FIGURE 1 Consensus aligned internal transcribed spacer 2 (ITS2) gene region for four crops spanning the first 75 bp from the forward primer fITS7. Ta, Triticum aestivum; Hv, Hordeum vulgare; Zm, Zea mays; Gm, Glycine max.

Briana K. Whitaker designed and validated a novel peptide nucleic acid (PNA) targeting the ITS2 gene region in barley and wheat. This PNA will substantially improve the cost efficiency of fungal surveys in the two globally important small grain crops: https://doi.org/10.1094/PHYTOFR-07-25-0066-SC 🌾

FIGURE 1 Timeline of major field activities during the cover crop and winter wheat growing season in 4 site-years.

Results from Gena Mahato et al. suggest that short-term, single-year cover crop rotations do not reduce the abundance of soilborne pathogens of winter wheat compared with fallow in the inland U.S. Pacific Northwest: https://doi.org/10.1094/PHYTOFR-01-25-0007-R

FIGURE 1 Differentially expressed ‘Candidatus Phytoplasma pruni’ genes upregulated (twofold log2, false discovery rate P ≥ 0.05) in Colladonus reductus leafhopper (white) and Prunus avium (black) sweet cherry tissues compared with non-differentially expressed genes (gray) that are involved in A, metabolic and biosynthetic processes; B, transport activity; C, replication, gene expression, and protein expression; or D, expressing structural, secreted, and hypothetical proteins.

“Differences in ‘Candidatus Phytoplasma pruni’ Gene Expression When Infecting Sweet Cherry Versus Leafhoppers,” by S. J. Harper et al. Learn more: https://bit.ly/4czEcqP

FIGURE 5 Phylogenetic relationships for the leafhopper haplotypes in the Deltocephalinae tribes Chiasmini (Athysanella and Doratura spp.) and Pendarini (Chlorotettix and Paraphlepsius spp.) samples collected on yellow sticky cards in southern Idaho and compared with sequences from GenBank based on a 585-bp region of the cytochrome oxidase gene. Numbers on the nodes of the maximum-likelihood (ML) tree represent the statistical support for ML (1,000 replicates). The tree is drawn to scale, with the branch lengths measured in substitutions per site. The tree is rooted to Circulifer tenellus. GenBank accession numbers are followed by genus and species names when available (samples from this study are highlighted in yellow). The best substitution model was GTR + G + I.

Results from Carl A. Strausbaugh, Erik J. Wenninger, and Eric Vincill contribute substantively to the cataloging of #leafhopper taxa present in southern Idaho and will aid in developing vector and disease management decisions. Learn more: https://doi.org/10.1094/PHYTOFR-04-25-0043-R

FIGURE 1 Map of locations where uniform trials were conducted to evaluate Sclerotinia stem rot (SSR) on soybean.

Farmers in the north central U.S. face soybean yield loss from #Sclerotinia sclerotiorum. Models from a meta-analysis by Hope Renfroe-Becton et al. power an interactive app to compare fungicide program probabilities for net returns and profitability: https://doi.org/10.1094/PHYTOFR-07-25-0068-R

FIGURE 1 Sample images of potato late blight progression based on leaf symptoms in the artificially inoculated cultivar Agata compared with healthy leaves. dpi, days postinfection.

Potato late blight affects potato cultivation worldwide. Rosita S. Fratini et al. tested ONT amplicon sequencing as a quantitative method for detecting and monitoring #Phytophthora infestans in artificially inoculated potato plants: https://doi.org/10.1094/PHYTOFR-02-25-0011-R

FIGURE 1 Inhibition of mycelial growth of Harringtonia lauricola (RL4) observed 20 days after inoculation. Potato dextrose agar plates were supplemented with 10% (vol/vol) of each Trichoderma filtrate and incubated in the dark at 25°C (Metabolite experiment I).

“Antibiosis, Endophytic Colonization, and Efficacy of Trichoderma Against the Laurel Wilt Pathogen in Avocado,” by Sara Salcedo-Sarmiento et al. Learn more: https://doi.org/10.1094/PHYTOFR-04-25-0036-R 🥑

FIGURE 2 Known and hypothesized roles of volatile organic compounds (VOCs). The double-headed arrows denote VOC-mediated organismal interactions. VOCs from individual organisms and those released from complex sources (e.g., greenhouse gases from the soil) affect diverse processes. Soils function as both sources and sinks of VOCs. PGPR, plant growth–promoting rhizobacteria. This illustration was reproduced from Bitas et al. (2013) (Bitas, V., et al., 2013, Sniffing on microbes: Diverse roles of microbial volatile organic compounds in plant health, Mol. Plant-Microbe Interact. 26:835-843) with permission from the American Phytopathological Society.

