Plant disease最新文献

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.

Fusarium Head Blight (FHB) can result in severe blighting of hemp grain and floral tissues. A multi-site field trial was conducted in 2022 and 2023 that included 3 different hemp cultivars with varying flowering time (early-, mid-, and late-flowering) and eight planting dates to detect and quantify early infection by F. graminearum. Asymptomatic terminal buds, female flowers, and/or male flowers were collected every 2 weeks beginning 2 to 3 weeks after planting and continuing until FHB symptoms were observed or plants reached maturity, resulting in 10 to 12 sampling dates per field. To detect and quantify F. graminearum, samples were subjected to a species-specific qPCR assay. Treatments including planting date and cultivar resulted in different levels of latent infection in each year and at each location. Despite latent infection being observed in vegetative tissues, infection was more prominent during flowering stages, indicating the importance of flowers for infection. Detections also appeared to be related to environmental factors such as rain and relative humidity. FHB symptoms were commonly observed 6 to 8 weeks after initial detection. Determination of when F. graminearum infection occurs in the field will help identify critical FHB management windows for hemp producers.

Pectobacterium carotovorum is a gram-negative phytopathogenic bacterium that causes soft rot disease on diverse plant species. It encodes the type III secretion system effector protein, DspE, and its chaperone, DspF. The DspE family proteins form water and solute channels in plant cells, flooding the apoplast to aid bacterial multiplication. In Pseudomonas syringae, the DspE ortholog, AvrE, upregulates abscisic acid (ABA) expression, leading to stomatal closure. In this study, a Pectobacterium carotovorum dspEF mutant did not cause leaf cell death in tobacco leaves. This observation is supported by the lower expression of PCWDE such as pelB, pelI, celV, prtW, and the quorum sensing system transcript expI in tobacco plants prior to visual symptoms (5 hours post-inoculation). Interestingly, neither dspE/F or hrpL mutation affected synthesis of QS signaling molecule AHL under microbiological settings. However, maceration symptoms occurred if leaves infiltrated with the dspEF mutant were kept under high humidity or detached post-infiltration. These leaves showed elevated transcription of ABA synthesis genes compared to infiltrated leaves maintained on the plant under ambient conditions. To validate this involvement, co-infiltration of ABA with the dspEF mutant restored its ability to cause maceration in attached leaves under ambient conditions. Overall, our data suggest that DspE/F facilitates host susceptibility by creating an aqueous apoplast, promoting ABA accumulation and stomata closure.

Wolfberry (Lycium barbarum) is an important economic crop with extremely high medicinal value; however, root rot disease leads to a serious decline in the yield and quality of wolfberry. In this study, we used one-year-old wolfberry seedlings as test material to explore the control effect of single or combined inoculation with arbuscular mycorrhizal (AM) fungus Rhizophagus intraradices and endophytic fungus Metarhizium robertsii on wolfberry root rot and preliminarily probed the related disease resistance mechanisms. The results showed that both R. intraradices and M. robertsii could successfully colonize the roots of wolfberry, and the combined inoculation significantly increased the colonization rate of R. intraradices and reduced the incidence of wolfberry root rot, with a control effect of 68%. Combined inoculation enables plants to absorb nitrogen and phosphorus more effectively by increasing the nutrient uptake area and activity of wolfberry roots, which helps to increase chlorophyll content and promote plant growth. It also improved the resistance of wolfberry to root pathogens by regulating endogenous hormones (significantly increasing the contents of salicylic acid, indole-3-acetic acid, gibberellin A3, and decreasing the content of abscisic acid) and enhancing defensive enzyme activities (superoxide dismutase, peroxidase, and ascorbate peroxidase). In terms of soil, the combined inoculation significantly increased the nitrogen content and enzyme activities (sucrase, urease, and catalase), creating a more favorable growth environment for wolfberry. In conclusion, AM fungus R. intraradices combined with endophytic fungus M. robertsii can effectively enhance the disease resistance of wolfberry to root rot and has certain biocontrol application potential (Graphical abstract).

Potentilla anserina L. is widely recognized for its extensive applications in traditional medicine and as a food source, harboring abundant bioactive compounds that confer significant medicinal and economic value. However, a severe disease consisting of leaf spots has adversely impacted P. anserina yield and quality in Heilongjiang Province, China. This study aims to identify the causal agent(s) of the disease, characterize the pathogen(s), and screen for effective control means. A total of 128 isolates were obtained from spotted leaves of P. anserina, with Alternaria tenuissima accounting for 68.7% and A. alternata for 32.3% of the isolates. These species were identified according to morpho-molecular characteristics and phylogenetic analyses. According to pathogenicity tests, A. alternata and A. tenuissima are both highly pathogenicity to P. anserina. In addition, all isolates were highly pathogenic to Astragalus laxmannii, Glycyrrhiza uralensis, and Trifolium pratense, moderately pathogenic to Artemisia argyi，and Beta vulgaris, and did not infect Mentha canadensis, Glycine max, Arachis hypogaea or Capsicum annuum. The isolates of A. alternata and A. tenuissima exhibited high sensitivity to benzoxystrobin and the biological control agent Paenibacillus polymyxa, with EC50 and IC50 values ranging from 0.09 to 0.57 µg/ml and 0.07 to 0.12 mg/ml, respectively. The efficacies varied between 96.1% and 97.5% at 480 μg/ml and between 95.1% and 97.1% at 240 mg/ml, respectively. According to this study, the pathogens responsible for P. anserina leaf spot in Heilongjiang, China, are A. tenuissima and A. alternata. Both showed high pathogenicity, but were effectively controlled by benzoxystrobin and Paenibacillus polymyxa, suggesting chemical treatments, intercropping and biocontrol as management strategies.

Monilinia fructicola, the most widely distributed species among the Monilinia genus globally, causes blossom blight, twig canker, and fruit rot on Rosaceae fruits. Despite previous studies, limitations still exist regarding virulence of M. fructicola. In this study, we identified a gene significantly upregulated during the early stages of infection. Bioinformatic analysis revealed that this gene encoded a protein containing the HAD_SAK_1 domain (abbreviated as HS1), and we named it MfHS1. Knockout and complemented transformants were generated and evaluated for environmental fitness. Results revealed that MfHS1 was involved in the regulation of osmotic stress and cell wall integrity. Additionally, microscopic observations showed that MfHS1 participated in the differentiation process of hyphal tips. Virulence assays indicated that the knockout transformant ΔMfHS1 exhibited significantly reduced virulence. Considering that MfHS1 is predicted as a non-classical secreted protein, it was transiently expressed in Nicotiana benthamiana leaves, and the induced plant cell death was observed, indicating that MfHS1 might trigger plant defense responses, e.g., programmed cell death, and supply nutrients to necrotic pathogens, thus aiding host infection. This study offers a new perspective for further understanding the pathogenic mechanisms of M. fructicola and developing control strategies.