Abstract
Drought and high temperature are the major abiotic stresses for wheat production. The present study investigated the effect of drought and chronic heat stress on physiological parameters of durum wheat lines derived from interspecific crosses and their association with yield. Seventy-seven durum wheat lines were evaluated during two seasons (2016–2017 and 2017–2018) for drought tolerance at Tessaout (Morocco) using irrigated and rainfed treatments and for heat tolerance at Wad Medani (Sudan). Five drought screening indices (alone or combined) and physiological parameters were used to assess drought and heat tolerance. Among the physiological parameters used, canopy temperature (CT) had moderate heritability and was significantly affected by both severe and moderate drought stresses. CT at early heading showed a stronger correlation with grain yield (GY) and total biomass (BY) under heat stress. The use of maximum quantum yield of PSII (Fv/Fm) for drought/heat screening was limited by the low genetic variation despite its significant correlation with yield under drought (r2 = 0.22) and heat (r2 = 0.4). The normalized difference vegetation index (NDVI) at vegetative stage was highly correlated with GY and BY and it showed high genotypic variation that can allow for efficient selection. The grain filling rate (GFR) was found to be highly correlated with GY and BY under heat stress. The modified stress tolerance index (MsSTI) had the highest association with GY under drought (R2 = 0.82) while the mean productivity (MP) was adapted to both optimal conditions (R2 = 0.77) and drought stress (R2 = 0.73). The computation of a mean score index (MSI) improved the selection efficiency under drought (R2 = 0.92). The results showed good potential for lines derived from wide crosses to increase variability for heat and drought adaptive physiological traits.
Highlights
Drought and heat are the major abiotic stresses affecting wheat productivity in the world
The objectives of this study are: (i) assess the heritability of some physiological traits and their association with grain yield under drought and heat stresses, (ii) examine the ability of tolerance indices and their combination to select the best genotypes for drought stress, and (iii) select pre-breeding lines from a durum wheat population derived from interspecific crosses with high yield potential and good levels of drought and tolerance
days to the heading (DHE) was significantly correlated with grain yield (GY) only in the second season with higher correlation under drought stress (r2 = −0.39) in comparison to optimal conditions (r2 = −0.31)
Summary
Drought and heat are the major abiotic stresses affecting wheat productivity in the world. Global wheat production is expected to decrease by 4.1% to 6.4% for every 1 ◦C increase in temperature as warming is already slowing yield gains in the majority of wheat production areas [3,4] These two abiotic stresses can occur at different wheat growth stages and affect several morphological, physiological, and molecular plant processes [5,6] resulting in significant yield losses [7,8,9,10]. These complex changes in addition to the high genotype by environment interaction limit the effectiveness of empirical selection for drought and heat tolerance [11,12], especially under the fluctuations of Mediterranean environments [11]. The development of drought and heat tolerant wheat cultivars requires an integrated breeding strategy that includes screening techniques for physiological and morphological adaptive traits in addition to the molecular tools to harness diverse genetic resources [6,13,14,15,16]
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