Identification and Studies of a Rice Mutant hya-1 with Semi-dwarf and Aneuploid Traits

A semi-dwarfing rice mutant hya-1,genetically unstable in plant height was obtained through space mutagenesis of Texianzhan 13.Compared to the wild type,hya-1 mutant was featured by semi-dwarfness,fewer tillers,slim culms,reduced grain number per panicle,low seed setting rate and low germination rate.Segregation of plant height in selfed progenies of the mutant was observed.Normal plants of selfed progenies,however,showed genetic stability.Plant height of F1 hybrid and F2 progenies generated from the cross between hya-1 mutant and Texianzhan 13 did not follow Mendelian inheritance.Furthermore,selfed-progenies of the mutant had abnormal chromosome numbers(e.g.2n=22,23,25 and 36 instead of 2n= 24).In addition,there were some pollen mother cells of hya-1 with 11 bivalents at the diakinesis stage of meiosis.Real-time quantitative PCR analysis of normal and semi-dwarf plants from selfed progenies of the mutant along with Texianzhan 13 showed equal copy number of chromosome in normal and wild type plants while the copy number of chromosome 8 and 11 differed in hya-1and semi-dwarf plants from the selfed progenies.It suggested that hya-1 mutant is a new aneuploid in which abnormal phenotype and genetic instability are caused by abnormal chromosome number and/or varying copy number of certain chromosomes.