Phytopathology最新文献

Fusarium oxysporum f. sp. vasinfectum (FOV) is a significant cotton (Gossypium spp.) pathogen causing vascular wilt, browning of the vascular tissues, and plant death in the most severe cases. This global disease is responsible for sizeable crop losses annually and is found in many cotton-producing regions, including the Republic of Uzbekistan and the United States. Specifically, FOV race 4 (FOV4) has been disrupting production for years. This study aimed to genetically characterize FOV4 isolates causing disease in the main cotton-producing region of Uzbekistan and compare them with FOV4 isolates from the United States. A field study conducted in the Bukhara region of the Republic of Uzbekistan in the spring of 2022 identified both FOV4 and new Fusarium isolates from Upland cotton exhibiting typical Fusarium wilt symptoms. Molecular markers were initially used to identify isolates of interest, and a phylogenetic analysis was performed using partial EF1-α sequences, followed by a comparative genomic analysis. We also report for the first time the isolation of F. solani and F. commune causing Fusarium wilt in Uzbekistan. Furthermore, we show that the FOV4 population within our sampling region of Uzbekistan may be dominated by a single biotype with an effector profile similar to that of FOV race 7. One of these effector proteins is also present in the F. commune isolate showing virulence to cotton. Whole-genome comparisons between FOV races can identify unique genetic markers for FOV4 and aid in the development of tools for breeding FOV-resistant cotton varieties.

Silicon (Si) supplementation permits plants to better deter infection. Supplementing hydroponically propagated Nicotiana tabacum with 1 mM potassium silicate (K₂SiO₃) reduced necrotic lesion development on detached leaves by both Botrytis cinerea and Sclerotinia sclerotiorum. Previously, a family of Si-induced genes was identified in N. tabacum. These genes were members of the solanaceous histidine-rich defensin (HRD) superfamily and were termed NtHRD1s (the first identified family of N. tabacum HRDs). Defensins were originally identified to participate in innate immunity. Thus, the NtHRD1s were tested for antimicrobial effects on plant pathogens. Transient expression of NtHRD1 genes within N. benthamiana leaves restricted the development of necrotic lesions caused by B. cinerea and S. sclerotiorum. Thus, the NtHRD1s may be an additional Si-responsive factor conferring beneficial effects on plants. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.

Plasmodiophora brassicae is an obligate biotroph that causes clubroot disease in cruciferous plants, including canola and Arabidopsis. In contrast to most known bacterial, oomycete, and fungal pathogens that colonize at the host apoplastic space, the protist P. brassicae establishes an intracellular colonization within various types of root cells and secretes a plethora of effector proteins to distinct cellular compartments favorable for the survival and growth of the pathogen during pathogenesis. Identification and functional characterization of P. brassicae effectors has been hampered by the limited understanding of this unique pathosystem. Here, we report a P. brassicae effector, PbPE23, containing a serine/threonine kinase domain, that induces necrosis after heterologous expression by leaf infiltration in both host and nonhost plants. Although PbPE23 is an active kinase, the kinase activity itself is not required for triggering necrosis in plants. PbPE23 shows a nucleocytoplasmic localization in Nicotiana benthamiana, and its N-terminal ²⁵TPDPAQKQ³² sequence, resembling the contiguous hydrophilic TPAP motif and Q-rich region in many necrosis and ethylene inducing peptide 1-like proteins from plant-associated microbes, is required for the induction of necrosis. Furthermore, transcript profiling of PbPE23 reveals its high expression at the transition stages from primary to secondary infection, suggesting its potential involvement in the development of clubroot disease.

