Phytopathology®

Fig. 1. Rice blast disease development on parental lines aus-196 and Black Hull Awn weedy rice (RR14) inoculated with four blast races: IB33, IC17, IE1K, and IG1. Leaf images were taken at 7 days postinoculation.

Rice blast, caused by the ascomycete fungus #Magnaporthe oryzae, is one of the most problematic diseases for rice production. Aron Osakina et al. identified Pi-ta/Pi-39(t)/Ptr as the key contributor to blast resistance in weedy rice: https://doi.org/10.1094/PHYTO-02-25-0051-R

Call for Papers! Seedborne Pathogens: Risks, Research, and Resilience

Seeds are critical to global food security—but also key pathways for pathogen spread. Submit your research papers that expand knowledge of seedborne and seed-transmitted plant pathogens to the forthcoming Phytopathology focus issue: https://apsjournals.apsnet.org/seedbornepathogens

Fig. 2. Xylem colonization of CML333 plants with green fluorescent protein-expressing Xanthomonas vasicola pv. vasculorum. A, Spray-inoculated leaf at 14 days postinoculation (dpi) showing vein colonization along the tip and edges of the leaf. B, Spray-inoculated 7 dpi leaf edge vein. C, Stem-wound-inoculated leaf at 14 dpi showing multiple veins colonized. D, Leaf vein cross-section at 7 dpi of leaf-cut-inoculated leaf. Both the protoxylem and metaxylem were colonized. E, Bacteria streaming from infected vein at 7 dpi from leaf-cut-inoculated leaf. Arrows: xy, xylem; v, vein.

“Vascular Pathogenicity of Xanthomonas vasicola pv. vasculorum in Maize Is Modulated by Tissue-Specific Host Resistance,” by Alexander Mullens et al. Read the article in #Phytopathology to learn more: https://doi.org/10.1094/PHYTO-05-25-0164-R

Fig. 1. Map of sampled locations across the lower peninsula of Michigan, with shape depicting the host sampled. A total of 569 isolates across all four hosts (wheat, corn, dry bean, and soybean) from 121 sites were utilized in this study.

To characterize the population of #Fusarium in Michigan, Mikaela Breunig et al. collected 569 isolates and determined species composition, TRI genotype, in vitro fungicide sensitivity, and fungicide field efficacy: https://doi.org/10.1094/PHYTO-06-25-0214-R

Digital phenotyping of sugar beet with symptoms of syndrome “Basses Richesses” (SBR) caused by ‘Candidatus Arsenophonus phytopathogenicus’ (ARSEPH).

Syndrome “Basses Richesses” (SBR) is a rapidly emerging sugar beet disease in central Europe that has a severe economic impact on the sugar beet industry. Justus Detring et al. provide foundational work for digitally phenotyping SBR: https://doi.org/10.1094/PHYTO-07-25-0239-R

Michigan is one of the largest producers of highbush blueberries in the U.S. Botrytis blossom blight is a major diseases in this region. J. A. Abbey et al. describe a new species, #Botrytis michiganensis, as an additional pathogen causing blossom blight: https://doi.org/10.1094/PHYTO-06-25-0223-R

Fig. 3. Camalexin levels in uninfected roots and Meloidogyne incognita infection sites of Arabidopsis plants with impaired glutathione biosynthesis during the migratory (24 h postinoculation) stage of infection. Camalexin was measured by high-performance liquid chromatography. Data points represent the means ± SE of three biological replicates. Significant differences are denoted by different lowercase letters, determined through analysis of variance followed by Tukey's honestly significant difference post hoc tests (P < 0.05). C, control; M, migratory.

M. Shamim Hasan et al. investigated the role of glutathione in #Arabidopsis thaliana during #Meloidogyne incognita infection using a combination of genetic, biochemical, and pharmacological approaches: https://doi.org/10.1094/PHYTO-03-25-0090-R

Fig. 1. Development of blast disease symptoms on wheat rachises. Rachises were inoculated with the Magnaporthe oryzae Triticum (MoT) isolate (4 × 103 conidia ml−1) and covered with a polythene bag for 48 h. Development of disease symptoms was monitored, and photographs were taken 10 days after inoculation. The blue circle indicates the area of infection by MoT.

