In vitro and in planta efficacy studies on T6 generation of transgenic Rojolele rice lines against the rice yellow stem borer (Scirpophaga incertulas Walker)

Abstract

One of the most destructive pests in cultivated rice (Oryza sativa L.) is the rice yellow stem borer (YSB; Scirpophaga incertulas Walker). YSB attacks rice plant throughout its life span, with the most devastating being during mature stage that causes a symptom called whiteheads. Every 1% of whiteheads symptoms resulted in 1% rice production losses. Planting YSB-resistant cultivars is a good strategy besides environmentally friendly. However, since the unavailability of YSB-resistant gene in rice germplasm, genetic engineering of rice to express Cry toxin from Bacillus thuringiensis (Bt) that is toxic to YSB is an alternative. Agrobacterium-mediated transformation has been conducted to introduce cry1B gene from Bt into a local javanica rice cultivar, Rojolele. The recombinant plasmid contains cry1B gene driven by wound-inducible promoter from maize proteinase inhibitor (mpi) gene and hygromycin phosphotransferase (hpt) selectable marker gene for transgenic plants selection. The presence of cry1B gene in transgenic rice plants was identified by PCR analysis. Four homozygous transgenic rice lines harboring cry1B gene have been obtained. The purpose of this experiment was to determine the efficacy of cry1B gene in homozygous transgenic rice lines against YSB at vegetative stage, in vitro and in planta at T6 generation. In vitro assay was performed in aerated Petri dishes using leaf samples under growth room condition, meanwhile in planta assay was done by subjecting the four homozygous transgenic rice lines to YSB under greenhouse condition. The results showed that the four homozygous transgenic rice lines tested were highly resistant to YSB compared to the wild-type Rojolele rice.