Journal of Plant Diseases and Protection最新文献

Wheat powdery mildew is caused by the fungus Blumeria graminis f.sp. tritici which can lead up to 40% of losses in the grain production. Chemical treatment with strobilurins (Quinone outside inhibitors—QoI) is widely used to control the disease. However, a point mutation in the cytochrome b gene (G143A) of the fungus can provide resistance to strobilurins-based fungicides. Five field samples of the fungus were collected from wheat infected plants, and DNA was extracted for the analysis. The bioassay indicated that all samples were resistant to the strobilurin azoxystrobin 50% (Amistar®, 500 g/kg) in in vivo tests. Molecular analysis (allele-specific PCR and sequenced amplicons) confirmed the presence of both alleles (resistant and susceptible to strobilurins) in all samples. To our knowledge, this is the first report of the presence of strobilurin resistance allele G143A in Blumeria graminis f.sp. tritici in Paraguay.

Spiroplasma citri, the causal agent of citrus stubborn disease (CSD), causes significant losses in citrus crops. An efficient pathogen detection system is critical for epidemiology studies, particularly when a large sample size is involved. In this study, we report the development of an immunomolecular assay, immunocapture real-time polymerase chain reaction (IC-qPCR), targeting the spiralin gene for direct detection of S. citri without DNA isolation. This method can use either plant sample extracts or media in which S. citri was cultivated. The IC-qPCR protocol demonstrated a limit of detection for pure S. citri culture at a Ct value of 36.523 with a 10³-fold dilution factor, making it equally sensitive as qPCR, which exhibited signal disappearance at a 10^–3 dilution (Ct value of 37.484). In contrast, the immunological double-antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA) test produced positive results up to a 10^–2 dilution only. For S. citri-infected citrus samples, the established IC-qPCR protocol had a limit of detection at 36.46 Ct with a 1/64-fold dilution factor, matching the sensitivity of qPCR, where signal disappearance occurred at a 1/64 dilution (Ct value of 37.21). On the other hand, the immunological DAS-ELISA test yielded positive results only up to a 1/16 dilution, with optical density (OD) values of 0.364 and 0.113 for 1/16 and 1/32 dilutions, respectively. The IC-qPCR assay shows no cross-reaction for any other highly related spiroplasma species and bacteria affecting citrus trees including Candidatus liberibacter, Xylella fastidiosa, and Xanthomonas campestris pv. citri. Therefore, IC-qPCR assay provides an alternative quick and very sensitive method to screening S. citri, with the advantage of not requiring any concentration or DNA purification steps while still allowing an accurate diagnosis of CSD.

Avocado (Persea americana Milll.) holds a pivotal position in global fruit crops, contributing significantly to the economies of tropical and subtropical regions. However, the rising incidence of diseases poses a substantial risk to avocado production. This comprehensive study investigated the disease landscape in Antalya, the largest avocado cultivation area in the Türkiye. A survey of 2537 avocado trees across 11 regions from 2020 to 2021 revealed alarming disease incidences, particularly in the eastern regions of Gazipasa and Alanya. Dieback, branch canker, anthracnose, and soil-borne root rot were identified as the primary diseases affecting tree canopies, twigs, and branches. Morphological and molecular analyzes unveiled a spectrum of pathogens, with Colletotrichum gloeosporioides dominating in the Mediterranean region. Notably, Phytophthora cinnamomi emerged as a severe threat, causing root rot and decline in avocado trees. Fusarium solani and Fusarium oxysporum, known for their association with tropical fruit crops, were identified in the western parts of Antalya. Additionally, we have detected Neofusicoccum parvum, Lasiodiplodia theobromae, and Neopestalotiopsis rosae in collected samples from avocado trees. The identified pathogens exhibited varying levels of severity in branch canker and anthracnose on avocado branches and leaves. Furthermore, pathogenicity evaluations shed light on the potential of these pathogens to induce severe symptoms, emphasizing the urgency for effective control measures. The exploration of cultural and biological control strategies are crucial for mitigating the impact of branch canker, dieback, and anthracnose diseases, ensuring the sustainability of avocado cultivation in the region.

