European Journal of Plant Pathology最新文献

The diversity of mycoflora associated with grass and sedges belonging to 24 species of eight plant families inhabiting three regions of the Hyrcanian Forest in Iran was surveyed. Fungal isolates were recovered from the roots, stems and leaves of plants, and ITS sequences of ribosomal DNA were determined. The 113 fungal isolates were categorized into the lowest taxonomic rank possible. Surprisingly, pathogen-like fungi encompassed 34% of the endophytic isolates. Colletorichum, Fusarium, and Alternaria, all genera containing important pathogenic species, were abundant. Occurrence of Fusarium was highest in root tissues, while Colletotrichum appeared more dominant in leaves and stems. Wheat seedlings were exposed to inocula of 25 of these endophytic isolates. Eleven isolates inhibited growth of the seedlings, whereas 14 isolates promoted growth compared to uninoculated controls. Further, wheat seedlings treated with isolates reported as etiological agents such as Parastagonospora nodorum and Fusarium sp., promoted growth. We report first-time isolation of Darksidea sp., a genus of root-colonizing dark septate endophytes (DSE), from herbaceous vegetation of Hyrcanian forests of Iran.

Verticillium dahliae is an economically important soilborne pathogen of tomato of which the microsclerotial inoculum can survive in the soil for extended periods of time. Previous studies, including two studies on tomato, reported that pre-plant microsclerotia soil densities can sometimes, but not always, predict the incidence or severity of Verticillium wilt. The overall objective of the study was to determine if V. dahliae pre-plant microsclerotia densities can be used as a predictive tool for the development of Verticillium wilt of tomatoes. A published qPCR assay was optimised and could detect 4.20 fg V. dahliae DNA (0.16 microsclerotia/g soil) from tomato field soils. There were no noticeable variations in the average number of microsclerotia per hectare across five commercial tomato fields, regardless of whether a high density (four composite samples from 20 soil cores/ha), medium density (four composite samples from 12 soil cores/ha), or low density (one composite sample from five soil cores/ha) sampling method was employed. A highly intensive sampling strategy (20 independently analysed soil cores/ha) was investigated for its predictive value in disease development since it allowed for correlation analyses to be conducted. A significant correlation (r = 0.578, P = 0.008) was evident between the number of microsclerotia pre-plant and disease severity during the season in only one of the three investigated fields; no correlation existed with yield. A glasshouse plant bioassay, using specific quantities of inoculated microsclerotia, established that the microsclerotia threshold required for significant disease development was five microsclerotia/g soil (283.8 fg DNA/g soil). However, one and two microsclerotia/g soil, although not causing significant symptoms, were able to sometimes infect the plants. This study showed that pre-plant V. dahliae soil densities do not have a disease predictive value in tomato, and that plant infection can develop at very low soil inoculum densities.

Epigenetic markers related to resistance require regenerating healthy trees from previously infected plant tissues. Thus, sanitizing and regenerating healthy citrus plants from previously Candidatus Liberibacter asiaticus (CLas)-infected tissues constitute a valuable need for breeding programs. Immersion in ampicillin + streptomycin solution and thermotherapy were evaluated separately for eliminating CLas from infected citrus propagules. Valencia sweet orange (Citrus × sinensis) and trifoliate orange (Citrus trifoliata) were chosen as genotypes that were highly and moderately susceptible to CLas, respectively. Infected budwood was used to graft nucellar material with or without CLas. Thirty-two months after inoculation, 2.5-cm grafts were collected and treated by 12 h immersion in an antibiotic solution (1 g/L ampicillin + 0.1 g/L streptomycin) or in autoclaved Milli-Q water, and subsequently grafted onto Rangpur lime (C. × limonia) rootstocks. In a second experiment, thermotherapy was evaluated for treating stem cuttings kept for 0, 1.5 and 10 min at 55 °C in a water bath. The antibiotics did not influence plant regeneration, but CLas was effectively eliminated from only 22.2% of the infected propagules of trifoliate orange up to 15 months after treatment. Thermotherapy at 55 °C for 1.5 min was ineffective in completely suppressing CLas from trifoliate orange plants eight months after treatment, and was harmful to citrus propagation, notably sweet orange. Antibiotic treatment did not eliminate CLas in sweet orange propagules, but a decrease in titer was recorded for both genotypes.