Seogchan Kang et al. review the materials, tools, and approaches employed to fabricate volatile organic compound sensor devices. Read the open access review in PhytoFrontiers: https://doi.org/10.1094/PHYTOFR-05-25-0053-RVW

Identification of a Quantitative Trait Locus on Chromosome 15 Conferring Resistance to Pythium irregulare in Soybean | PhytoFrontiers™ Pythium irregulare (syn. Globisporangium irregulare) has emerged as a key contributor to soybean yield losses, showing consistently high prevalence and aggressiveness across multiple geographic surveys for soybean seedling disease. High levels of cross-...

“Identification of a Quantitative Trait Locus on Chromosome 15 Conferring Resistance to Pythium irregulare in Soybean,” by Christopher Detranaltes et al. Learn more: https://doi.org/10.1094/PHYTOFR-05-25-0049-R

FIGURE 1 Fusarium pathogen occurrence at different sites and in different years

Gena Mahato et al. examined downy brome, the most prevalent grassy weed in dryland wheat production of the U.S. Pacific Northwest, as a model system to study the role of grassy weeds in #Fusarium crown rot occurrence and potential transmission: https://doi.org/10.1094/PHYTOFR-04-25-0032-R

Evaluating the Ability of Californian Grapevine-Isolated Trichoderma saturnisporopsis Strain RSI and Trichoderma asperellum Strain TLI to Reduce Fungal Trunk Diseases | PhytoFrontiers™ Grapevine trunk diseases (GTDs) reduce global grape production and require vineyards to be replanted every 10 to 15 years. One possible management option is to deploy biocontrol agents such as those based on the fungal genus Trichoderma. Therefore, the ...

Eric Antrim, Margaret L. Ellis, and Christopher M. Wallis identified and evaluated two Californian strains of #Trichoderma for their potential to combat common fungal pathogens associated with grapevine trunk diseases. Learn more: https://doi.org/10.1094/PHYTOFR-04-25-0034-SC

FIGURE 1 Box plot of soybean cyst nematode (SCN) egg count by cropping history in experiment 1. The x axis presents the cropping history treatments. The y axis presents the SCN egg count per pot. SCN egg counts were performed 30 days postinfestation (n = 6).

“Soybean Cyst Nematode Reproduction and Soybean Biomass: The Legacy of Soil Cropping Histories,” by Melanie Medina López, Soledad Benitez Ponce, and Horacio D. Lopez-Nicora. Learn more: https://doi.org/10.1094/PHYTOFR-06-25-0057-R

IGURE 1 Michigan counties sampled for sugarbeet leaves symptomatic with Cercospora leaf spot in 2021 to 2022 (highlighted in gray): Arenac, Bay, Clinton, Gratiot, Huron, Midland, Saginaw, Sanilac, and Tuscola. Field locations indicated with open circles for 2021 and filled triangles for 2022. Map generated using the ‘ggplot’ package (Wickham 2016) in R Statistical Software (v.4.1.1; R Core Team 2021) using methods from McCoy (2021).

Sugarbeets produce over half of domestic sugar in the United States, and Michigan is the fourth-highest U.S. producer. Alexandra P. Hernandez et al. characterized fungicide resistance in #Cercospora beticola populations from #sugarbeet in MI: https://doi.org/10.1094/PHYTOFR-03-25-0028-R

FIGURE 3 Disease index of charcoal rot in strawberry plants (cultivar Albion) grown in soil treated with different fumigants in a field experiment in Silvan, Victoria, Australia. There were three periods of fruiting in the cropping cycle. Bars represent the least significant difference at each measurement, where P = 0.05. Note: Dec–Feb = summer, Mar–May = fall, Jun–Aug = winter, Sep–Nov = spring.

