ADHESION OF COLLETOTRICHUM-GRAMINICOLA CONIDIA TO CORN LEAVES - A REQUIREMENT FOR DISEASE DEVELOPMENT

Ungerminated conidia of Colletotrichum graminicola, the causal agent o f anthracnose leaf blight of corn, adhered to corn leaves within minut es of contact. Adhesion approached 30 % of the conidial population by 30 min on the fourth and fifth leaves of 5-week-old plants. In contras t, adhesion of conidia on the eighth or ninth leaf of 8-week-old plant s reached a maximum of only 20 % by 2 h suggesting that the adhesion o f ungerminated conidia to the leaf is influenced by leaf age. Germinat ion of conidia began 6 h after inoculation. Within 3 h after germinati on was first observed, the percentage adhesion increased and reached a new maximum level, indicating that a second phase of adhesion occurre d as a result of germination. These results show that adhesion of unge rminated conidia as well as conidial germlings is essential to the inf ection process and the successful development of disease by C. gramini cola. Scanning electron microscopy and micromanipulation of adhered co nidia revealed both the alteration of the leaf surface to which the co nidia had been adhered and the presence of a possible adhesive materia l on the contact surface of the ungerminated conidia and the contact s urface of the conidial germ tube.