Independent and combined effects of high temperature and drought stress around anthesis on wheat

Abstract

High temperature and drought stress are projected to reduce crop yields and threaten food security. While effects of heat and drought on crop growth and yield have been studied separately, little is known about the combined effect of these stressors. We studied detrimental effects of high temperature, drought stress and combined heat and drought stress around anthesis on yield and its components for three wheat cultivars originating from Germany and Iran. We found that effects of combined heat and drought on the studied physiological and yield traits were considerably stronger than those of the individual stress factors alone, but the magnitude of the effects varied for specific growth‐ and yield‐related traits. Single grain weight was reduced under drought stress by 13%–27% and under combined heat and drought stress by 43%–83% but not by heat stress alone. Heat stress significantly decreased grain number by 14%–28%, grain yield by 16%–25% and straw yield by 15%–25%. Cultivar responses were similar for heat but different for drought and combined heat and drought treatments. We conclude that heat stress as imposed in this study is less detrimental than the effects of those other studied stresses on growth and yield traits.

Assessing the Potential of Extra-Early Maturing Landraces for Improving Tolerance to Drought, Heat, and Both Combined Stresses in Maize

“…Compared with the NS environment, HS, DS, and DSHS, on the averaged reduced GY by~23%, 49%, and 58%, respectively (Tables 1 and 2), suggesting that the effect of the combined stresses on GY of the extra-early maize accessions was higher than the individual effects but lower than their sum (hypo-additive effect). These results corroborated the findings of earlier workers who reported higher yield losses from the combined effects of DS and HS than DS and HS applied alone in cereals including maize [17,19,29,46]. The high GY loss under DSHS compared to HS and DS could be attributed to the interaction effects of HS and DS on stomatal movements [46].…”

“…These results corroborated the findings of earlier workers who reported higher yield losses from the combined effects of DS and HS than DS and HS applied alone in cereals including maize [17,19,29,46]. The high GY loss under DSHS compared to HS and DS could be attributed to the interaction effects of HS and DS on stomatal movements [46]. Stress-induced changes in morpho-physiological properties of the maize accessions might have caused osmotic imbalances under DSHS, resulting in the high yield losses.…”

“…Stress-induced changes in morpho-physiological properties of the maize accessions might have caused osmotic imbalances under DSHS, resulting in the high yield losses. Under DS at elevated temperatures, plants either close their stomata to prevent water loss or keep stomata opened to cool the leaves through transpiration [46]. The long delay in anthesis and silking (by ≥8 days) under HS and DSHS was most likely the result of severe cold stress due to harmattan at the time of planting, that might have delayed seed emergence and extended pre-flowering developmental stages.…”

“…Worse of all, DS and HS often co-occur under natural field conditions and their combined effects on growth, GY and related traits can either be synergistic, antagonistic or hypo-additive [21][22][23][24]. Recently, we screened 36 early maturing maize accessions for tolerance to abiotic stresses and found that on average, GY was reduced by 46%, 55% and 66% under DS, HS and DSHS conditions, respectively [19]. The high GY loss under DSHS reflects hypo-additive effect of DS and HS, which under extreme conditions could force farmers to abandon their farmlands [18,25].To meet the food and feed needs of the projected population by 2050, it is essential for maize improvement programs in SSA to focus on the development of maize varieties with climate-adaptive traits, specifically, enhanced DS and/or HS tolerance either through conventional or biotechnology means.…”

Novel Alleles for Combined Drought and Heat Stress Tolerance in Wheat

“…For instance, wheat production in Mediterranean climate zones such as Australia, southern Europe and the northwest of the United States is largely based on dry land, characterized by drought in combination with high temperatures around anthesis and early grain filling (Izanloo et al, 2008;Schillinger et al, 2008;Gbegbelegbe et al, 2016;Toreti et al, 2019). At reproductive stages wheat yields are especially vulnerable with drought and heat stress reducing spikelet fertility, grain number, single grain weight, and grain filling duration (Prasad et al, 2011;Mahrookashani et al, 2017).…”