Shoot branching control by reduced culm number 4 in rice (Oryza sativa L.)

Shoot branching is a major factor in plant architecture and an important agronomic trait for productivity. In the present study, we characterized reduced culm number 4 (rcn4) mutants in rice, namely rcn4-1 and rcn4-2. rcn4 developed axillary buds precisely at each leaf node, but the outgrowth of these buds was inhibited. To determine whether rcn4 is involved in a branch-inhibiting strigolactone pathway, we characterized the double mutant of rcn4 and a tillering dwarf mutant, dwarf10 (d10), which is defective in strigolactone synthesis. The axillary bud activity of rcn4d10 double mutant was between that of the rcn4 and d10 mutants suggesting that Rcn4 controls axillary bud activity and is independent of D10 in the strigolactone associated branching inhibition pathway. Molecular mapping study demonstrated that Rcn4 is located between simple sequence repeat markers RM6581 and RM6608 on the long arm of rice chromosome 1. We suggest that Rcn4 is a good candidate for further investigation of the strigolactone independent branching pathway. (C) 2009 Elsevier Ireland Ltd. All rights reserved.