Journal of Phytopathology最新文献

Plant diseases have become a problem, as both the quality and quantity of agricultural products can be significantly reduced. The goal of the research is to detect the infection in the plant leaf so that it can be cured before spreading of disease to other plants. The aim of the research is to find out the severity of the leaf disease so that it can be cured based on the level of severity. Also, crop loss can be predicted by using the severity loss. For object localization, we utilize 10,640 tomato leaf images of various classes from the PlantVillage standard repository. As a baseline for future work, we propose a model based on the Mask R-CNN architecture with ResNet-50 as the backbone that effectively performs instance segmentation for these six diseases. The dataset is annotated by using the VGG annotator tool and this annotated dataset would have been used to train the ‘Mask R-CNN model’ and the ResNet50 backbone, fine-tuning the network's weights to accurately detect and segment diseased regions on leaves. The outcomes of the suggested model achieved an average accuracy of 91.3% by using multiple performance indicators like accuracy, precision and F1 score and Recall. Based on the outcome, the severity of the disease is being identified on a scale of 0, 1, 2 and 3.

A novel Modified Deep Fuzzy Clustering (MDFC) based classification model involves four major phases. They are preprocessing, segmentation, feature extraction and finally, detection and classification phase. To reduce noise and smooth the edges of the input image of the cotton crop, bilateral filtering is first used as a preprocessing approach. Next, a modified deep fuzzy clustering is suggested for the segmentation procedure that creates a collection of segments from the preprocessed image. The segmented image is then processed to extract relevant characteristics by using an enhanced Pyramid of Histogram Orientation Gradient (PHOG), Local Directional Ternary Pattern (LDTP), and statistical-based features. In order to detect and classify cotton crop diseases more effectively, this paper proposes a hybrid system. Here, the features are put through a detection phase, after which the extracted features are trained in the Bidirectional Gated Recurrent Unit (Bi-GRU) model to determine whether or not the cotton crop is infected. Once it is detected to be diseased, the type of disease is classified via an improved Recurrent Neural Network (RNN). In terms of several performance metrics, the proposed model is validated in comparison with the traditional approaches. The MDFC-based classification model outperforms existing models with a specificity of 0.9687 at a learning rate of 90. In contrast, other models achieve lower specificities: Bi-GRU (0.8436), RNN (0.8359), CNN (0.8654), LSTM (0.8769), SVM (0.7983), VGG16 (0.8619), DCNN (0.8725), BI-RNN + BI-LSTM (0.7869), and NN + CNN (0.85478).

Blueberry (Vaccinium spp.) has been extensively planted in Morocco due to its nutritional value and economic importance. Botryosphaeria canker or stem blight of blueberry has emerged as one of the most destructive diseases affecting global production of this crop. This disease causes wood symptoms such as necrotic lesions, internal wood discoloration, and stem blight. Similar symptoms were found on blueberry farms in the Northwestern region of Morocco. Lasiodiplodia pseudotheobromae was isolated from the diseased tissues of blueberry. The identification of the causal agent was confirmed by morphological and molecular characterization through sequence analysis of two loci, the internal transcribed region (ITS) and beta-tubulin (βtub). The pathogenicity test was performed on blueberry twigs and indicated that L. pseudotheobromae causes damage to blueberry plants. This is the first report of L. pseudotheobromae on blueberry in Morocco.

Low temperatures are a key condition for various phytopathogenic bacteria, by favouring their pathogenic potential and the development of plant diseases. So far, the signal transduction pathways related to low temperatures in phytopathogenic bacteria are little understood. The occurrence of intracellular oxidative stress under this condition has been suggested as a molecular event belonging to this signalling pathway. In this study, using the Pseudomonas savastanoi pv. phaseolicola model bacteria, we evaluated intracellular redox state under low-temperature (18°C) conditions. Generation of an oxidative-stress biosensor (pKL1) and fluorometry analyses with the P. savastanoi pv. phaseolicola-roGFP2 bioreporter strain were performed. At low temperatures (18°C) the response capacity or roGFP2 oxidation diminished in relation to 28°C. Likewise, changes in the intracellular redox potential of P. savastanoi pv. phaseolicola during its growth at 28°C and 18°C were observed, with greater oxidation degree in cells grown at 18°C. These results demonstrated that low temperatures induce intracellular oxidative stress in P. savastanoi pv. phaseolicola. From this study, the oxidative stress is established as part of the cellular response to low-temperature conditions in this bacteria. This is the first report of the relation of oxidative stress with low-temperature conditions in phytopathogens bacteria.

Turcicum leaf blight (TLB) of maize is caused by Exserohilum turcicum. The TLB resistance is mainly associated with qualitative race-specific resistance that is linked to several Ht genes namely Ht1, Ht2, Ht3, HtM, HtN, HtNB and HtP. However, quantitative TLB resistance also occurs, but its mechanisms are poorly understood. In this study, tolerance or insensitivity to chlorosis and necrosis of E. turcicum culture filtrate was associated with quantitative TLB resistance. A novel detached maize seedling assay was developed for E. turcicum culture filtrate using methanol-treated modified Fries medium. Screening of E. turcicum isolates of races 2, 3, 23, 3 N, 23 N and 123 N against 61 maize inbred lines with diverse levels of resistance to TLB was conducted in the greenhouse by fungal inoculation and the detached seedling culture filtrate assay. Using an isolate of race 123 N, which can overcome all the qualitative resistance genes, a simple linear regression model (R² = 0.68, p = .90) for the 61 inbred lines was established between disease severity from foliar inoculations and culture filtrate symptom rating of the detached seedling assay. Two maize lines CML474 and CML483 had relatively high culture filtrate symptom ratings but very low disease severity with foliar inoculation indicating that these sources of quantitative TLB resistance may be unrelated to tolerance to E. turcicum culture filtrates, whose effect on seedlings could be due to the toxin known as HT-toxin or monocerin.

