Development of Bt rice potential for yellow stem borer control

Abstract

Rice (Oryza sativa L.) production is always threatened by biotic and abiotic stresses. Both stresses can reduce rice productivity and quality. Yellow stem borer (YSB; Scirpophaga incertulas Walker) is one of the biotic stresses and is reported as the most destructive pest of tropical rice insects. The application of pesticides is less effective since the insect larvae live and feed inside the stem, thus inhibiting pesticides to reach the larvae. Planting YSB-resistant cultivars is a good strategy besides environmentally friendly. However, no sufficient level of resistance to YSB has been identified among rice germplasm collection, making the use of conventional breeding methods is difficult. Bacillus thuringiensis (Bt) is a Gram-positive bacterium produces insecticidal proteins, Cry toxins that are toxic to YSB. The introduction of cry genes from Bt into rice plants by using genetic engineering has been widely and successfully carried the out. A number of strategies have been conducted to increase the expression level and to prolong the effectiveness of Bt toxins in transgenic rice, including plant codon usage-optimized genes, the use of strong promoters and wound-inducible promoters and gene stacking. Insect bioassays under laboratory, greenhouse and field conditions showed that transgenic rice plants harboring and expressing cry genes are highly resistant to YSB compared to the original cultivars from which transgenic plants were developed. Thus, the development of transgenic rice plants harboring and expressing cry genes from Bt is a good strategy to build plant resistance against YSB.