Extra Early-Flowering (exe) Mutants in Einkorn Wheat Generated by Heavy-Ion Beam Irradiation

Four extra early-heading mutants, named extra early-flowering1 (exe1), exe2, exe3, and exe4, were identified in diploid einkorn wheat (Triticum monococcum L.) following heavy-ion beam mutagenesis. Based on their phenotypes in the field, the four exe mutants were classified into two groups: Type I (moderately extra early-heading type; exe1 and exe3) and Type II (extremely extra early-heading type; exe2 and exe4). Analysis of VERNALIZATION 1 (VRN1), a flowering promoter gene, showed that it was more highly expressed at earlier stages of vegetative growth in Type II mutants than in Type I mutants. Our analyses indicate that the difference in earliness between Type I and Type II mutants is associated with differences in the expression level of VRN1.