first_pagesettingsOrder Article Reprints Open AccessArticle Conferring of Drought and Heat Stress Tolerance in Wheat (Triticum aestivum L.) Genotypes and Their Response to Selenium Nanoparticles Application by Ahmad A. Omar 1,2,*,†ORCID,Yasmin M. Heikal 3ORCID,Ehab M. Zayed 4,†ORCID,Sahar A. M. Shamseldin 5,Yossry E. Salama 6,Khaled E. Amer 6,Mostafa M. Basuoni 7ORCID,Sawsan Abd Ellatif 8 andAzza H. Mohamed 2,9,*ORCID 1 Biochemistry Department, Faculty of Agriculture, Zagazig University, Zagazig 44519, Egypt 2 Citrus Research and Education Center, University of Florida, IFAS, Lake Alfred, FL 33850, USA 3 Botany Department, Faculty of Science, Mansoura University, Mansoura 35516, Egypt 4 Cell Study Research Department, Field Crops Research Institute, Agricultural Research Center, Giza 12619, Egypt 5 Botany Department, Women’s College for Arts, Science and Education, Ain Shams University, Cairo 11566, Egypt 6 Crop Science Department, Faculty of Agriculture, Damanhour University, Damanhour 22516, Egypt 7 Botany and Microbiology Department, Faculty of Science (Boys), Al-Azhar University, Cairo 11884, Egypt 8 Bioprocess Development Department, Genetic Engineering and Biotechnology Research Institute (GEBRI), City for Scientific Research and Technology Applications, New Borg El-Arab 21934, Egypt 9 Agricultural Chemistry Department, Faculty of Agriculture, Mansoura University, Mansoura 33516, Egypt * Authors to whom correspondence should be addressed. † These authors contributed equally to this work. Nanomaterials 2023, 13(6), 998; https://doi.org/10.3390/nano13060998 Submission received: 31 January 2023 / Revised: 23 February 2023 / Accepted: 7 March 2023 / Published: 9 March 2023 (This article belongs to the Special Issue Physiological and Molecular Responses of Plants to Engineered Nanomaterials) Downloadkeyboard_arrow_down Browse Figures Versions Notes Abstract In this study, the role of selenium nanoparticles (SeNPs, 10 mg·L−1) has been investigated in modulating the negative effects of drought and heat stresses on eight bread wheat (Triticum aestivum L.) genotype seedlings. Those genotypes included Giza-168, Giza-171, Misr-1, Misr-3, Shandweel-1, Sids-1, Sids-12, and Sids-14. The study included six treatments as follows: regular irrigation with 100% Field Capacity (FC) at a temperature of 23 ± 3 °C (T1), drought stress with 60% FC (T2), heat stress of 38 °C for 5 h·day−1 (T3), foliar spray of 10 mg·L−1 of SeNPs only (T4), a combination of drought stress with foliar spray of 10 mg·L−1 of SeNPs (T5), and heat stress with foliar spray of 10 mg·L−1 of SeNPs (T6). The experiment continued for 31 days. Foliar application of SeNPs improved the plant growth, morpho-physiological and biochemical responses, and expression of stress-responsive genes in wheat (T. aestivum L.) seedlings. Overall, morpho-physiological traits such as plant height (PH), shoot fresh weight (SFW), shoot dry weight (SDW), root fresh weight (RFW), and root dry weight (RDW) of wheat genotypes grown under different conditions ranged from 25.37–51.51 cm, 3.29–5.15 g, 0.50–1.97 g, 0.72–4.21 g, and 0.11–1.23 g, respectively. From the morpho-physiological perspective, drought stress had a greater detrimental impact on wheat plants than heat stress, whereas heat stress significantly impacted the expression of stress-responsive genes. Stress responses to drought and heat varied between wheat genotypes, suggesting that different genotypes are more resilient to stress. Exogenous spraying of 10 mg·L−1 of SeNPs improved the photosynthetic pigments, photosynthetic rate, gas exchange, and transpiration rate of wheat plants and enhanced drought and heat tolerance by increasing the activity of antioxidant enzymes including catalase (CAT), ascorbate peroxidase (APX), and superoxide dismutase (SOD) and the expression level of stress-responsive genes. Our results showed that spraying wheat seedlings with 10 mg·L−1 of SeNPs enhanced SOD activity for all genotypes as compared to the control, with the Sids-12 genotype having the highest value (196.43 U·mg−1 FW·min−1) and the Giza-168 genotype having the lowest (152.30 U·mg−1 FW·min−1). The expression of PIP1, LEA-1, HSP70, and HSP90 stress-responsive genes was more significant in tolerant genotypes (Giza-171 and Giza-168) than in sensitive ones (Misr-1 and Misr-3) in response to drought and heat stresses. Under stress conditions, the shoot and root fresh weights, photosynthetic pigment content, stomatal conductance (SC), and transpiration rate (TR) were positively correlated with plant height (PH), while root and shoot dry weights, malondialdehyde (MDA), proline, hydrogen peroxide (H2O2), and APX were negatively correlated. Multivariate analysis and biplot results revealed that genotypes Giza-168, Giza-171, Sids-12, and Sids-14 performed well in both stress situations and were classified as stress-tolerant genotypes. These best genotypes may be employed in future breeding projects as tools to face climate change. This study concluded that various physio-biochemicals and gene expression attributes under drought and heat stress could be modulated by foliar application of SeNPs in wheat genotypes, potentially alleviating the adverse effects of drought and heat stress.