Phytopathology最新文献

Sugar beet is a crucial sugar crop with substantial economic and nutritional value. The occurrence of damping-off disease severely impacts sugar beet quality and yield. Here, we successfully isolated two endophytes from sugar beet, and these were identified as Bacillus albus SB-3 and Pseudomonas chlororaphis SB-35 based on morphological observation and molecular identification. Both SB-3 and SB-35 exhibited nitrogen-fixing and potassium mobilization capabilities, with SB-35 demonstrating additional traits, including phosphate solubilization. SB-3 and SB-35 promoted the growth of sugar beet, resulting in increased biomass, and improved soil available nutrients. SB-3 and SB-35 had exhibited extracellular protease activities and inhibited the mycelium growth of Rhizoctonia solani. In independent pot experiments, SB-3 and SB-35 significantly controlled the damping-off of seedlings for sugar beet. Further analysis indicated that SB-3 and SB-35 may alter the microbial community structure, reducing the abundance of R. solani, promoting the recruitment of beneficial microorganisms, such as Hypocrea, Peziza, and Talaromyces, to occupy ecological niches, and thereby reducing pathogen load. The two bacterial strains modulated the diversity and community structure of rhizosphere microorganisms, suggesting a microbiome-mediated mechanism underlying their host-beneficial effects. This study advances our understanding of harnessing endophytes to enhance sugar beet productivity and suppressing sugar beet damping-off caused by R. solani.

In phytopathogenic fungi, ATG24 has been identified as the first mitophagy receptor and evolutionarily conserved. However, its roles in fungal development and pathogenicity vary among species and necessitate further exploration across more diverse fungal genera. In this study, we dissected the molecular functions and underlying mechanisms of the mitophagy receptor ATG24 homolog in the soilborne hemibiotrophic fungus Verticillium dahliae. VdATG24 contains a PX domain, a BAR domain, and an AIM (Atg8-family Interacting Motif) and is a crucial component for prohibitin-mediated mitophagy triggered by both nitrogen deprivation and a mitophagy-specific activator in V. dahliae. Deletion of VdATG24 inhibited the growth rate, shortened the distance between septa, reduced the spore production, and impacted the microsclerotia formation of V. dahliae, without altering spore morphology or sporulation mode. Assessments of pathogenicity further demonstrated that VdATG24 contributes to fungal virulence through the promotion of host colonization. Mechanistically, we uncovered that ATG24 mediates melanin biosynthesis, facilitates protein secretion during the infection process, and indirectly attenuates host immunity, as evidenced by the identified key components and associated biological processes/pathways via transcriptome analyses and subsequent experimental verification. Our data collectively underscore the pivotal roles and preliminary molecular mechanisms of VdATG24 in modulating hyphal growth, conidiation, microsclerotia formation, and virulence in V. dahliae.

Climate change is projected to increase the intensity and frequency of drought in several regions, potentially impacting aphid-virus-plant relationships. Here, we investigated the combined effects of water regime and virus infection on plant traits, virus transmission, and aphid feeding behavior. Two factorial experiments were established that combined (i) four virus treatments-single infection with cucumber mosaic virus (CMV; non-persistent), single infection with cucurbit aphid-borne yellows virus (CABYV; persistent), double infection, and mock control-with (ii) five water regimes on melon cultivar Bazán (experiment 1) or two water regimes on melon cultivar Piel de Sapo (experiment 2). Virus and drought reduced plant dry weight, number of leaves, and leaf area. In experiment 1, drought reduced the symptom severity on CMV-infected plants. Severe drought did not affect the CMV inoculation rate, but transient, moderate water stress reduced the transmission rate of CABYV. In experiment 2, drought and virus infection altered the feeding behavior of Aphis gossypii. On well-watered but not on droughted plants, both CABYV and double infection with CABYV and CMV reduced passive phloem sap ingestion (E2 waveform), critical for transmission of persistent viruses, in comparison with mock-inoculated controls. On droughted plants, aphids produced shorter intracellular punctures (potential drop waveform), associated with transmission of non-persistent viruses. However, potential drop duration was not reduced for aphids that fed on droughted plants infected with CMV or with both CMV and CABYV. Despite the significant impact of drought on the plant phenotype, drought combined with virus infection had no impact on aphid feeding behavior related to virus transmission.

