Impact of positive selection on incidence of different viruses during multiple generations of potato seed tubers in Uganda
This article (PDF) in Potato Research assesses to what extent positive selection over several seasons can reduce six different virus incidences in seed lots of different starting quality in Southwestern Uganda. Smallholder farmers in Uganda commonly use seed potato tubers from the informal sector, especially by seed recycling over several generations. Therefore, seed tubers are highly degenerated with viruses and other pathogens, resulting in poor yield and quality of the produce. Over one cycle of multiplication, degeneration management by positive seed selection was already found to be efficient in reducing virus diseases compared with the farmer’s method of selection. For this study, multi-seasonal trials were carried out in three locations, with five seed lots from four sources and three cultivars. The results clearly show that crops planted with seeds from positive selection have a reduced virus incidence compared to those from farmers’ selection when the treatments are applied over multiple (in this case, three) seasons, thereby reducing the level of secondary infection in the next-season crop. However, this reduction of virus incidence by positive selection was not found for all virus species, and the reduction was less strong than expected. An important factor for the limited gain by positive selection may be a high (risk for) primary infection in this region. Institutes and private seed growers should invest in more reliable virus testing and seed production management. However, due to financial constraints of smallholder farmers, this cannot be seen as a silver bullet for Uganda. Positive selection as an innovative seed degeneration management method for resource poor farmers is currently the best-to-fit and a resilient method; this suggests farmers have to be trained in good seed management practices to achieve the best possible potato yields.