Critical Values of Porosity in Rice Cultures of Isaria fumosorosea by Adding Water Hyacinth: Effect on Conidial Yields and Quality

Conidia of the entomopathogenic fungus Isaria fumosorosea are used to control insect pests in crops. Commercially available mycoinsecticides manufactured with this fungus are produced on a large scale via solid-state cultures (SSC). In order to favour gaseous exchange in SCC, texturizers can be added to increase porosity fraction (ε). This work presents results of water hyacinth (Eichhornia crassipes) as a novel texturizer. A mixture of parboiled rice (PR), with a ε = 0.23, was used as a substrate, which was then mixed with water hyacinth (WH amendment) as a texturizer at different proportions affecting ε. Strains CNRCB1 and ARSEF3302 of I. fumosorosea yielded 1.6 (1.49–1.71) × 10⁹ and 7.3 (7.02–7.58) × 10⁹ conidia per gram of initial dry rice after 8 days, at ε values of 0.34 and 0.36, respectively. Improvement of conidial yields corresponded to 1.33 and 1.55 times, respectively, compared to rice alone using WH amendment in the mixtures PR:WH (%) at 90–10 and 80–20. In addition, infectivity against Galleria mellonella larvae was maintained. This is the first report of the use of water hyacinth as a texturizer in SSC, affecting ε, which is proposed a key parameter in conidia production by I. fumosorosea, without affecting conidial infectivity.