Rice plants exhibit increased chilling tolerance and oligosaccharide production after acclimation

ABSTRACT Tolerance to low temperatures can be enhanced in plants acclimated to low but harmless temperatures. This study examined chilling survival (4°C for 10 days) in 10-day-old Hokkaido rice cultivar seedlings following an initial acclimation at 12°C for five days. In addition, the effect of acclimation on changes in soluble sugar content in shoot tissue was examined. Acclimation resulted in 88–100% survival of six Hokkaido rice cultivars subsequently subjected to chilling compared with no survival among unacclimated seedlings. Acclimation of the Hokkaido rice cultivars ‘Oboroduki’ and ‘Kitaaoba’ extended the chilling exposure survival time by eight and 10 days, respectively. Soluble sugar contents in the rice shoots increased during the acclimation treatment, which peaked on the third day, especially that of sucrose. Upon exposure to chilling, the sucrose content decreased through day five in acclimated plants, whereas it increased in unacclimated plants compared with pre-chilling levels. The oligosaccharide contents increased in the acclimated and unacclimated plants upon exposure to chilling, with higher contents at days five and 10 in the acclimated plants than in unacclimated plants. Rice plants with high survival rates after chilling acclimation treatment tended to have higher oligosaccharide content. Furthermore, chilling acclimated rice seedlings showed higher survival rates and better initial growth than those of rice seedlings that had not been acclimated outdoors. These results highlight the potential of chilling acclimation establishment in rice seedlings before paddy transplantation to facilitate tolerance to short-term low temperatures. Graphical Abstract