Impact of UV-B Radiation and Irrigation Frequency on Growth Performance and Tuber Yield of Different Sweet Potato (Ipomea batatas L.) Genotypes

Abstract

Introduction: Sweet potato (Ipomoea batatas L.) is an important food security crop grown at different region of Ethiopia. However, its productivity is influenced by biotic and abiotic factors including Ultraviolet B (UV-B) radiation and moisture stress. . However, the level of damage varies based on the sensitivity of plants. Therefore, the present study was designed to study the impact UV-B radiation and irrigation frequency on growth performance, physiology and tuber yield of sweet potato varieties. The experiment was conducted under greenhouse conditions, at Hawassa University during January to May of the year 2016 and 2017.The experiment was laid out in complete randomized design in factorial arrangement with three replications. The experiment consisted of three different factors:1) With and without UV-B radiation (0.25wm-2s-1); 2) three irrigation intervals (daily, every three days and every seven days) and 3) two sweet potato varieties (Aawassa-83 and Kulfo). The analysis of variance indicated that, vegetative growth, leaf water content, water use efficiency and tuber number per plant were significantly affected by combined effect of irrigation interval, UV-B radiation and variety. Extended moisture stress for three days with the involvement of UV-B radiation significantly reduced number of leaves by 30.5% (Awassa-83) and by 18.4% (Kulfo); leaf area by 49.4% (Awassa-83) and 53.6% (Kulfo) reduced stomata aperture by 3?m and tuber yield by 50% as compared to daily irrigated crops and UV-B untreated varieties. Vegetative growth and yield reduction was stronger under combined effect than moisture stress alone or UV-B radiation alone. However, Kulfo variety had maximum water use efficiency (36.26 μmol mmol-1) than Awassa 83 under extended moisture stress condition.