The impact of terminal heat stress on yield and heat tolerance of bread wheat

Abstract

<span class="fontstyle0">In arid and semi-arid regions of the world bread wheat (</span><span class="fontstyle2">Triticum aestivum </span><span class="fontstyle0">L.) yield is highly<br />limited due to late season heat stress, mostly occurring during the reproductive phase. Hence the<br />current study was conducted to evaluate the effect of late season heat stress on grain yield and<br />yield components of 20 spring bread wheat cultivars. For this purpose, a stripe block experiment<br />including four sowing dates (6</span><span class="fontstyle0">th </span><span class="fontstyle0">of November, 6</span><span class="fontstyle0">th </span><span class="fontstyle0">of December, 5</span><span class="fontstyle0">th </span><span class="fontstyle0">of January and 4</span><span class="fontstyle0">th </span><span class="fontstyle0">of<br />February) as vertical plots and 20 cultivars in horizontal plots was implemented with three<br />replicates in North-East of Ahwaz, Khuzestan, Iran during 2007-2008 and 2008-2009 growing<br />seasons. The results indicated that the main effect of year, sowing date, cultivar and interaction<br />between sowing date and cultivar were significant for all studied traits. However, no significant<br />interaction was found between year and other factors. Comparison of means showed that grain<br />yield in the second year was higher than the first year. The maximum and minimum values<br />(6.048 ton ha</span><span class="fontstyle0">-1 </span><span class="fontstyle0">and 1.754 ton ha</span><span class="fontstyle0">-1</span><span class="fontstyle0">) were obtained when seed sowing was performed on 6</span><span class="fontstyle0">th </span><span class="fontstyle0">of<br />November and 4</span><span class="fontstyle0">th </span><span class="fontstyle0">of February, respectively. The maximum grain yield (5.019 ton ha</span><span class="fontstyle0">-1</span><span class="fontstyle0">) was<br />related to Atila cultivar whereas the minimum yield (3.662 ton ha</span><span class="fontstyle0">-1</span><span class="fontstyle0">) was obtained from Inia 66<br />cultivar. In general, the maximum and minimum grain yields were produced by Atila cultivar<br />sown on 6</span><span class="fontstyle0">th </span><span class="fontstyle0">of December and Seri82 and Roshan sown on 4</span><span class="fontstyle0">th </span><span class="fontstyle0">of February, respectively. The<br />results suggest that Arvand, Vee/Nac, Atila and Baiat cultivars as heat tolerant cultivars and<br />Roshan, Hamoon, Seri82, Star, Inia66 and Darab2 as susceptible cultivars may be used in heat<br />tolerance studies.</span>