Tan Sclerotia of Sclerotinia sclerotiorum from Lettuce

A tan sclerotia forming strain of Sclerotinia was found on a diseased lettuce plant in the field in the spring of 1981. Apothecia produced from the tan sclerotia were white, while apothecia produced from black sclerotia of Sclerotinia sclerotiorum are typically brown. The tan sclerotia lacked a dormancy period, with myceliogenic germination occurring on potatodextrose agar and moist sand. Although ascospores of the tan isolate were slightly larger and more irregular than those of S. sclerotiorum, other morphological and pathogenic aspects of the two isolates were similar. The tan sclerotial isolate is considered an aberrant strain of S. sclerotiorum.