Morphology of conidia of Cochliobolus sativus from untreated and fungicide-treated barley seed

Abstract

Conidia of Cochliobolus sativus from untreated seed are straight, curved, or occasionally triradiate, are multicellular, and produce bipolar germ tubes, but aseptate conidia of different sizes also occur. A narrow channel or plate occurs at the position of invagination between outer and inner layers of endospore wall. Conidiophores from untreated or treated seeds are pitted as seen in electron micrographs. Multiradiate conidia with reduced lumina occur after treatment with Panogen Px and conidia from Panogen Px, Polyram 80, and Dithane M45 treatments produce lateral or bipolar germ tubes. Brown bands, coincident with the channel or plate, occur in conidia exposed to Res-Q, Polyram 80, Dithane M45, SWF 790, SWF 810, and SWF 840 treatments. Obovate conidia occur on Hexa-treated seed. Evidence is presented suggesting that fungicides enter the conidia via terminal germination areas rather than the conidiophore.