Grapevine Roditis leaf discoloration-associated virus (GRLDaV) is a type of virus that infects grapevines. This research aimed to determine the prevalence of GRLDaV in Turkey vineyards and investigate the genetic diversity and population structure of the selected viral isolates from Turkey compared to isolates from other countries. In this study, 800 shoot samples from Turkey vineyards were collected in late spring and autumn from different regions. The samples were analysed by RT-PCR targeting the partial RNaseH-like gene region of the virus genome. The overall prevalence of GRLDaV was 8.1% among the samples. Phylogenetic analysis of the GRLDaV genome showed that the GRLDaV isolates were clustered into two major lineages. The nucleotide diversity (π) value of Group I, including only Mediterranean isolates, was lower than Group II, suggesting little variation among isolates. Even though π values were low among the geographical regions in Turkey, the region with the highest nucleotide diversity was the Aegean population, followed by the Eastern and Mediterranean populations. Comparison between nonsynonymous and synonymous substitutions showed that negative selection acts on synonymous amino acids. Along with neutrality tests and gene flow analyses, it was emphasized that genetic drift played an important role in shaping the GRLDaV populations. This study provides important information on the prevalence and genetic diversity of GRLDaV in Turkey vineyards. The findings will help to develop better strategies to manage and control this virus, which can cause significant economic losses in grape industries.

Anastomosis groups belonging to the genus Rhizoctonia are phytopathogenic fungi that affect many agricultural crops and are well distributed globally. Among these, Rhizoctonia solani is the dominant, aggressive, widely distributed and the most extensively studied species within the Rhizoctonia genus because of its dominance as a plant pathogen. However, limited attention has been given to other Rhizoctonia species as they were believed to have little or no role in causing diseases on potatoes. Recently, accumulating information indicated that binucleate Rhizoctonia (BNR), previously considered to be saprophytic, mycorrhizal and even biocontrol agent, is phytopathogenic on many agricultural crops including potato. Up until now, there has been no comprehensive review on BNR. However, there is an intense need to understand its taxonomy, biology, detection, genomics and management, not only due to the growing increased survival and occurrence in various climatic conditions. The limited diagnostic methods, and genomic knowledge make understanding and managing of BNR species difficult. This review outlines the information available in peer-reviewed literature regarding the BNR anastomosis groups associated with potato diseases, geographical distribution, detection methods, genomics, nomenclature and taxonomical evolution along with some possible management and control strategies.

Heidari, M., & Aeini, M. (2024). Stenotrophomonas maltophilia causing maize (Zea mays L.) seedling soft rot disease, an emerging threat to maize crop. Journal of Phytopathology, 172, e13299. https://doi.org/10.1111/jph.13299

In the above published article, Figure 1b does not adequately represent the symptoms of the disease and may be misleading to readers. We are providing a corrected version Figure 1 that more accurately depicts the data.

We apologize for this error.

To understand the castor wax layer's multifaceted contribution to Amphobotrys ricini pathogenesis, the hydrophobic components of cuticular wax were analysed from waxy and non-waxy castor genotypes. Gas chromatography–mass spectrometry (GC–MS) technology enabled the stable detection and quantitative determination of various fatty acids and terpenoids. The investigation revealed a significant presence of triterpenoid compound ‘lupeol’, accounting for approximately 53.6% of the wax composition in the waxy genotype (DCH-519), which was absent in non-waxy genotype (ICS-324). On exposure to lupeol, about 93.3% of conidia germinated leading to rapid mycelium growth and sporulation of A. ricini. SEM analysis of waxy and non-waxy genotypes infected with A. ricini confirmed faster germination and production of longer germ tubes on waxy genotype compared with non-waxy genotype, which may likely due to early recognition of the suitable host in the presence of lupeol, ultimately aiding in speedy germination and growth of the pathogen setting pace for pathogenesis.

Bacterial diseases cause colossal losses in vegetable crops and are considered major limiting factors for the commercial production of vegetables around the globe. Among bacterial diseases, angular leaf spot of cucumber caused by Pseudomonas syringae is one of the most economically important diseases that cause substantial economic loss to the cucumber crop. In this study, the in-vitro and in-vivo effects of different strains (X1–X15) of the nematode symbiotic bacterium Xenorhabdus nematophila was determined on the growth of P. syringae in different selected media (TB, SB, SOB, SOC, YT and LB) and at different pH levels (6.5, 7.5 and 8.5) and on the incidence of angular leaf spot disease on potted cucumber plants. According to the results, maximum growth inhibition of P. syringe (25 mm) was observed in the case of strain X12, followed by strains X10 (23 mm), X8 (21 mm) and X6 (20 mm), while maximum colony growth was observed in the control. Moreover, this P. syringae growth inhibition by the X12 strain of X. nematophila was significantly maximum in SB medium and at pH 7.5. Results of the in-vivo experiment with potted plants showed a maximum incidence (90%) of angular leaf spot disease in control plants, while a minimum disease incidence (15%) was observed for the plants treated with two times dilution of X. nematophila culture, followed by ten times (23%) and fifty times (35%). The overall results of this study demonstrate the inhibitory effect of X. nematophila on the growth and incidence of P. syringae and underscore its putative role in the biological management of plant pathogenic bacteria.