Plant disease最新文献

Tobacco Fusarium root rot, caused mainly by Fusarium oxysporum and F. solani, poses a major threat to tobacco production by severely impairing root function and reducing yield and quality. In the context of sustainable agriculture, biological control has gained increasing attention as an environmentally friendly and effective alternative to chemical pesticides. This study evaluated four tobacco rhizosphere Bacillus strains to clarify how key biological traits relate to field performance in controlling Fusarium root rot. Strains were assessed for antifungal activity, indole-3-acetic acid (IAA) production, chemotaxis toward root exudates, biofilm formation, and colonization capacity. Significant differences were observed, with G12 and G51 exhibiting the most favorable profiles. Both showed strong antifungal activity (42.42%-57.50%), robust chemotaxis toward root exudates from healthy tobacco plants (RCI up to 35.86), efficient biofilm formation, and successful colonization of tobacco tissues. Greenhouse assays demonstrated that G12 and G51 reduced disease indices to below 10.00 and achieved control efficacy above 90%, approaching that of chemical treatment. Multi-location field trials in 2024-2025 further confirmed their effectiveness, with both strains reducing disease incidence by more than 60% and consistently improving agronomic traits. G51 provided the most stable yield benefits across years and sites, while G12 and G51 also accelerated the decline of chlorophyll and leaf nitrogen content at later stages, suggesting a role in promoting earlier maturation. Overall, this study establishes a link between chemotaxis, biofilm formation, colonization, and field efficacy, underscoring the importance of integrating multiple biological traits when screening biocontrol agents. These findings provide scientific support for the application of tobacco rhizosphere Bacillus strains in the sustainable management of Fusarium root rot.

Walnut anthracnose is caused by pathogenic fungi of the genus Colletotrichum. Current detection approaches primarily depend on single-pathogen assays, which frequently fail to identify complex Colletotrichum populations in field environments, often resulting in a high rate of false negatives. To overcome this constraint, we developed a broad-spectrum detection method using recombinase polymerase amplification combined with a lateral flow dipstick (RPA-LFD), enabling rapid detection of Colletotrichum species. Targeting the conserved internal transcribed spacer (ITS) region, we designed specific primers and probes, selecting the optimal set through systematic screening. The assay specifically identified Colletotrichum species without cross-reacting with other walnut-associated fungi. The optimized RPA-LFD detection system exhibited a 10 min reaction time at 39°C and showed distinct sensitivity thresholds, detecting C. fioriniae, C. gloeosporioides, C. godetiae, C. karsti and C. nymphaeae at 10 pg/μL, while achieving 100 pg/μL for C. fructicola and C. siamense. This RPA-LFD system is simple to operate, with high sensitivity and specificity. It enables visual result interpretation and shows broad application potential in walnut anthracnose management.

This study evaluated the efficacy of ozone nanobubbles (O₃-NB) as a foliar treatment to suppress cucumber powdery mildew was evaluated in a controlled bioassay under optimal and suboptimal relative humidity (RH) conditions. O₃-NB solutions were generated at three concentrations (0.54 ± 0.08, 1.16 ± 0.23, and 2.08 ± 0.22 mg L^-1) and compared with oxygen nanobubbles (O₂-NB) and distilled water controls. In a 20-day growth chamber bioassay under three relative humidity conditions (≤40 %, 65-73 %, and ≥95 % RH), leaves treated with 0.5 mgL^-1 O₃-NB exhibited suppression of powdery mildew by approximately 20 ± 3.2 % and 33 ± 4.6 % compared to the control at moderate and low humidity. However, efficacy declined under high relative humidity (≥95 % RH). A 16-week hydroponic study confirmed that foliar application of O₃-NB at 0.5-2 mg L^-1 caused no adverse effects on cucumber growth, yield, or physical appearance. Although, efficacy was lower than typically reported for conventional fungicides, O₃-NB offers a potentially safer, residue-free alternative for integrated pest management programs, particularly during withholding periods where chemical fungicides cannot be used.

