| At present, more than 70 semidwarf or dwarf plants had been identified, but most of them had impractical pleiotropic phenotypes and unfavorable effects on many agronomic characters therefore restricting their use in breeding. Conventional genetic analysis revealed that most of the semidwarf genes in cultivars were controlled by an allele at the sd1 locus. The frequent use of the single semidwarf gene might cause genetic vulnerability to pests and diseases. Therefore, it was essential to develop an alternative or new source of semidwarf genes to broaden the genetic basis of the semidwarfism.A spontaneous dwarf mutant in this study was identified from an indica cultivar 3037. This dwarf mutant not only had short and stout stem, but also had one more internode with short, thick and dark green leaves. We tentatively designated the dwarf mutant as ipd1 (internode plethora drawf1). Segregation of the F2 population from crosses between ipd1 and 3037 was 3:1, which indicated that the phenotype of ipd1 was controlled by a single recessive gene.α-Amylase production from embryoless half-seeds of wild-type and ipd1 showed that clear zones were observed in agar plates which contained 3037's and ipd1's half-seeds when treated with GA3, which suggested that the mutant's GA signal pathway might have no difference with Wild-type's. Exogenous GA could stimulate the shoot growth in ipd1, which demonstrated that the mutant might be caused by deficiency in GA biosynthesis. To determine the function of IPD1, F1 was got from the crosse between 3037 and homozygous ipd1, then 1,052 F2 segregants were used for fine mapping, and IPD1 was finally delimited to a 100 kb region on the short arm of chromosome 3, this work provided an important basis for finally cloning of IPD1 gene. |
