Abstract
The availability of a large mutant population is an important genetic resource for functional genomic studies and breeding. Katy, a publicly available long grain tropical japonica rice variety with an excellent package of disease resistance and suitable agronomic traits, was used to develop a large mutant population. A combination of ethyl methane sulfonate (EMS), fast neutron (FN), and gamma irradiation (60Co) treatments were applied at varying dosages to develop the population. Approximately 7500 rice seeds were each treated with EMS (0.4%, 0.8%, and 1.2%) and 60Co (200 Gy), and approximately 10,000 rice seeds were exposed to 7.7 Gy, 26.3 Gy, and 49.4 Gy dosages of FN. Mutation effects were initially evaluated at the M2 generation by assessing chlorophyll biosynthesis deficiencies. The mutation effects of each line were detected at 1.04% for 0.4% EMS, 5.04% for 0.8% and 1.2% EMS, 2.9% for 26.3 Gy FN, 3.2% for 49.4 Gy FN, and 5.04% for 60Co 200 Gy for the M2 population. After seeds were advanced to M4 using a single seed breeding strategy, the genotype identity of 189 randomly selected lines was verified with nine simple sequence repeat markers and 96 randomly selected lines were evaluated for mutant morphological phenotypes. The analysis uncovered slightly higher frequencies of morphological mutants at M4 than was observed in the M2 generation. These findings suggest that the Katy putative mutant population consisting of 23,558 individuals is a potential asset for rice functional genomics studies and breeding.
Highlights
Rice (Oryza sativa) is one of the most important food crops that provide essential calories to more than 3.5 billion people
We created and released a large putative mutant population using the tropical japonica rice variety Katy for disease resistance, adapted yield, and acceptable quality. Using this putative mutant population, we identified a lesion mimic mutant created by ethyl methane sulfonate (EMS) [24] and blast susceptible mutant M2354 created by fast neutrons [18]
We suggest that this large putative mutant population will be a valuable resource for rice functional genomics studies and breeding
Summary
Rice (Oryza sativa) is one of the most important food crops that provide essential calories to more than 3.5 billion people. Easy methods of transformation and abundant transcription profiles have made rice an excellent model crop for functional genomics [2]. Biological functions of about 2000 rice genes from genes for high-yield to disease resistance [1,2,3] have been determined, most of which with a map-based cloning strategy [3]. While map-based cloning has been proven to be one of the most successful methods of studying gene function, it requires contrasting the phenotype and genotype of both parents which are often not available, for genes contributing minor phenotypic effect and genes involved in multiple biological functions via epigenetic mechanisms [4,5,6]
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