CHEMICAL MUTAGENESIS IN TWO Cuphea SPECIES

Abstract

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