Crop resistance to Andean weevil in Bolivian hillside potato production. Final Technical Report.

This project has completed the evaluation the potential of anti-feedant genes, available to PSP on a royalty-free basis, for the control of Andean potato weevils (APW). These insects are a severe problem for Bolivian and Peruvian subsistence potato growers at altitudes above 2,800m. Tuber damage by APW influences both nutritional and commercial value of tubers. Previous work in Peru has established that levels of c50%, 25-50% and 1-25% cause loss in market values of potatoes of 67%, 50% and 17% respectively. There has been much effort in both by scientists in both USA and Australia at developing cultural control practices. They are infrequently adopted by farmers because they are time consuming, or require materials that are not affordable. One option growers favour in Peru is chemical control and there is farmer pressure for this approach within Bolivia. Several pilot studies have shown tuber infestation levels of 30- 50% can be reduced to c15% by Integrated Pest Management (IPM). The aim of this work is to assess the potential of new traits for APW resistance to be used within IPM for full control of weevils. In total three sets of experiments funded by DFID now suggest that Kunitz Soybean Trypsin inhibitor has adverse effects on an Andean weevil. Scientists at the International Potato Centre (CIP) reported the initial finding but PSP sought their verification by a second lab. Lines identified as promising at CIP expressed wheat α-amylase inhibitor plus soybean Kunitz trypsin inhibitor (SKTi) or just the proteinase inhibitor alone had efficacy. A second group of experiments in Centre for Plant Sciences at Leeds as an adjunct to another grant (R6830) confirmed efficacy for SKTi. The results have now been extended in small grant of £7.5k. They establish that SKTi reduces the fecundity of female weevils. Females that consume SKTi producing 50% less eggs than females fed control potatoes. The effect is restricted to feeding as larvae. On the two previous occasions the effect was 65% (at CIP) and 80% (at CPS, Leeds). Overall it is clear that SKTi expressing potatoes provides an important resistance trait of value within an integrated management of weevil pests of potato for subsistence cropping systems in the Andean region. Such potatoes do not require modifications to farmers' existing management practices and could be provided at no additional cost and may provide environmental benefits through a reduction in insecticide use. This approach to weevil control may also have potential for control of weevils on other crops such as banana.