Md. Saiful Islam et al. biochemically demonstrate that blast resistance in S615 is, in part, correlated with its strong antioxidant defense responses to #Magnaporthe oryzae Triticum infection, providing a physiological basis for this resistance mechanism: https://doi.org/10.1094/PHYTO-06-25-0206-R

FIGURE 1 Chemotaxis in Xanthomonas: Chemo-attractants and repellents present in the micro-environment of host exudates bind to the chemoreceptors (Mcp) present in the inner membrane of Xanthomonas. Based on binding, CheA is recruited by CheW and auto-phosphorylation happens. CheR and CheB drive methylation and demethylation events, respectively. CheY and CheB are phosphorylated as response regulators. Phosphorylated CheY regulates flagella-mediated clockwise rotation (CR). Phosphorylated CheB turns off kinase activity of CheA through demethylation, inhibits phosphorylation of CheY, and regulates flagella-mediated counterclockwise rotation (CCR).

Arkaprabha China et al. discuss recent advances in understanding how #Xanthomonas integrates environmental and host-derived signals to regulate its pathogenicity. Read the open access review in #Phytopathology: https://doi.org/10.1094/PHYTO-05-25-0183-RVW

Fig. 1. Directed acyclic graph (DAG) representing causal paths for powdery mildew and management costs. Arrows are edges that indicate postulated causal relationships between variables. Red arrows indicate edges that are assumed always to be present based on prior knowledge. Variables are described in the text and Table 1. Colors indicate exogenous variables (gold), disease incidence (gray), spray date (blue), type of fungicide use (green), and annual costs (orange).

#Phytopathology Editor’s Pick: “How Do Growers Respond to Host Resistance? A Conditional Gaussian Bayesian Network for Causal Inference of Fungicide Cost Savings,” by Jae Young Hwang et al. Learn more: https://doi.org/10.1094/PHYTO-06-25-0199-R

Check out the first published articles in “Exploring Pantoea: Dual Roles in Plant Health and Disease.” Submit your work by March 31 to be included in the Pathogen Spotlight!

https://bit.ly/3Ml7fnt
https://bit.ly/4twpfw2
https://bit.ly/4ckzihf
https://bit.ly/4aFS8hC

Fig. 1. Isolation and detection of the pathogen in sorghum glumes and leaves. A, Glumes and leaves with red lesions. B and D, Yellow vegetative and C and E, white aerial mycelia of the pathogen isolated from glumes (B and C) and leaves (D and E) separately.

Licheng Wang et al. present the first report of the pathogenicity of #Fusarium thapsinum to sorghum glumes, as well as its genome characteristics. Learn more: https://doi.org/10.1094/PHYTO-02-25-0067-R

Fig. 9. Schematic diagram of plant growth promotion and disease resistance mechanisms in strains SB-3 and SB-35. A, Growth promotion mechanisms. B, Disease resistance mechanisms against Rhizoctonia solani. See the main text for model details.

Kexin Li et al. 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: https://doi.org/10.1094/PHYTO-05-25-0159-R

Fig. 1. Hymenium formation of Thanatephorus cucumeris anastomosis subgroup 3-TB (AG-3-TB) strains on the different host crops and the surface soil near tomato stems.

Findings from Minghuan Wang et al. indicate that host plant species, strain differences, urea, and fungistatic stress significantly influence #Thanatephorus cucumeris sporulation, revealing the pivotal role of spore production in the disease development: https://doi.org/10.1094/PHYTO-02-25-0086-R

Fig. 4. Lesion growth plotted against lesion area and lesion age. Yellow curves represent linear or nonlinear quantile regression fits; green lines show loess-smoothed trends. X axis limits were set to display all data points within the 99th percentile; models were fitted, and predictions are shown only within this range, due to limited data beyond this threshold. All coefficients of the regression models were statistically significant (P < 2.2 × 10−16).

Using deep learning-based image analysis, Jonas Anderegg et al. tracked 6,889 individual lesions caused by #Zymoseptoria tritici on 14 wheat cultivars across two field seasons, enabling 27,218 precise measurements of lesion growth in the field: https://doi.org/10.1094/PHYTO-05-25-0187-R

Fig. 1. Standard curves for cox2 and ypt1 (McDougal et al. 2021) assays using a fivefold serial dilution of Phytophthora pluvialis (NZFS 3032) DNA. qPCR was carried out using six technical replicates. Coefficient of determination (R2), slope, and amplification efficiency are presented. Error bars represent the standard deviation. Neither assay showed positive amplification at the lowest serial DNA dilutions corresponding to 2.56 fg of DNA per qPCR. Cq, quantification cycle.

