Abstract
Ozone (O3) is the main photochemical oxidant that causes leaf damage in many plant species. It has been thought that O3-induced visible leaf injury causes decrease of photosynthesis, resulting reduction of grain yield. However, recent study showed that degree of visible leaf injury is not necessarily corresponding to reduction rate of grain yield in O3-exposed rice, suggesting that these may be regulated in different mechanisms. To identify gene loci that affect rice grain yield under O3 exposure condition, QTL analysis was performed using Sasanishiki/Habataki chromosome segment substitution lines (CSSLs). As the result, we identified the loci, which affects O3-induced yield loss, near RM3430 marker in chromosome 6. Previous study showed that APO1 gene, locating near this marker, influences rice grain yield through affecting primary rachis number. Thus, expression analysis of APO1 was carried out. In young panicles, transcript level of APO1 was the highest and its expression was significantly suppressed in O3-exposed Habataki but not in O3-exposed Sasanishiki. This indicates that reduction of grain yield in O3-exposed Habataki may be caused by suppression of APO1 expression by O3.
