Developmental biology of sclerotia of Sclerotium rolfsii

Sclerotial initials of Sclerotium rolfsii reached the maturation phase when transferred onto a new growth medium only if taken from original medium with their surrounding mycelium; but when transferred onto a medium supplemented with 10−4 M iodoacetic acid or 10−2−10−3 M disodium ethylene-diaminetetraacetic acid (Na2EDTA), initials continued their development and became cream-yellow in color even when taken with no mycelium. Sclerotia at the late development phase continued their development and reached maturation when transferred without mycelium onto a non-supplemented medium. Addition of 10−2 ML-cysteine to the transfer medium resulted in inhibition of sclerotial development at both phases, whether or not initials and developing sclerotia were transferred with surrounding mycelium.It is suggested that factors supplied by the mycelium are involved in initiation, development, and maturation of the sclerotia of S. rolfsii. Phenylthiourea can replace these factors only at the phase of initiation whereas iodoacetic acid and Na2EDTA are effective at both initiation and development. All these hypothetic factors are inhibited by L-cysteine.