Native bacillus thuringiensis rt delta-endotoxin production in a low-cost culture medium for spodoptera frugiperda control in corn seedlings

Abstract

Bacillus thuringiensis (Bt) is a bacterium that produces insecticidal crystal inclusions targeted to particular groups of insects. Spodoptera frugiperda (Sf) (Lepidoptera: Noctuidae) is a major corn pest in northwestern Argentina so it is important to produce these toxins as an alternative to chemical pesticides since they have no adverse effects on man, animals or beneficial insects. The aim of this study was to assess delta-endotoxin production in a low-cost medium and to test protection of corn seedlings. The Bt RT strain was grown in a 3 l fermentor using an optimized medium containing cerelose, whey, powdered milk, vinasse, sucrose, starch and soybean meal. Three treatments were evaluated: healthy seedlings (T1), infested seedlings with Sf (T2) and infested seedlings with the formulation (T3). Dry weight of shoots was determined on the 7th day. The estimated delta-endotoxin (mg/L) during fermentation was: 361.62 (24 h), 418.92 (48 h), 567.57 (72 h), 560.72 (96 h) and 664.32 (120 h). The average dry weights (g) were: 0.32 (T1), 0.26 (T2) and 0.29 (T3). For semifield assays, significant differences between T1 and T2 (α =0.05) were detected while no significant differences were observed between T1 and T3.