Abstract
Potato (Solanum tuberosum L.) is an important crop in Uganda but production is low. There is not a well-functioning official seed system and farmers use potato tubers from a previous harvest as seed. This study investigated how effectively the seed technology positive selection enhanced yield and underlying crop characteristics across multiple seasons, compared to the farmers’ selection method. Positive selection is selecting healthy plants during crop growth for harvesting seed potato tubers to be planted in the next season. Farmers’ selection involves selection of seed tubers from the bulk of the ware potato harvest. Positive selection was compared to farmers’ seed selection for up to three seasons in three field trials in different locations in southwestern Uganda using seed lots from different origins. Across all experiments, seasons and seed lots, yields were higher under positive selection than under farmers’ selection. The average yield increase resulting from positive selection was 12%, but yield increases were variable, ranging from − 5.7% to + 36.9%, and in the individual experiments often not significant. These yield increases were due to higher yields per plant, and mostly higher weights per tuber, whereas the numbers of tubers per plant were not significantly different. Experimentation and yield assessment were hampered by a varying number of plants that could not be harvested because plants had to be rogued from the experimental plots because of bacterial wilt (more frequent under farmers’ selection than under positive selection), plants disappeared from the experimental field and sometimes plants did not emerge. Nevertheless, adoption of positive selection should be encouraged due to a higher production and less virus infection of seed tubers in positive selected plants, resulting in a lower degeneration rate of potato seed tubers.
Highlights
Potato (Solanum tuberosum L.) is one of the main staple crops for food and nutrition security in Uganda (Whitney et al 2017), where it serves as a cash crop for smallholder farmers (Gildemacher et al 2009; Olanya et al 2012)
For yield and its underlying components, the full outcome of the ANOVAs and the means for the individual treatments in the three experiments are shown in Tables [2, 3] and 4; the supplementary data on yields per tuber size class, maximum ground cover and stem number per plant are shown in the supplementary material (Supplementary Tables 2A–4A)
Results of the 1st season are included in Fig. 1 to show variation across seasons but are not included in the statistical analysis because the seed planted in the first season had not yet been subjected to the experimental selection treatments
Summary
Potato (Solanum tuberosum L.) is one of the main staple crops for food and nutrition security in Uganda (Whitney et al 2017), where it serves as a cash crop for smallholder farmers (Gildemacher et al 2009; Olanya et al 2012). One of the most important yield-defining factors in potato production is the quality of the seed tubers planted (Struik and Wiersema 1999; Haverkort and Struik 2015). Tubers for seed are mostly taken from the bulk of the ware potato harvest and selected based on size and visual inspection. This method is further referred to as “farmers’ selection” or FS. These successively cycled seed tubers are often highly degenerated due to accumulation of tuber-borne pests and diseases (especially viruses and bacteria), resulting in poor yield and poor quality of the harvest (Turkensteen 1987; Salazar 1996; Struik and Wiersema 1999; Thomas-Sharma et al 2016)
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