Combined Effect of Multiple Chemical Mutagens and Treatment Duration on the Germination of Rice Hybrids in M1F1 Generation

Background: Mutation breeding is one of the important techniques for creating genetic variability and developing improved crop varieties with desirable traits. Chemical mutagens such as ethyl methanesulfonate (EMS), sodium azide (NaN3), colchicine and organic solvent dimethyl sulfoxide (DMSO) have been frequently used in plant mutation breeding programs. However, the combined effects of multiple chemical mutagens and their treatment durations on plant germination, growth and development are not well understood. Methods: This study investigated the combined effects of chemical mutagens comprising of EMS, Sodium azide, colchicine and DMSO on the germination of five commercial rice (Oryza sativa L.) hybrids in the M1 generation. Seeds were treated in the mutagen solution for varying durations ranging from 4 to 24 hours. Result: Significant differences were observed in germination rates among the hybrids and across treatment durations. The highest germination rate of 3.08% was observed in Arize 6444 Gold with a 4-hour treatment, while the lowest rate of 0.17% was recorded in Srichakra 1168 with a 24-hour treatment. Overall, germination rates decreased with increasing treatment duration, likely due to the cumulative mutagenic effects and DNA damage. Srichakra 1168 exhibited the highest tolerance to the mutagen mix, while DPS-Virat was the most sensitive. Despite the low germination rates, the surviving M1 plants may harbor a range of desirable and undesirable mutations, presenting opportunities for identifying valuable mutants with improved traits in subsequent generations. This study highlights the importance of optimizing mutagen combinations and treatment conditions to balance the induction of genetic variability with the maintenance of seed viability in mutation breeding programs for rice improvement.