• Home
  • Biotechnology
  • Evaluation of bioassays for testing Bt sweetpotato events against sweetpotato weevils


Evaluation of bioassays for testing Bt sweetpotato events against sweetpotato weevils

Sweetpotato weevil (Cylas puncticollis) Boheman is a serious pest throughout Sub-Saharan Africa region and is a big threat to sweetpotato cultivation. Ten transgenic sweetpotato events expressing Cry7Aa1, Cry3Ca1, and ET33-34 proteins from Bacillus thuringiensis (Bt) were evaluated for resistance against C. puncticollis. Four bioassays used were: (i) 1st instar larva in an artificial diet using root powder of transgenic events, (ii) whole root of transgenic events infested with female adults, (iii) root chip, and (iv) small root of transgenic events both infested with egg-plugs. DAS-ELISA analysis showed variation in Cry protein concentration among the events that ranged between 0.1 and 0.394 μg g-1 of root fresh weight. The highest protein quantity was observed in the event carrying the ET33-34 transcript. In general, transgenic events had no significant effect on larval survival (P= 0.28) and pupal (P = 0.86) development, though maximum pupation of 96% was observed on event CIP410009.12 that had very low expression levels of cry3Ca1 gene. Root chips were prone to damage by fungi and desiccation especially during the first larval instar. The whole root bioassay had less handling injuries to weevils compared with other methods. However, it requires a large number of adult females for oviposition and roots per event to
be tested to obtain efficacy results with statistical rigour. The small root egg plug bioassay required much fewer roots and experimental insects to assess larval mortality and development. The root chip method was the least desirable because of susceptibility to fungal and bacterial contamination. In addition, this method was the most labour intensive in terms of frequent replacement of root chips for weevil development. Hence, the most
appropriate method for testing Bt efficacy in sweetpotato is the small root egg-plug bioassay. Nonetheless, none of the transgenic events tested provided weevil control probably because of low Cry protein expression in storage roots.

Key Document Information

Authors: Rukarwa R.J., Prentice K., Ormachea M., Tovar J., Mukasa S.B., Ssemakula G., Jan Kreuze, Robert Mwanga, Marc Ghislain

Subject: Weevil resistance through biotechnology

Publication Date: 2013

Publisher: African Crop Science Society

Contributors: Jane Maurine Gati

Format: pdf

Language: English

Keywords: Cry genes, Cylas puncticollis, Ipomoea batatas


Rukarwa, R. J., K. Prentice, M. Ormachea, J. F. Kreuze, J. Tovar, S. B. Mukasa, G. Ssemakula, R. O. M. Mwanga, and M. Ghislain. 2013. "Evaluation of bioassays for testing Bt sweetpotato events against sweetpotato weevils." African Crop Science Journal 21 (3):235-244.

Learn Everything You Ever Wanted to Know about Sweetpotato!

13 Trainer of Trainers Modules in 4 Languages



Follow us

About us

This site provides a venue for sweetpotato scientists, practitioners, and farmers to share, discuss, and generate new knowledge. Information is also available for the general public to learn more about sweetpotato. The goal is to build a vibrant community of practice, providing easy access to technical and scientific information concerning sweetpotato. Anyone who registers can contribute to the site. Together we will work to enhance nutrition and food security for millions of people.

Get started

The global meeting place for people interested in all things related to Sweetpotato. Share your research and experience, ask and answer questions, meet