First Report of Pythium Myriotylum as a Causal Agent of Crown and Root Rot in Soilless Green Bean Cultivation in Italy

Green beans are the unripe young fruit of common bean (Phaseolus vulgaris). Italy is one of European larger producers, together with Spain, of green beans with 140,000 t of fresh vegetable. To increase green bean production and quality, its cultivation includes soilless growing. In the summer 2016, during a survey in a commercial greenhouse farm in central Italy (Latium region), over 200 out of one thousand green bean plants (P. vulgaris cv. “Valdarno”) showed symptoms of crown and root rot followed by wilting. Plants were cultivated in pot with sterile perlite and coconut fiber with no recycled-water irrigation system. The infected crowns and roots appeared water soaked with a cinnamon brown color and dead plants occurred in distinct and well delimited areas. Microbial isolations were performed from ten diseased plants previously abundantly washed under running tap water. Fragments cut from the margin of sub epidermal stem lesions were plated on P5ARP. A Pythium species was consistently isolated and 3 si...