Red rust disease, caused by the algal pathogen Cephaleuros spp., poses an increasingly significant threat to oolong tea (Camellia sinensis) cultivation. Currently, however, effective management is hindered by a lack of species-specific diagnostic methods and limited analysis of host-response physiological changes. In this study, the region-wide survey was conducted, species-specific molecular diagnostics, multi-scale microscopy, and host biochemical analysis (pigments and antioxidants) were utilized to investigate Cephaleuros diversity, invasion biology, and host responses in oolong tea. Across 785 composite leaf samples, the overall Cephaleuros positivity rate was 30.19%, with incidence significantly higher detection rate in Chaozhou, Guangdong (46.59%) than in Fujian (7.58%). Genotyping via psaA-targeted qPCR revealed strikingly distinct regional distributions: C. parasiticus was predominantly detected in Chaozhou (95.3%), whereas C. virescens was the only identified species in Fujian, with no mixed infections identified. Histological analysis of Chaozhou samples revealed subepidermal thalli beneath both leaf surfaces, accompanied by palisade/spongy necrosis, which suggested deeper tissue invasion by C. parasiticus. To characterize host responses, we quantified photosynthetic pigments and antioxidant enzymes in lesion centers and margins across representative cultivars. In green-leaf cultivars, infection was generally associated with decreases in chlorophyll a and b (with significance varying by cultivar), whereas carotenoid responses were modest and cultivar dependent. In contrast, two etiolated mutants exhibited significant increases in chlorophyll a (2.0-3.7-fold) and carotenoids (~1.5-1.6-fold), and anthocyanin increased by ~62% in the etiolated Juduozai mutant. Antioxidant enzyme activity was spatially structured, with peroxidase (POD) and catalase (CAT) strongly induced at lesion margins (POD increase 39-248%), while lesion centers exhibited reduced activity (5-41%). Superoxide dismutase (SOD) showed a modest increase at the lesion margins (increase 18-31%). A composite "reaction index" (POD+SOD at lesion margins) was used to classify cultivars into high and moderate response categories. These findings provide new insights into the ecological dynamics and host responses associated with Cephaleuros infection in oolong tea and highlight the potential for using these indicators in cultivar selection and disease management strategies.

Oat stem rust, caused by Puccinia graminis f. sp. avenae (Pga), is a devastating fungal disease that poses a serious threat to global oat production. In recent years, with the expansion of oat cultivation area and the shortage of resistant cultivars in China, the prevalence of this disease has shown an increasing trend. There is an urgent need to clarify the population structure and virulence characteristics of P. graminis f. sp. avenae for effective disease management and resistance breeding. From 2023 to 2024, this study collected a total of 186 oat stem rust samples Hebei Province, China. Single isolates were obtained through single-uredinium, and physiological race identification and virulence frequency analysis were conducted using 12 single-gene differential lines. Additionally, two predominant P. graminis f. sp. avenae races were selected to evaluate the seedling and adult-stage resistance of 59 oat cultivars (lines). The results showed that 188 single-uredium isolates were obtained from 158 viable samples (with a survival rate of 85.0%), and seven physiological races were identified: TJD, TJN, TKN, TJB, TBD, TGD, and TJL. Among them, TJD was the predominant race (occurrence frequency 37.7% in 2023, 38.8% in 2024), TJN was the sub-predominant race (28.2% in 2023, 31.3% in 2024), and the frequencies of the remaining five races were all below 17.6%. This indicates that the P. graminis f. sp. avenae population structure in China is relatively stable with low virulence diversity. All isolates were virulent to Pg1, Pg2, Pg3, and Pg4, while avirulent to Pg6, Pg13, and Pg16. The virulence frequency to Pg10 ranged from 3.1% to 20.8%. In total, 31 (52.6%) oat cultivars were resistant to all tested races of P. graminis f. sp. avenae in field test in 2023-2024. This study supplements global P. graminis f. sp. avenae surveillance data, clarifies the race composition and virulence dynamics of P. graminis f. sp. avenae in northern China, and provides a scientific basis for the integrated management of oat stem rust and the breeding of resistant cultivars.

Pear decline, caused by 'Candidatus Phytoplasma pyri', has emerged in Chilean pear orchards in recent years. While several Cacopsylla species are potential vectors of 'Ca. P. pyri', the disease's full epidemiological cycle remains uncertain. Cacopsylla bidens, present in Chilean orchards, has recently been reported as a vector. This study conducted year-long surveys in two commercial pear orchards across different Chilean regions, capturing C. bidens in zones with 'Ca. P. pyri'-infected pear trees. All developmental stages were collected, with peak abundances occurring in March and April. Outside the study zones, C. bidens were found in pine trees but not in adjacent cultivated areas. Two seasonal morphotypes, summer and winter forms, were identified. Molecular analysis detected 'Ca. P. pyri' in a high proportion of insects, with maximum infection rates in March and April. These findings advance our understanding of 'Ca. P. pyri' spatial and temporal dynamics and its potential role in 'Ca. P. pyri' spreading under Chilean field conditions.

