Effects of inoculum type and propagule concentration on shelf life of Pesta formulations containing Fusarium oxysporum Foxy 2, a potential mycoherbicide agent for Striga spp.

Abstract

The lack of an adequate shelf-life in mycoherbicidal products has been an obstacle to their commercialization. Therefore, experiments were conducted to study the effect of inoculum type and concentration on the viability of the encapsulated propagules of Fusarium oxysporum , abbreviated as Foxy 2, in Pesta granules during storage. Pesta granules were made with different inocula of Foxy 2, including: microconidia, a mixture of mycelia and microconidia, and fresh as well as dried chlamydospore-rich biomass, each with three different inoculum concentrations. All granular preparations (0.5–2 mm, particle size) were stored at 4 °C or at room temperature (21 ± 3 °C) for 1year. All Pesta granules containing chlamydospore-inoculum retained higher viability (up to 100%) than those with mycelial and/or microconidial inocula, irrespective of inoculum concentration and storage temperature. Microconidial and mycelial preparations were not viable after 1 year at room temperature. Throughout the year, the viability of fresh and dried chlamydospore-rich biomass was not significantly affected by the concentration of chlamydospores in the formulation at 4 °C or room temperature. Thus, 85–100% viability of Foxy 2 propagules can be achieved in Pesta granules (0.5–2 mm) for at least 1 year by formulating chlamydospore-rich biomass and storing at a temperature of 4 °C. This information has significant implications in enhancing shelf-life of Foxy 2 products thereby helping us to overcome this obstacle to commercialization.