Variation in performance on cry1Ab-transformed and nontransgenic rice varieties among populations of Scirpophaga incertulas (Lepidoptera : Pyralidae)from Luzon Island, Philippines

We quantified variation in performance under greenhouse conditions among se ven populations of Scirpophaga incertulas (Walker) from Luzon Island, Phili ppines, on three rice varieties: 'IR58' transformed with the cry1Ab gene fr om Bacillus thuringiensis Berliner, and nontransgenic IR58 and IR62. On IR6 2, S. incertulas performance did not differ among provinces for any of the 10 parameters measured, but there was a significant effect of town within p rovince for one parameter, 20-d-old larval weight. Larval survival after 48 h on cry1Ab-transformed IR58 did not differ significantly among provinces, but did differ significantly among towns within a province. There was no g eographic variation in larval survival after 48 h on control plants of IR58 . Surviving insects from the cry1AB-transformed IR58 were transferred to IR 62 to complete development. There was no geographic variation in the percen tage of insects completing development to adult emergence and the time requ ired by the transferred female insects to complete development. However, th ere was variation among provinces in male developmental time. The absence o f geographic variation on nontransgenic IR58 and the very limited variation on IR62 indicated that there was little variation in general vigor among t he S, incertulas populations and thus that the Variation in performance on cry1Ab-transformed IR58 was probably attributable to differences in suscept ibilty to Cry1Ab.