Four extra early-flowering mutants, named extra early-flowering1 (exe1), exe2, exe3, and exe4, were identified in Triticum monococcum strain KU104-1 following heavy-ion beam mutagenesis. The four exe mutants fell into two groups, namely Type I (moderately extra early-flowering type; exe1 and exe3) and Type II (extremely extra early-flowering type; exe2 and exe4). Analysis of plant development in a growth chamber showed that the speed of leaf emergence was accelerated in exe mutants at the reproductive stage compared to wild-type (WT) plants. The speed of leaf emergence was faster in Type II than Type I plants. Analysis of VERNALIZATION 1 (VRN1), a flowering promoter gene, showed that it was more highly expressed in seedlings at early developmental stages in Type II mutants than Type I mutants. These findings indicate that the difference in earliness between Type I and Type II mutants is associated with the level of VRN1 expression. The original KU104-1 is an einkorn wheat strain that carries a null allele of the VRN2 gene, a repressor of flowering. Thus, our results indicate that the level of VRN1 expression controls earliness in exe mutants independently of VRN2.

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Four extra early-heading mutants, named extra early-fl owering1 ( exe1 ), exe2 , exe3 , and exe4 , were identifi ed in diploid einkorn wheat ( Triticum monococcum L.) following heavy-ion beam mutagenesis. Based on their phenotypes in the fi eld, the four exe mutants were classifi ed 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 fl owering 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 .