Eric Magembe1, Marc Ghislain1, Arinaitwe Abel Byarugaba2, Alex Barekye2 Li Hui3, Taheri Ali3, and Zhou Suping3
1 International Potato Center, P.O. Box 25171, Nairobi 00603, Kenya
2 Kachwekano Zonal Agricultural Research and Development Institute (KaZARDI), National Agricultural Research Organisation (NARO), P.O. Box 421, Kabale, Uganda
3 Tennessee State University, Agricultural Biotechnology Building, College of Agriculture,
3500 John A Merritt Blvd, Nashville, TN 37209 USA
Potato, the 3rd world food crop, is an increasingly important crop that provides both food and cash income. Late blight (LB) remains the most devastating disease of potato with about 15-30% annual yield loss in sub-Saharan Africa, affecting mainly smallholder farmers. The disease is controlled almost exclusively by applying from 3 to 15 sprays of fungicides per season which affect farmers health and the environment. We have transferred 3 resistance genes from wild relatives of the potato (RB, Rpi-blb2 from Solanum bulbocastanum, Rpi-vnt1.1 from S. venturii) into the 5 farmer- and consumer-preferred varieties ‘Desiree’, ‘Victoria/Asante’, ‘Shangi’, ‘Tigoni’ and ‘Jalene’. Several transgenic events were tested in the lab, greenhouse and in the field. Target capture sequencing (TCS) was used to identify the T-DNA integration sites for 34 potato events and T-DNA break point on either end. Majority of events had intact T-DNA and the flanking potato sequences were majorly from the potato genome which led us to identify the chromosomal position of insertion. One event, Vic.172, was found to have an ideal T-DNA insertion site and further evaluated for resistance to late blight, phenotypic characterization, and agronomic performance in field conditions at three locations during three seasons in Uganda. These trials were conducted by comparison to the variety Victoria from which Vic.172 derives, using identical fungicide treatment, except when evaluating disease resistance. During all seasons, the transgenic event Vic.172 was confirmed to have complete resistance to late blight disease, whereas Victoria plants were completely dead by 60–80 days after planting. Tubers from Vic.172 were completely resistant to LB after artificial inoculation. Differences in agronomic performance were not statistically significant except for marketable yield in one location under high productivity conditions. Overall, the results of the comparative assessment of the phenotype and agronomic performance revealed that transgenic event Vic.172 did not present biologically significant differences in comparison to the variety Victoria it derives from. A field detection assay for event Vic.172 was developed and validated. It is rapid method that takes about 2.5 hours from sampling to results which involves field DNA isolation. This tool will help post-release monitoring by the biosafety authority and other partners in line with good stewardship practices.