Genome saturation with mutations

In spite of the large number of high-activity mutant strains isolated, none of them preserved its original activity after further selection. Since nitrosoalkylamides (NAA) were used to derive the parental strain M82 (Grusina et al., 1974), it is possible that the genome of this strain is already saturated with NAA-inducible point mutations, so that the treatment with NMB, another NAA mutagen, could not elicit stable mutants in this strain. 

Our Ml populations are, generally 100,000 to 200,000 plants In size. Thus, the calculations above suggest that we routinely saturate the genome with all possible EMS-lnduced mutations. Furthermore, the high seed yield per plant and tl small size of thallana seed make mutant selections using 1.0 x lO M2 seed feasible. 

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