Effects of moisture stress on leaf appearance, tillering and other aspects of development in Triticum tauschii

A glasshouse study was conducted to describe the dynamics of leaf and tiller appearance of four accessions of T. tauschii (Tt 04, Tt 17, Tt 65 and Tt 74) and to determine the influence of moisture stress (treatments were high and low moisture, imposed seven days after transplanting) on these and other aspects of development in this wild wheat. Under high moisture conditions, accessions differed greatly in flag leaf dimensions, culm length and seed number per spike, the values being lower in Tt 04 than in the other accessions. Low moisture strongly reduced values for these traits, with Tt 04 being least affected, but overall, there was no apparent association between the values obtained for these variables in the high moisture conditions and the effects of moisture stress. For three of the four accessions, final leaf number on the main culm was significantly lower in the low moisture treatment than in the respective control (P < 0.05), but the differences between treatments (ca. 0.5 leaves or less) were very small. Maximum tiller number, on the other hand, was strongly reduced by low moisture, and initiation of tillering was inhibited until water was reapplied. There were no apparent after-effects of the moisture regime on the rate of subsequent tiller appearance. The four accessions differed in their leaf appearance rates, giving phyllochron values (117-142 degrees Cd leaf(-1)) within the range reported for hexaploid wheat. Low moisture tended to increase phyllochron, but in only one accession was this effect significant. Thus, depending on the accession, low moisture did not affect, or slightly decreased (by ca. 15-20%) the rate of leaf appearance. These effects were similar to those reported for cultivated wheat suggesting that there would be little scope for using these accessions of T. tauschii in breeding for stress tolerance.