The transmission of Fusarium subglutinans from maize seeds to seedlings

Abstract

The transmission of Fusarium subglutinans from maize (Zea mays) seeds to seedlings has not been clearly demonstrated. The objectives of this study were to determine whether P. subglutinans is seed transmitted, and to confirm this through fulfilment of Koch’s postulates. For a maize seed lot, surface-disinfected seeds plated on malt agar showed an 8% infection level with P. subglutinans, but non-surface-disinfected seeds tested by the deep freezing blotter method revealed 96% seed infection with F. subglutinans. Seedling emergence and seedling infection were assessed following sowing of surfacedisinfected and non-surface-disinfected seeds in moist sterile sand under aseptic conditions in a glasshouse with mean daily temperatures of 14–17°C. F. subglutinans had no effect on seedling emergence and survival, but produced disease symptoms which included shoot and leaf blight, shoot wilting, seedling stunting, heavy colonisation of coleoptiles, and node damage. F. subglutinans was recovered from all the parts of the seedlings, but with the lowest incidences in the leaves. The transmission rates of 88% and 10% recorded for non-surfacedisinfected and surfacedisinfected seeds, respectively, were similar to the respective seedborne inoculum levels, suggesting that under favourable conditions F. subglutinans may be effectively transmitted from maize seeds to seedlings. Koch’s postulates for the pathogenicity of F. subglutinans isolated from seedlings infected from seedborne inoculum were fulfilled. It is therefore concluded that F. subglutinans can be seed transmitted.