CHEMICAL MUTAGENESIS IN TWO Cuphea SPECIES

Presoaked (24 h at 20 °C) seeds of Cuphea tolucana Peyr. and C. wrightii A. Gray were treated with mutagens at 20 °C in two experiments. Experiment 1 treatments were: distilled water (DW), 0.05 M PO4 buffer (pH 7), 0.01 M ethyl methanesulfonate (EMS) (each applied for 8 h), 0.02 M EMS (applied for 4 h), 0.04 EMS M, 0.08 M EMS, or 0.16 M EMS (each applied for 2 h). Experiment 2 treatments were: DW, 0.1 M PO4 buffer (pH 3), 0.0005 M sodium azide (SA), 0.001 M SA, or 0.002 M SA (each applied for 2 h). None of the treatments had significant effects on emergence and height of M1 plants nor were any macro-mutations noted in the M2 generations. In a third experiment, DW, 0.04 M EMS, or 0.001 M SA were applied for 2 h at 30 °C to presoaked (48 or 72 h at 30 °C) seeds of C. tolucana and C. wrightii. Compared to EMS, SA had deleterious effects on height in the M1, emergence was better for C. tolucana than for C. wrightii, and C. wrightii plants grew taller after a 72-h pre-soak than after a 48-h presoak. M2 progenies were evaluated in the field. None of the presoak-treatment combinations increased variation significantly in several quantitative characters, no macro-mutations were detected in C. wrightii, but a fertile, small-leaved, decumbent mutant with very short internodes was noted in C. tolucana. Mutation rates were greatest for the 72 h presoak-EMS combination.Key words: Cuphea tolucana, Cuphea wrightii, ethyl methanesulfonate, sodium azide, medium-chain triglycerides, lauric acid