Analysis of the earliness per se 3Am Locus (Eps-3Am) in an Einkorn Wheat Mutant (Triticum monococcum L.) Revealed a Link to the Circadian Clock

In temperate grasses, such as wheat and barley (Hordeum vulgare L.), earliness per se is understood as the intrinsic difference in flowering time of fully vernalized plants grown under long day conditions. In the current study, two einkorn wheat lines, RIL25 (early) and RIL71 (late), were selected from a RILWA1 population (Triticum monococcum L. x Triticum boeoticum Boiss.) to generate a new F2 population for fine mapping of the Eps-3A^m locus. About 650 F2 individuals were screened for genetic recombinations and new markers were added utilizing the physical map from barley chromosome 3H. This way, the locus could be delimited to ca. 350 kb and contained only two putative genes. Moreover, both genes were found to be deleted in the mutant parent of the RILWA1 population KT3-5 (Triticum monococcum L.) as well as in RIL25. One of the two genes deleted in the KT3-5 mutant belonged to the circadian clock which is known to regulate the photoperiodic flowering pathway. Therefore, two experiments were performed to verify whether circadian clock distortions could be observed: (i) results received from delayed fluorescence measurements indicated that the mutant KT3-5 had indeed an affected rhythm of the chloroplastic clock compared with wild type line KT3-1. And (ii) secondly, obtained gene expression data from a time-course qRT-PCR experiment on two key nuclear clock genes, TmTOC1 (timing of CAB2 expression 1) and TmLHY (late elongated hypocotyl), supported our hypothesis that the Eps-3A^m locus had been affected in a gene belonging to the circadian clock.