#Phytophthora pluvialis is present in the United States, New Zealand, the United Kingdom, and Belgian forests. R. O'Neill et al. designed a qPCR assay targeting a multiple-copy mitochondrial gene to increase the sensitivity of P. pluvialis detection: https://doi.org/10.1094/PHYTO-01-25-0020-R

Fig. 3. Correlation matrix of the different parameters used to score for resistance to black rot on leaves. PRL_P21 and PRL_P43, plant resistance level in semi-controlled conditions at, respectively, 21 and 43 days postinoculation (dpi). LRL_P21 and LRL_P43, leaf resistance level in semi-controlled conditions at, respectively, 21 and 43 dpi. PRL_V, plant resistance level in the vineyard. LRL_V, leaf resistance level in the vineyard. Values inside circles indicate the Spearman's correlation coefficient for each pairwise comparison.

“Identification of New Sources of Resistance to Black Rot in a Collection of Vitis Species,” by Vincent Dumas et al. Learn more: https://doi.org/10.1094/PHYTO-03-25-0112-SC

Fig. 2. Effect of azithromycin on Lasiodiplodia theobromae strain CGMCC3.20151, the pathogen of tea leaf spot. A and E, Control (CK; 0 μg/ml) for 12 and 24 h. B and F, Azithromycin at the 30% effective concentration (EC30; 56.09 µg/ml) for 12 and 24 h. C and G, Azithromycin at EC50 (140.61 μg/ml) for 12 and 24 h. D and H, Azithromycin at EC90 (1,328.22 μg/ml) for 12 and 24 h. Black arrows show development of daughter hyphae. Yellow arrows indicate increased hyphal irregular swelling. Rectangles indicate protoplasts in hyphae becoming granulated. Scale bar = 50 μm.

#Lasiodiplodia theobromae significantly reduces the yield and quality of tea in tea-producing regions because of the lack of effective control methods. Atta Ur Rehman et al. evaluated the antifungal activity of azithromycin against L. theobromae: https://doi.org/10.1094/PHYTO-05-25-0190-R

Fig. 3. Haustorial maturation is completely suppressed in A to F, CcRpp1.6.11.1-positive versus G to L, the null soybean leaves.

Asian soybean rust (ASR) threatens soybean production, especially in South America. The pigeonpea gene CcRpp1 confers strong ASR resistance. Mark A. Chamberlin et al. dissected its mechanisms via cytological, transcriptomic, and metabolomic analyses: https://doi.org/10.1094/PHYTO-02-25-0048-R

Fig. 1. Antifungal activity of Bacillus subtilis M-4 cell-free filtrate (CFF) and pellet against Macrophomina phaseolina at different concentrations A, on an agar plate and B, in a broth medium. C, Percentage of growth inhibition. D, Reduction in fungal biomass. Values are means ± standard errors of independent replicates. Different letters indicate significant differences between treatments, which were analyzed using Duncan's multiple comparison test (P ˂ 0.05). Asterisks indicate significant differences between treatments at P < 0.05: *P < 0.05; **P < 0.01; ***P < 0.001. Two-tailed P values were calculated between control and treatment using Student's t test.

The ability of #Macrophomina phaseolina (MP) to form microsclerotia makes it hard to control. Priyanka Chauhan et al. evaluated effective charcoal rot disease management using Bacillus subtilis M-4, which exhibits strong biocontrol potential against MP: https://doi.org/10.1094/PHYTO-03-25-0098-R

“What an impressive list! I was very pleased to see that plant disease epidemiology was well-represented with one-third of the landmark papers.” —Harald Scherm (University of Georgia)

Explore the virtual issue: https://apsjournals.apsnet.org/landmarksphyto

Fig. 1. Principal component (PC) and model-based cluster analysis of the 921 tetraploid wheat lines, including the North Dakota State University (NDSU) durum wheat breeding population (DWND), durum wheat landrace (DWL), and cultivated emmer (CE) wheat.

Cultivated emmer wheat's broad genetic diversity could be leveraged for bacterial leaf streak (BLS) resistance breeding. Hayat Khan et al. evaluated BLS severity in 508 emmer wheat lines at the seedling stage under controlled environmental conditions: https://doi.org/10.1094/PHYTO-02-25-0071-R

Fig. 1. “Vacuole-like” structural aberrations (indicated by red arrows) in the soybean cyst nematode (SCN; Heterodera glycines) eggs 5 days after treatment with fungal filtrate under in vitro conditions. A, Vacuole-like structures in SCN eggs. B, Vacuole-like structures in enclosed first-stage juveniles and emerging second-stage juveniles (J2s). C, Vacuole-like structures in hatched J2s. D, Hatched J2s in potato dextrose broth (PDB) control without vacuole-like structures. E, Eggs in PDB control. Scale bar = 45 µm.

