Effect of prism generated discreet wavelengths of light on germination and post-germination development of Colletotrichum dematium var circinans (Berk.) v. Arx

Spores, harvested from 8 da old colonies ofColletotrichum dematium varcircinans (Berk.) v. Arx, were placed on slides under shimmed coverslips and subjected to 10 min irradiation with wavelengths of light ranging from 400 to 750 nm. Controls consisted of spores exposed to 10 min of fluorescent or tungsten light, or to continuous dark. Germination, and production of sessile and non-sessile appressoria, and germ-tubes was monitored. In addition position of germ-tubes on spores was noted and germination types were classified by numbers of germ-tubes and sessile and non-sessile appressoria produced. When compared to dark controls certain wavelengths, 400, 450, 600 and 650 nm, appeared to be inhibitory to germination and post-germination development, while others, 500, 550 and 750 nm, appeared to be stimulatory. Spores irradiated with some of the wavelengths (550, 700, 750 nm) that affected other responses produced the smallest percentage of sessile appressoria (approx. 10%). Placement of germ-tubes was not affected by treatment. More germ-tubes were produced from spore bottoms (53%) than tops (32%), and tips (15%). The fewest number of germ-tubes was produced from spore centers and from one tip. Thirteen germination types were noted. About 53% of spores germinated with one germ-tube, one non-sessile appressoria, and no sessile appressoria. The remaining 47% were distributed throughout the remaining 12 types, and ranged from 21% to less than 1% of the total. Treatments did not affect this distribution.