Histopathological assessment of the infection of maize leaves by Fusarium graminearum, F. proliferatum, and F. verticillioides

Young maize plants were inoculated on unfolded mature leaves and on folded immature leaves with Fusarium graminearum, Fusarium proliferatum, and Fusarium verticillioides suspensions. Infection and symptom development of disease on these asymptomatic mature leaves and immature leaves were then documented. Subcuticular infection was found by the three Fusarium species on both symptomatic and symptomless leaves. The three Fusarium species penetrated the stomata of immature leaves by the formation of appressorialike structures, infection cushions or by direct penetration. Infection by the three species of Fusarium via stomata is reported here for the first time. The superficial hyphae and reemerging hyphae of the three species produced conidia. The macroconidia of F. graminearum produced secondary macroconidia and F. proliferatum formed microconidia inside the leaf tissues that sporulated through stomata and trichomes. The infection of maize leaves by the three species of Fusarium and their sporulation may contribute inoculum to cob and kernel infection. (C) 2016 British Mycological Society. Published by Elsevier Ltd. All rights reserved.