Plant disease最新文献

Wheat (Triticum aestivum L.) is one of the major crops and a staple food for approximately 35% of the world population. Wheat production is constantly threatened by stripe rust, one of the most devastating wheat diseases, which is caused by Puccinia striiformis f. sp. tritici (Pst). Improving the disease resistance of wheat cultivars is the most efficient and sustainable way to control stripe rust. In this study, we aimed to explore the novel resistance resources in a collection of 180 cultivated emmer wheat accessions (T. turgidum ssp. dicoccum) collected from 32 countries on five continents. The cultivated emmer wheat accessions were genotyped by wheat Illumina iSelect 9 K single-nucleotide polymorphism (SNP) array, and phenotypes were evaluated in a greenhouse using four races and in five field environments. Conducting a genome-wide association study, we identified 14 quantitative trait loci (QTLs) associated with stripe rust resistance. Two QTLs, QYr.emmer-4A.2 and QYr.emmer-6A, confer all-stage resistance, and 12 QTLs, located on chromosomes 1A, 2A, 2B, 3A, 3B, 4A, 5A, 5B, 7A, and 7B, confer adult plant resistance (APR) to stripe rust. Compared with the known stripe rust resistance QTLs, most of the QTLs identified in this study are very likely novel QTLs. The APR QTL, QYr.emmer-7A, was consistently detected among multiple data sets from different environments and was validated using a biparental mapping population. The SNPs, simple sequence repeat markers and the genomic loci identified in this study will provide very useful information for QTL mapping and resistance breeding programs.

Areolate mildew, caused by two Ramulariopsis species (R. gossypii and R. pseudoglycines), is an important re-emergent cotton disease in the Southeastern United States. This disease has been considered of secondary importance, but the recent prevalence and high incidence observed in cotton regions have raised concern about its importance. Timely applications of quinone outside inhibitor (QoI) fungicides have been suggested to manage this disease, but QoI-resistance development is frequently detected for many fungal pathogens. In 2023, Ramulariopsis spp. isolates collected from Georgia were tested for species identification and for QoI resistance using molecular assays. Sequencing results revealed that all six isolates tested belong to R. pseudoglycines, confirming the presence of this species for the first time in Georgia. The partial amplification of the cytochrome b gene showed that 83.3% of isolates had the G143A mutation, and no other amino acid substitution was observed. This also represents the first report of QoI-resistant isolates showing the presence of this amino acid substitution in R. pseudoglycines in the United States.

Bacteriophages are viruses capable of infecting bacterial cells. Lytic phages, which infect and kill bacterial cells, are of interest in disease management in human, animal, and plant systems. In plant pathology, the biocontrol of bacterial diseases is of heightened interest because of the lack of efficacious options in many pathosystems. Numerous papers have been published in the past few decades on phage that target plant pathogenic bacteria, and a large majority of these have been focused on phage isolation and characteristics that highlight the promise and potential of phage as biocontrol agents. In contrast, relatively few of these papers have reported results from studies conducted in the field. Of the recent papers (2022 to 2025) reporting field studies, disease efficacy results are inconsistent. We argue that field studies should be an essential component of phage biocontrol research to understand how to best utilize and deploy phages to generate consistently effective disease management.

Effective management of whitefly (Bemisia tabaci) infestations and tomato yellow leaf curl virus (TYLCV) is vital for sustainable vegetable production in southwest Florida. This study introduces a robust framework that integrates satellite-based crop identification with disease risk profiling to support areawide pest control efforts. Using Sentinel-2 satellite imagery and machine learning, we accurately identified crop types throughout the growing season, allowing us to correlate whitefly populations, TYLCV incidence, and specific crop distributions. Spatial analysis revealed significant autocorrelation up to 1,750 m for both whitefly and TYLCV across the season extending to 5,000 m from January to April, which emphasizes the need for timely management in these zones. Temporal analysis showed a strong influence of temperature on whitefly populations and TYLCV incidence during the February to May period, with positive correlations observed at multiple lag times and window sizes, particularly between 30 and 85 days (P < 0.001) and window sizes from 20 to 50 days. Conversely, rainfall showed weaker correlations, suggesting that temperature is a more critical factor. The dispersal of whitefly populations was further influenced by nearby vegetable fields, with correlations extending up to 9,000 m during peak months. These results underscore the critical role of temperature patterns and spatial crop arrangements in shaping pest dynamics. Our approach offers a scalable model for proactive monitoring and management, promoting resilience and sustainability in agricultural systems facing similar pest and virus challenges globally.

