Mycelial growth and production of oxalic acid by virulent and hypovirulent isolates of Sclerotinia sclerotiorum

Abstract Hypovirulent dsRNA-containing, and virulent dsRNA-free, isolates of Sclerotinia sclerotiorum were compared for mycelial growth and oxalic acid production in liquid culture. When harvested at 14 days post-inoculation, hypovirulenr isolates 91 and 215 produced less dry mycelium than virulent isolates 191 and 275C in potato-dextrose broth (PDB) and PDB amended with sodium succinate (PDBSS). All isolates produced more oxalic acid per gram dry mycelium When grown in PDBSS than in PDB. In a time course study, hypovirulent isolates 91 and 275 produced less mycelium (0.23 and 0.03 g dry wt.) and oxalic acid (0.22 and 0.01 mg/mL) than virulent isolates 191 and 275C (0.81 and 0.91 g dry wt., and 0.50 and 0.63 mg oxalic acid per millilitre, respectively) at 15 days post-inoculation. The amount of oxalic acid produced per gram dry mycelium reached a maximum for virulent isolates 191 and 275C at 3 and 5 days post-inoculation. Hypovirulent isolate 91 reached a maximum at 9 days post-inoculation, and hypovirule...