Identification and fine mapping of a multi‐tillering semi‐dwarf gene in rice

Plant height is one of the most important agronomic traits of rice. So far, more than 80 genes related to dwarf mutants had been cloned in rice, but most of them cause severe dwarf and other adverse phenotypes, which is difficult to apply in rice breeding. Here, we identified a novel multi-tillering semi-dwarf line sde , a near-isogenic line of ZX5T. Compared with ZX5T, sde performed proportionally shortened internodes. Thus, sde is a semi-dwarf of “dn” type. The longitudinal sections of stem showed that the decrease of cell number should be the major mechanism for sde semi-dwarfism. Moreover, sde was insensitive to exogenous GA 3 and GR24. Genetic analysis revealed that sde was controlled by single recessive nuclear gene. To isolate SDE gene, a map-based cloning method was employed using F 2 recessive plants derived from a cross between sde and NJ6. Finally, the target SDE gene was located to a 58 Kb region on the short arm of chromosome 6. There were 9 predicted opening reading frames located in this region, but only one nucleotide substitution (C to T) has been detected in the first exon of Os06g0154200 between sde and ZX5T, which result in a substitution of amino acid (R to W). Additionally, expression of Os06g0154200 in the culm and panicle of the sde was significantly increased compared to ZX5T. Interestingly, SDE shared the common locus with tillering dwarf mutant DWARF3 ( D3 ) gene, suggesting sde may be a novel weak allelic of D3 . Collectively, we here identified a novel multi-tillering semi-dwarf line sde , which would provide novel dwarf source and improving the genetic diversity for important agronomic traits of rice and the main component of plant architecture.