Parassitismo di Trichoderma harzianum su cistosori di Polymyxa betae

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Abstract
Parasitism of Trichoderma harzianum on Cystosori of Polymyxa betaeTransmission electron microscope investigations revealed that cystosori of Polymyxa betae Keskin are, in vitro conditions, parasitized and completely degraded by Trichoderma harzianum Rifai. The hyperparasite showed a high ability in colonizing excised, surface‐sterilized lateral roots of sugar beet and in invading the cystosori present in them. Both the walls of the root cells and of the cysts are enzymatically perforated. However, in cysts penetration, mechanical forces are also involved. After penetration, cysts undergo a rapid degradation and finally they appear to be completely empty or to contain only small amounts of degradated cytoplasm.Cyst walls are also strongly altered and deformed and only two thin osmiophylic residual layers are detectable.