The screening of mutants and construction of mutant library for Oryza sativa cv. Nipponbare via ethyl methane sulphonate inducing

Following the sequencing of rice genome, the functional analysis of unidentified genes is gaining wide importance. Mutant isolation is one of the effective ways to isolate and clone the target genes and analyze their functions. To find the various mutants in the same genetic background, seeds of Oryza sativa cv. Nipponbare were treated with ethyl methane sulphonate (EMS). A total of 1056 mutants were screened for five categories in M-2 generation with the seedling frequency of 26.29aEuro degrees at three-leaf stage, but only 264 mutants were verified in M-3 generation with a frequency of 6.57aEuro degrees. Among the mutants verified in M-3 generation, the frequency of leaf mutation was the highest (2.22aEuro degrees), followed by seedling height (1.74aEuro degrees) and the abiotic stress tolerance mutant (1.47aEuro degrees). Nineteen characteristic mutations, including a big group of abiotic stress tolerant mutants such as herbicide resistant, salt tolerant and drought tolerant were identified at this stage. By observation of rice growth characteristics at different developmental stages, another 220 mutants have been isolated and verified in the M-3 generation with the mutant frequency of 53.9aEuro degrees covering about 28 mutant traits. Among those identified, the highest frequencies were obtained for appearance of brown rice mutant with 18.37aEuro degrees, followed by panicle mutant with 13.47aEuro degrees, and grain mutants with 9.06aEuro degrees. All the mutants screened above were suitable for gene function analysis and for utilization in agronomy.