Conidia production of Isaria fumosorosea (Hypocreales: Cordycipitaceae) in organic substrates through two propagation techniques

Abstract

In the last decades, the use of entomopathogenic fungi for the control of pest insects has increased globally, however a key step to achieve the successful application of fungal propagules as biocontrol agents depends of various factors, inoculum production being one of the essential stages for these microorganisms to be used in pest management programs. The objective of this study was to evaluate the production of conidia by solid fermentation and biphasic culture in different sporulation matrices for four native isolates and a strain of Isaria fumosorosea that have been shown potential for the control of various insects at the laboratory level. The experimental design was completely randomized, two propagation methods were used with six treatments and ten repetitions per treatment; the data were analyzed using an analysis of variance and the means were compared using the Tukey test (p≤ 0.05). In the production by solid fermentation the minimum value of 5.30 × 10⁵ conidia g^-1 was registered with the pericarp of peanut and the maximum of 2.35 × 10⁷ conidia g^-1 in the corn grain; in the biphasic culture the minimum of 7.60 × 10⁵ conidia g^-1 was observed in birdseed and the maximum of 2.07 × 10⁷ conidia g^-1 in rice. The differences were significant (p ≤ 0.05) in the production by method and by substrate, in solid fermentation 6.84 × 10⁶ conidia g^-1 and in biphasic culture 8.85 × 10⁶ conidia g^-1. In the production by substrate, the rice showed 1.75 × 10⁷ conidia g^-1 and the lesser canary seed concentration (7.80 × 10⁵ conidia g^-1). The average production per isolate and / or strain was of the order of 10⁶ and significant difference was registered (p ≤ 0.05) among the fungi, the isolate HIB-9 showed concentration in average higher in the production (7.90 × 10⁶ conidia g^-1) and the isolated HIB-19 was the least effective, with only 1.08 × 10⁶ conidia g^-1. The results obtained show marked differences between the isolates with respect to their capacity to use the different substrates used as propagation media to obtain conidia of I. fumosorosea.