Plant disease最新文献

Rhizoctonia solani is a soil- and seed-borne fungus, manifesting as black scurf and stem canker disease, resulting in substantial yield and quality losses globally. This fungus reproduces asexually through hyphae and sclerotia. Its genetic diversity is organized into 14 anastomosis groups (AGs), with AG3-PT being the predominant group on potato. Global trade of seed potatoes, though vital for agricultural development, inadvertently transmits the pathogen across regions. Disease development is influenced by environmental and agronomic factors, leading to severe outbreaks and economic impact. Accurate diagnosis is challenging due to the pathogen's genetic complexity, necessitating a transition from traditional culture-based and biochemical methods to molecular, genomic, and emerging digital technologies. Methods such as PCR, isothermal amplification, sequencing, sensor-based biosensing, and AI-driven imaging have improved the detection, quantification, and non-invasive monitoring of the pathogen. Combining these diagnostic methods into a tiered framework provides prospects for efficient disease surveillance, informed management decisions, and sustainable potato production systems.

Pomegranate is a high value crop severely affected by diseases caused by bacteria, viruses and fungi, especially those caused by Alternaria alternata. This pathogen is responsible for two major diseases black heart rot and black spot disease. Heart rot begins as a latent infection in the flower stigma, leading to internal aril necrosis, whereas black spot manifests as external necrotic lesions. While this review focuses on Alternaria diseases, it differentiates these symptoms from distinct internal rots caused by other fungi like Colletotrichum spp. and Fusarium spp. and surface lesions caused by Pseuodocercospora spp. and Curvularia spp. We examined current knowledge on Alternaria epidemiology, and the influence of physiological factors like fruit pH and calcium on susceptibility. Disease control remains challenging due to limited fungicides and pathogen latency, some promising solutions include biological control with Bacillus species, antifungal extracts, and detection via X-ray and AI-based imaging. Ultimately, a deeper understanding of these diseases and improvement of management strategies is essential to sustain global pomegranate yield and quality.

Pseudomonas coronafaciens pv. coronafaciens (Pcc), the causal agent of Bacterial Halo blight (BHB) on oat, has been infrequently reported in the United States, with historical records limited to the 1920s through the 1960s. In 2023, oat trial fields in Aberdeen, Idaho were severely infected with an unknown disease that formed necrotic lesions on leaves. Preliminary identification based on colony morphology suggested a pathogen belonging to the genus Pseudomonas. Subsequent polymerase chain reaction amplified a 298 bp fragment that is diagnostic to Pcc. Further analysis using whole-genome sequencing confirmed 99.6% average nucleotide identity (ANI) with Pcc. This marks the first detection of Pcc in Idaho, and the first detailed description of the pathogen in the United States after over half a century. Host range and pathogenicity assessments on multiple cereal crops showed that Pcc was pathogenic on oat, barley, and corn. However, wheat, rye and triticale displayed chlorosis and early cell death in response to the pathogen. Evaluation of oat and barley genotypes revealed resistance in the two crop species to be rare with only 2.5, and 4.5% of oat and barley genotypes exhibiting some level of resistance. Notably, the four resistant and moderately resistant barley genotypes identified in this study: DH170472, Celebration, Legacy and Quest are the first to be reported as sources of resistance to BHB. Results of the present study provide a basis for further research toward a better understanding of disease epidemiology, the genetics of host-pathogen interaction and the management of BHB on oat, barley and corn.

Ralstonia pseudosolanacearum is a soil-borne bacterial pathogen responsible for bacterial wilt disease in a wide range of host plants, including solanaceous crops. In this study, we collected 22 bacterial wilt isolates from solanaceous crops in seven sampling plots across the Kongo Central region of the Democratic Republic of Congo (DRC). The genomic characterization of these isolates identified a single haplotype belonging to the R. pseudosolanacearum phylotype I sequevar 31 genetic lineage. We assembled the genome sequence of one representative strain RUN6904, placed it in a phylogenetic context, and identified its type III effector repertoire. We demonstrated the virulence of the DRC isolates on tomato and showed the resistance of the AG91-25 eggplant accession likely triggered by the recognition of the RipAX2 type III effector from these isolates.

