Document Type : Research Paper
Authors
1
Ph.D. Student, Department of Genetics and Plant Breeding, Ahvaz Branch, Islamic Azad University, Ahvaz, Iran
2
Associate Professor, Department of Plant Production and Genetics, Shoshtar Branch, Islamic Azad University, Shoushtar, Iran
3
Research Assistant Professor, Safiabad Agricultural and Natural Resources Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO), Dezful, Iran
4
Assistant Professor, Department of Plant Production and Genetics, Shoshtar Branch, Islamic Azad University, Shoushtar, Iran
10.22124/cr.2025.31331.1875
Abstract
Introduction
Heat stress is a growing threat to food security and agricultural production. The use of stress tolerance indices are one of the most promising methods for selection of stress tolerant genotypes among researchers. The diallel crossing method has been introduced as a desirable scheme for selecting parental lines to obtain superior hybrids. Valuating lines for combining ability in early generations is an essential step in producing desirable hybrids. The aim of this research is to estimate the general combinability and the specific combinability of lines and to evaluate stress tolerance indices in order to determine the best desirable and heat stress tolerant lines and hybrids.
Materials and methods
In this experiment, six lines and their one-way hybrids (15 hybrids resulting from diallele crosses) were evaluated in two independent experiments, early sowing date (July 15, heat stress conditions) and recommended sowing date (August 15, non-stress conditions) in a randomized complete block design with three replications in the summer of 2019 at the Safiabad Agricultural Research and Education Center of Dezful, located in south western Iran. Days until processing and yield and yield components were measured as the important characters. Heat stress tolerance and sensitivity indices were calculated for lines and hybrids. To estimate General Combining Ability (GCA) and Specific Combining Ability (SCA) for corn grain yield and its components under heat stress and normal conditions, the second method of Griffing’s diallel crosses was used. All analyses were performed using Minitab version 16 and Diallel-SAS software.
Research findings
Considering the positive and significant correlation of MP, GMP, STI, HA and TOL indices with yield under both normal and heat stress conditions, these indices were introduced as the best selection indices. Considering the results of the best indices, principal component analysis and biplot, the lines C3-95-3, C3-95-9 and C3-95-10 and the hybrids C3-95-3×C3-95-9, C3-95-3×C3-95-10 and C3-95-9×C3-95-10 are heat tolerant. The effects of specific combining in both heat stress and normal conditions for grain yield traits, days to maturity, number of rows of grains and grains per row in hybrids C3-95-3×C3-95-9 and C3-95-9×C3-95-10 were positive and significant. According to the obtained results, the three parents C3-95-10, C3-95-9 and C3-95-3, in addition to being tolerant to heat stress and performing better than other lines under heat stress conditions, also had the ability to transfer these traits to hybrids.
Conclusion
High temperature stress indices can be effectively used to screen heat-tolerant genotypes. Selected lines can be used as potential sources of heat stress tolerance in further heat stress-tolerant breeding programs. Given the significant effects of SCA for grain yield traits, number of grains per row, and number of days to maturity, and the low GCA/SCA ratio, the more important contribution of non-additive effects in controlling these traits is more evident. Therefore, since the superiority of crossing cannot be reliable in the selection process and has a low breeding value, heterosis can be used due to non-additive effects and gene dominance in controlling the relevant traits and it is hoped to produce suitable hybrids.
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