The coevolution of virulence reduces the effectiveness of host resistance to pathogens, posing a direct threat to forest species and their key ecosystem functions. This is a threat to limber pine (Pinus flexilis), an endangered species in Canada due to rapid decline mainly driven by white pine blister rust caused by Cronartium ribicola. We present the first report of a new, virulent race of C. ribicola (designated vcr4) that overcomes limber pine major gene (Cr4) resistance (MGR). Field surveys found that three parental trees (pf-503, pf-508, and pf-2015-0070) were cankered with white pine blister rust in Alberta, but their progenies showed MGR-related phenotypic segregation postinoculation with an avirulent race of C. ribicola (Avcr4). Genotyping of their progenies using Cr4-linked DNA markers and a genome-wide association study provided additional support that these cankered parental trees had Cr4-controlled MGR. To confirm the presence of vcr4, aeciospores were collected from the cankered pf-503 tree to inoculate resistant seedlings that had survived prior inoculation using the Avcr4 race, as well as seedlings of two U.S. seed parents, one previously confirmed with MGR (Cr4) and one without MGR, respectively. All inoculated seedlings showed clear stem symptoms, confirming that the virulent race is vcr4. These results provide insights into the evolution of C. ribicola virulence and reinforce caution on deployment of Cr4-controlled MGR. The information will be useful for designing a breeding program for durable resistance by layering both R genes with quantitative trait loci for resistance to white pine blister rust in North America.

Potato cyst nematodes (PCNs) are notorious pathogens in all major potato production areas worldwide. Mainly due to the low mobility of this soil pathogen, PCN infestations are mostly observed as patches ("foci") that only cover a fraction of the acreage. In-field presymptomatic localization of these pathogens is valuable, as it would allow for the localized application of control measures. Although the mapping of foci is technically feasible, it is unpractical, as it would require the analysis of numerous soil samples. We investigated whether chlorophyll fluorescence (Chl-F) could be suitable as a rapid, nondestructive method for early PCN detection. To this end, the impact of four Globodera pallida densities on the Chl-F of tomato was investigated in a phenotyping greenhouse for 26 days. Furthermore, the classical plant performance indicators of biomass and root surface area were compared with Chl-F. Thermal dissipation (NPQ) and an estimate of the photosynthetic rate (Φ_PSII) responded at 1 day postinoculation, and Φ_PSII was most sensitive to low PCN infection levels. Chl-F parameters responded more readily to PCN infection than biomass and root surface area. The maximum quantum yield of photosystem II (F_v/F_m) and the potential activity of photosystem II (F_v/F₀) initially increased at low PCN infection levels, whereas a sharp decrease was observed at higher infestation levels. Hence, our data suggest that low PCN levels promoted plant performance before becoming detrimental at higher levels. Although Chl-F allowed for early and sensitive PCN detection, it remains to be investigated whether these signals can be distinguished from those produced by other belowground stressors in the field. [Formula: see text] Copyright © 2025 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.

Calonectria pseudoreteaudii causes a serious and widespread disease known as Calonectria leaf blight in Eucalyptus plantations of southern China. Little is known regarding the population biology or reproductive biology of this pathogen in the affected areas. The aims of this study were to investigate the genetic diversity, population structure, and reproductive mode of C. pseudoreteaudii from affected Eucalyptus plantations of southern China. Ten polymorphic simple sequence repeat markers were developed for the species and were used to genotype 311 isolates from eight populations. The mating types of all isolates were identified using the MAT gene primers. The results revealed a high level of genetic diversity of the pathogen in all investigated populations. Of the 90 multilocus genotypes detected, 10 were shared between at least two populations. With the exception of one population from HuiZhou, GuangDong (7HZ), the most dominant genotype was shared in the seven remaining populations. Discriminant analysis of principal components and population differentiation analyses showed that the 7HZ population was well differentiated from the others and that there was no significant differentiation between the remaining populations. Analysis of molecular variance suggested that most molecular variation was within populations (86%). Index of association analysis was consistent with a predominantly asexual life cycle for C. pseudoreteaudii in the studied regions. Although both mating types were detected in seven of the eight populations, the MAT1-1/MAT1-2 ratios in these populations deviated significantly from the 1:1 ratio expected in a randomly mating population.

We report high-quality genomes of three strains of Xanthomonas citri pv. mangiferaeindicae, the causal agent of mango bacterial canker disease, including the pathotype strain of this pathovar and two strains from Burkina Faso that emerged a decade ago. These strains hosted two to three plasmids of sizes ranging from 19 to 86 kb. Genome mining revealed the presence of several secretion systems and effectors involved in the virulence of xanthomonads with (i) a type I secretion system of the hlyDB group; (ii) xps and xcs type II secretion systems; (iii) a type III secretion system with several type III effectors, including transcription activator-like effectors; (iv) several type IV secretion systems associated with plasmid or integrative conjugative elements mobility; (v) three type V secretion system subclasses (Va, Vb, and Vc); and (vi) a single i3* type VI secretion system. The two strains isolated in Burkina Faso from mango (Mangifera indica) and cashew (Anacardium occidentale) differed by only 14 single-nucleotide polymorphisms and shared identical secretion systems and type III effector repertoires. Several transcription activator-like effectors were identified in each strain, some of which may target plant genes previously found implicated in disease development in other xanthomonad-associated pathosystems. These results support the emergence in Burkina Faso a decade ago of very closely related strains that became epidemic on mango and cashew (i.e., two distinct host genera of a same plant family). These new genomic resources will contribute to better understanding the biology and evolution of this agriculturally major crop pathogen.

