Sclerotial germination and ascospore formation of Claviceps gigantea Fuentes, De la Isla, Ullstrup y Rodríguez

Abstract

The disease known as “horse´s tooth†in maize (Claviceps gigantea) can affect grain yield up to 90 %. In this research, the time of sclerotial germination and the development of the sexual structures were studied in field and laboratory. A design was implemented with substrate and time of incubation at 4 °C as factors. Percent of germinated sclerotia, time of germination, and formation of stromatic heads were evaluated. In laboratory, sclerotia germinated only when on residual charcoal, incubated for 3 months at 4 °C followed by 2 months at 22.24 °C, resulting in 55 % germination. Sclerotia germinated produced an average of five heads per sclerotium 15 d after primordial were produced. In field conditions, the primordial appeared after the sclerotia were incubated for 3 months at 4 °C and 64 d at an average temperature of 14.07 °C. In both types of sclerotia, primordia released thin, elongated ascospores after 23 d, showing that the appearance of primordia and maturity did not occur at the same time. Ascospores release from the stromatic heads was documented. The pathogen was identified morphologically and molecularly as Claviceps gigantea.