Relationship between initial water content of the substrate and mycelial growth and sporulation of the nematophagous fungi, Paecilomyces lilacinus and Pochonia chlamydosporia

Abstract

Experiments were undertaken to relate the effects of three rates of initial water content (1.0:1.0; 1.5:1.0; and 2.0:1.0) in a solid substrate (wheat bran) with mycelial growth and conidia production of the nematophagous fungi Paecilomyces lilacinus PDBC PL55 and Pochonia chlamydosporia PDBC PC57, and to relate the effects to substrate characters. Increase in water content of the substrate resulted in increased moisture content and saturation in terms of water activity. A negative relationship was observed between the proportion of initial water content in wheat bran and spore yield of P. lilacinus PDBC PL55 and P. chlamydosporia PDBC PC57. The increase in water content of the substrate also increased the duration of mycelial growth, time to completion of sporulation and total time for one cycle of production. Increased moisture content of the wheat bran resulted in a higher final moisture level in the substrate (74-76%), which in turn resulted in a longer time (8-9 days) required to dry the substrate to 15-18%, compaction and bacterial contamination. The optimum proportion of water to be added initially to wheat bran for conidial production by P. chlamydosporia and P. lilacinus was 1:1(v/w).