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

In arid and semi-arid regions of the world bread wheat (Triticum aestivum L.) yield is highlylimited due to late season heat stress, mostly occurring during the reproductive phase. Hence thecurrent study was conducted to evaluate the effect of late season heat stress on grain yield andyield components of 20 spring bread wheat cultivars. For this purpose, a stripe block experimentincluding four sowing dates (6th of November, 6th of December, 5th of January and 4th ofFebruary) as vertical plots and 20 cultivars in horizontal plots was implemented with threereplicates in North-East of Ahwaz, Khuzestan, Iran during 2007-2008 and 2008-2009 growingseasons. The results indicated that the main effect of year, sowing date, cultivar and interactionbetween sowing date and cultivar were significant for all studied traits. However, no significantinteraction was found between year and other factors. Comparison of means showed that grainyield in the second year was higher than the first year. The maximum and minimum values(6.048 ton ha-1 and 1.754 ton ha-1) were obtained when seed sowing was performed on 6th ofNovember and 4th of February, respectively. The maximum grain yield (5.019 ton ha-1) wasrelated to Atila cultivar whereas the minimum yield (3.662 ton ha-1) was obtained from Inia 66cultivar. In general, the maximum and minimum grain yields were produced by Atila cultivarsown on 6th of December and Seri82 and Roshan sown on 4th of February, respectively. Theresults suggest that Arvand, Vee/Nac, Atila and Baiat cultivars as heat tolerant cultivars andRoshan, Hamoon, Seri82, Star, Inia66 and Darab2 as susceptible cultivars may be used in heattolerance studies.