Brassica oleracea var. sabellica: A New Host of Agroathelia delphinii in Soilless Cultivation Systems in Central Thailand

Kale (Brassica oleracea var. sabellica), known for its high nutritional value and health benefits, has gained significant popularity. Recently, kale grown in soilless systems has also become increasingly popular, as these systems offer better environmental control and improve overall quality, making them an ideal method for cultivating kale. However, in 2023–2024, several kale plants exhibited severe symptoms of seedling and stem rot leading to losses of over 70% in both quality and yield. In this study, the infectious isolates were obtained from stem rot kale grown in soilless cultivation greenhouses across three provinces in central Thailand. The pathogens were identified through a combination of morphological characteristics and molecular techniques, utilizing nucleotide sequences from the internal transcribed spacer (ITS1-5.8S-ITS2) and large subunit ribosomal RNA (LSU rDNA). Pathogenicity tests and Koch’s postulates on 2-month-old kale plants confirmed that the fungus was responsible for causing brown stem lesions and rot. Morphological features and multilocus sequence analysis (MLSA) identified the pathogen as Agroathelia delphinii. This research represents the first report of A. delphinii infecting kale in Thailand, offering crucial insights for accurate disease diagnosis and the development of effective management strategies in soilless cultivation systems, which is essential for improving productivity in increasingly variable environments.