Lepidopteran stem borers infest up to 87% of maize growing areas in Kenya causing grain yield loss of 15% annually. The Bt technology for maize that utilizes genes that encode delta-endotoxins; proteins derived from the soil bacterium Bacillus thuringiensis (Bt) has been developed. The Bt toxins protect the plants against the pests but are harmless to humans, animals, and most other insects. Transfer of Bt based resistance to adapted maize germplasm in Kenya is being pursued. A permit to introduce leaves from maize transformed with Bt genes was issued by the Kenya National Biosafety Committee. Bioassays were carried out to identify the effective Bt genes against five Kenyan stem borers: Chilo partellus, Chilo orichalcocliellus, Busseola fusca, Eldana saccharina, and Sesamia calamistis. The cry l Ab protein was the most active against all species as shown by the least area of leaves consumed and by the high percentage of larvae that were killed. Chilo partellus was affected by all cry proteins, except cry l E. Eldana saccharina was the least affected by any cry protein. Chilo orichalcocliellus was most affected by cry l Ab and cry l B proteins. Sesamia calamistis was affected by cry l Ab and cry l Ab-l B proteins. CrylE protein was not active against any species. The tested Bt cry proteins were not effective in the control of B. fusca. Perhaps a cocktail of 2-3 cry of those proteins being expressed at high levels or other Bt cry proteins like crylC may show control. These results also indicate the specificity of Bt toxins even among lepidopteran stem borers. A prospective control has therefore, been identified for the most destructive borer ,C. partellus which is also the most widely distributed in Kenya.

Global Maize Program

English

0409|AGRIS 0401|AL-Maize Program

Juan Carlos Mendieta

INT2460

CIMMYT Staff Publications Collection