INFECTION OF MAIZE SILKS BY A NATIVE FUSARIUM (Fusarium graminearum) ISOLATE IN ARGENTINA

Resumen

Some species of the genus Fusarium cause different diseases in corn, such as stalk rot and ear rot, which affect its yield and quality. F. graminearum Schwabe (Teleomorph Gibberella zeae) is one of the prevalent species of Fusarium producing these diseases in the Argentinean core corn area. Fusarium spp. can enter the ear through the silk channel or through wounds caused by insects or birds. The objectives of this work were: 1) to evaluate the ability of a native F. graminearum isolate to infect maize flowers; and 2) to determine the most effective time for fungal infection event. To do this, corn ears were inoculated by spraying at 3 different times: (a) prior to fecundation, (b) on fecundation, and (c) on senescent silks. One portion of silk was stained to determine the presence of the fungus and fungal infection with an optical microscope, and the other portion was placed in acidified potato glucose agar (APGA) to verify the presence of F. graminearum. It was concluded that silks are receptive along all their exposed length, and penetration of F. graminearum takes place before and during fecundation and at silk senescence, with more infection level at fecundation and on senescent silks. F. graminearum presence in senescent silk tissues shows the necrotrophic ability of this pathogen and a high plasticity of adaptation to environmental conditions which are not optimal to cause infections.