The fresh and dried whole plant (CF and CD respectively) of Cympopogon citratus essential oils (EOs) and its fractions, were tested, for their antifungal activities against Bipolaris oryzae and Fusarium moniliforme; respectively responsible of brown spot and bakanae disease of rice (Oryzae sativa L). Their chemical compositions were obtained by GC-GC/MS analysis and correlated with their biological activities. All six collected EO fractions of C. citratus contain myrcene, limonene, α-gurjunene, neral and geranial, but in different proportions. Neral (45.64 - 79.00%) predominant in CD₁, CD₂, CD_m, CF_m, and geranial (18.79 - 45.64%) in CF₁, CF_2; were found as major components. A positive correlation between the biological activity and the predominant constituent (citral) content was not always apparent. Carvacrol acetate and farnesol (2E, 6Z) were found only in EO fractions from fresh plants (CF₁, CF₂, CF_m), and have high antifungal activity against B. oryzae and F. moniliforme compared to that of fractions from dried plants (CD₁, CD₂, CD_m). The EO fractions collected within the first 60 min starting from the moment the first drop of EO was dropped (CF₁, CD₁), were more active than the fractions collected after 61 min (CF₂, CD₂). Cedrol, hexahydrofarnesyl acetone, γ-decalactone, β-bisabolol, α-muurolol, cavacrol and β-eudesmol, were present in low amount in CF₂ and CD₂ and absent in CF₁ and CD₁. The results serve as benchmark for researchers/industries, in fast and better targeting bioactive compounds and identify plausible interactions that may exist between constituents of an essential oil for a given biological activity.

Fusarium crown rot (FCR) is a significant global issue in wheat production. Planting resistant cultivars is the most effective strategy for mitigating FCR damage. However, breeding for FCR resistance is challenged by the lack of a reliable and high-throughput method for rapid and accurate assessment of numerous genotypes. This study evaluated FCR resistance in 50 wheat genotypes using the common soil-based method. None of the genotypes were immune or highly resistant and only 6.0% (three genotypes) showed moderate resistance at the seedling stage. Resistant and susceptible genotypes were then selected for preliminary experiments. A rapid water-culture method for assessing FCR resistance in wheat seedlings was developed. Seedlings were planted in petri dishes and inoculated by spraying conidial suspensions. This new method, which takes 15 days (about 50% of the time required for soil-based methods), requires minimal space and eliminates variability associated with soil or potting mixes. The disease index correlation between water-culture and soil-based methods was significant (p < 0.01) with a correlation coefficient of 0.901. The resistance evaluation consistency among 50 genotypes using both methods was 94.0%, indicating high reproducibility and strong agreement with soil-based results. Therefore, this new method should be a valuable tool for initial screening of FCR-resistant germplasms from numerous genotypes in breeding programs.

Olive anthracnose caused by Colletotrichum spp. is the most important olive fruit disease worldwide. We hypothesize that induced water deficit in olive trees generates anatomical and biochemical changes which contribute to anthracnose fruit rot resistance. A three-year experiment was conducted in Arbequina under two irrigation treatments: fully irrigated (no water stress) and non-irrigated (moderate water stress), from pit hardening until harvest. At harvest, fruits were inoculated both in planta and in vitro with an isolate of C. acutatum s.l. Our results showed that fruits grown under moderate water stress had significantly lower disease incidence and severity compared to those grown without water stress. Additionally, moderate water stress increased the activity of the enzymes related to hydrogen peroxide scavenging (Catalase and Peroxidase) and enhanced cuticle fruit thickness. Together, these factors contributed to a greater resistance to C. acutatum s.l. infection, both in vitro and in planta, reflected by different area under the disease progress curve (averaging 45% and 30% lower incidence and severity, respectively). These findings could explain differences in disease expression observed in olive orchards across seasons and managements practices.

Phytophthora infestans (Mont.) de Bary is an oomycete plant pathogen that causes late blight in potato (Solanum tuberosum L.) and tomato (Solanum lycopersicum L.). This review documents the population structure of P. infestans in northern and eastern Europe, and aims to explain the differences between populations of P. infestans in this region and in western Europe. Populations of P. infestans are influenced by many factors, e.g., migrations related to the movement of potato seed tubers, possibility of sexual reproduction, changes in climate, and agricultural management practices. All the presented factors may have a significant impact on the P. infestans population structure. The knowledge on P. infestans populations varies strongly depending on country and time, even within the rather intensively studied region of eastern and northern Europe. Our review indicates some knowledge gaps, such as a lack of data for some countries and gaps in some years in population monitoring. This indicates the need to continue the monitoring of P. infestans populations.

