Novel indica basmati line (B-370) expressing two unrelated genes of Bacillus thuringiensis is highly resistant to two lepidopteran insects in the field

We report the first field trials of indica basmati rice expressing two Bt genes, cry1Ac and cry2A simultaneously. Different transgenic lines were sown under field conditions for two consecutive years (2001 and 2002). Artificial infestation of yellow stem borer (YSB, Scirpophaga incertulas) and natural infestation of rice leaf folder (RLF, Cnaphalochrocus medinalis) were studied. Transgenic lines showed up to 100% and 98% resistance against YSB at vegetative and flowering stages, respectively, with 98% additional resistant against RLF as compared with the control. Variation in some morphological characteristics, e.g., the average number of tillers, plant height and maturity, were also observed. Transgenic lines produced up to 59% more grains than control plants under artificially augmented conditions, while up to an 8% increase was recorded under natural infestations. All lines expressed high level of Cry proteins when compared with commercially released cultivars of Bt cotton, maize and potato. It was also observed that although toxin titer substantially decreased with increasing age of the plants, it remained well within the limits necessary to kill the target insects. It was also observed that the transgenic lines released Bt toxins from roots into Murashige and Skoog basal medium, hydroponic cultures and soil, which could be detected through sandwich ELISA. On the basis of these results these lines seem good candidates to be released as the first commercial cultivars of Bt indica basmati rice.