Conidial sporulation of Stemphylium solani under laboratory conditions and infectivity of the inoculum produced in vitro

Abstract

Stemphylium solani is an important foliar pathogen that infects many agricultural plants, especially solanaceous plants. The difficulty inducing sporulation in pure culture is a limiting factor for research on the different pathosystems involving S. solani. In this study, the influence of the culture medium, photoperiod with alternating temperatures, Petri dish cover materials (glass, polystyrene and PVC film) and stress factors of the colonies were investigated in the conidia production. Six sequential assays were performed with four isolates of S. solani, obtained from tomato plants. The inoculum produced was evaluated for infectivity on tomato plants under greenhouse conditions. The addition of fresh tomato juice to the agar medium and incubation temperatures of approximately 25 °C favoured mycelial growth. The ability to sporulate in vitro varied with the isolate, but in general the conidia production was significantly higher in V8 medium at 25 °C 6 h−1 light and 10 °C 18 h−1 of darkness. Sporulation was lower in glass Petri dishes but higher in transparent polystyrene dishes. The methodology allowed the production of viable and infective inoculum in sufficient quantity to inoculate plants under experimental conditions.