Biological control of soybean cyst #nematode (SCN) using fungi associated with cyst nematodes shows promise. Vijay Kunwar et al. screened 75 fungal isolates across 55 species associated with different cyst nematodes to assess antagonistic effects on SCN: https://doi.org/10.1094/PHYTO-03-25-0094-R

Fig. 1. Schematic illustration of the experimental workflow for evaluating seed transmissibility of apple chlorotic leaf spot virus, apple green crinkle-associated virus, apple hammerhead viroid, apple rubbery wood virus 2, apple stem grooving virus, apple stem pitting virus, and citrus concave gum-associated virus in Malus × domestica.

Anna O. Wunsch et al. conducted a large-scale seedling grow-out experiment using seeds harvested from 51 trees infected by several combinations of six viruses and one viroid to evaluate their seed transmission capabilities. Learn more: https://doi.org/10.1094/PHYTO-06-25-0208-SC

Fig. 1. Workflow of water regime and virus treatment in experiments 1 and 2. M-C, moderate-continuous water stress; M-T, moderate-transient water stress; S-C, severe-continuous water stress; S-T, severe-transient water stress; DAT, days after transplant; FC, field capacity; CMV, cucumber mosaic virus; CABYV, cucurbit aphid-borne yellows virus; ELISA, enzyme-linked immunosorbent assay; EPG, electrical penetration graph.

An increase in the intensity and frequency of drought could impact aphid–virus–plant relationships. Jaime Jiménez et al. explored the combined effects of water regime and virus infection on plant traits, virus transmission, and #aphid feeding behavior: https://doi.org/10.1094/PHYTO-04-25-0130-R

Fig. 8. The role and associated biological processes of VdATG24 in both the growth and pathogenicity of Verticillium dahliae.

Hongxuan Li et al. dissected the molecular functions and underlying mechanisms of the mitophagy receptor ATG24 homolog in the soilborne hemibiotrophic fungus #Verticillium dahlia: https://doi.org/10.1094/PHYTO-01-25-0029-R

Fig. 1. Angular leaf spot (ALS) on common bean. A, ALS symptoms on common bean differential line G11796. B, Conidia of Pseudocercospora griseola. C, Fasciculate conidiophores. Scale bars: B = 25 µm and C = 150 µm.

Editor’s Pick: “Population Genomics of Pseudocercospora griseola Reveals New Groups in the Middle American Clade and the Presence of the Endophytic Bacterium Achromobacter xylosoxidans,” by Luz M. Serrato-Diaz et al. Learn more: https://doi.org/10.1094/PHYTO-09-24-0302-R

Fig. 2. Subcellular localization of CsNsdD in Colletotrichum siamense. A, Subcellular localization of CsNsdD in the conidia of C. siamense. B, Subcellular localization of CsNsdD in the hyphae of C. siamense. White arrows indicate the position of nuclei with the green fluorescent protein (GFP) signal, and the nucleus was further stained by DAPI (4′,6-diamidino-2-phenylindole) for visualization. CsWT-eGFP, the wild-type strain transformed with the eGFP gene; CsNsdD-eGFP, the wild-type strain transformed with the CsnsdD-eGFP fusion gene. Bars = 10 μm. DIC, differential interference contrast.

The genus #Colletotrichum infects over 3,000 monocot and dicot plant species, inflicting substantial economic losses globally. Jinhong Wang et al. characterized the GATA transcription factor NsdD in C. siamense and C. graminicola, respectively. Learn more: https://doi.org/10.1094/PHYTO-07-25-0238-R

Fig. 1. Map of the study area of Qinghai and Gansu. A, The winter and spring wheat growing areas. B, Sampling locations from which Puccinia striiformis f. sp. tritici isolates were collected in this study.

“Range of the Key Oversummering Regions of Puccinia striiformis f. sp. tritici in Northwestern China Has Expanded Westward,” by Liang Huang et al. Read the article to learn more: https://doi.org/10.1094/PHYTO-05-25-0180-R

Fig. 1. Phylogenetic relationships and motif patterns of predicted coiled-coil nucleotide-binding site leucine-rich repeat (CNL) and Toll/interleukin-1 receptor nucleotide-binding and leucine-rich repeat (TNL) proteins from the complete rubber tree genome.

The specific relationship between NLR genes and anthracnose resistance in rubber trees remains poorly understood. Xianbao Liu et al. comprehensively identified all NLR family members in the reference genome of the wild rubber tree accession MT/VB/25A 57/8: https://doi.org/10.1094/PHYTO-09-24-0273-R