High temperature is a major determinant of wheat development and growth and causes yield loss in many regions of the world. This study was conducted to assess heat stress effects on yield and yield related traits of wheat. The 144 recombinant inbred lines derived from the cross of Kauz (heat tolerant) and MTRWA116 (susceptible) together with some commercial cultivars were evaluated during 2006–2007, 2007–2008 under normal and heat stress (late sowing) conditions. Grain yield, head length, kernels per spike, spiklets per spike, plant height, grain filling duration, peduncle length and 1000 kernels weight were measured. The results showed a significant difference among RILs for all traits in stress and control conditions. High temperature significantly decreased all traits specially grain yield (46.63%), 1000-kernel weight (20.61%) and grain filling duration (20.42%). Grain yield was most affected and spikelets per spike was least affected (11.77%). Grain yield under heat stress was directly correlated (r = 0.49) with yield in normal condition. Head length and grain yield had the highest (93.18%) and the lowest (62.97%) heritability, respectively. Peduncle length and grain filling duration showed the highest correlation with yield under both normal and heat stress conditions suggesting that these two traits could be used as reliable screening tools for development of heat-tolerant genotypes

The chamazulene and α-(−)-bisabolol contents and quality of the chamomile oil are affected by genetic background and environmental conditions. Salicylic acid (SA), as a signaling molecule, plays a significant role in the plant physiological processes. The aim of this study was to evaluate the chemical profile, quantity, and improve the essential oil quality as a consequence of the increase of chamazulene and α-(−)-bisabol using salicylic acid under normal and heat stress conditions by the gas chromatography-mass spectrometry (GC-MS) technique. The factorial experiments were carried out during the 2011–2012 hot season using a randomized complete block design with three replications. The factors include four salicylic acid concentrations (0 (control), 10, 25 and 100 mg·L⁻¹), and three chamomile cultivars (Bushehr, Bona, Bodegold) were sown on two different planting dates under field conditions. Fourteen compounds were identified from the extracted oil of the samples treated with salicylic acid under normal and heat stress conditions. The major identified oil compositions from chamomile cultivars treated with salicylic acid were chamazulene, α-(−)-bisabolol, bisabolone oxide, β-farnesene, en-yn-dicycloether, and bisabolol oxide A and B. Analysis of variance showed that the simple effects (environmental conditions, cultivar and salicylic acid) and their interaction were significant on all identified compounds, but the environmental conditions had no significant effect on bisabolol oxide A. The greatest amount of chamazulene obtained was 6.66% at the concentration of 10 mg·L⁻¹ SA for the Bona cultivar under heat stress conditions, whereas the highest α-(−)-bisabolol amount attained was 3.41% at the concentration of 100 mg·L⁻¹ SA for the Bona cultivar under normal conditions. The results demonstrated that the application of exogenous salicylic acid increases the quantity and essential oil quality as a consequence of the increase of chamazulene and α-(−)-bisabolol under normal and heat stress conditions.

The objective of this study was to investigate the effect of exogenous application of salicylic acid concentrations on the physiological and biochemical traits and essential oil content of chamomile under normal and heat stress conditions as induced by delayed sowing. The experiments were conducted during 2011–2012 as a factorial using a randomized complete block design with three replications, in a very hot region. The factors included five salicylic acid concentrations (0 (control), 1, 10, 25 and 100 mg·L⁻¹) and three chamomile cultivars (Bushehr, Bona, Bodegold). The seeds of chamomile were sown on two different sowing dates including an optimum planting date and a late planting date. The physiological traits (plant height, capitol diameter, 1000 grain weight, fresh and dried flower weight), total chlorophyll, proline and essential oil content were investigated. Analysis of variance showed that the effect of the environmental conditions (normal and heat stress) was significant on all physiological and biochemical traits with the exception of the essential oil content. The heat stress decreased physiological traits and total chlorophyll in comparison with the normal conditions but it had no significant effect on the essential oil content. Findings indicated that the application of exogenous salicylic acid improves essential oil content in chamomile cultivars under environmental heat stress conditions.

The authors wish to make the following corrections to their paper