Durian (Durio zibethinus) is an economically important tropical fruit endemic to Southeast Asia. Hainan is a new region for durian cultivation. Foliar diseases of durian were common at all durian orchards during field surveys carried out from October 2023 to October 2024 in Hainan, China. In this study, Fusarium species associated with durian foliar disease in Hainan (China) were studied based on multilocus phylogenetic analyses using translation elongation factor 1-α (tef1), partial RNA polymerase second largest subunit (RPB2), and calmodulin (CaM). Six Fusarium species including F. pernambucanum, F. sulawesiense, F. hainanense, F. irregulare, F. mangiferae and F. concentricum were identified. Pathogenicity tests showed that all six species were pathogenic to detached wounded and unwounded durian leaves except F. irregulare, which only induced visible symptoms on wounded durian leaves. The findings from this study expand the pathogenic fungal species on durian as this is the first report of these Fusarium spp. causing durian leaf disease worldwide.

Crown rust, caused by Puccinia coronata f. sp. avenae (Pca), remains a persistent threat to oat production in Australia. To monitor recent shifts in virulence and population structure, 30 Pca isolates collected during the 2024 growing season across major Australian oat-producing regions were analysed. Virulence analysis of 30 isolates using 52 oat differential lines identified 25 unique races that were not detected in previous years. Whole-genome sequencing of 28 of these isolates were analysed in the context of a broader historical Australian and international genomic datasets including isolates from Taiwan, South Africa, USA. Results confirmed the uniqueness of the Australian Pca population and revealed well-established genotypic lineages persisting over multiple years, with L18 and L16 being dominant. Notably, L16 was again present in Western Australia after being undetected in 2023, while L18 maintained its prevalence for a third consecutive season. Beyond these dominant groups, phylogenetic analysis and a k-mer containment analysis also identified a novel and genetically distinct lineage, designated as L19, represented by one isolate collected in WA. To add to the characterisation of lineage L19, we recorded virulence phenotypes on a small collection of current commercial cultivars. These findings enhance understanding of Pca diversity and emphasise the importance of surveillance approaches that integrate phenotypic and genomic surveillance.

Xanthomonas arboricola pv. pruni (XAP) causes bacterial spot of peach. Current disease management in the southeastern USA mainly relies on routine applications of copper and oxytetracycline (OTC), but copper-tolerant and OTC-resistant XAP have been reported in South Carolina (SC) peach orchards. To study the prevalence and persistence of copper-tolerant and OTC-resistant XAP, a survey was conducted across seven SC and Georgia peach orchards/farms annually during 2021 to 2024. Of the 1,741 XAP isolates collected, 4.4% were copper sensitive; 24.3%, 65.5%, and 5.8% were copper-tolerant up to 150 (LCT150), 175 (LCT175), and 200 µg/ml of copper sulfate pentahydrate, respectively. All the OTC-resistant isolates (24.9% of the population) came from the three conventional SC orchards and contained tetC. In the same orchards, trees with OTC-resistant isolates had significantly higher bacterial spot incidence and severity on both fruit and leaves than the other trees, while higher bacterial leaf spot incidence was observed on trees with LCT175 vs. LCT150 XAP, suggesting potential negative impact of OTC resistance and copper tolerance on the chemical spray programs. In each orchard, bacterial spot incidence, severity, and defoliation increased over time within each season, but the percentage of the resistant/tolerant XAP population remained similar. Regardless of the spray programs utilized, copper-tolerant and OTC-resistant XAP populations have been consistently recovered from the sampled trees across years. Season-long chemical spray programs are still valuable for this disease, but the prevalence and persistence of copper-tolerant and OTC-resistant XAP emphasizes the need for resistance management and development of novel disease management strategies.

The recent expansion of cotton acreage in the semi-arid Northern High Plains of Texas has raised concerns about the potential widespread distribution of Verticillium dahliae, the causal agent of Verticillium wilt, into these areas. These concerns were primarily driven by the use of lower seeding rates; lower summer air temperatures; the absence of completely resistant cultivars; and the region's proximity to the Southern High Plains, where the pathogen is endemic. This study was conducted to assess Verticillium wilt risk, based on microsclerotia density, in the Northern High Plains. Soil samples were collected from 26 cotton fields across 10 counties, and viable microsclerotia in 40 cm³ of soil per field were quantified using a plating assay with semi-selective media. Microsclerotia were detected in 88.4% of fields: 38.5% of fields were categorized as high risk (microsclerotia/cm³ ≥ 10), 23.1% as moderate risk (3 < microsclerotia/cm³ ≤ 9.9), 26.9% as low risk (0 < microsclerotia/cm³ ≤ 3), and 11.5% showed no detectable risk (microsclerotia = 0). All isolates/phylotypes tested belonged to the defoliating pathotype. Management recommendations tailored to the risk categories are discussed. The detection of microsclerotia in 88.4% of the fields surveyed, with 38.5% categorized as high risk, indicates a concerning level of inoculum and highlights the need for continued surveillance and further research on phenotypic and genotypic characterisation.