Over the past century, citrus tristeza virus (CTV) has inflicted serious losses to the global citrus industry, primarily through the two most destructive diseases in citrus hosts: decline (tristeza) and stem pitting. Due to its widespread distribution, CTV has attracted significant attention from researchers worldwide. As the result of collective efforts, the industry has managed to mitigate the impact of CTV and avoid catastrophic outcomes. However, the virus remains a continually evolving threat, with new variants emerging and spreading into new areas. In light of the history of severe CTV outbreaks and an ongoing risk the virus poses to global citriculture, we assembled a team of leading CTV experts from major citrus-producing regions to prepare this Feature Article. The article provides an overview of the current global status of CTV, discussing its spread and impact, and outlines the management strategies employed around the world to protect citrus production and ensure its long-term sustainability.

North Dakota (ND) is the largest commercial producer of dry beans (Phaseolus vulgaris L.) in the US. Both dry beans and soybeans (Glycine max (L.) Merr.), are suitable hosts to soybean cyst nematode (SCN; Heterodera glycines Ichinohe), making SCN a serious production threat to both crops in ND. SCN can reduce yield by up to 56% in dry beans under heavy infestation. Host resistance is one of the best strategies to manage SCN. Resistance sources in dry beans remain limited for different SCN populations prevalent in this region. Thus, this study screened 196 dry bean genotypes, including 139 breeding lines and cultivars obtained from the North Dakota State University (NDSU) Dry Bean Breeding Program and 57 germplasm accessions from the United States Department of Agriculture-Germplasm Resource Information Network (USDA-GRIN) for their responses to SCN HG type 2.5.7. The genotypes were screened twice under controlled growth chamber conditions. Female Index (FI%) was calculated to determine resistance responses. Among the dry bean market classes from NDSU, slow darkening pinto was the least susceptible (FI = 48.0), followed by black (FI = 56.7), both belonging to the Middle-American gene pool. From the Andean gene pool, light red kidney was the most susceptible (FI = 88.2). None of the breeding lines and cultivars tested were resistant, but 19 accessions from USDA-GRIN showed moderate resistance to HG 2.5.7 from ND. The findings document valuable information to understand SCN reproduction in dry beans and develop SCN-resistant cultivars for ND and beyond in the future.

Cover crops, like winter wheat, are potential substrates for anaerobic/biological soil disinfestation (ASD) but lignin to nitrogen (N) ratio changes with growth stage and likely impacts ASD treatments due to decomposition rate effects. We evaluated wheat cover crop residue as an ASD amendment at three growth stages with varying lignin to N ratios on survival of Fusarium cugenangense, Globisporangium sylvaticum and Rhizoctonia fragariae. Treatments included 1) ASD treatment with vegetative stage residue, 1:1 lignin:N, 2) ASD treatment with early reproductive stage residue, 2:1 lignin:N, 3) ASD treatment with mature residue, 7:1 lignin:N, 4) ASD treatment with wheat bran, 1:1 lignin:N, and 5) a non-amended (non-ASD treatment) control. The experiment was conducted in a growth chamber at 25°C to 35°C. During incubation, high concentrations of volatile fatty acids (3.4 to 12 mmol VFA/kg soil at days 3 and 7) were detected in ASD treatments with low lignin to N ratio (1:1 or 2:1) cover crop residues, or wheat bran, which were higher than in ASD treatments with mature wheat residue and the non-amended control (< 1.5 mmol VFA/kg soil at days 3 and 7). ASD treatments with low lignin to N ratio cover crop residues significantly reduced F. cugenangense populations compared to all other treatments, with a 68 to 75% reduction compared to the non-amended control. Similar suppression of G. sylvaticum was observed with low lignin to N ratio cover crop residues compared to the non-amended control (> 96%), although wheat bran was also effective. For R. fragariae, survival was 55 and 73% lower in ASD treatments with vegetative stage residues or wheat bran compared to the non-amended control. Lower lignin to N ratio amendments enhanced VFA production and improved pathogen suppression; thus, using cover crops at earlier growth stages when lignin to N ratio is lower may optimize ASD outcomes.

