An Episode of High Temperature before or after Tuber Initiation Impairs Potato Tuber Growth.

Potato is the most important non-cereal crop for world food security. It is adapted to mild conditions but its production is rapidly shifting to warmer regions where more and longer episodes of high temperatures are likely to limit its yield. This study investigated the physiological response of potato to an episode of high temperature either before or after tuber initiation; monitoring growth during and after the treatment period. There were two glasshouse experiments: one in which the high-temperature treatment was applied before tuber initiation and the other where it was applied during early tuber development. Each experiment had three treatments: the control, with plants grown at 22°C, and two high-temperature treatments in which plants were exposed to an episode of either 26°C or 30°C. Potato plants (cv. Royal Blue) were first grown in control conditions. At 35 days after planting (DAP) (first experiment) or 43 DAP (second experiment), treatment groups were transferred to either 26°C or 30°C for nine days before being returned to control conditions. Surprisingly, the final tuber yield was impacted to a similar extent whether the high-temperature episode was applied before or after tuber initiation. Whole-plant dry matter and leaf area, and leaf area on the main shoot were also lower in the treated plants in both experiments. However, lateral shoots had higher leaf area (both experiments) and more dry matter (second experiment). Past studies have linked lower tuber yields to reduced activity of starch synthase and increased gibberellic acid content at high temperatures. In this study, tuber filling continued to be suppressed after the end of the high-temperature period, and plant growth and elongation of the main shoot were impaired at the end of the high-temperature period. These indicate that another mechanism was involved. Current research is aimed at elucidating this mechanism.