Plant disease最新文献

Puccinia striiformis f. sp. tritici (Pst) is a destructive pathogen renowned for its dual reproductive modes, an asexual stage on wheat and a sexual stage on barberry (Berberis), which makes wheat cultivars vulnerable to newly emerging races. However, little has been known about the impact of treatment on barberry plants on declining population genetic diversity and race composition. In this study, we selected six barberry-wheat coexisting sites in which Pst occurs sexually as treatment and control groups for experimental purposes. The treatment group was treated with triadimefon fungicides on barberry at the early pycnial stage to suppress sexual reproduction. Conversely, the control group represented sexual reproduction without fungicide application. Pst populations from wheat fields close to barberry with and without fungicide treatment were phenotyped on Chinese differentials and genotyped using a DNA microarray. The results showed the treatment population displayed a lower heterozygosity level (F_hom = -0.36945, Tajima's D = 0.285033) and a lower genetic diversity (π = 0.000156053) compared with the control population (F_hom = -0.41745, Tajima's D = 0.955451, π = 0.000184483), and a significant difference was observed between both populations (P < 0.001; P < 0.05). The treatment population identified 17 new races and 3 known races, and the control population identified 46 new races and 8 known races. The treatment population (α = 4.644) showed a lower diversity of the standard races than that of the control population (α = 5.194) based on a set of 25 Yr-single gene lines. Our results showed the significant impact of fungicide application on barberry to minimize the emergence of new races and the level of genetic diversity. This study provides guidance to growers, emphasizing the importance of timely fungicide application on barberry to ensure the long-term resistance durability of wheat cultivars against stripe rust.

Vascular streak dieback (VSD) poses a significant threat to the sustainability of woody ornamentals in the United States, particularly Cercis spp. (redbud). This study aimed to develop reliable molecular diagnostic tools for detecting Ceratobasidium sp. D.P. Rogers (Csp), the fungus consistently detected from VSD-symptomatic redbuds and other woody ornamentals. Molecular markers can provide rapid and accurate detection for fastidious fungi such as Csp that are challenging to recover in culture media. However, current molecular tools for Csp detection lack sensitivity and specificity. To address this, specific PCR and quantitative PCR (qPCR) primers were developed, targeting the internal transcribed spacer (ITS) genetic region. The existing primers for the second-largest subunit of RNA polymerase II (RPB2), translation elongation factor 1-alpha (TEF1-α), and ATP synthase subunit 6 (ATP6) genetic regions of Rhizoctonia fungi were also redesigned to enhance the sensitivity and accuracy of detection for Csp. The CP-qP-Csp primer set, with a detection limit of 86.02 pg/μl, effectively detected Csp in VSD-symptomatic tissues, cultures, and soils and is recommended for molecular detection of Csp from woody ornamentals in the U.S. Cross-platform validation across seven laboratories confirmed the robustness of the assays. These findings provide nursery producers with critical early-detection capabilities, potentially preventing significant economic losses and contributing to the sustainability of woody ornamental production. Future research will focus on refining these assays for field applications and exploring the genetic characteristics of Csp across different hosts and pathogen interactions to better understand the epidemiology of VSD.

Vascular streak dieback (VSD) is a serious new threat to woody ornamental plant production in the United States. From April to November of 2022, 2023, and 2024, a survey was conducted by the Virginia Department of Agriculture and Consumer Services to determine the distribution and impact of a fastidious Ceratobasidium sp. D.P. Rogers (Csp) fungus associated with VSD of woody ornamental plants in production nurseries in Virginia. Csp was detected using PCR and quantitative PCR from 285 of 997 plants tested (28.6%), representing 44 broadleaf and 2 coniferous host genera from 53 nurseries and 8 landscape sites across 37 municipalities. In a phylogenetic analysis based on internal transcribed spacer, large ribosomal subunit, rpb2, tef1-α, and atp6 sequences, the Virginia isolates were identical to isolates from Tennessee and strongly supported as a distinct species from Ceratobasidium theobromae. The robustness of the species-specific CP-qP-Csp and Than-ITS1/2 PCR primer sets used to detect Csp was also compared with detection limits of 186 and 1,164 fg/μl of Csp DNA, respectively. For sequencing, the basidiomycete-specific ITS1-F/4-B primer set was able to target Csp from xylem tissue from 52% of 50 samples tested, although the universal fungal ITS1/4 set failed to target Csp from xylem tissue. Questions regarding the detection, associated symptoms, and impact of this putative pathogen in Virginia are discussed.

