TILLER DEVELOPMENT AND CONTRIBUTION TO YIELD UNDER DIFFERENT MOISTURE REGIMES IN 2 TRITICUM SPECIES

The number of productive tillers is an important yield component in wheat and is affected by water stress and genetic factors. A greenhouse experiment was conducted during spring 1992 at ICARDA, Tel Hadya, Syria, with eight genotypes representing two Triticum species (Triticum turgidum L. ssp. durum and Triticum aestivum L. ssp. aestivum) under four soil-moisture regimes (95 %, 75 %, 55 %, and 35 % field capacity) to study the effect of water deficit on tiller development and tiller contribution to grain yield. In the highest watering regime appearance of Tiller 1 was delayed in both species. Also Tiller 2 was suppressed in this treatment in durum, while its appearance was delayed in aestivum. In the driest treatment, a majority of the tillers were suppressed and the ones which emerged were delayed. In durum, the heat units required to produce successive leaves on the tillers were higher than that for the main stem and increased with increasing water stress, causing high rate of tiller abortion. In aestivum, each tiller, once produced, developed leaves at the same rate as on the main stem. Phyllochron of tillers as well as main stem was not affected by water stress in aestivum. In aestivum, contribution by tillers to yield was higher than that of durum in all treatments. Results indicate that early appearance of tillers and faster rare of leaf appearance under water stress result in higher tiller survival and greater tiller contribution to final yield. Hence, tiller dynamics under water stress can be used as a selection criterion for breeding for drought tolerance.