The Selection of Gamma-Ray Irradiated Higher Yield Rice Mutants by Directed Evolution Method

Area of Science:

• Agricultural Science
• Genetics and Molecular Biology
• Plant Breeding

Background:

• Traditional breeding methods for high-yield rice varieties can be time-consuming.
• Gamma-ray irradiation is a known mutagenic agent used to induce genetic variations in plants.
• Directed evolution principles are widely applied to improve microorganisms and proteins.

Purpose of the Study:

• To develop and apply a novel selection strategy for identifying higher-yielding rice mutants.
• To evaluate the yield performance and genetic stability of induced mutants.
• To investigate the underlying reasons for yield enhancement in selected mutants.

Main Methods:

• Gamma-ray irradiation of five high-yielding Japanese rice varieties.
• Selection of M2 plants based on total panicle weight.
• Multi-year yield trials with replicated plot design.
• Genotyping using 96 single nucleotide polymorphism (SNP) markers.
• Phenotypic trait analysis.

Main Results:

• Four higher-yield mutants (FukuhibikiH6, FukuhibikiH8, YamadawaraH3) were successfully selected.
• Mutants FukuhibikiH6 and FukuhibikiH8 showed significant yield increases of 1.2% to 22.5% compared to the original variety.
• Mutant YamadawaraH3 exhibited a yield advantage of 2.7% to 3.9%.
• No significant genotypic differences were observed between mutants and their original varieties at 96 SNP markers.
• Phenotypic differences were marginal and inconsistent, suggesting physiological basis for yield increase.

Conclusions:

• The novel selection method, inspired by directed evolution, effectively identified superior rice mutants.
• Higher yields in selected mutants are attributed to physiological traits rather than significant phenotypic or genotypic alterations.
• This approach offers a promising strategy for accelerating crop improvement in rice breeding programs.