Abstract: A total of 500 diverse diploid rice materials, including 313 indica and 187 japonica accessions, were collected. Calli were treated with colchicine for chromosome doubling. Three approaches, namely morphological identification, root-tip chromosome counting and flow cytometry analysis, were adopted for ploidy identification. Fifty pairs (100 accessions in total) of diploid-tetraploid materials were further selected for comparative analysis of agronomic traits including plant height, grain length, grain width, 1 000-grain weight, seed-setting rate and growth duration. In total, 208 new autotetraploid rice germplasms were obtained, with an average doubling efficiency of 41.6%. The doubling efficiency of japonica (46.5%) was higher than that of indica (38.7%). Compared with their diploid counterparts, 78% of autotetraploid plants exhibited dwarfing. All tetraploid accessions showed enlarged grain length and grain width, as well as increased 1 000-grain weight, with a maximum increment of 140.5%. Their growth duration was prolonged by 10.3% on average (from 98.1 d to 108.2 d). By contrast, seed-setting rate decreased in all tetraploid materials, dropping from 73.3% to 31.0% on average.

Key words: tetraploid rice, new germplasm materials, high-efficiency creation