Xylella fastidiosa is a xylem-limited plant-pathogenic bacterium responsible for several economically significant plant diseases, including Pierce's disease in grapevine. Current control strategies face significant challenges in completely eradicating this pathogen. As such, phage-based biocontrol has gained increasing interest as a biocontrol tool in crop management. In this study, we expand current knowledge on X. fastidiosa phage diversity by reporting the isolation and characterization of 35 novel phages (ViSe_1 to ViSe_35) capable of infecting European X. fastidiosa subsp. fastidiosa strains. These phages were isolated from sewage samples using a collection of Xanthomonas spp. and X. fastidiosa strains as primary hosts. Phylogenetic analysis revealed a substantial genomic diversity, with phages being taxonomically classified in five distinct families: Schitoviridae, Mesyanzhinovviridae, Casjensviridae, Autographiviridae and Tectiviridae. Genomic analysis supports the proposal of four novel new genera and nine new species. Both highly specific and polyvalent phages were recovered, mostly depending on the isolation technique. All phages were able to infect strains from X. fastidiosa subsp. fastidiosa ST1, with fifteen of them consistently and completely inhibiting bacterial growth. Notably, none of the phages harbored genes associated with lysogeny, virulence or antibiotic resistance, suggesting a lytic life cycle and reinforcing their potential as biocontrol agents.

Anthracnose, caused by Colletotrichum spp., is an important fungal disease prevalent in strawberry nurseries and fruit production. Paenibacillus polymyxa, a plant growth-promoting rhizobacterium, effectively inhibits various fungal pathogens and their associated diseases. In this study, a fusaricidin synthetase gene (fusA)-disrupted mutant generated from a strawberry strain TP3 of Paenibacillus polymyxa was used to demonstrate the requirement of fusA for disease suppression directed by this beneficial bacterium. In contrast to the wild-type strain TP3, this fusA-disrupted mutant was unable to produce fusaricidins, but increased biofilm biomass; however, it reduced the inhibition of fungal growth and decreased the suppression of anthracnose symptom development in strawberry. Nevertheless, this fusA-disrupted mutant showed enhanced colonization on strawberry leaves and roots compared to the wild-type strain TP3 did. A callose deposition assay indicated that P. polymyxa TP3-directed strawberry anthracnose suppression by root-drenching required fusaricidins to enhance plant immunity. This research validates the role of fusaricidins in P. polymyxa TP3-directed induction of disease resistance and facilitates the application of P. polymyxa as a health enhancer for sustainable crop production, especially for strawberries.

Stem rust, caused by Puccinia graminis f. sp. tritici (Pgt), is a devastating disease that threatens wheat (Triticum aestivum L.) production worldwide. Developing resistant wheat varieties is crucial, as genetic resistance provides a more sustainable approach than chemical control. In this study, we evaluated 361 genetically diverse wheat accessions for resistance to four Pgt races, TMLKC, QFCSC, HKHJC, and LBBLC which can overcome multiple known resistance (R) genes. Seedling responses varied widely, with most genotypes showing susceptibility. However, a subset exhibited strong resistance: 17.5% against TMLKC, 24% against QFCSC, 11.5% against HKHJC, and 23.5% against LBBLC. To identify genetic loci associated with resistance, we conducted a genome-wide association study (GWAS) using the disease phenotypic data combined with 302,524 high-quality single nucleotide polymorphisms (SNPs) data. The analysis revealed 34 significant marker-trait associations (MTAs) for stem rust resistance, distributed across 14 wheat chromosomes. Out of 34 significant MTAs, 15 were located near previously reported Sr genes, MTAs, or QTLs associated with stem rust resistance. The remaining 19 MTAs corresponded to the genomic regions that may contain possibly novel resistance genes. Candidate gene analysis of the significant MTAs revealed genes that may potentially play a role in disease resistance. The identified MTAs can potentially be used to transfer resistance loci to develop stem rust-resistant wheat varieties.

