Studies of Hot Water Treatments for Curtailing Seed-Associated Mycoflora

Abstract

The effects of immersion of maize seed in water at 55, 57 and 60°C, for varying times were assessed in terms of fungal status, seed germination and seedling establishment. These assessments were conducted immediately after treatment, after re-dehydration for 2 days in a cool air stream and following a 1 month storage period under either cold (4°) or ambient (25°) conditions (RH 33% and 91%, respectively). The level of internal contamination, represented almost entirely by Fusarium moniliforme [Gibberella fujikuroi], declined significantly when assessed immediately after the treatment, the efficacy of which increased with increasing temperature and duration of treatment. Although there was an associated decline in germination when treated for longer than 15 and 5 minutes at 55 and 57°, respectively, seedling emergence was unaffected by a treatment duration of 5 minutes. Subsequent storage for 1 month, even under conditions that would normally encourage fungal proliferation (i.e. 25° and 91% RH), did not alter the initial effect of the treatment, for short durations, on infestation levels and seedling establishment. However, seed vigour was somewhat reduced. Therefore, while treatment at 60° was too extreme, that at 55 and 57° showed promise in producing a crop less prone to fusarial pathogenesis.