SCM2

Name: STRONG CULM2 (SCM2)

Type: rice QTL

Position: the long-arm region of chr06

Length: 15kb

Summary： The use of fertilizer results in tall rice plants that are susceptible to lodging and results in reduced plant yields. Using chromosome segment substitution lines, scientists identified an effective quantitative trait loci (QTL) for culm strength, which was designated STRONG CULM2 (SCM2). Positional cloning of the gene revealed that SCM2 was identical to ABERRANT PANICLE ORGANIZATION1 (APO1). A near-isogenic line carrying SCM2 showed enhanced culm strength and increased spikelet number because of the pleiotropic effects of the gene. Although SCM2 is a gain-of-function mutant of APO1, it does not have the negative effects reported for APO1 overexpressing mutants, such as decreased panicle number and abnormal spikelet morphology.

Function: In contrast to previously reported APO1-overexpressing mutants, NIL-SCM2 shows a positive effect of APO1, that is, an increase in the spikelet number per panicle without a decrease in the panicle number. Therefore, SCM2 confers lodging resistance and also increases grain yield.

Evolution: To evaluate the effect of SCM2 on lodging resistance, an NIL carrying a 484-kb region from the distal part of chr6 of Habataki was developed.There was no difference in the flowering time between NIL-SCM2 and Koshihikari. The APO1 expression levels in Koshihikari, NIL-SCM2 and Habataki were compared. The culm diameter of NIL-SCM2 and Koshihikari was also compared. In NIL-SCM2, the diameters of the minor and major axes in all the internodes were significantly wider than in Koshihikari. In contrast, the QTL SCM2, a weaker allele of APO1, is more suitable for breeding as it increases spikelet number without reducing panicle number. The identification of lodging-resistance genes by QTL analysis combined with positional cloning is a useful approach for improving lodging resistance and overall productivity in rice. Identifying superior alleles of agriculturally important genes in natural variants can be accomplished through allele mining, an emerging new molecular approach in crop improvement.

Reference:

 Taiichiro Ookawa;Tokunori Hobo;Masahiro Yano;Kazumasa Murata;Tsuyu Ando;Hiroko Miura1;Kenji Asano;Yusuke Ochiai;Mayuko Ikeda;Ryoichi Nishitani;Takeshi Ebitani;Hidenobu Ozaki;Enrique R. Angeles;Tadashi Hirasawa & Makoto Matsuoka
 New approach for rice improvement using a pleiotropic QTL gene for lodging resistance and yield.
 Nature Communications, 2010