The pine wood nematode (PWN), Bursaphelenchus xylophilus, is one of the most serious invasive forest pests, responsible for pine wilt disease (PWD). Currently, there are no effective, environmentally friendly control methods available. RNA interference (RNAi) technology has been extensively utilized to screen functional genes in eukaryotes and to explore sustainable pest management approaches through genetic engineering. In this study, we identified 353 predicted lethal genes in PWN by comparing its genome with those of lethal genes from Caenorhabditis elegans. We selected five predicted lethal genes (Bxy1177, Bxy1239, Bxy1104, Bxy667, and BxyAK1) with identification values exceeding 60% to evaluate their nematicidal effects on PWN. We tested the double-stranded RNA (dsRNA) of these genes using two methods: firstly, soaking in a synthesized dsRNA solution in vitro, or secondly, feeding on a dsRNA-engineered endophytic fungus, Fusarium babinda. Following dsRNA ingestion, either through soaking or fungal feeding, the expression of genes Bxy1177, Bxy667, Bxy1104, and BxyAK1 was significantly suppressed. Notably, nematode populations that consumed fungi expressing dsL1177 and dsAK1 showed substantial declines over time. These findings provide novel insights and a practical foundation for employing endophytic fungi-expressed dsRNA in sustainable pest management strategies.

NmrA homologs have been reported as conserved regulators of the nitrogen metabolite repression (NMR) in various fungi. Here, we identified a NmrA homolog in Verticillium dahliae and reported its functions in nitrogen utilization, growth and development, and pathogenesis. VdNmrA interacts with V. dahliae AreA protein and regulates the expression of a typical NCR target, the formamidase gene. VdNmrA deletion mutants exhibited significantly slower colony growth on media with Gln or Arg. Furthermore, VdNmrA deletion impaired hyphal growth, spore production, hyperosmotic stress tolerance, and melanin biosynthesis. Less ROS was produced in VdNmrA mutants, and the NADPH oxidase genes noxA and noxB showed lowered expression level compared to the wild type. VdNmrA mutants exhibited reduced virulence on cotton and Arabidopsis compared with wild type strains. Our results indicated that VdNmrA functioned as an NMR repressor and played important roles in nutrient utilization, fungal development, stress tolerance and pathogenicity in V. dahliae.

Rhizopus stolonifer is known for causing soft rot in fruit and vegetables during postharvest. Although it has traditionally been considered a saprophyte, it appears to behave more like a necrotrophic pathogen. In this study, we propose that R. stolonifer invades host tissues by actively killing host cells and overcoming the host defense mechanisms, as opposed to growing saprophytically on decaying plant matter. We tested this hypothesis by characterizing R. stolonifer infection strategies when infecting four fruit hosts (tomato, grape, strawberry, and plum). We started by generating a high-quality genome assembly for R. stolonifer using PacBio sequencing. This led to a genome size of 45.02 Mb, an N50 of 2.87 Mb, and 12,644 predicted loci with protein-coding genes. Next, we performed a transcriptomic analysis to identify genes that R. stolonifer preferentially uses when growing in fruit versus culture media. We categorized these infection-related genes into clusters according to their expression patterns during the interaction with the host. Based on the expression data, we determined that R. stolonifer has a core infection toolbox consisting of strategies typical of necrotrophs, which includes a set of 33 oxidoreductases, 7 proteases, and 4 cell wall degrading enzymes to facilitate tissue breakdown and maceration across various hosts. This study provides new genomic resources for R. stolonifer and advances the knowledge of Rhizopus-fruit interactions, which can assist in formulating effective and sustainable integrated pest management approaches for soft rot prevention.