Article révisé par les pairs
Résumé : Effects on three sulfonate esters, a nitrosamine and γ-radiation have been compared on the basis of mutation rate, sterility and lethality. The most powerful mutagen was ethyl-methane-sulfonate (EMS) inducing up to 16 per cent chlorophyll mutants. After, we have respectively methyl-N-nitro-N′-nitrosoguanidine (MNG) 12 per cent, methyl-methane-sulfonate (MMS) 7·5 per cent, γ-radiation 5·5 per cent and butyl-methane-sulfonate 2·3 per cent. Increase of mutation frequency can arise from decreased lethality in treated plants. Mutagenic efficiencies compared with toxicity correspond fairly well to those obtained for induced sterility. By decreasing power we have EMS > MNG > MMS > γ BMS. Comparison of induced sterility related to chlorophyll mutation frequency showed a maximal efficiency for EMS, meaning that for the same number of induced mutations, this alkane sulfonate induced less sterility. Relations of mutagenic effects with concentration are linear after irradiation, exponential after MNG or EMS and rather sigmoidal after BMS and MMS. Evidence was obtained of preferential induction of some chlorophyllian phenotype with the mutagen utilized. EMS induced relatively few albina as compared with γ-rays. Chlorophyll mutation spectra differed not only with the nature of the mutagen but also with experimental conditions, temperature and pH. Genome itself can interfere to preserve or eliminate some mutations. Mean segregation ratios of M2 chlorophyll mutations are widely lower than 25 per cent. Their values which is an indication of the mutated sector increases in the direction MMS < γ < MNG < EMS. The analysis of these segregation ratios made us consider the occurence of two or three initials as origin of the generative tissue. Some external conditions can increase the mutation rate. Temperature during the treatment increased the reactivity of MNG. In the case of EMS, seed presoaking has the same action. Increase of pH of the mutagenic solution results in an increase of mutated plants after MMS treatments. Differential sensitivity to EMS appeared in three strains of Arabidopsis from different geographical origins. These differences are concerned as well with the mutability as the biological reactions of the treated generation. © 1969.