated from potato and vegetables grown in fields with a history of potato cultivation suggests that seed tubers imported from Europe may be the main source for Pbr in Israel. To the best of our knowledge, this is the first study that describes biodiversity and population structure of P. brasiliense isolated from potato and vegetables under hot climate conditions.  相似文献   

13.
The resistance of eight potato cultivars to tuber soft rot caused by E. carotovora subsp. atroseptica was assessed in 2 years using three different test methods. Similar cultivar resistance rankings were obtained for any one method within a year and between years for two methods (single site, infectivity titration), but not for the third (vacuum infiltration). However, the ranking of cultivars differed for the three methods. Ranking was not affected by inoculating the cortex or the more susceptible medullary tissue, or by assessing rotting in terms of infection frequency or lesion size, but it was affected by oxygen concentration during incubation. Differences among cultivars were greater when inoculated tubers were incubated anaerobically than when incubated with 5% oxygen. There was no relationship between the relative susceptibilities of cultivars to tuber soft rot in storage in January/February and those of mother tubers after planting.  相似文献   

14.
Four extracts of Arisaema erubescens tubers by acetic acetal (AAE), benzinum (BZE), n-butanol (NBE) and chloroform (CFE) were obtained to evaluate their molluscicidal activities against the snail Oncomlania hupensis. The responses of choline esterase (ChE), alkaline phosphatase (ALP), esterase (EST), superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) to the extracts (NBE) were also investigated. In the four extracts (AAE, BZE, NBE and CFE), NBE showed the highest toxicity on the snails after 48 h exposure. NBE also showed the time- and concentration-dependent effect, for example, the LC90 values of the NBE were decreased from 365.5 mg/L (24 h) to 36.4 mg/L (96 h). At the end of exposure to NBE (LC50 concentration), the activities of ChE and ALP in snail tissues (cephalopodium and liver) decreased significantly. Isozyme electrophoresis profiles indicated that responses of isozymes (EST, SOD and GSH-Px) to NBE were more intense in liver than in cephalopodium. After 72 h exposure to NBE, the EST activity in snail liver decreased and some enzyme bands (EST1 and EST4) disappeared. But the activities of SOD 1 and GSH 2 in liver increased after 48 h exposure. The results indicated that NBE was the highest toxic component in the four extracts. The decline of the detoxification ability and the oxidative damage in snail tissues might be the main reason for the molluscicidal activities.  相似文献   

15.
In 1991 and 1992, 12 potato cultivars were screened at two locations for resistance to blackleg, after vacuum infiltration of the seed withErwinia carotovora subsp.atroseptica orE. chrysanthemi. Cultivar differences for resistance toE.c. subsp.Atroseptica andE. chrysanthemi were found which were consistent over locations and years. Seed tubers of the same cultivars were also screened for resistance to bothErwinia spp. by using a tuber slice inoculation method. Correlation coefficients for comparisons between resistance to blackleg in the field and tuber tissue resistance under aerobic or anaerobic conditions were not significant. This could partly be explained by drastic changes in relative tuber tissue resistance of the cultivars within a 5 weeks period after planting in the field. Presprouting of seed tubers in diffuse daylight had a less pronounced effect on relative tuber tissue resistance than planting in the field. Monitoring the process of mother tuber decay during the growing season of 1993 after vacuum infiltration withE.c. subsp.atroseptica andE. chrysanthemi revealed that cultivars differed in the extent to which these bacteria enhanced the process of mother tuber decay. These differences partly explained the cultivar differences for resistance to blackleg in the field.Abbreviations Eca Erwinia carotovora subsp.atroseptica - Ech Erwinia chrysanthemi - NOP Noordoostpolder - Wag Wageningen  相似文献   

16.
The symptoms of gall or hairy root do not occur in the interactions between wheat (Triticum aestivum L.) and other monocotyledonous plants, with Agrobacterium tumefaciens or Agrobacterium rhizogenes. However, both bacteria colonized wheat root surfaces at similar levels (2.0 × 107 colony forming U g−1 root) and grew without inhibition in suspension with intact or wounded wheat embryos or root segments present. Suspension-cultured wheat embryo cells grown in 7.4 m M O2 displayed 23% cell death after 1 h exposure to Agrobacterium cells, while the extent of cell death with 2.1 m M O2 averaged 8%. Cultured wheat embryo and root cells rapidly produced hydrogen peroxide (H2O2) when contacted with A. tumefaciens or A. rhizogenes. Production of H2O2 was lower at 2.1 m M O2 than 7.4 mM O2. Browning and autofluorescence of epidermal cells of callus derived from wheat embryos and wheat roots was observed after inoculation with Agrobacterium. An increase in ferulic acid was detected in the walls of roots exposed to Agrobacterium. However, neither lignin nor callose was detected by diagnostic staining methods. These findings suggest that Agrobacterium induced a resistance-like response in wheat that may reduce the efficacy of transformation and limit the normal symptom formation.  相似文献   