Scott W. Mattner, Dylan J. McFarlane, and Ian J. Porter explored the effects of methyl bromide phase-out on charcoal rot of strawberry in Australia. Learn more: https://doi.org/10.1094/PHYTOFR-03-25-0027-R 🍓

FIGURE 1 Symptom rating scale (0–4) of zucchini yellow mosaic virus (ZYMV) and cucurbit yellow stunting disorder virus (CYSDV) on cantaloupe leaves (Cucumis melo var. Gold Express).

Research from Savana Marina Martinez, Kristal Watrous, and Kerry Elizabeth Mauck suggests that elicitor products may be viable options for decreasing virus severity in cantaloupe. Learn more: https://doi.org/10.1094/PHYTOFR-03-25-0021-R 🍈

FIGURE 4 Bacteria in the A, rhizosphere and B, leaf epiphyte microbiomes of table beet from samples collected in New York in 2021 and 2022. The heat trees depict community composition of taxa detected in at least 90% of samples for each sample type. Node size and color indicate the percentage of total reads and the total number of amplicon sequence variants (ASVs) assigned to each node. Stars indicate taxa with higher abundance compared with bulk soil communities.

Eric Branch et al. evaluated bacteria and fungi in the #rhizosphere and #phyllosphere microbiomes and identify the core taxa of table beet. Learn more: https://doi.org/10.1094/PHYTOFR-03-25-0022-R

FIGURE 3 Green fluorescent protein (GFP) fluorescence microscopy. Comparison of Free GFP, P3-GFP, P3-5-GFP, and CLRDV-M-GFP under fluorescence microscopy in infiltrated cotton cotyledons. The first column in each panel shows the GFP fluorescence, and the second column is the brightfield-GFP overlay.

Wilson C. Clark et al. report the first infectious clones of a U.S. isolate of #cotton leafroll dwarf virus and provide new knowledge about the biology of #poleroviruses. Learn more: https://doi.org/10.1094/PHYTOFR-11-24-0122-R

FIGURE 4 Number of Pseudotsuga menziesii and Picea engelmannii × glauca seed lots tested positive for Fusarium spp. based on three subsamples of 100 seeds per lot analyzed with the Fusarium genus real-time PCR assay. The names of the seed lots identified as positive for Fusarium spp. with this assay are indicated above or within the bars.

“Fungal Community Profiling and Pathogen Detection in Conifer Seed Lots: Benchmarking Oxford Nanopore DNA Metabarcoding Against Conventional Methods,” by Nicolas Feau et al. Learn more: https://doi.org/10.1094/PHYTOFR-02-25-0017-R

PhytoFrontiers Protocols

Introducing a new article type in PhytoFrontiers: Protocol papers detail in-depth, reproducible methods relevant to plant health. Learn more about submitting a protocol paper (scroll to the bottom for more information): https://apsjournals.apsnet.org/page/phytofr/about

FIGURE 1 Analysis of the reverse transcription PCR products (expected size 606 bp) using 1% agarose gel electrophoresis. Lane 1 contains the DNA ladder, Lane 2 the positive control (F330 isolate), Lane 3 water only, Lane 5 sample F161, Lane 6 sample F163, and Lane 7 sample F165. The remaining samples in Lanes 4, 7, and 9–12 did not produce the expected bands and were virus negative.

Vishwesh Dayal, Caleb Paslay, and Akhtar Ali present the first report, detection, and phylogenetic analysis of bell pepper #endornavirus isolates infecting pepper in Oklahoma: https://doi.org/10.1094/PHYTOFR-03-25-0026-R 🫑

FIGURE 1 High-throughput sequencing of apple petiole, grape cane, and grape petiole panels. Each data point represents the number of reads generated from each sample for each virus from each laboratory. Each sample has three points. The y axis is log-transformed.

Wide adoption of HTS-based diagnostics faces several hurdles. Peter Abrahamian et al. validated a library preparation protocol for plant virus and viroid detection in three woody plant groups across three U.S.-based laboratories: https://doi.org/10.1094/PHYTOFR-03-25-0025-R

FIGURE 2 Three Z strains inhibit growth in cultures of agrobacteria.

Research from Matthew Brown et al. found that plipastatins have potential as a preventive product to protect crop species against diverse genotypes of pathogenic #agrobacteria. Learn more: https://doi.org/10.1094/PHYTOFR-05-25-0047-R

FIGURE 1 RNA sampling schematic. B73 maize plants were grown for 30 days in the greenhouse courtyard. Treated plants were exposed in a Phyllachora maydis-infested field for 10 days and brought back to develop tar spot. Nontreated plants remained in the greenhouse courtyard to serve as the non-exposed treatment. Exposed plants were sampled at 10 days post-exposure (dpe) and 24 dpe. Non-exposed plants were similarly sampled at 10 and 24 days. Images showing symptoms sampled on leaves at 10 and 24 dpe. nonexp, non-exposed. Illustration created using BioRender.

