Document Type : Research Paper
Authors
1
Genetic research department, Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran (* Corresponding author: nafash.2017@gmail.com)
2
Genetic research department, Seed and Plant Improvement Institute, Agricultural Research, Education and Extension Organization, Karaj, Iran
3
Agricultural and Natural Resources Research Center of Khuzestan, Agricultural Research, Education and Extension Organization, Ahwaz, Iran
10.22124/cr.2023.25872.1794
Abstract
Introduction
In the Mediterranean climates with mild winters like Khuzestan province, Iran, wheat is planted in autumn, and heat stress occurs only during the reproductive growth stage of wheat. In these regions, delayed planting causes the flowering and grain filling stages to be exposed to high temperatures, and the quantitative and qualitative performance of wheat decreases. Genetic improvement is one of the strategies to combat heat stress. Considering the importance of genetic resources for tolerance to environmental stresses tolerance, the present research was conducted to screen the wheat genetic collection of the National Plant Gene Bank of Iran for tolerance to terminal heat stress and to identify tolerant accessions.
Materials and methods
In plant materials of this experiment were 236 bread wheat accessions along with three control varieties (Chamran, Chamran2 and Aflak), which were planted in an augmented design in the research field of Agricultural and Natural Resources Research Center of Khuzestan province, Ahvaz, Iran, in 2015-2016 crop year. The experiment was carried out in two planting dates, on-time planting date according to the region's custom at late November as normal conditions, and delayed planting at early January with the aim of heat stress during the reproductive growth stage of wheat. The measured traits included spike length, 100-grain weight, plant height, number of grains per spike, number of spikelets per spike, number of florets per spikelet, number of days to heading, number of days to maturity, grain filling duration, and five spikes grain weight. For data statistical analysis, descriptive statistics were firstly estimated under both normal and heat stress conditions, and then the relationships among traits were investigated using correlation coefficients. Principal component analysis was used to reduce the volume of data and cluster analysis was perfomed to group the studied genotypes.
Research findings
The results of this experiment showed that terminal heat stress reduced the average of all studied traits, so that the highest decrease was observed in five spikes grain weight and the number of grains per spike. Based on the results of correlation coefficients under both normal and heat stress conditions, a positive and significant correlation was observed between five spikes grain weight and yield components traits, and a negative and significant correlation between five spikes grain weight and days to heading and days to maturity. Based on the results of principal component analysis, 72.54% and 80.53% of the total variance were explained by two and three main components under normal and heat stress conditions, respectively. The results of principal component analysis also indicated that the wheat accessions KC12977, KC12980, KC13013, KC13043, and KC13087, with the characteristics of early flowering and early maturity and higher values of five spikes grain weight, number of grains per spike, grain filling duration and number of florets per spike, were valuable accessions and have the sufficient potential to be used in breeding programs for heat stress tolerance. The results of cluster analysis separated the studied accessions into six group, and the fourth group including 62 accessions along with the control cultivars, had the highest average for number of florets per spike, number of grains per spike, and five spikes grain weight, as well as the lowest average for days to heading and days to maturity under both normal and heat stress conditions. and were recognized as the most tolerant group to heat stress. by three main components. In addition, the studied accessions were divided into six groups using cluster analysis.
Conclusion
The results of this study showed that there was a high genetic diversity among the studied bread wheat accessions in terms of terminal heat stress tolerance. Some genetic samples such as KC12977, KC12980, KC13013, KC13043 and KC13087, were valuable genotypes for the traits of early flowering and early maturity, as well as grain yield and yield components. The high diversity in these genetic resources, especially the tolerant accessions identified in this experiment as above mentioned, can be used to improve heat stress tolerance in future breeding programs.
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