Black rot, caused by Phyllosticta ampelicida, is a notable example of a recent reemerging disease of grapevine (Vitis vinifera). The pathogen infects young, actively growing plant parts and may have a large effect on yield, even at low incidence. A strategy to control grapevine black rot is to develop resistant varieties through breeding programs aimed at introducing the resistance into the susceptible V. vinifera. However, a complete picture of the existing sources for resistance in the Vitis species is missing. In this work, we evaluated a collection of Vitis species for resistance to black rot in the vineyard in natural conditions of infection over a 3-year period and validated the results using a bioassay for the evaluation of resistance in semi-controlled conditions. Our results confirmed the resistance to black rot previously reported for several species and identified new sources of resistance. The majority of the species identified as resistant come from America, whereas almost all species of Asian origin are susceptible. Because they displayed strong resistance, under field conditions and after artificial inoculation, the new sources of resistance reported here have a high potential to be used in future breeding programs.

Sorghum is the fifth most cultivated cereal; however, sorghum cultivation suffers from various threats. Fusarium thapsinum is the causal agent of sorghum stalk rot worldwide. However, there is no report on the genome characterization of F. thapsinum and its pathogenicity to sorghum glume. In this study, an F. thapsinum strain was isolated from the leaves and glumes of sorghum with red spot disease in Yibin, China. According to Koch's postulates, the strain was re-incubated on sorghum leaves and glumes. At 10 days postinoculation, red spots appeared, and the pathogen was re-identified as F. thapsinum and named FL-4, which indicated that F. thapsinum was pathogenic to sorghum leaves and glumes. The morphological characteristics of F. thapsinum in sorghum leaves were observed using scanning electron microscopy. Furthermore, genome sequencing indicated that the FL-4 genome assembly was 41.97 Mb with a GC ratio of 47.85%, N₅₀ 0.8 Mb, and 13,576 genes, including 1,124 secretory protein-coding genes and 5 antibiotic resistance genes. The basic characteristics of the genome were illustrated in a Circos map. Furthermore, all proteins were functionally annotated using the EggNOG, KEGG, GO, FVF, and PHI databases. This is the first report on the pathogenicity of F. thapsinum to sorghum glumes, as well as its genome characteristics. Considering the pathogenicity of F. thapsinum to sorghum and its broad appearance worldwide, F. thapsinum may be a destructive pathogen to sorghum, requiring greater attention. This research also provides a theoretical basis for further research on phytopathology.

Bacterial leaf streak (BLS), caused by the bacterial pathogen Xanthomonas translucens pv. undulosa (Xtu), is an important disease affecting wheat production worldwide. Recently, the Northern Great Plains of the United States-a key region for durum wheat and hard red spring wheat-has reported an increased prevalence and severity of BLS. Growing resistant wheat varieties remains the most effective and environmentally friendly strategy to mitigate yield losses caused by this disease. The extensive virulence and genetic diversity of Xtu strains, coupled with the quantitative genetic architecture of wheat-pathogen interactions, highlight the critical need to identify diverse sources of resistance. Cultivated emmer wheat offers a broad genetic diversity that could be leveraged for resistance breeding. In this study, we evaluated BLS disease severity in 508 cultivated emmer wheat lines at the seedling stage under controlled environmental conditions. Fourteen emmer wheat lines exhibited high levels of resistance to BLS. One quantitative trait locus (QTL) on chromosome 1A was consistently identified across multiple models from genome-wide association mapping, accounting for 6.1% of the total phenotypic variation. The favorable allele of the most significant marker, S1A_305713424, was observed to be absent in both durum wheat landraces and breeding lines, suggesting that this favorable allele may have been lost during domestication from cultivated emmer wheat. These findings may represent a valuable germplasm resource for breeding BLS-resistant durum and bread wheat varieties. Further investigation is needed to validate the QTL effect in durum wheat, identify the candidate gene, and elucidate the underlying resistance mechanism associated with the identified QTL.

Wheat stripe rust, caused by the biotrophic fungal pathogen Puccinia striiformis f. sp. tritici (Pst), is among the top crop diseases incurring huge economic losses worldwide. Identification of new stripe rust resistant sources that can be easily used in wheat cultivar development is essential for food security. PI 622129, an Iranian wheat landrace, exhibits high resistance to the predominant U.S. Pst races. A recombinant inbred line (RIL) population from the cross PI 622129 × Stardust was genotyped using SNPs generated by genotyping-by-sequencing. The RIL population was evaluated for responses to the Pst race PSTv-37 at the seedling stage in three environments, and quantitative trait loci (QTL) analysis revealed four QTL for stripe rust resistance on chromosome arms 2DS, 5BS, 2AL, and 7BL. Of these, QYr.stars-2DS and QYr.stars-5BS are major QTL explaining 21-38% and 11.6-27.2% of the total phenotypic variance, respectively, in three experiments. QYr.stars-2DS is a new stripe rust resistance locus that was identified in the interval of 2.58-5.54 Mb on chromosome arm 2DS based on the Chinese Spring IWGSC RefSeq v2.1 reference genome. Another QTL, QYr.stars-5BS, is close to Yr47 and was delimited to the interval 8.1 - 9.0 Mb in the reference genome. QYr.stars-2AL and QYr.stars-7BL were mapped to the terminal and QTL-rich regions on chromosome arms 2AL (750.8 - 752.5 Mb) and 7BL (718.1 - 721.2 Mb), respectively. KASP markers were developed to facilitate the rapid introgression of these QTL into locally adapted lines via marker-assisted selection.

