Expression of Vernalization Requirement and Spikelet Number in Synthetic Hexaploid Wheats and their Triticum tauschii and Tetraploid Wheat Parents

Abstract

Vernalization requirement, as measured by days from sowing to ear emergence (plants grown under an 18-h photoperiod), and spikelet number per ear were recorded for 17 synthetic hexaploid wheats and the six tetraploid (Triticum durum) and the nine diploid T. tauschii parents used to synthesize them. The tetraploid parents and the synthetic hexaploids had spring phenotypes (little or no vernalization requirement) whereas the T. tauschii parents were all winter types (strong vernalization requirement). The tetraploid wheats and the synthetic hexaploids reached ear emergence 50.3 to 63.8 d and 58.2 to 75.3 d after sowing, respectively, while the T. tauschii lines reached ear emergence 114.3 to 179.5 d after sowing. The spring habit of the synthetic hexaploids demonstrates the epistasis of spring over winter habit. It is considered that with a presumed single vrn locus in the diploid species T. tauschii the range of ear emergence in these lines is consistent with the action of multiple alleles at that locus. Although there was no general epistasis for spikelet number, the tetraploid parents appear to be exerting more influence over spikelet number in the synthetic hexaploids than T. tauschii. The well established association between the duration from sowing to ear emergence and spikelet number was not evident either within each ploidy group or when the 32 lines were considered together.