The utilization of stripe rust resistance genes or quantitative trait loci (QTL) is an effective strategy to diversify resistance sources and delay the breakdown of rust resistance in the Longnan region, a hot spot for stripe rust in China. Wheat cultivar Lanhangxuan 122 has shown high adult-plant resistance (APR) to stripe rust in this region. In this study, a population comprising 221 recombinant inbred lines (RILs) derived from a cross between Lanhangxuan 122 and susceptible cultivar Huixianhong was evaluated for APR in field trials at two locations in the 2021-2024 cropping seasons. Bulked segregant exome sequencing (BSE-Seq) combined with composite interval mapping (CIM) analysis was employed for genetic analysis. Three stable loci, QYr.L122-1BL, QYr.L122-2DL, and QYr.L122-3BL, were identified with average phenotypic variance of 7.4%, 16.1%, and 7.8%, respectively. The closely linked SSR and KASP markers were developed for each locus. Candidate genes were identified within the mapped intervals of the three loci. Furthermore, through field evaluation combined with marker-assisted selection (MAS), 32 advanced wheat lines with all three QTL along with high-quality were selected from crosses involving Lanhangxuan 122 and other elite wheat cultivars such as Shiyou 4045, Zhoumai 38, and Zhoumai 18. These lines show potential for release as new cultivars or parents in breeding for durable resistance to stripe rust. This study provides information on stable stripe rust loci, candidate genes, and available KASP markers for wheat stripe rust resistance breeding.

Although WSR has been commonly observed and studied in the Middle East, in Jordan the last reports date from the late 1980s. The objectives of this research were to conduct a national survey of WSR in Jordan, assess the race composition and genotypic diversity of the Pgt population and to evaluate a 162 durum wheat genotypes for stem rust response against isolates of two major Pgt races recovered from stem rust samples collected in this study. A total of 78 WSR live samples and 74 dead samples from 49 fields were collected in 2018. In addition, three historical samples were analyzed. One hundred Pgt isolates derived from the live samples were race-typed and 14 representatives of the identified races were genotyped with a 17 core SNP assay that distinguish major genetic clades. The dead and the historical Pgt samples were all SNP genotyped. Five races were identified from the live samples: PKTTF, TKFTF, TKFTP, TKKTF, and TTRTF. The most frequent race was TKKTF (75%) followed by TKFTF (14%), and TTRTF (9%), whereas races PKTTF and TKFTP were detected from only one isolate each. Selected Pgt isolates representing the five races identified were differentiated into five known genetic clades/sub-clades: III-B, race TTRTF; IV-C, race PKTTF; IV-E.1, race TKFTP; IV-E.2, race TKKTF; and IV-F, race TKFTF. The dead samples were genotyped as clades: IV-E.2 (73.7%), III-B (18.1%), and IV-E.1, IV-F, and Co-A22 at frequencies less than 4%. Minor allelic variations at one or two SNP loci were observed among the dead samples. The dead sample genotyped as Co-A22 was identical to European reference isolates from the early 1980s. From the 36 single uredinial pustules derived from the historical samples, two genotypes were detected: clade III-A and, Co-A22. Seedling resistance was observed in durum wheat landraces and cultivars to two of the major races identified in Jordan, as 52 (32.1%) and 99 (61.1%) genotypes evaluated exhibited a resistant response to races TTRTF and TKKTF, respectively. Infection types in the range of '2-' to '2+' were predominant in this germplasm. Forty-six (28.4%) accessions were resistant to both races, including 1 cultivar and 45 landraces.

Rice kernel smut, caused by Tilletia horrida, poses a major threat to rice production in the US. To manage this disease, growers primarily rely on the midseason preventive applications of propiconazole, a fungicide. Propiconazole belongs to the class of demethylation inhibitors (DMIs) that, hinders the fungal sterol synthesis. In recent years, reports of reduced efficacy and failures of propiconazole fungicides in managing kernel smut have become increasingly widespread across the US. This study aimed to assess the resistance of T. horrida isolates to propiconazole and to identify the molecular basis of the resistance. In vitro tests were conducted using three T. horrida isolates from organic rice fields with no history of fungicide applications to establish a baseline EC50 for propiconazole, which was determined to be 0.02 mg/L. We screened for resistance with additional 66 T. horrida isolates collected from various regions across the US. The results revealed that 84% of the isolates exhibited EC50 exceeding the baseline of 0.02 mg/L. Among these, 57% had EC50 values above 0.05 mg/L, while 39% and 23% showed EC50 greater than 1 mg/L and 2 mg/L, respectively. Further genome analysis of the T. horrida unveiled the presence of a single copy of the Cyp51 gene, the target of DMIs. The sequence analysis of the Cyp51 protein in propiconazole-resistant T. horrida isolates revealed five amino acid substitutions: G22A, R183K, V279A, L387I, and G494S. This study marks the first investigation into propiconazole resistance in T. horrida and its association with amino acid mutations in the Cyp51 gene. These findings highlight an urgent need to search for alternative fungicides with different modes of action to effectively manage kernel smut in rice.