Influence of phenology on grain yield variation among barley cultivars grown under terminal drought

We investigated the influence of sowing time and genotypic variation for phenology on grain yield of barley in south-eastern Queensland. Over 3 seasons, 8 trials with 10 cultivars and 1 trial with 4 cultivars were conducted under either irrigated or terminal drought conditions at 2 locations. Rainout shelters ensured the development of severe terminal water stress. Trials were either sown on a common date, as conducted in traditional multi-environment trials, or over 3 weeks to synchronise anthesis among cultivars of different phenologies. Within the common sowing date trials, variation (P < 0.01) existed among cultivars for grain yield. From the 6 common sowing trials there was a negative correlation (P < 0.05) between grain yield and days to anthesis; that is, the shorter duration cultivars expressed the highest grain yield. Variation in days to anthesis accounted for 48-72% of the variation for grain yield. In the staggered sowing trials, where anthesis of all cultivars occurred within 4 or 2 days of the mean anthesis date, variation for grain yield was small or non-significant, and there was no association between grain yield and days to anthesis. The staggered sowing experiment with 10 cultivars indicated that duration of the vegetative phase was important in determining total dry matter production at maturity when cultivars were grown under terminal drought. Long-duration cultivars sown earlier had greater total dry matter at maturity than short-duration cultivars. This was associated with a greater water extraction by the long-duration cultivars, especially at depth, which remained inaccessible to later sown, short-duration cultivars. However, due to the low harvest index of the long-duration cultivars, grain yield of long- and short-duration cultivars was comparable when anthesis of cultivars was synchronised. When sown at the same time, a short-duration cultivar is advantageous because of a high chance of escaping water stress that develops during the critical development stage of anthesis. The results from the staggered sowing date experiments, however, indicated that the long-duration cultivars, when sown earlier in the season, had no yield disadvantage in comparison with the short-duration cultivars sown later in the season. Therefore, there is scope to develop barley cultivars of later phenology than is currently available to provide Queensland farmers with the option of utilising early rainfall events which are sometimes the only planting opportunity