17.
Thaxtomins are unique 4-nitroindol-3-yl containing dioxopiperazines that cause dramatic plant cell hypertrophy and seedling stunting. This family of phytotoxins is produced by Streptomyces species that cause diseases of root and tuber crops; its members are essential for pathogenicity. The symptoms produced by thaxtomin A suggest several potential plant cell targets including the plasma membrane, various components of the cytoskeleton and the cell wall. Dramatic increases in cell volume in onion seedling hypocotyls, radish seedling hypocotyls and tobacco suspension cultures, in response to 0.05–1.0 μM thaxtomin A, suggested that this phytotoxin is interacting with one or more conserved plant cell targets. Onion root tip cells treated with thaxtomin A concentrations at or below that which inhibited onion root growth were binucleate or had abnormal cell plates. Thaxtomin A (1.0–3.0 μM) inhibited normal cell elongation of tobacco protoplasts in a manner that suggested an effect on primary cell wall development. In summary, these data suggest that thaxtomin A alters, either directly or indirectly, the deposition or composition of monocot and dicot plant cell walls in ways that affect the wall integrity and the ability of the cell to progress normally through cytokinesis.  相似文献   

18.
Differences in the content of steroid glycoalkaloids (SGA) were noted in the peels of potato tubers cultivars Alpha, Cara, Désirée and LT-7. Cultivar LT-7 had always the highest SGA content, Désirée was intermediate and Alpha and Cara had the lowest SGA content, regardless of growing conditions, tuber ageing and tuber treatments. Tubers grown during the summer developed the highest SGA content as compared to those grown in the spring and winter seasons, respectively. Tubers grown during winter showed an increase in SGA toward the end of the storage period. Similar results were obtained with tubers of LT-7 grown in a greenhouse under cool temperatures in combination with short days (which imitate the winter conditions in Israel). A decrease in SGA content was observed in tuber slices treated with a fungal cell-wall preparation fromPhytophthora citrophthora. This decrease was much stronger in the pith than in the peel, indicating a possible role for SGA in the defence mechanism because peels are the first part of the tuber to be invaded by pathogens. The above results were observed in tubers of all cultivars regardless of the growing season or tuber ageing.  相似文献   

19.
Soft rot and blackleg of potato caused by pectinolytic bacteria lead to severe economic losses in potato production worldwide. To investigate the species composition of bacteria causing soft rot and black leg of potato in Norway and Poland, bacteria were isolated from potato tubers and stems. Forty-one Norwegian strains and 42 Polish strains that formed cavities on pectate medium were selected for potato tuber maceration assays and sequencing of three housekeeping genes (dnaX, icdA and mdh) for species identification and phylogenetic analysis. The distribution of the species causing soft rot and blackleg in Norway and Poland differed: we have demonstrated that mainly P. atrosepticum and P. c. subsp. carotovorum are the causal agents of soft rot and blackleg of potatoes in Norway, while P. wasabiae was identified as one of the most important soft rot pathogens in Poland. In contrast to the other European countries, D. solani seem not to be a major pathogen of potato in Norway and Poland. The Norwegian and Polish P. c. subsp. carotovorum and P. wasabiae strains did not cluster with type strains of the respective species in the phylogenetic analysis, which underlines the taxonomic complexity of the genus Pectobacterium. No correlation between the country of origin and clustering of the strains was observed. All strains tested in this study were able to macerate potato tissue. The ability to macerate potato tissue was significantly greater for the P. c. subsp. carotovorum and Dickeya spp., compared to P. atrosepticum and P. wasabiae.  相似文献   

20.
Brassica rapa (chinese cabbage) is one of the main vegetable crops grown in Asian countries. Pectobacterium carotovorum subsp. carotovorum causes severe economic loss in this crop as well as in other Brassica crops through soft rot disease. Cysteine proteases like bromelain, papain or ficin show toxic effects to herbivorous insects and pathogenic bacteria. They have been known to be critical factors in plant defence mechanisms. The current study investigated the effect of bromelain gene (BL1) of pineapple (Ananas comosus L. Merrill) on enhancing resistance to soft rot in transgenic Brassica rapa ‘Seoulbaechu’. Three homozygous T2 lines were inoculated with Pectobacterium carotovorum subsp. carotovorum and BL8-2 line showed the lowest rate of infected leaves (RIL) in both wound inoculation and non-wound inoculation, when the non-infected line showed 100 % RIL in both cases. The highest expression of BL1 gene was also observed in BL8-2 homozygous line. Thus, the over-expressed BL1 gene conferred enhanced resistance to soft rot in Brassica rapa.  相似文献   

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