INHERITANCE OF DWARFING GENES IN LACTUCA-SATIVA L

Several dwarf mutants were isolated to study the regulation of stem elongation in lettuce (Lactuca sativa L.). These mutants were selected from an M(2) population of rapid-cycling lettuce (Early Flowering strain) treated with 0.03% (v/v) ethyl methanesulfonate (EMS) during germination, A hypocotyl elongation assay was developed to allow rapid screening of seedlings in the laboratory, Plants that exhibited reduced hypocotyl length were selected, At maturity, the selected plants were smaller than the wild type, having dark green leaves, greatly reduced stem length, and modified flower morphology. A diallel study among nine of these mutants indicated there are four dwarfing loci, Alleles dwf-1, dwf-3, and dwf-4 resulted from the treatment procedure, while dwf-2 probably existed in the original material but was undetected, Allele dwf-4 appears to express only in the presence of dwf-2, The most obvious phenotypic difference among the alleles is in the range of plant height,from less than or equal to 3cm to greater than or equal to 30 cm.