The increasing prevalence of Phytophthora crown and trunk cankers on almond in California, especially in newly planted orchards, and pathogen resistance to older fungicides warranted the evaluation of new treatments for improved management. In two orchard trials, Nonpareil almond trees grafted on two rootstocks were soil-inoculated with Phytophthora cactorum, and the soil was treated with ethaboxam, fluopicolide, mandipropamid, oxathiapiprolin, or selected mixtures that were compared to potassium phosphite (KPO3) and mefenoxam. All fungicides except mefenoxam significantly reduced the incidence of disease. Oxathiapiprolin overall resulted in the highest reduction with few or no trees dying. Fluopicolide ranked second with efficacy similar to KPO3. Ethaboxam was the least effective. Binding of oxathiapiprolin to dry soil was demonstrated in field and laboratory studies, stressing the importance of application to pre-wetted soil followed by irrigation. In greenhouse and field studies where trunks of soil-treated trees were wound-inoculated, systemic uptake of the new Oomycota fungicides as well as of mefenoxam and KPO3 into rootstocks and scions of almond trees was evident. Our studies demonstrate that oxathiapiprolin and fluopicolide can provide highly effective control of Phytophthora crown and trunk cankers in young almond orchards. The less effective ethaboxam should be used in mixture with another fungicide such as fluopicolide. Based in part on our studies, oxathiapiprolin was registered on almond in 2021, and registration of fluopicolide, ethaboxam, and mandipropamid (nursery use only) is ongoing. With a range of modes of action available in the future, resistance management can be practiced with fungicide mixtures and rotations.

Powdery mildew is one of the most common diseases affecting indoor hemp (Cannabis sativa L. <0.3% tetrahydrocannabinol) cultivation. The primary causal organism is the biotrophic fungus Golovinomyces ambrosiae, whose polycyclic nature and short latent phase allow it to rapidly produce asexual conidia that spread to other plants. Control strategies that rely on the use of fungicides are limited by the efficacy of products that are registered for use on hemp, thus the breeding of resistant cultivars is critical. Two resistance genes and one susceptibility gene involved in powdery mildew resistance have been described for C. sativa. In the present work, we evaluated the susceptibility to G. ambrosiae of 70 C. sativa entries in one year and 98 in a second year, including accessions from the United States Department of Agriculture - Agricultural Research Service germplasm repository, breeding lines, and commercial cultivars. Entries represented different geographic origins, levels of improvement, and market classes. The trials were inoculated with G. ambrosiae, and disease severity was rated on a weekly basis. A wide range of disease severity was observed among and within entries. Several entries displayed no or very low levels of disease across years, suggesting that they have genetic resistance to G. ambrosiae. This screening provides a foundation for further characterization of the mechanisms of powdery mildew resistance in hemp and contributes to broaden the publicly available phenotypic data that will better serve stakeholders who rely on germplasm collections.

Root-knot nematodes (Meloidogyne spp.) are a major constraint to black pepper (Piper nigrum L.) in Espírito Santo (ES), Brazil. No state-wide comprehensive surveys have been conducted so far, and the influence of crop rotation and resistance evaluation is not explored. To address these gaps, 253 root samples were randomly collected from plants across four key microregions of ES. Species diversity, mix-population, and distribution were determined using a polyphasic approach that combined esterase isozyme phenotyping with mitochondrial COII and NADH5 sequencing. In addition, the resistance of the main cultivars 'Bragantina BR-124' and 'Kottanadan' was evaluated using the reproduction factor (Rf), while the influence of preceding crops on nematode occurrence was assessed through a Chi-square test of independence (χ²) and correspondence analysis. Meloidogyne spp. were detected in 94% of the samples (240/253), with mixed infections in 26.7% (64/240) of the fields distributed across 16 municipalities using esterase electrophoresis test. Three species were identified: M. arenaria (88/240), M. incognita (80/240), and M. javanica (8/240). Statistical analyses revealed strong associations between preceding crops and nematode occurrence, particularly M. javanica with papaya (Carica papaya) and sugarcane (Saccharum officinarum), and M. incognita with robusta coffee (Coffea canephora). Resistance screening showed that 'Bragantina BR-124' and 'Kottanadan' were immune to M. enterolobii (Rf = 0), resistant to M. paranaensis (Rf < 1), moderately resistant to M. javanica (Rf = 1.09 and 1.56), but highly susceptible to M. arenaria (Rf = 9.19 and 3.48) and M. incognita (Rf = 4.87 and 2.55). These findings establish the first state-wide baseline for Meloidogyne diversity, distribution, and cultivar resistance in black pepper and demonstrate the critical role of land-use history in shaping nematode communities. The exceptionally high incidence of Meloidogyne spp. in ES black pepper fields is likely linked to the use of infected planting material and preceding crops, underscoring the urgent need for certified nematode-free seedlings, nursery monitoring, and breeding programs incorporating resistance from wild Piper accessions to ensure the long-term sustainability of black pepper cultivation.