Stewart's wilt of maize, caused by the gram-negative bacterium Pantoea stewartii subsp. stewartii, is one of the economically important diseases of the crop around the globe. The disease has not yet been reported in Iran. Following preliminary observation of suspected symptoms on maize plants in Southeastern Iran in 2019, a 4-year comprehensive field survey and sampling program was initiated across maize-growing areas in the country to monitor the occurrence and distribution of the disease. During 2019 to 2022, 180 maize fields were surveyed, from which 400 symptomatic and asymptomatic maize samples were collected. Among dozens of bacterial strains isolated from leaves and stems of maize plants, 22 strains phenotypically resembled those of Pantoea spp. Species-specific PCR and multilocus phylogenetic analyses using the sequences of atpD, gyrB, infB, and rpoB genes showed that P. stewartii subsp. stewartii is the causal agent of Stewart's wilt in Iran. All strains induced leaf chlorosis and plant stunting on maize plants under greenhouse conditions 7 to 15 days postinoculation, confirmed with accomplishment of Koch's postulates. These 22 strains were isolated in Bushehr, Fars, Hormozgan, Kermanshah, Khuzestan, Kohgiluyeh-Boyer Ahmad, and Sistan-Baluchistan provinces. Results of the present study confirmed the occurrence of P. stewartii subsp. stewartii causing Stewart's wilt of maize in Iran. The occurrence of Stewart's wilt on maize in Iran can lead to yield reduction, trade restrictions, increased control costs, and threats to food security. Considering the quarantine status of the pathogen in Iran, strict inspections are warranted to combat potential threats due to Stewart's wilt epidemics in the country.

Significant yield losses of peppers (Capsicum spp.) are caused by infection with begomoviruses (genus Begomovirus, family Geminiviridae). Breeding for host resistance to begomovirus is the most effective, sustainable method to mitigate losses, so pepper germplasm has been screened for resistance sources. Although host resistance against specific begomovirus species has been found, breeding for broad resistance to multiple species and mixed infections remains a challenge. We previously cloned two begomovirus resistance genes: recessive pepy-1, encoding Pelota, and dominant Pepy-2, encoding RNA-dependent RNA polymerase. Here, we inoculated pepper plants with a single species or with two Old World or two New World begomoviruses to evaluate the resistance conferred by single or multiple resistance genes. Our results demonstrated that introgression of pepy-1 and Pepy-2 in the homozygous state conferred durable resistance even to coinfections with two highly virulent begomoviruses. The findings provide a theoretical basis for accelerating DNA marker-assisted breeding for begomovirus resistance in pepper.

Banana, a globally significant economic fruit, faces major production constraints due to pests and diseases. Recently, banana fruit rot and rachis rot have emerged in several banana plantations across Guangxi, China. This study aims to identify the pathogens of the diseases and investigate their potential interrelations. Pathogenicity tests were conducted on banana plants with eight representative strains isolated from the rachides and fruits of Cavendish (AAA) and Pisang Awak (ABB) banana cultivars. Pathogen identification was achieved through morphological, physiological, and biochemical tests coupled with phylogenetic analysis based on multigene sequences. Comparative analyses were then performed on growth and pathogenic virulence of the bacteria isolated from the fruits and rachides of the two banana cultivars. The pathogens causing fruit rot and rachis rot in Cavendish bananas were identified as Dickeya zeae, while those responsible for the same diseases in Pisang Awak bananas were identified as D. fangzhongdai. In addition, D. zeae strains exhibited optimal growth at pH 7.0, whereas D. fangzhongdai strains showed optimal growth at pH 7.5. Strains isolated from rachides exhibited higher motility and pectinase activity compared with those isolated from fruits of the same host. D. zeae exhibited significantly higher virulence toward Cavendish bananas, whereas D. fangzhongdai showed greater virulence toward Pisang Awak. This study provides the first evidence of D. zeae causing both rachis and fruit rot in bananas and D. fangzhongdai as a causal agent of banana fruit rot. Furthermore, each pathogen demonstrated distinct host preferences, with D. zeae predominantly infecting Cavendish cultivars and D. fangzhongdai targeting Pisang Awak. These findings offer new insights into the bacterial rot diseases of bananas caused by Dickeya spp.

Pesticides are widely used in agriculture to protect crops from animal pests, diseases, and weeds, helping to maintain yields under diverse production conditions. However, their widespread and repeated use has led to environmental contamination, biodiversity loss, and growing concerns about human health. While Integrated Pest Management (IPM) and organic farming have sought to reduce pesticide dependency, both approaches still permit pesticide use, and their adoption remains limited due to technical and economic constraints. In this context, we explore the feasibility of a third way: pesticide-free agriculture based on agroecological crop protection (ACP) principles. Drawing from the Rés0Pest experimental network launched in France in 2012, we present ten years of results from nine sites covering a range of pedo-climatic conditions and socio-economic contexts. Rés0Pest implemented cropping systems that excluded all pesticide use, including seed treatments, while maintaining synthetic fertilizer inputs. The systems were co-designed through participatory methods, following a system experiment approach that evaluates the effects of a combination of cropping practices and their interactions on cropping system performance over the long term. Results showed that in pesticide-free systems, it is possible to achieve yields comparable to conventional and higher than organic systems and, in some cases, generate higher net farm income. Pest and pathogen crop damage did not significantly increase over time, although weed management remained a key challenge. These findings suggest that technically and economically viable pesticide-free arable systems are possible under certain conditions, and that new solutions are needed to support their adoption across a wider range of contexts. We discuss implications for research, farming, and policy, and emphasize the need for adaptive experimentation and systemic performance assessment to support agroecological transitions.

