MONOCERIN IN EXSEROHILUM-TURCICUM ISOLATES FROM MAIZE AND A STUDY OF ITS PHYTOTOXICITY

Three Exserohilum turcicum strains from France, isolated from maize, p roduced a lipophilic phytotoxin that has been structurally characteriz ed as monocerin. This molecule causes brown necrotic lesions on punctu red leaves, the size of which is in direct relation with the dose appl ied. It also inhibits the root growth of pregerminated seeds: the medi an dose (ID50) being around 10(-3) M. It decreases the viability of ma ize root cap cells and mesophyll protoplast suspensions: the ID(50) wa s 2.5-5 x 10(-4) M for cells and around 8 x 10(-5) M for protoplasts.