Plant disease最新文献

Neofusicoccum laricinum, an important pathogenic species, causes shoot blight of larch. In China, large areas of Larix principis-rupprechtii forests are threatened by this pathogen. Currently, this pathogen is on the list of quarantine pests in China. Because of the widespread and severe damage caused by N. laricinum, a reliable and accurate diagnostic tool is urgently needed. In this study, we first identified Nlar12009 as a N. laricinum-specific gene through genomic sequence data and bioinformatic analysis. Specific primer pairs and DNA probes were designed to detect the target pathogen using a novel recombinase polymerase amplification assay with a lateral flow dipstick (RPA-LFD) method. We optimized the RPA-LFD assay to ensure high specificity to N. laricinum. Our results showed that the assay exclusively detected N. laricinum isolates with no cross-reaction with other isolates of fungal and oomycete species and nematodes. Furthermore, our detection technique exhibited a 10-fold higher sensitivity (10 fg/ml) than conventional polymerase chain reaction for N. laricinum detection. Our developed RPA-LFD assay is proved to be a highly specific, sensitive, time-saving, and convenient method for the diagnosis of N. laricinum and shows great potential in field application.

The gray mold (Botrytis cinerea; Botrytis) is the main disease affecting grapevine production in Chile. Succinate dehydrogenase inhibitors belonging to the carboxamide fungicide family are a key tool for the control of Botrytis in grapevines from the Chilean Central Valley. This study aimed to determine the sensitivity of the Chilean Botrytis population to the new generation carboxamide pydiflumetofen. Conidial germination (CG) and germ-tube elongation (GTE) sensitivity assays were conducted on 200 single-spore isolates collected during the 2016 to 2017 season. The mean effective concentration that inhibited 50% (EC₅₀) of CG in the Botrytis population was 0.0545 μg/ml, with mean values of 0.066 and 0.042 μg/ml for table and wine grapes, respectively. The mean EC₅₀ value of GTE was 0.000245, 0.0003, and 0.0019 μg/ml for the total, table grape, and wine grape populations, respectively. The comparison between pydiflumetofen and fludioxonil, a highly efficient fungicide carrying a different mode of action, showed 87.5 and 97.5% of Botrytis control with an EC₅₀ threshold of 0.1 μg/ml in table grape and wine grape populations, respectively. No cross-resistance between pydiflumetofen and fludioxonil was detected. For nine isolates with reduced pydiflumetofen sensitivity, we evaluated SdhB mutations using a qPCR-HRM diagnostic system. Two isolates carried the sdhB^P225/H272R genotype, and two isolates carried the sdhB^P225/H272Y genotype. Additional analysis of SdhB mutant isolates determined that pydiflumetofen controls wild-type as well as sdhB^P225/H272R and sdhB^P225H/H272 mutants. Pydiflumetofen does not control CG in the sdhB^P225/H272Y mutant but is effective in the GTE control. Pydiflumetofen significantly controls Botrytis independently of the SdhB genotype in wounded berry assays. This condition resembles the berry cracking due to heavy rainfall right before harvest, as seen in recent years in the Chilean Central Valley. The findings demonstrate that pydiflumetofen effectively controls the grapevine Botrytis population, suggest a moderate risk of pydiflumetofen resistance, and highlight the significance of incorporating genetic data into the design of control programs.

Maize stalk rot is a soilborne disease that poses a serious threat to maize production worldwide, with the most significant cause being fungal stalk rot. The development of a visual and rapid detection method for the maize stalk rot pathogen is significant for its prompt and accurate identification, enhancing agricultural production efficiency, and implementing timely preventive measures. These measures will help safeguard the maize yield and quality, ultimately reducing agricultural losses. In this study, we aimed to develop an efficient method to detect maize stalk rot pathogens. We focused on three pathogenic fungi commonly found in maize-producing regions worldwide: Fusarium verticillioides, F. proliferatum, and F. graminearum. Based on translation elongation factor 1-α, we developed a rapid detection technique using recombinase polymerase amplification-CRISPR/Cas12a, combined with test strips to develop an on-site rapid visual detection test for these pathogens. The method showed detection sensitivity for F. verticillioides, F. proliferatum, and F. graminearum within 20 min at concentrations of 7.8 pg/μl, 0.11 ng/μl, and 0.13 ng/μl, respectively. The sensitivity increased with increasing reaction time. Testing of field disease samples indicated that the method is effective in detecting nucleic acids obtained through crude extraction methods. In conclusion, we developed a visually rapid detection technology that does not rely on complex instruments and equipment for the on-site early detection of F. verticillioides, F. proliferatum, and F. graminearum in the field to implement effective control measures, ensuring stable and high maize yields.

