Disease Lesion Mutants

Abstract

A frequently seen but very rare event, population-wise, is the single apparently diseased plant that appears in large populations in the farmer’s corn field. These spontaneous variants, like similar frequent cases arising in small populations from treatment of pollen with the chemical mutagen ethyl methanesulfonate (EMS), are, in fact, mutants. The disease “symptoms” are caused by noninfectious Mendelian inherited disease lesion mimic mutations, most of which are dominant (Neuffer and Calvert 1975; Hoisington et al. 1982; Walbot et al. 1983). These mutants are called les. The dominant mutants in our laboratory now number 23. Seventeen of these have been located to nine chromosome arms, but only one likely pair of alleles was found among these 17 located mutants. Utilizing the birthday paradox statistic, the presence of one pair of alleles among the 17 mutants tested indicates that there are likely to be as many as 200 possible loci conferring the Les phenotype(s). [The birthday paradox is a calculation of the population size required to explain the number of “matches” in a sample from the population; with 365 days in the year, in a group of 20 people, there is likely to be one pair with the same birthday: (1 + 2 + 3 … 19)/365.]