First Report of <i>Sclerotinia sclerotiorum</i> Causing Stem Rot Disease in Cow Cockle ( <i>Vaccaria hispanica</i> ) in Türkiye

Vaccaria hispanica (Mill.) Rauschert, commonly known as cow cockle, has recently gained attention as a valuable industrial and medicinal plant. It is rich in bioactive compounds, including 1 µm starch grains, triterpenoid saponins, and various phytochemicals (Kernan and Ferrie 2006, Ari et al. 2022). In December 2023, symptoms of wilt and white rot were observed on V. hispanica plants at Akdeniz University Research Greenhouses in Antalya, Türkiye (36°53′53″N, 30°38′15″E; approximately 1000 m2). Approximately 30% of the plant population exhibited severe effects or complete desiccation. Early symptoms included white, cottony fungal growth on stems. As the disease progressed, lateral branches dried and black, irregular sclerotia formed on split stems. In advanced cases, complete plant death occurred. To isolate the pathogen, root and stem tissues (1 cm2) from three infected plants were surface-sterilized and cultured on potato dextrose agar (PDA). Plates were incubated in the dark at 25°C. White, cottony mycelium developed initially, followed by the formation of black sclerotia around the plate edges within 15 days. Sclerotia ranged in size from 1.02–3.91 × 1.10–7.37 mm (mean: 2.80 × 3.69 mm; n = 75). Based on morphological characteristics, the fungus was identified as Sclerotinia sclerotiorum according to Sharan and Mehta (2008). For the pathogenicity test, mycelial plugs (~0.5 cm2) were applied to five 45-day-old seedlings grown in pots. Razor wounds were made on stems (1–2 cm above soil), and mycelial plugs were applied using moistened cotton and sealed with parafilm. In control plants, sterile PDA medium was placed on the injured tissues with moistened cotton and then wrapped with parafilm. Only inoculated plants developed disease symptoms and sclerotia within 15 days. The fungus was then re-isolated from the stems of these diseased plants. For further confirmation of the species, genomic DNA was extracted from the re-isolated mycelia using the CTAB method (Doyle and Doyle 1990). For molecular identification, β-tubulin, EF1α, 28S rRNA, and ITS regions were amplified using the primers Bt2a/Bt2b (Glass and Donaldson 1995), EF1-728F/EF1-986R (Carbone and Kohn 1999), LR0R/LR05 (Vilgalys and Hester 1990), and ITS1/ITS4–ITS1/ITS5 (White et al. 1990), respectively. The resulting sequences were deposited in GenBank under the accession numbers β-tubulin: PX216760, EF1α: PX216759, 28S rRNA: PX206243, and ITS: PQ047774. The sequenced parts of the genes were 304, 439, 674 and 406 bp and showed 100% (EF1α), 99,76% (β-tubulin), 99, 13% (28S rRNA) and 95% (ITS) nucleotide identity with the corresponding sequences (AF341647.1, KF545201.1, AY187067.1 and MG824957.1). To the best of our knowledge, this is the first report worldwide of stem rot disease caused by S. sclerotiorum on V. hispanica, posing a significant phytopathological threat to its future commercial cultivation as a crop with high medicinal and industrial potential.