Strategic mixtures of biological control agents (BCA) with demethylation inhibitor (DMI) fungicides to control diseases of fruit crops can result in additive interaction, synergism, or antagonism. To evaluate the compatibility of eight commercial DMI fungicides with the BCA Bacillus subtilis AFS032321, marketed as Theia, bacteria were cultured in nutrient broth with 0, 10, 50, 100, and 150 µg/ml of each DMI fungicide at 30°C on a shaker rotating at 180 rpm and the optical density (OD600) was measured after 24 and 48 h. In addition, nutrient agar (NA) was enriched with the same concentrations and an endospore suspension was streaked out to count colony-forming units (CFU/ml) and measure the colony diameter. Results showed vegetative cell growth was strongly inhibited at > equal to 50 µg/ml difenoconazole and > equal to 100 µg/ml tebuconazole. All other DMI fungicides had little impact on B. subtilis AFS032321 cell growth at any concentrations tested. Interestingly, mefentrifluconazole significantly promoted colony growth (diameter) at all concentrations on NA. Theia applied at label rate combined with vegetative growth-promoting DMI fungicide mefentrifluconazole (formulated as Cevya) or vegetative growth-suppressing DMI fungicide difenoconazole (formulated as Inspire) at 150 µg/ml a.i. (active ingredient) were investigated against gray mold of cherry. Disease incidence and severity 5 days after inoculation indicated the best control efficacy and synergism (+10.2) for the mixture Theia + Cevya. For the mixture Theia + Inspire an antagonistic effect (-6.8) was calculated. Our results indicate that compatibility between biological and conventional fungicides must be considered if they are used in mixtures or together in integrated spray programs.

Maize yield is threatened by increasing incidences of head smut disease caused by Sporisorium reilianum. To help breeders identify S. reilianum-resistant maize lines, the availability of efficient screening systems would be an advantage. Here we assessed maize lines with distinct levels of field resistance against head smut disease in greenhouse experiments using two different inoculation techniques. Addition of mixtures of mating-compatible sporidia to the soil at the seedling stage of the plant did not lead to plant disease, and we could detect only marginal amounts of fungal DNA in apical meristems at 18 days after inoculation. Inoculation of the maize lines by leaf-whorl inoculation led to both high disease incidence and prominent levels of fungal DNA in apical meristems in all tested maize lines regardless of their field resistance levels. Thus, S. reilianum entering the plant via the leaf whorl can escape existing resistance mechanisms of currently known field-resistant maize lines. Since field-resistant lines are also resistant to inoculation via teliospore-contaminated soil, we propose teliospore addition to seeds at the time of sowing (rather than leaf-whorl inoculation of seedlings) combined with quantitative detection of fungal DNA in apical meristems, as an efficient screening procedure to discover field-resistant lines. However, screening maize plants for resistance against the leaf-whorl inoculation method might be promising for the discovery of novel resistance mechanisms needed to develop durably resistant maize lines.

Botrytis cinerea is the causal agent of gray mold, a disease that attacks many plants worldwide. This phytosanitary problem was reported in orchards in the State of Mexico, Mexico, specifically in pomegranate crops. This study isolated this phytopathogen from fruits collected in the municipality of Chilcuautla, state of Hidalgo, Mexico, indicating that the disease is spreading across the country. Two strains of phytopathogens, MIC and MID, were obtained after conducting Koch's postulates. These strains were identified molecularly by amplifying and analyzing the concatenated sequence of the regions that correspond to the internal transcript spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (G3PDH), and DNA-dependent RNA polymerase subunit II (RPB2). In vitro confrontation tests demonstrated that B. velezensis 160 inhibited the development of both strains of B. cinerea under study through the action of nonvolatile thermostable and volatile metabolites. Applying this bacteria to pomegranate orchards for two consecutive years (2022, 2023) decreased the incidence, severity, and progression of the disease. We conclude that this bacterium can be used as a fungicide to control gray mold in pomegranate crops.

Aspergillus flavus and the produced aflatoxins cause great damage to crop production, food security, and human health. The control of A. flavus and aflatoxins in the grains during storage is a great challenge to humans worldwide. In this study, we investigated the potential of the strain TR-18, isolated from the rhizosphere of tea plants, in controlling A. flavus and aflatoxins. The results demonstrated that TR-18 greatly inhibited A. flavus growth in dual cultural tests by the production of antifungal volatiles. TR-18 was identified as Flavobacterium johnsoniae through biochemical analysis and a 16S rRNA phylogenetic tree. Moreover, TR-18 effectively inhibited A. flavus growth and aflatoxin production in peanuts during storage. Further analysis of TR-18's volatiles was conducted by gas chromatography-tandem mass spectrometry. Five authentic compounds were identified in the volatiles of TR-18: methyl thiolacetate, dimethyl disulfide (DMDS), methyl isovalerate, 5-methyl-3-hexanone, and S-methyl 3-methylbutanethioate. DMDS with a relative content of 54.92% (peak area normalization) was the most abundant compound in the volatiles. The minimal inhibitory concentration of DMDS against A. flavus growth was 50 μl/liter (compound volume/airspace volume). The other compounds also showed a great inhibition rate (more than 90%) to A. flavus at 200 μl/liter. In addition, TR-18 exhibited broad antifungal activity against other six important phytopathogens, that is, Fusarium graminearum, F. verticillioides, Colletotrichum graminicola, C. fructicola, Alternaria alternata, and Botrytis cinerea, with inhibition rates ranging from 52.90 to 98.70%. In conclusion, F. johnsoniae TR-18 with the production of five types of antifungal volatiles could be used as potential biocontrol agents in controlling pathogenic fungi and associated mycotoxins in the grains during storage.