Effects of phenylthiourea on growth and sclerotial formation of Sclerotium rolfsii and Whetzelinia sclerotiorum

Abstract

The growth rate of Sclerotium rolfsii and Whetzelinia sclerotiorum was reduced when 5 × 10−4 to 2 × 10−3 M l-phenyl-2-thiourea (PTU) was incorporated into synthetic media and potato dextrose agar (PDA). Whetzelinia sclerotiorum produced heavy aerial mycelia and few, if any, sclerotia in synthetic glucose-nitrate liquid medium containing 10−3 and 2 × 10−3 M PTU. At the same PTU concentrations in PDA, W. sclerotiorum formed abnormal sclerotia covered with a yellowish green exudate. Sclerotium rolfsii produced unusual patterns of aerial mycelia and no sclerotia on media containing 2 × 10−3 M PTU. With 5 × 10−4 and 10−3 M PTU, S. rolfsii produced sclerotial initials and some of these developed into atypical clumps of sclerotia. A yellow pigment developed when S. rolfsii grew on media containing PTU.