Sarah Lewis

An earliness per se gene, designated Eps-Am1, was mapped in diploid wheat in F2 and single-seed descent mapping populations from the cross between cultivated and wild Triticum monococcum accessions. A QTL with a peak on RFLP loci Xcdo393 and Xwg241, the most distal markers on the long arm of chromosome 1Am, explained 47% of the variation in heading date. Progeny tests for the two F2:3 families with critical recombination events between Xcdo393 and Xwg241 showed that the gene was distal to Xcdo393 and linked to Xwg241. Progeny tests and replicated experiments with line #3 suggested that Eps-Am1 was distal to Xwg241. This gene showed a large effect on heading date in the controlled environment experiments, and a smaller, but significant, effect under natural conditions. Eps-Am1 showed significant epistatic interactions with photoperiod and vernalization treatments, suggesting that the different classes of genes affecting heading date interact as part of a complex network that controls the timing of flowering induction. Besides its interactions with other genes affecting heading date, Eps-Am1 showed a significant interaction with temperature. The effect of temperature was larger in plants carrying the DV92 allele for late flowering than in those carrying the G3116 allele for early flowering. Average differences in heading date between the experiments performed at 16°C and 23°C were approximately 11 days for the lines carrying the Eps-Am1 allele for early flowering but approximately 50 days for the lines carrying the allele for late flowering. The large differences in heading time observed between plants carrying the G3116 and DV92 alleles when grown at 16°C, suggest that it would be possible to produce very detailed maps for this gene to facilitate its future positional cloning.