Abstract

PITRE RUIZ, Leanis; HERNANDEZ-FERNANDEZ, Javier  and  BERNAL VILLEGAS, Jaime. Toxicity of Bacillus thuringiensis recombinant δ-endotoxins on Guatemalan potato moth (Tecia solanivora) (Lepidoptera: Gelechiidae) larvae. Rev. colomb. biotecnol [online]. 2008, vol.10, n.2, pp.85-96. ISSN 0123-3475.

The specific toxicity of Cry1Aa, Cry1Ac, Cry1B and Cry1C recombinant proteins from Bacillus thuringiensis (Bt) was determined on Tecia solanivora first instar larvae. Mass breeding of this insect was established in laboratory conditions: 58 ± 5% relative humidity, 18 ± 5ºC temperature and 23 h dark and 1 h light photoperiod. A semi-natural diet was supplied consisting of brown pastusa variety potato slices sterilised with preserver solution (7 g/L ascorbic acid and 5 g/L methylparabene) as it was steady over time, thereby guaranteeing the reproducibility of results and was easy to assess. The recombinant proteins were also evaluated at 0.1 µg/cm² concentration to find significant differences between them. Mortality percentage results indicated that there were no differences between the B thuringiensis Cry1Aa, Cry1Ac, Cry1B and Cry1C delta-recombinant endotoxins (p<0.01 and p<0.05); however, difference s were seen when comparing them with the reference B. thuringiensis var. kurstaki HD1 strain. CL₅₀ was calculated for the four toxins, testing at 0.05, 0.1, 0.15, 0.2, 0.25 and 0.3 µg/cm² protein concentration. Probit Polo PC software was used for determining that the CL50 obtained inside this rank was: Cry1Aa 0.103, Cry1Ac 0.107, Cry1B 0.085 and Cry1C 0.112 µg protein/cm². It was clear that the evaluated d-endotoxins had high toxicity on T. solanivora larvae, the Cyr1B protein being slightly stronger. This result is promissory for further research on genetic engineering aimed at obtaining transgenic T. solanivora-resistant potato crops.

Keywords : Bacillus thuringiensis; bioassay; recombinant endotoxin; Tecia solanivora; pastusa potato variety.

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