CONDITIONING SCLEROTIA OF SCLEROTINIA-SCLEROTIORUM FOR CARPOGENIC GERMINATION

Sclerotia from one isolate of Sclerotinia sclerotiorum produced on cornmeal/vermiculite medium were subjected to seven different treatments at 8 C over an 8-wk period to overcome dormancy and promote carpogenic germination. The conditioning treatments of the sclerotia included 1) none (immediate use), 2) incubating dry in petri plates, 3) incubating on moistened filter paper in petri plates, 4) burying in masonry sand in clay pots and leaching with water 2-3 times per week, 5) suspending in bags of fiberglass screen in a pipette washer and constantly rinsing, 6) placing in flasks of water under constant aeration, and 7) placing in flasks of water with no aeration. Following treatment, the sclerotia were incubated on moist sand at 20 C for 4-6 wk. Sclerotia that were not conditioned or conditioned dry in glass petri plates did not germinate. Carpogenic germination increased as the conditioning duration increased, and was greatest after 8 wk of conditioning in a constant rinsing environment. Carpogenic germination of an additional 24 isolates was subsequently examined at conditioning temperatures of 4, 8, 16, and 24 C in flasks of water under constant aeration. Germination of New York isolates was almost eliminated at 24 C, but isolates from other locations varied in their response to conditioning at high temperature. The optimal temperature range for conditioning of all isolates was 8-16 C. As sclerotial size increased, the number of germinating sclerotia and apothecia produced per sclerotium also increased.