Genetic engineering of rice plastids for insect pest control (1996-99)

Mr. J.L. Nandadeva, IRRI, Los Banos, Laguna, The Philippines
Prof. I. Potrykus, Institute of Plant Science ETHZ, 8092 Zürich

Goal
In view ot the expected widespread release of transgenic rice varieties carrying Bt toxin genes, questions regarding the sustainability of future pest management approaches and the potential ecological hazard imposed by transgenic plants have been addressed. In this context, the following points are considered to be of high importance: a) the development of restistance of target insects toward Bt toxins, and b) the effects of transmission of the transgenes from rice to related species.

Objectives

• to generate transgenic rice breeding lines with cry gene(s) integrated into the plastid genome (i.e. transplastomic plants.)

Rice is one of the world’s most important crop plants, with a production reaching more than 500 million metric tons in 1994. Considerable losses (up to 10 million tons / Y) are caused by lepidopterous stem borers. Despite breeding efforts during the past 3 decades, no rice variety with a useful level of resistance against stem borers could be developed. Recently, transgenic Japonica varieties [9] and Indica elite breeding lines [23] have been developed that are effectively protected against the most destructive insect pests of rice in Asia, the yellow stem borer (Scirpophaga incertulas) and the striped stem borer (Chilo suppressalis). The protection is a result of ¶-endotoxin accumulation in plant cells, encoded by a cry gene of the entomocidal, spore forming soil bacterium Bacillus thuringiensis. These approaches demonstrate the potential of geneticalyy engineered rice varieties in future insect pest control strategies.