Evaluation of stem soluble carbohydrate accumulation and remobilization in spring bread wheat genotypes under terminal heat stress conditions in Ahwaz in Iran

To evaluate the capability of different spring bread wheat genotypes for storage and remobilization of stem water soluble carbohydrates (WSC) and their response to heat stress conditions during grain filling period, a field experiment was carried out as factorial arrangement in randomized complete block design with three replications in 2010-2011 growing season under Ahwaz conditions in Iran. The experimental factors consisted of 10 medium maturity spring bread wheat genotypes (Chamran, Atrak, Aflak, Dez, Falat, Darab-2, Kavir, Pishtaz, S-78-11, S- 83-3) and two sowing dates; optimum (12 November) and the late sowing date (21 December). Results showed that spring bread wheat genotypes were significantly different in stem specific weight, WSC concentration and content, stem WSC remobilization and its efficiency. In heat stress conditions in the late sowing date, the amount of WSC remobilization from stem to grain and its efficiency increased by 29% and 33%, respectively. In both sowing dates, maximum stem specific weight had significant association with maximum WSC concentration and the amount of remobilized WSC, and it was considered as a suitable criteria for selecting genotypes with maximum storage and remobilization capability of stem reserves. In the late sowing date, grains.pike-1 was positively correlated with WSC remobilization. This implies the effect of sink strength on increasing water soluble remobilization. However, there was no simple relationship between grain yield and stem reserves remobilization under heat stress conditions during grain filling period. Some genotypes supported grain growth either by maintaining green leaf area and current photosynthesis or by increasing remobilization of more stem reserves, under heat stress conditions.