Liberation of Protoplasts from the Mycelium of Phytophthora

Abstract

Spherical protoplast-like bodies were released from the mycelia of Phytophthora cinnamomi and P. parasitica on digestion of their hyphal walls with an extracellular enzyme preparation from Streptomyces sp. in media of appropriate osmotic pressure. Protoplast liberation was observed when using as osmotic stabilizer either sucrose or mannitol (0.2 [image]-0.8 [image]); maximum response at about 0.4 [image]-0.6 [image]. Although hyphal wall digestion was always extensive, the amount of protoplast release varied widely under seemingly similar conditions. Protoplasts were liberated from the Phytophthora mycelium by 2 mechanisms: bud-like emergence in which cytoplasm was squeezed through a small pore in the wall usually located at or near a hyphal apex; or intercalary hyphal swelling, which consisted of the swelling and rounding off of short hyphal segments whose walls became progressively thinner until they were no longer visible. Both types of protoplast were osmotically sensitive and disintegrated upon dilution of the suspending media.