Emily M. Roggenkamp et al. provide an initial survey of maize responses to #Phyllachora maydis and identifies candidate genes that may be important in host–pathogen interactions. Learn more: https://doi.org/10.1094/PHYTOFR-12-24-0136-R

FIGURE 1 C and D, the facilities of Campo Limpio–Revap and E and F, field research plots of the National University of Agriculture–Camayagua Campus.

Meeting Review: “Highlights from the II Agricultural Science Symposium, Honduras, 2024,” by Cesar Escalante et al.: https://doi.org/10.1094/PHYTOFR-05-25-0048-MRVW

FIGURE 1 Predicted essential genes under different growth conditions. Number of predicted essential genes after bacterial propagation in grapevine, almond, or culture medium (PD3). Genes listed are predicted as “essential” in all replicates of the specified treatment but not under the other conditions. Genes were categorized based on functional predictions from the reference genome annotation.

“In Planta Transposon Sequencing for Virulence Gene Identification in Xylella fastidiosa,” by Lindsey Burbank et al. Read the article in Volume 5, Number 3 of PhytoFrontiers: https://doi.org/10.1094/PHYTOFR-10-24-0111-R

FIGURE 2 A, Samples from cacao (Theobroma cacao) with an abnormally small pod, as is sometimes seen in plants infected with Cacao mild mosaic virus. B, Leaves of mallow (Pavonia sp.) with mosaic symptoms characteristic of virus infection. C, Virus-like symptoms on durian (Durio sp.).

Previously, cacao mild mosaic virus (CaMMV) was reported only on cacao. Alina S. Puig et al. found CaMMV strains on non-cacao hosts that shared a high identity with cacao-infecting strains, suggesting recent movement between cacao and other species. https://doi.org/10.1094/PHYTOFR-10-24-0108-R

Fluopyram is a seed treatment used for sudden death syndrome management in soybean. Nabin K. Dangal et al. found that that nanofertilizers and nitrogen fertilizers may enhance the performance of fluopyram. 🫛 Learn more: https://doi.org/10.1094/PHYTOFR-01-25-0005-R

Effect of Fungicide Application Timing on Gray Leaf Spot and Tar Spot Disease Severity, Standability, and Yield of Corn in Iowa | PhytoFrontiers™ Foliar diseases such as gray leaf spot (GLS) and tar spot negatively affect corn yields when improperly managed. Field trials done in Iowa from 2021 to 2023 compared the effect of one fungicide application at each of four corn growth stages (V6, V12, R1...

“Effect of Fungicide Application Timing on Gray Leaf Spot and Tar Spot Disease Severity, Standability, and Yield of Corn in Iowa,” by Cody J. Schneider, Rashelle L. Matthiesen, and Alison E. Robertson. 🌽 Read the article in Volume 5, Number 3 of PhytoFrontiers: https://bit.ly/4myfSXW

FIGURE 1 Average monthly temperature and rainfall observed during the 2020 growing season. Data gathered from an automatic weather station.

The relationship between scion physiology and leaf microbiome is largely unexplored. Glodia Kgobe et al. explored the influence of rootstock genotype on the scion berry and leaf mycobiome, nutrient content, and physiological activities: https://doi.org/10.1094/PHYTOFR-09-24-0098-R

FIGURE 1 Estimated posterior mean number of germinated Colletotrichum siamense conidia (solid black points) and the 66 and 95% credible intervals (CI; blue shaded bars) out of a mean of 150,000 treated conidia sprayed with a solution of hydrogen peroxide and peracetic acid at a surface coverage density of 20, 30, 40, 50, and 60% on a black plastic sheet surface (Study 7). Observed data are plotted as semi-transparent points. CFU, colony forming unit.

Warren E. Copes, Quentin D. Read, and Barbara J. Smith evaluated the effectiveness of disinfectants against Colletotrichum siamense on 6 common surfaces found in ornamental plant production systems. Learn more: https://doi.org/10.1094/PHYTOFR-12-24-0131-R