Crop resistance to the nematodes Globodera and Nacobbus in Bolivian hillside potato production. Final Technical Report

Abstract

The two nematode pests of potato in the Alti Plano and Valles of Bolivia are Globodera spp (potato cystnematode) and Nacobbus aberrans (Rosary nematode or false root-knot nematodes). They have been ranked by Bolivian scientists and socio-economists as 3rd and 1st equal respectively of pests and diseases of potato in Bolivia. Globodera can be controlled by rotation but most of the 400,000 small farmers in Bolivia lack the land area to accommodate the 5-6 years break between potatoes that this approach requires. Such infrequent cropping does not harvest sufficient potatoes to provide the rural poor's calorie need from this crop. There is no currently effective method of controlling Nacobbus when host weeds prevail in the field between potato crops. This work has shown unequivocally that cystatins can provide partial resistance against both nematodes. In contrast, no natural resistance is effective against both nematodes. Efficacy was shown for Globodera in 2 containment and 2 UK field trials. Furthermore transgenic resistance was obtained using more than one cystatin and with more than one cultivar. Transformation was achieved of both S tuberosum tuberosum and a hybrid of this subspecies with S. tuberosum andigena. The latter subspecies has proven difficult to regenerate and transgenic lines have yet to be generated using it. This work and further development of constructs is being continued within R7294. Bolivia has limited experience with the transgenic crops. This project has made a significant contribution to addressing biosafety issues in that country. It established standard operating procedures for work with GM potato. An incinerator was built and a glasshouse altered to improve its value as a containment facility. The project helped define Bolivian governmental approaches to the subject and was the catalyst for the DFID/CIP conference on GM potato for developing world needs in Manchester in June 2000. Field experiments without transgenic material demonstrated that male sterile potato can set seed when growing at least 20m from a cultivar that donated fertile pollen. This transfer did not happen in a subsequent year at another locality probably because of a lack of Bombus bees at that site. The biosafety hazard of gene introgression was addressed by transforming a male sterile cultivar (Revolution) and by making constructs and by generating male sterile potato plants by molecular means. The will be screened for male sterility in R7294. We treat as the primary priority the need to address by technology any biosafety hazard that can be identified. Work outside of the project has indicated the inherent food safety of the technology approaches we have developed. It is our strongly held opinion that the anti-nematode transgenic technology should only be implemented within an IPM scheme. The level of resistance is already sufficient to prevent damage with the 3-4 year rotation that prevails in Bolivia. Further enhancement of the approach will be the main output from R7294. The project also investigated the potential of some anti-insect potato plants developed by Pestax for which PSP has a royalty-free licence. The work built on some equivocal findings at the International Potato Centre (CIP). The lines were shown in this project and that at CIP to have little efficacy against potato tuber moth. However two lines expressing soybean Kunitiz trypsin inhibitor and the anti-nematode plants expressing a cystatin did show efficacy against the Andean weevil, Rhigopsidius tucumanus. The effect was on fecundity of females after they fed on tubers expressing the putative anti-weevil proteins. In addition there was some evidence for either reduced viability or readiness to hatch of those eggs that were laid. Overall the best line provided 80% reduction in the fecundity of the weevil and c90% control when the reduced egg hatch was also considered. These findings are to be confirmed by feeding adults on leaves of the transgenic plants in a small supplementary grant. This project has identified promising anti-nematode technology of potential benefit to Bolivia and many other developing countries. This technology has already been donated to DFID. It also indicates that Andean weevils on potato in Bolivia and neighbouring countries could be controlled transgenically