Froghoppers are the main pests of pasture and sugarcane, among which the genera Deois and Mahanarva stand out. These pests have been causing serious losses in the cultures of the region of Tangará da Serra, state of Mato Grosso, Brazil. The fungus Metarhizium anisopliae is considered an efficient agent for the biological control of insects, possessing various factors of virulence, including the production of proteases considered essential in the process of penetration through the insect’s cuticle. The purpose of this work is to analyze the production of extracellular proteases from isolates of M. anisopliae, using cuticular and noncuticular substrates to ascertain their influence on the expression of these enzymes. Four M. anisopliae isolates collected in the region of Tangará and the isolate R3 BB 40 used for the biological control of froghoppers in the sugarcane plantations of the Itamarati sugar mills (Nova Olimpia, MT, Brazil) were used. The enzymatic activity was determined from the Enzyme Relation Index (ERI) in Minimum Medium (MM) without glucose, with the addition of casein, gelatin and cuticle from adult Mahanarva fimbriolata and Deois flavopicta. The UNEMAT 03, UNEMAT 04, UNEMAT 05, UNEMAT 06 and R3-BB-40 isolates presented ERI values varying from 1.82 ± 0.062 to 2.16 ± 0.027 with gelatin substrate and from 1.60 ± 0.076 to 2.08 ± 0.063 with casein. The cuticular substrates showed colony growth, but revealed no halo (ERI = 1). All the isolates presented ERI with gelatin>casein>cuticle substrate, with the highest values going to the R3-BB-40 and UNEMAT 05 isolates. Isolates display natural variability in terms of extracellular protease production and under these conditions the cuticles proved to be an inadequate substrate for the detection of proteolytic activity.
entomopathogenic fungi; proteases; Mahanarva fimbriolata; Deois flavopicta
