J. of Agricultural Chemistry and Biotechnology, Mansoura Univ., Vol 11 (12): 365 - 373, 2020 Journal of Agricultural Chemistry and Biotechnology Journal homepage: www.jacb.mans.edu.eg Available online at: www.jacb.journals.ekb.eg * Corresponding author. E-mail address: mkhirshy@aun.edu.eg DOI: 10.21608/jacb.2021.54316.1007 Assessment of Heat Tolerance in Some Wheat Species and Interspecific Hybrids El-Rawy, M. A. ; Aya Abdelreda ; B. E. S. Abd El-Fatah and M. Youssef * Genetics Department, Faculty of Agriculture, Assiut University, Assiut, Egypt Cross Mark ABSTRACT Twelve accessions including two diploid, four tetraploid and six hexaploid genotypes were used in this study to assess heat tolerance in wheat. All possible crosses were made and the resulted hybrids with their parents were subsequently evaluated for heat tolerance in two sowing dates. Evaluation was based on 1000 grain weight, grain yield per plant, cell membrane thermostability and tetrazolium chloride reduction. Results revealed significant variability among wheat genotypes and hybrids in all evaluated traits under favorable and heat stress conditions. However, tetraploid genotypes showed the highest performance under heat stress followed by hexaploid and diploid genotypes, respectively. According to results of heat tolerance index, one tolerant and one susceptible parent from each ploidy level along with 6 related interspecific hybrids were chosen to be involved in molecular analysis. Target region amplification polymorphism (TRAP) markers were used based on fixed primers of heat shock protein genes. TRAP clearly confirmed the morpho-physiological findings and generated a dendrogram which was quietly like that of morpho-physiological data. TRAP was able to generate one and five specific bands for diploid and hexaploid genotypes respectively, while no specific bands were generated for tetraploid. In addition, the different genomes showed some shared bands between each other revealing their relationship. Interestingly, two specific bands for tolerant genotypes of different ploidy level were generated which were absent in all susceptible genotypes. Findings herein are of high importance and could help in successive breeding programs for wheat improvement. Keywords: Triticum, Heat shock protein, PCR, CMS, TTC INTRODUCTION Wheat is an important cereal that is used as an important product for human consumption in most areas of the world. The genus Triticum is grouped into diploids (2n=2×=14), tetraploids (2n=4×=28) and hexaploids (2n=6×=42). Triticum aestivum, the common bread wheat, contains three different but genetically related genomes (A, B and D) with a total genomic size of 1.7x10 10 base pairs, illustrating the complex nature of wheat genome (Abd El- Fatah et al., 2017). The main losses in wheat production are due more to abiotic stresses such as drought, salinity and high temperatures than to biotic stresses. Therefore, understanding the effects of these stresses becomes indispensable for wheat breeding programs that have relied mainly on genetic variations present in the wheat genome through conventional breeding. (Abhinandan et al., 2018). Temperature is involved in determining growth, heading, flowering and wheat production for that it is one of the important factors in plant growth (Heo et al., 2020). With the growing worry about global warming and rising earth temperatures, it is very important to know the proteins that supply thermo-tolerance to crop plants. One such gene family involved in heat stress tolerance is heat shock protein (HSP) family (Kumar et al., 2020). HSPs play in plants a wide variety of roles including stress signal transduction, protecting and repairing damaged proteins and membranes, protecting photosynthesis, and regulating cellular redox state (Asthir et al., 2015). HSPs are classified based on their molecular weight, which ranges from 10 to 200 kDa. There are six major subfamilies of HSPs, namely HSP100, HSP90, HSP70, HSP60, HSP40, and small HSP (Kumar et al., 2020). High temperature affects yield decrease by about 8.0 and 2.6% for corn and wheat, respectively for every Celsius degree of increase in global average temperature (Zhao et al., 2017). In addition, the photosynthetic product translocation rate to different plant parts is reduced under high temperature stress caused by decrease in membrane stability (Farooq et al., 2011). Moderate but prolonged time of heat stress outcome to gradual senescence, while intensive heat stress for a short time leads to denaturation and aggregation of proteins, resulting in plant death (Hasanuzzaman et al., 2013). Many physiological processes in plants are often measured as a stander of heat tolerance phenotypes. The electrolyte leakage is an index of reduction of cell membrane thermostability (CMS) and reverberate the performance of wheat genotypes subjected to in vitro heat shock (Farooq et al., 2011). Furthermore, the reduction of tetrazolium triphenyl chloride is one of the physiological evaluation assays for heat stress. It is considered as an index of respiratory enzyme inactivation or mitochondrial dysfunction reflecting the relative level of cell viability (Tewolde et al., 2006 and Mirza et al., 2013). Genetic diversity evaluation at molecular level gave an important overview to understand the genome variability among species. Thus, molecular analysis of different related species would help in successive breeding approaches. Among several molecular markers available in detecting