A revisit of mutation induction by gamma rays in rice (Oryza sativa L.): implications of microsatellite markers for quality control

Abstract

Mutation techniques have been used for generating genetic variation and breeding new varieties during the past decades. However, the skepticism has also persisted during the course on the sole mutational origin of genetic variation in mutated populations. We addressed this issue using three unique rice genetic lines in this study. First, we confirmed that gamma rays had significant effect on the growth of M1 plants, leading to significant reduction of fertility, seed set and plant height at doses 200 Gy and above. Second, we proved that out-crossing derived genetic variants existed in M2 population (0.8%) and among selected putative mutants (0–33.3%), in addition to induced mutants. Third, we demonstrated that true induced mutant lines had identical microsatellite haplotypes to their parents. We proposed microsatellite assay as a method to exclude any genetic contaminants from induced mutants, with appropriate numbers for different levels of power based on reported microsatellite mutation rate and microsatellite polymorphic index.