GERMINATION AND THE ROLE OF EXTRACELLULAR-MATRIX IN ADHESION OF UREDINIOSPORES OF UROMYCES-VICIAE-FABAE TO SYNTHETIC SURFACES

Urediniospores and sporelings of Uromyces viciae-fabae on hydrophilic or hydrophobic synthetic substrata, produce extracellular matrix and adhere. Three phases of extracellular matrix release were observed with TEM & LTSEM: (a) from the spore surface post-imbibition, (b) extrusion of digested polymers from the germ pore by growth of the incipient germ-tube, and (c) progressive asymmetric distribution dorsiventrally along the extending germ-tube. During the first 20 min post-hydration, fewer spores adhered to cellulose acetate than to more hydrophobic substrata, indicating that hydrophobic interactions contribute to adhesion at this stage. On all surfaces, adhesion increased between 40-120 min due to release of lysed pore material and extracellular matrix produced concurrent with germ-tube growth. Inhibition of beta-glucosidase with 50 MM-D-gluconic acid lactone, did not affect initial spore adhesion and germ pore lysis but germ-tube growth and the associated increase in adhesion were inhibited. It is proposed that the pre-invasion process of urediniospores involves passive and active phases of non-specific adhesion.