Ips sexdentatus is a destructive bark beetle species distributed widely throughout Türkiye, particularly affecting pine and spruce trees, that has symbiotic relationships with various fungal species, although there is limited information available about these interactions. The aim of this work was to elucidate the fungal interactions associated with I. sexdentatus populations in five distinct Pinus nigra stands in the Western Mediterranean Region of Türkiye. The surface and internal fungal diversity of 250 adult I. sexdentatus collected in the field were determined and a total of 864 pure fungal isolates obtained. The isolates were grouped morphologically and representative isolates from each morphological group were subjected to DNA isolation followed by PCR using fungal ITS (Internal Transcribed Spacer) primers. Fifty-one isolates were identified (1 isolate was identified to class level, 27 to genus and 23 to species), demonstrating the presence of 23 fungal taxa in I. sexdentatus, recorded for the first time globally. In addition, the presence of the entomopathogen Beauveria bassiana, an entomopathogenic species in I. sexdentatus is the first record for Türkiye. The fungal diversity of the sample areas was determined using Shannon–Wiener, Simpson and Bray–Curtis indices. Based on the Shannon–Wiener and Simpson diversity indices, the fungal diversity in the sampled areas was similar. To the best of our knowledge, this is the first report identifying fungal species associated with I. sexdentatus populations in Türkiye.

Fusarium oxysporum f. sp. pisi (Fop) is a highly destructive root rot pathogen for the pea (Pisum sativum L.) plant. In this study, the presence of F. oxysporum isolates was detected during the 2020–2021 growing season in plants showing symptoms of root rot in provinces of Turkey (Bursa, Afyonkarahisar, İzmir and Aydın) important for pea production. The pathogen was identified by its colony growth on various media, morphological characteristics and, molecular characterization based on DNA sequencing and SCoT markers. The pathogenicity of 183 isolates obtained from the roots of disease symptomatic plants was tested after artificial inoculation of pruned roots of seedlings by dipping in a conidia suspension of the isolates. Disease severity was scored and the length of brown lesions on the stem, extending from the base, was measured for each isolate. The isolates showed very large variation (0%-80%) for disease severity. A total of 50 isolates showing high stem-lesion lengths within different disease severity ranges were selected and evaluated for their effect on plant growth parameters such as plant height, number of seeds per pod and number of pods per plant. There were significant positive correlations between the reduction (%) in plant height and lesion length, and disease severity. These isolates can potentially cause yield losses in Turkey's pea cultivation based on the measured stem lesions which could be an indication of the pathogenicity of different Fop isolates. New information about pathogenic variability in Fop isolates from Turkey will be valuable for detecting races of this pathogen and resistance of pea genotypes.

The investigation aimed to assess three methods for inducing resistance in Solanum tuberosum L. (potato) plants against Soft Rot Pectobacteriaceae (SRP) bacteria. The approaches involved the incorporation of elicitors into the in vitro nutrient medium during plant cultivation, pre-planting of seeds soaked in water-containing elicitors, and irradiating in vitro cultivated potato plants with 21 kJ/m² of ultraviolet C light (UVC). The research validated the authors’ hypothesis, that the use of specific elicitors and UV-C light could induce resistance in potato plants against SRP bacteria, identifying the most effective elicitation technique for potato plants under experimental conditions. Two elicitors, specifically 50 μM salicylic acid and 250 μg/mL proline, were determined to be the most potent under experimental conditions. Supplementation of the Murashige and Skoog medium (MS) with 50 μM salicylic acid resulted in 21% of infected plants exhibiting no symptoms of infection on the 14th-day post-inoculation, and all plants treated with 10, 30, 35, 40, 45, or 50 μM of salicylic acid displayed a diminishing rate of infection progression. Plants growing with 25 µM SA were visually characterized by faster growth rates and higher vegetative mass relative to both control and test variants. Similarly, the incorporation of 250 μg/mL proline into the MS medium caused a response with 37.5% of plants showing no disease symptoms on the 14th day post-inoculation.