Effect of Solar Ultraviolet-B plus End of Day Light and Its Exclusion on Growth Performance and Dry Weight Accumulation of Two Sweet Potato Cultivars (Ipomoea batatas L.) on Different Altitudes

UV-B radiation and EOD light (EOD) quality has both signaling and damaging effects based on the dosage and time of exposure. At highland areas UV-B decreases crop productivity and also light quality increase at high elevation area but EOD light quality effect was not researched based on altitude. Therefore, in the present study a field experiment was conducted to investigate the effects of UV-B radiation, EOD light and its exclusion on growth performance and biomass accumulation of sweet potato cultivars on different altitude. The treatments consisting of UV-B exclusion, UV-B+ EOD light exclusion, + UV-B and (control) were studied on two sweet potato cultivars, Kulfo and Hawassa-83. The experimental design was laid out in split plot design with factorial combinations. According to the result, the highest UV-B radiation (1693.0 mw m-2 s-2) was recorded at highlands and the lowest (1107.1 mw m-2 s-2) was recorded at lowland areas. Also EOD light quality was low at lowland. Cultivar and altitude significantly affected growth and net assimilation rate but exclusion only affected growth rate. On dry weight accumulation, cultivar and altitude had high impact but exclusion affected tuber and specific leaf dry weight. Exclusion by cultivar interaction affected net-assimilation rate and specific leaf dry weight but exclusion by altitude interactions affected growth rate, net-assimilation rate and tuber dry weight. Altitude by cultivar doesn’t have any significant effect on growth performance but it has considerable effect on dry biomass accumulation. In conclusion, high UV-B at highland and low EOD time light quality at lowland negatively influenced growth performance and biomass of sweet potato cultivars