VQ proteins, characterized by the FxxhVQxhTG motif, comprise a family involved in plant defense responses. Walnut (Juglans regia) yield and quality are severely affected by Colletotrichum gloeosporioides causing anthracnose, necessitating understanding the molecular response mechanisms. Therefore, in this study, the VQ genes of J. regia (named JrVQ) were identified from the walnut genome based on bioinformatics tools (such as PFAM and SMART), and their transcriptional changes in response to anthracnose under controlled inoculation and natural infection in two varieties (resistant 'Xiangling' and susceptible 'Xilin3') were analyzed using real-time quantitative PCR. As a result, 15 JrVQ genes (JrVQ1 to JrVQ15) were identified, whose open reading frames were 225 to 1,182 bp with isoelectric points ranging from 5.94 to 10.67. These JrVQs were distributed across nine chromosomes out of a total of 32. Their protein secondary structures consisted of α-helices, extended chains, and random coils. Most of the cis-elements in the promoters of JrVQ genes were related to stress response. The expression of JrVQ genes could be induced in leaves, green husks, and stems and reached maximum level at 6 or 9 dpi under both conditions. Especially the expression of JrVQ10 and JrVQ9, the most prominent ones, reached 6.11 and 5.96, respectively. Moreover, the induction of JrVQs was higher in 'Xiangling' than in 'Xilin3' and was significantly correlated with the C. gloeosporioides infection process as well as the activity of total antioxidant enzyme, a key indicator of anthracnose resistance. These results suggested the involvement of JrVQs in the regulation of walnut anthracnose response.

Silver nanoparticles (AgNPs) exhibit strong antimicrobial properties against plant pathogens. However, studies on the application of AgNPs, synthesized using the fungus Trichoderma harzianum, to control the growth of Ganoderma boninense Pat, which causes basal stem rot (BSR) in oil palm (Elaeis guineensis Jacq.), have not been reported. Therefore, this study aimed to assess the potential of AgNPs, biologically synthesized using T. harzianum, as a biofungicide and evaluate their effect on the growth of G. boninense in vitro and in vivo. Secondary metabolite compounds were identified using Fourier transform infrared spectroscopy (FTIR) and gas chromatography-mass spectrometry (GC-MS), and the presence of AgNPs was confirmed by a brown color change, followed by UV-Vis spectroscopy, particle size analysis, and in vitro testing. The FTIR and GC-MS results showed that isothiocyanate (N=C=S) and n-hexadecanoic acid (20.51%) were present as the antifungal compounds. The AgNPs synthesized using T. harzianum were detected at approximately 410 nm and had a nanoparticle size of 77.3 nm. In vitro application of the AgNPs at a concentration of 100 mg·liter^-1 exerted a significant inhibitory effect on the growth of G. boninense. This result was consistent with the findings on palm oil seedlings. The AgNPs-Th can suppress the severity of BSR disease and can stimulate the vegetative growth of oil palm plants. In conclusion, this study expanded the current understanding of antifungal effects of AgNPs synthesized using T. harzianum and revealed their potential to suppress BSR caused by G. boninense in oil palm plantations.

Fusarium oxysporum, first identified in Yunnan Province as the causal agent of saffron corm rot, causes a destructive soil-borne disease that has become a devastating threat to saffron cultivation in Shangri-La, causing over 50% mortality. This pathogen infects saffron corms, leading to vascular browning and rot, ultimately causing plant death and severe production losses. Given the crucial role of the rhizosphere microbiome in plant immunity and soil ecology, deciphering pathogen-microbiome interactions is essential for developing sustainable disease-control strategies. High-throughput sequencing of ITS/16S rRNA (Illumina MiSeq) was combined with arbuscular mycorrhizal fungi (AMF) analysis to compare the community structures of fungi, bacteria, and AMF in the rhizosphere of healthy and diseased saffron. The effects of soil physicochemical factors on microbiome assembly were systematically evaluated. The rhizosphere microbiome of diseased plants was significantly dysregulated: (1) pathogen-related taxa (e.g., Lauriomyces) proliferated, while saprotrophic functional taxa (e.g., Mortierella elongata) underwent community restructuring; (2) disease-suppressive taxa (e.g., fususidium) were enriched, while symbiotic mycorrhizal fungi (AMF) essential for nutrient acquisition sharply declined; (3) the soil parameter-microbiome relationship changed under different health conditions:available phosphorus (AP) and available potassium (AK) drove the aggregation of pathogenic soil fungi, while pH/organic matter (OM) dominated the aggregation of healthy soil fungi; (4) Knufia and Phomopsis were important taxa regulating soil ammonia oxidation and plant vitality. Fusarium infection disrupts the rhizosphere balance by inhibiting beneficial symbionts and promoting the colonization of pathogenic or saprotrophic microorganisms, ultimately compromising the innate resistance of saffron. Our findings reveal the rhizosphere ecological mechanism underlying corm rot progression and provide a microbiome informatics framework for the selection of biocontrol agents and rhizosphere engineering. Moreover, the worker safety benefits from the reductions in psychic emanations mandate industry adoption.