ULTRASTRUCTURAL ASPECTS OF COLLETOTRICHUM-GRAMINICOLA CONIDIUM GERMINATION, APPRESSORIUM FORMATION AND PENETRATION ON CELLOPHANE MEMBRANES - FOCUS ON LIPID RESERVES

Colletotrichum graminicola, a plant pathogen, was investigated at cyto chemical and ultrastructural levels during conidium germination. Cytoc hemical optical tests and electron microscopy observations showed that the cytoplasm of ungerminated conidia was filled with small lipid bod ies which were mobilized during the germination process. Appressoria w ere able to penetrate the cellophane membranes and exhibited an abunda nt extracellular matrix, which extended from the cellular wall to the cellophane surface. The presence of large lipid bodies in close proxim ity to vesicles, mitochondria and microbodies was demonstrated in the appressorium cytoplasm. These observations suggest that the glyoxylate cycle may be involved in lipid processing. A reaction product mediate d by acid phosphatase was detected inside germ tube vacuoles, implying a lyric function for these organelles, Altogether, these changes indi cate an intense remodeling process, high metabolic activity and lipid processing for germination and appressorium formation.