Physiological Role of Quantitative Trait Loci On Chromosome 5 and 12 for Controlling Male Sterility Caused by Low Temperature At the Booting Stage in Rice.

Low temperature at the booting stage severely limits rice productivity by inhibiting pollination because it decreases the production of sound pollen.  To clarify the quantitative trait loci (QTLs) associated with the processes of fertilization under low temperature stresses, we grew 214 recombinant inbred lines, derived from a cross between Tohoku-PL3 (cold-tolerant line) and Akihikari (cold-sensitive cultivar), both under low and normal temperature conditions during reproductive growth including the booting stage.  Data was collected on heading date, anther length and spikelet fertility from plants grown under both temperature conditions.  The processes of fertilization under low temperature were divided into three components; (1) the formation of pollen mother cells (factor 1, represented by the anther length under normal temperature (mm)), (2) efficiency of sound pollen production per pollen mother cells (factor 2, represented by a proportion of anther length at low temperature (mm) to anther length at normal temperature (mm)), and (3) efficiency of fertilization per sound pollen (factor 3, represented by a proportion of spikelet fertility (%) to anther length at low temperature (mm)).  We detected two QTLs that are associated with spikelet fertility at low temperature condition.  The two QTLs that are located on chromosome 5 and 12 were related to the factor 3 and 2 described above, respectively.  This finding would be useful for rice breeding programs aimed at improving cold tolerance using QTL pyramiding.