Abstract
BackgroundTo improve our understanding about the physiological mechanism of grain yield reduction at anthesis, three spring wheat genotypes [L1 (advanced line), L2 (Vorobey) and L3 (Punjab-11)] having contrasting yield potential under drought in field were investigated under controlled greenhouse conditions, drought stress was imposed at anthesis stage by withholding irrigation until all plant available water was depleted, while well-watered control plants were kept at 95% pot water holding capacity.ResultsCompared to genotype L1 and L2, pronounced decrease in grain number (NGS), grain yield (GY) and harvest index (HI) were found in genotype L3, mainly due to its greater kernel abortion (KA) under drought. A significant positive correlation of leaf monodehydroascorbate reductase (MDHAR) with both NGS and HI was observed. In contrast, significant negative correlations of glutathione S-transferase (GST) and vacuolar invertase (vacInv) both within source and sink were found with NGS and HI. Likewise, a significant negative correlation of leaf abscisic acid (ABA) with NGS was noticed. Moreover, leaf aldolase and cell wall peroxidase (cwPOX) activities were significantly and positively associated with thousand kernel weight (TKW).ConclusionDistinct physiological markers correlating with yield traits and higher activity of leaf aldolase and cwPOX may be chosen as predictive biomarkers for higher TKW. Also, higher activity of MDHAR within the leaf can be selected as a predictive biomarker for higher NGS in wheat under drought. Whereas, lower activity of vacInv and GST both within leaf and spike can be selected as biomarkers for higher NGS and HI. The results highlighted the role of antioxidant and carbohydrate-metabolic enzymes in the modulation of source-sink balance in wheat crops, which could be used as bio-signatures for breeding and selection of drought-resilient wheat genotypes for a future drier climate.
Highlights
To improve our understanding about the physiological mechanism of grain yield reduction at anthesis, three spring wheat genotypes [L1, L2 (Vorobey) and L3 (Punjab-11)] having contrasting yield potential under drought in field were investigated under controlled greenhouse conditions, drought stress was imposed at anthesis stage by withholding irrigation until all plant available water was depleted, while wellwatered control plants were kept at 95% pot water holding capacity
Genotypes were significantly different for osmotic adjustment (OA) and highest value of OA was recorded in genotype L2 while lowest was in L1 (Table 2)
RWC relative water content, abscisic acid (ABA) Abscisic acid, cell wall invertase (cwInv) Cell wall invertase, cytoplasmic invertase (cytInv) Cytoplasmic invertase, vacuolar invertase (vacInv) Vacuolar invertase, cell wall peroxidase (cwPOX) Cell wall peroxidase, monodehydroascorbate reductase (MDHAR) Monodehydroascorbate reductase, glutathione S-transferase (GST) Glutathione- S-transferase, Ψπ Leaf osmotic potential, OA Osmotic adjustment, An Photosynthesis, Gs Stomatal conductance, E Transpiration rate, BM Plant biomass, grain yield (GY) Grain yield, number of grains spike− 1 (NGS) Number of grains spike-1, kernel abortion (KA) Kernel Abortion, thousand kernel weight (TKW) Thousand kernel weight and harvest index (HI) Harvest index P* < 0.05, P** < 0.01 and P*** < 0.001 selected as drought tolerant and drought sensitive, respectively, while L2 was of moderately tolerant
Summary
To improve our understanding about the physiological mechanism of grain yield reduction at anthesis, three spring wheat genotypes [L1 (advanced line), L2 (Vorobey) and L3 (Punjab-11)] having contrasting yield potential under drought in field were investigated under controlled greenhouse conditions, drought stress was imposed at anthesis stage by withholding irrigation until all plant available water was depleted, while wellwatered control plants were kept at 95% pot water holding capacity. Limited water availability at these stages directly affects grain number and grain weight leading to severe reduction in yield potential [1]. In the past, this crop has been improved [4] there is a need to understand the in-depth physiological mechanism to breed droughtresilient wheat. Plant drought avoidance is achieved through closure of stomata. Plant genotypes having high yield potential under drought often regulate their stomata to maintain higher photosynthetic rate while lowering transpiration rate an enhancement of water use efficiency results in a less reduction of biomass and grain yield [6, 7]
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