In Spring 2022, philodendron plants in South Italy showed rotting and drop of inflorescences. Inspecting the inner part of the inflorescences, abundant white mould was observed. Hyphodermella rosae was isolated from symptomatic tissues and found to be responsible of the disease after Koch’s postulate accomplishment. Morphological and molecular characterization by ITS, RBP and TEF sequencing, as well as further phylogenetic analyses, validated the identification of strain CREA OF 1276 among H. rosae. This work is the first report of H. rosae as causal agent of white rot in philodendron in Italy and worldwide and also represents a new description of pathogenic lifestyle of this corticoid species.

The ability to diagnose crop diseases is crucial which affects the crop yield and agricultural productivity. The primary area of study for crop disease diagnostics now centres on deep learning techniques. However, deep learning techniques require high computational power, which limits their portability. This paper used the variation of convolution neural network model LeNet-5 for classification and the Otsu multi-thresholding method with an optimization algorithm for the segmentation of the images. The classifier is trained using the Plant Village dataset which contains images of tomato leaves with various types of diseases. This method is highlighted for its high accuracy in disease identification. Additionally, to assess its ability to perform well with new, unseen data, real-time diseased images are tested in the proposed method. This can ensure that the method can effectively generalize beyond the initial dataset it was trained on. The performance using the dataset can be calculated using precision, recall, F1-score, and accuracy. These are compared with three existing approaches Xception, ResNet50, and VGG16 from this comparison the proposed approach gives the best accuracy for classification.

Stilbocrea banihashemiana is a recently described species of ascomycete fungi (Bionectriaceae) that causes canker and dieback diseases on fig and barberry, and dieback on loquat trees. Previous studies suggested this pathogen might affect other trees including economically important fruit crops, such as almonds, apples, and olives. This study assessed the susceptibility of 40 tree species belonging to 20 plant families, including fruit-bearing, ornamental, and edible landscape plants, to S. banihashemiana. The assessment was conducted by wound-inoculating detached shoots and one-year-old saplings with the pathogen. Based on five parameters of induced lesions, we clustered the inoculated tree species using the principal component analysis approach. The results of the approach revealed four distinct groups of tree species based on their susceptibility traits. Almond, apricot, eucalyptus, poplar, and red mulberry clustered in one group as susceptible hosts. The majority of the species examined, which included both tropical and temperate trees, were categorized as moderately susceptible. Platanus and sweet orange were identified as non-host-resistant species, while Arizona cypress, garden privet, and olive were classified as low susceptible. Moreover, our findings suggest a correlation between temperature and the aggressiveness of S. banihashemiana. This study revealed that the emerging pathogen, S. banihashemiana, could have a broader host range than currently recognized. The accidental introduction of this pathogen through the global trade of live host plants may pose a significant threat to economically important trees in temperate and subtropical regions.

Whitefly, Bemisia tabaci, nymphs and sucking sap adults, is one of the most damaging pests of potato, Solanum tuberosum. Excessive use of pesticides causes environmental pollution and the death of beneficial insects, so it is necessary to search for safer controlling alternatives. An experiment was carried out during seasons 2020–2021 and 2021–2022, under field conditions in Egypt. The objective of this study was to identify the main constituent compounds of peppermint and eucalyptus essential oils prepare coarse emulsion (CE) and nanoemulsion (NE) of both peppermint and eucalyptus essential oils and evaluate their efficiency against the whitefly, B. tabaci, in potato cultivars and the effect of these emulsions on the chemical components of potato leaves. The results revealed that the toxicity of the emulsions decreased with increasing time after spraying. The second spray which took place at a 10-day interval was more effective than the first spray. During the season of 2021, three days following the second spray, the tested emulsions' toxicity was highly effective. The reduction percentages of nymph for peppermint coarse emulsion (PCE), peppermint nanoemulsion (PNE), eucalyptus coarse emulsion (ECE), eucalyptus nanoemulsion (ENE) and imidacloprid were 82.64, 84.14, 73.26, 72.72 and 89.03, but they were 78.58, 83.27, 77.85, 69.97 and 89.26 compared with 2022. A moderately positive correlation was identified between temperature, specific humidity, wind speed and the effectiveness of the emulsions. This indicates that higher levels of temperature, humidity and wind speed were associated with increased efficacy of the emulsions. The study of the phytochemicals (total soluble protein, total carbohydrate, total phenolic contents and peroxidase activity). PCE and ECE achieved a slight decrease in protein levels. Also, ECE increased total plant carbohydrates. All treatments did not affect the phenolic compounds of potato leaf plants except ENE, which caused an increase in phenolic compounds. All treatments decreased the nitrogen plants' contents, while PCE, PNE, and ENE increased the potassium content. All treatments increase the activity of peroxidase (POX) compared with untreated plants. The formulations PNE and ENE might be an interesting alternative for integrated pest management of B. tabaci nymphs.

