Physiological variability of Fusarium verticillioides causing post flowering stalk rot in maize

Abstract

Post flowering stalk rot of maize caused by Fusarium verticillioides is the major disease and the occurrence of variability in the pathogen is one of the key factors for difficulty in management of the disease. The effect of temperature regimes showed the maximum radial growth and highest sporulation was obtained at 30℃ by all six isolates of F. verticillioides. At pH 7 maximum radial growth of all isolates was obtained except FV 1 and FV 7 isolates which produced maximum radial growth at pH 6. Highest sporulation of all six isolates was seen at pH 6. Exposure of pathogen to continuous dark (24 hours) condition yielded maximum radial growth in all isolates except in FV 6 isolate which produced maximum radial growth when it was exposed to continuous light (24 hours). Optimum sporulation of all the six isolates was seen under continuous dark condition followed by alternate cycles of 12 hours light and 12 hours darkness. Isolates FV 2 and FV 7 were produced maximum radial growth on soluble starch, whereas FV 3 and FV 6 isolates on sucrose. Fructose and maltose produced maximum radial growth of FV 1 and FV 5 isolate respectively. Optimum sporulation of all six isolates was obtained by supplying fructose and sucrose as carbon source.