Hop (Humulus lupulus) production in the eastern United States has increased in recent years, prompting the need to understand emerging fungal pathogens in this region. This study is the first population genetics analysis of Diaporthe humulicola, a recently described pathogen causing halo blight. A total of 71 D. humulicola isolates from Michigan, New York, Minnesota, and Canada were sequenced and analyzed using Illumina 150 x 150 bp reads with a 10x coverage. Single nucleotide polymorphisms were discovered and filtered using the Genome Analysis Toolkit. After filtering and clone correction, 63 isolates remained for downstream analysis. Population structure was determined to have three clusters and was supported using STRUCTURE, principal component analysis, and discriminant analysis of principal components. Analyses show that Michigan isolates are closely clustered with isolates from Canada and New York, and one isolate from Minnesota. The rest of the Minnesota isolates clustered in an independent cluster. Minnesota isolates appear to have high levels of population differentiation when compared to the different populations exhibiting a high fixation index, a measure of population differentiation and low nucleotide diversity. Mating type was determined for each isolate, with the Mat1-2-1 present in 61.9 percent of the whole population. We also detected signals of recombination in each of the fungal populations with higher levels in Michigan and Canada. These findings highlight the genetic complexity and regional differentiation of D. humulicola populations, with implications for disease management and hop breeding programs.

Xanthomonas albilineans causes leaf scald disease in sugarcane, leading to white streaks on leaves, stunted growth, and potentially plant death. With the smallest genome in the genus, its compact size likely reflects adaptation to a specialized lifestyle. Here, we present the first in planta transcriptome of X. albilineans, obtained 48 hours post-inoculation using dual RNA-Seq-a technically demanding approach due to minimal bacterial load relative to host material. Despite only 0.05% of the more than forty billion sequenced bases corresponding to the bacterial cells, we successfully recovered and analyzed its gene expression. Compared to the transcriptome in vitro, we found that during early infection, the bacteria targets sugarcane-specific cell wall components, facilitating tissue invasion. Notably, transcriptomic data suggest that X. albilineans may utilize a distinct metabolic route for the catabolism of lignin-derived compounds, funneling aromatic intermediates into central metabolism through the protocatechuate pathway. This may represent an adaptation to plant-derived aromatic substrates not previously described in other Xanthomonas species. The upregulation of chemotaxis and motility genes indicates active systemic colonization, while phosphorelay systems enhance environmental adaptation. Bacterial fitness is also supported by production of albicidin and upregulation of type IV secretion system (T4SS) and some T5SS genes, whereas T3SS SPI-1 is inactive during early infection. These findings underscore the bacterium's reliance on specific metabolic genes to degrade sugarcane's recalcitrant wall, thrive in the xylem, and migrate to other tissues. Understanding its genomic arsenal and gene expression in sugarcane provides valuable insights for managing leaf scald disease and mitigating impact on production.

Fusarium Head Blight (FHB), primarily caused by Fusarium graminearum, damages cereal crops by inducing discoloration of spikes and producing deoxynivalenol (DON), which contaminates grains. A TaqMan multiplex real-time PCR previously demonstrated a strong correlation between DON and Fusarium biomass measured by Fusarium Tri5 over barley Actin, though a weaker association with severity. To investigate this observed disconnection, we analyzed data from 340 spikes of susceptible (Explorer) and resistant (AAC Synergy) barley at rating, sourced from a single field plot inoculated with F. graminearum and categorized according to severity rating categories (SRC). F. graminearum load was measured externally via the Tri5 gene, internally through Fusarium biomass and colony-forming units (CFU), in addition to DON levels, to identify reliable infection indicators. Significant Genotype × SRC interactions were observed across all measurements, including Tri5 (P-value = 0.0003), biomass (P-value = 0.0031), CFU (P-value = 0.0012), and DON (P-value = 0.0022). The genotype influenced Tri5 and CFU but did not significantly affect biomass or DON levels. SRC had a notable impact on all four metrics, with higher visual severity correlating with increased Tri5 levels, Fusarium DNA ratios, and CFU counts, thereby indicating greater fungal presence and biomass. Although severity correlated strongly with these measurements, it did not account for differences in genotype response. The combination of real-time PCR and CFU assays offers potential for improving future screening for FHB resistance. These findings underscore the importance of employing diverse measurement approaches to accurately evaluate F. graminearum infection in barley spikes.