Sweetpotato is a staple crop grown in the Kyushu and the Kanto regions. Recently, commercial sweetpotato production has been attempted in the cooler regions of Hokkaido. Sweetpotato is a crop with weak tolerance to low-temperature stress. Therefore, it would be important to breed low-temperature-tolerant sweetpotato cultivars to expand its cultivation areas. In the case of evaluating the low-temperature tolerance of sweetpotato lines by rooting, 15ºC or a slightly higher temperature is critical. In this study, we determined low-temperature tolerance standard lines from the results of the field experiments performed in the region of low-temperature during the growth period of sweetpotato. The testing methods of low-temperature tolerance were established using the lines. In the upcoming stage, we continued the screening of sweetpotato worldwide genetic resources using mainly a low-soil-temperature testing device and identified highly tolerant lines that were used as parental lines in the cross-breeding. We successfully obtained several promising lines with low-temperature tolerance, just as well as high yield and quality. These lines would be examined to be registered as commercial cultivars in the future. Furthermore, these lines would also be important as parental lines in a general breeding program.

In this study, varietal differences in seminal root elongation angle among 52 barley cultivars were investigated using the hydrogel medium method. There were considerable differences in seminal root elongation angles among cultivars, with a minimum of 0° (Shunrai and Hokuriku kawa 48) and a maximum of 58.8° (Beau Fiber), and a mean of 23.7°. The seminal root elongation angle of barley grown in the Hokuriku and Nagano regions, where clay soils prevail, was smaller than that of barley grown in other areas.