First Report of Colletotrichum sansevieriae Causing Anthracnose of Snake Plant (Dracaena trifasciata) in Ohio and its Draft Genome.

Dracaena trifasciata (Prain) Mabb. is a popular houseplant in the United States. In September 2021, two diseased samples from two Ohio homeowners were received by the Ornamental Pathology Laboratory at The Ohio State University. Each sample included one or two detached leaves displaying circular gray water-soaked lesions scattered throughout the lamina and blighted areas with concentric rings bearing brown to black acervuli. Lesions covered between 25 and 50% of the leaf surface. Isolations were made by excising small portions of leaf tissue from the margin of the lesions, surface-disinfesting in 10% bleach for 45 s, rinsing in sterile water, and plating on potato dextrose agar (PDA). Plates were incubated at 23°C for one week. Two representative isolates, one per sample (FPH2021-5 and -6), were obtained by transferring hyphal tips to fresh PDA plates. Mycelia of both isolates were aerial, cottony, grayish-white, producing spores in a gelatinous orange matrix, and appeared gray to olivaceous-gray on the plate underside. Conidia produced by both isolates were cylindrical, single-celled, hyaline, measuring 12.02 to 18.11 (15.51) × 5.03 to 7.29 (6.14) µm (FPH2021-5; n=50) and 15.58 to 20.90 (18.39) × 5.63 to 8.27 (7.05) µm (FPH2021-6; n=50). Appressoria were globose to subglobose, single-celled, dark brown to sepia, measuring 6.62 to 13.98 (8.97) × 5.05 to 6.58 (6.58) µm (FPH2021-5; n=50), and 6.54 to 11.32 (8.63) × 4.54 to 8.94 (7.09) µm (FPH2021-6; n=50). Genomic DNA (gDNA) samples were extracted from both isolates and the internal transcribed spacer (ITS) region was amplified using primers ITS1F/ITS4 (Gardes and Bruns, 1993; White et al. 1990). GenBank BLAST sequence analysis resulted in 99.83% (FPH2021-5; GenBank Acc. No. OP410918.1) and 100% (FPH2021-6; OP410917.1) identity with 100% query coverage to the type strain of Colletotrichum sansevieriae Miho Nakam. & Ohzono MAFF239721 or Sa-1-2 (NR_152313.1; Nakamura et al. 2006). Whole genome sequencing was conducted for FPH2021-6 and the assembly was deposited in GenBank (JAOQIF000000000.1). The glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and ß-tubulin (ß-tub) regions were either extracted from the genome of FPH2021-6 (OP414603.1 and OP414601.1, respectively) or amplified from FPH2021-5 gDNA using primers GDF/GDR (OP414604.1) and Bt-2b/T1 (OP414602.1), respectively (Templeton et al. 1992; Glass and Donaldson 1995; O'Donnell and Cigelnik 1997). A multilocus partitioned analysis (Chernomor et al. 2016) based on concatenated sequences of ITS, GAPDH, and ß-tub using ModelFinder (Kalyaanamoorthy et al. 2017) was performed to build a maximum likelihood tree (IQ-TREE v2.0.3; Nguyen et al. 2015), suggesting that these two isolates are phylogenetically closer to the type strain from Japan than to a previously reported isolate 1047 from Florida (Palmateer et al. 2012). To fulfill Koch's postulates, two parallel leaf sections from one 10-inch D. trifasciata 'Laurentii' plant maintained in a 1.3-liter container were selected. Three wounds were made in each section using a sterile syringe needle. A 10-µl drop of either a 1×106 conidia/ml suspension of isolate FPH2021-6 or sterile water was placed on each wound. The plant was covered with a plastic bag for two days post-inoculation (DPI) and maintained in a greenhouse at 25°C with a 12- h photoperiod. The experiment was conducted twice. Grayish water-soaked lesions, acervuli, and leaf blight were observed on the inoculated sections 3, 10, and 14 DPI, respectively, while no symptoms appeared on the sections treated with sterile water. C. sansevieriae was re-isolated from the lesions and confirmed to be identical to the original isolate based on ITS sequencing and morphological examinations. To the best of our knowledge, this is the first report of C. sansevieriae on D. trifasciata in Ohio and the first genome draft of an isolate from the United States. Availability of whole-genome sequence data is paramount for resolving species identification in this highly diverse fungal genus, and a powerful tool to conduct comparative genomic analyses in the future.

A metabolomics-guided approach to discover Fusarium graminearum metabolites after removal of a repressive histone modification.

Many secondary metabolites are produced by biosynthetic gene clusters (BGCs) that are repressed during standard growth conditions, which complicates the discovery of novel bioactive compounds. In the genus Fusarium, many BGCs reside in chromatin enriched for trimethylated histone 3 lysine 27 (H3K27me3), a modification correlated with transcriptional gene silencing. Here we report on our progress in assigning metabolites to genes by using a strain lacking the H3K27 methyltransferase, Kmt6. To guide isolation efforts, we coupled genetics to multivariate analysis of liquid chromatography-mass spectrometry (LCMS) data from both wild type and kmt6, which allowed identification of compounds previously unknown from F. graminearum. We found low molecular weight, amino acid-derived metabolites (N-ethyl anthranilic acid, N-phenethylacetamide, N-acetyltryptamine). We identified one new compound, protofusarin, as derived from fusarin biosynthesis. Similarly, we isolated large amounts of fusaristatin A, gibepyrone A, and fusarpyrones A and B, simply by using the kmt6 mutant, instead of having to optimize growth media. To increase the abundance of metabolites underrepresented in wild type, we generated kmt6 fus1 double mutants and discovered tricinolone and tricinolonoic acid, two new sesquiterpenes belonging to the tricindiol class. Our approach allows rapid visualization and analyses of the genetically induced changes in metabolite production, and discovery of new molecules by a combination of chemical and genetic dereplication. Of 22 fungal metabolites identified here, 10 compounds had not been reported from F. graminearum before. We show that activating silent metabolic pathways by mutation of a repressive chromatin modification enzyme can result in the discovery of new chemistry even in a well-studied organism, and helps to connect new or known small molecules to the BGCs responsible for their production.

Whole-Genome Sequence Data for the Holotype Strain of Diaporthe ilicicola, a Fungus Associated with Latent Fruit Rot in Deciduous Holly.

Diaporthe ilicicola is a newly described fungal species that is associated with latent fruit rot in deciduous holly. This announcement provides a whole-genome assembly and annotation for this plant pathogen, which will inform research on its parasitism and identification of gene clusters involved in the production of bioactive metabolites.