Genotypic Variation in Potato Growth and Yield Response to Water Stress During two Production Seasons in Northwest Ethiopia

Water stress during low-rainfall periods (Mesino and Belg) constrains the potato from meeting full yield potential in northwest Ethiopia. Farmers tend to grow local varieties in these seasons but these varieties have not been tested for their water stress tolerance. Therefore, the present study was conducted to evaluate major Ethiopian local varieties for their drought tolerance under controlled conditions in two growing seasons, and to compare these with a few selected varieties from outside sources. Nine local varieties and six new varieties were tested in the screen house at Adet Agricultural research center in both Mesino and Belg seasons for their response to moderate water stress conditions during 2014. All varieties were grown under two water regimes (well-irrigated and stressed) maintained by monitoring soil moisture. The results showed that, averaging across varieties, the marketable tuber yield losses due to water stress in Mesino (residual production) and Belg seasons were 28% and 67%, respectively. Substantial differences between varieties in growth and yield response to both growing season and water stress were also observed. In the Mesino season, although no variety out-yielded the main local variety, ‘Siquare’, under drought conditions, “Belete”, “CIP-395109.34”, “Abadamu” and “Granola” had showed the lowest water stress susceptibility index (SSI) and higher marketable tuber yield in stress condition. In the Belg season, ‘Granola’ followed by ‘Abadamu’ and “Gera” had the highest marketable tuber yields under both irrigated and stress conditions and the lowest water stress susceptibility index. Traits associated with high marketable yield potential and stability under stress condition include: high harvest index, increased root length, relatively few deformed and small sized tubers under stress. The results indicated potential for improving dry season potato production in Ethiopia by utilizing both selected local and new varieties.