Einkorn Wheat (Triticum monococcum) Mutant Extra-Early Flowering 4, Generated by Heavy-Ion Beam Irradiation, Has a Deletion of the LIGHT-REGULATED WD1 Homolog

A mutant showing extra early-flowering and named extra early-flowering4 (exe4) was induced in a previous study by heavy-ion beam mutagenesis of Triticum monococcum strain KU104-1. The exe4 mutant shows heading about 45 days earlier than wild-type KU104-1 in the field. In the present study, we sought to identify the gene that was mutated in exe4 by performing a modified whole-genome sequencing analysis. This analysis exploited a short-read library preparation that uses a modified adaptor and duplex-specific nuclease (DSN) for the efficient elimination of highly repeated sequence elements within genomes. The whole-genome sequence analysis and PCR analysis using an M2 segregation line indicated that the extra-early flowering pheno-type of exe4 is associated with a deletion of a gene for a WD repeat protein, named here WHEAT WD REPEAT 1 (WWDR1). Phylogenetic analysis of amino acid sequences showed that the gene is a homolog of Arabidopsis LIGHT-REGULATED WD1 (LWD1) and LWD2, which are circadian clock regulatory genes.