Insect-induced galls are regulated outgrowths of plant tissues that result from unique and mutual interactions between host plants and gall-inducing insects. The insects, mainly belonging to the orders Hemiptera, Hymenoptera, Thysanoptera, and Diptera, induce gall formation through activities such as oviposition, feeding, secretions, and chewing. These activities trigger morphogenetic and physiological factors, leading to the development of distinct forms of galls. It is noteworthy that about 90% of gall-inducing insects exhibit host specificity. This review investigates the biochemical and metabolic changes that occur when plants and insects interact. These insects use enzymes such as polygalacturonase, pectinesterase, cellulase, and proteinase present in their saliva to assist in breaking down the plant's cuticle and cell wall during the infestation. This process disrupts the subcellular environment, resulting in a chemical shock at the infestation sites. Stressful conditions stimulate the generation of action potential in plants, activating channels and causing faster depolarization of the plasma membrane. Additionally, under stress, plants may generate high levels of reactive oxygen species (ROS), leading to an oxidative burst at sites of infection. ROS triggers necrosis through a hypersensitive response. Gall-inducing insects disrupt the normal metabolism of host plants, resulting in a series of biochemical changes and metabolic imbalances. These changes promote the formation of new plant tissues, which require the production of plant growth hormones and ultimately alter the host plant's phenotype.

The symptoms caused by viroids differ, ranging from asymptomatic to mild-or-severe symptoms. Pepper plant symptoms caused by the Pepper chat fruit viroid (PCFVd) are mild compared to those affecting tomato plants; however, there is not much more known of the symptomatology on pepper plants. Symptoms that could be used for disease virulence assessment in pepper plants were elucidated from 31 commercial pepper cultivars belonging to Capsicum annuum and C. frutescens that had been purchased from agricultural shops. The plants were mechanically sap-inoculated at the seedling growth stage and observed weekly for symptom development, with disease virulence evaluations performed at 4, 8, and 12 weeks post inoculation. Infection of all plants was verified based on reverse transcription-polymerase chain reaction, along with visual evidence of growth reduction, including leaf rugosity and leaf size reduction, a narrow canopy of the blocky and elongated fruit shapes for C. annuum and explicit apical stunting with small apical leaves of the elongated fruit type for C. frutescens. The disease virulence assessment was designed based on these symptoms to produce a score with 0–10 disease virulence levels (DVLs). The results showed that the pepper cultivars displayed responses to PCFVd with DVL scores of 1.00–8.00, with no PCFVd transmission being recorded from seeds to seedlings for the 3 test cultivars. This finding indicated that the genetic resources of pepper cultivars against PCFVd were as low as 1.00 DVL. However, the low DVL pepper cultivars could provide an inoculum source to other susceptible plants via mechanical transmission.

Molecular methods are one of the most effective tools to monitor fungicide resistance. Long-read sequencing is an emerging technology in the field of plant pathology. We developed a PCR-based Oxford Nanopore Technologies amplicon sequencing method allowing the simultaneous detection and quantification of Plasmopara viticola variants conferring fungicide resistance to complex III inhibitors, zoxamide and oxathiapiprolin in the same vineyard population. Analysis of cyt b gene variants in natural P. viticola populations showed that almost all samples (23 out of 24 populations) collected in France contain variants G143A, S34L and/or E203-DE-V204 insertion. In the analysed populations, only cyt b reads with both substitutions S34L and G134A were detected at significant levels, suggesting the selection of resistant strains to both QoI fungicides and ametoctradin. French P. viticola population P36 with low sensitivity to oxathiapiprolin did not contain oxysterol binding protein sequences with both variants G770V and N837I, suggesting the presence of two different genotypes of P. viticola strain in this population. Zoxamide insensitivity associated with β-tubulin variants carrying the C239S substitution was detected in Italian vineyard populations but not in France.