Weevil Resistant Sweetpotato Through Biotechnology
A farmer survey conducted in Uganda revealed that weevils are responsible for 28% of crop losses every year. According to the literature, losses can be up to 90% during dry periods. As sweetpotato is at times the only food available, this can be quite devastating. The impacts of weevils can affect not only food security, but also sweetpotato production, marketability, healthiness, and sustainability, especially in areas experiencing longer dry periods.
The aim of this project is to develop weevil-resistant sweetpotato varieties through breeding and biotechnology. Bacillus thuringiensis (Bt) is a soil bacterium that is well-known for its insecticidal activity. Synthetic genes that produce the proteins active against the two weevil species attacking the sweetpotato can be developed and introduced into the plant to confer pest resistance.
Research has taken place in the US at the Auburn University and at the National Crops Resources Research Institute (NaCRRI) in Uganda; the CIP biotechnology lab in Peru; Makerere University in Uganda; BecA and Kenyatta University in Kenya, and lately at the Donald Danforth Plant Science Center in the US. Work is also going on at the University of Puerto Rico Mayaguez in the US. The University of Valencia and the Gent University have been partners from the very start.
Key Project Information
This research program aims at the development of weevil resistant (WR) varieties of sweetpotato using biotechnology for sub-Saharan Africa. Two genetic engineering strategies are pursued: (1) the accumulation in the storage root of a weevil-toxin derived from Bacillus thuringiensis, the Bt sweetpotato; (2) the expression of RNAi inhibitory of weevil essential genes in the storage root, the RNAi sweetpotato. The first and the oldest strategy is based on three weevil resistant genes expressing Cry proteins known to be toxic against the African weevils. Close to a hundred transgenic events were tested, but none proved to control weevils likely due to low accumulation of the Cry toxin in the storage root. New transgenic events with new improvedcry genes were produced and are currently tested. The second strategy, complementary to the Bt technology, is promising since both weevils species larvae can be killed if RNAi targets specific essential genes.
We are currently synthetizing the genes that will induce a RNAi mechanisms in the storage root. Recently, we show that weevil resistance will also bring health benefits by avoiding intoxication by consuming undamaged parts of infected SP roots which have considerable amount of ipomeamarone, a toxic phytoalexin. Today, as we know that sweetpotato is naturally transgenic, we expect consumer distrust of the safety of transgenic sweetpotato to decrease.