The Effect of Breeding for Tallness on Yield, Yield Components and Phenology of the Bread Wheat Cultivar "Excalibur"

Document Type : Research Paper

Authors

1 MSc. Student,, Department of Plant Production and Genetics Engineering, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran

2 Ph.D. Department of Plant Production and Genetics Engineering, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran

3 Assistant Professor, Department of Plant Production and Genetics Engineering, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran

4 Ph.D, Department of Plant Production and Genetics Engineering, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran

5 Associate Professor, Department of Plant Production and Genetics Engineering, Faculty of Agriculture, Shahid Bahonar University of Kerman, Kerman, Iran

Abstract

Introduction
Bread wheat (Triticum aestivum L.) is one of the most important food crops worldwide. Plant height is a key agronomic trait that directly influences grain yield. Optimizing wheat plant height according to environmental conditions can maximize grain productivity. To further investigate the effects of increased plant height on grain yield and early maturity in the bread wheat cultivar "Excalibur", this recent study was conducted across multiple regions.
 
Material and Methods
To investigate the effects of increasing plant height on grain yield and early maturity in the bread wheat cultivar "Excalibur," the recent study was conducted. In this study, the cultivars Excalibur and Roshan, the Excalibur semi-tall line (derived from the fourth backcross generation of Excalibur × Roshan), along with several local cultivars, were evaluated using a randomized complete block design with four replications. The experiment was conducted under different climatic conditions, including well-watered regimes (Arzuiyeh, Dashtkar, and Negar regions) and rain-fed conditions (Kazerun and Sepidan) during the 2022-2023 growing season. Several parameters were recorded, including grain yield (ton/ha), the number of spikes per square meter, the number of grains per spike, thousand-grain weight (gr), plant height (cm), days to heading, days to maturity, and grain-filling period. Data analysis of variance and mean comparison using the LSD test were performed in SAS v9.1 software, and figures were drawn in Excel 2016 software.
 
Results and Discussion
The results showed in the regions of Orzueeyeh, Kazerun, and Sepidan, increasing plant height had no effect on phenological traits. However, in Dashtkar and Negar regions, increased plant height extended the number of days to heading but reduced the grain filling period, resulting in no change in maturity time. The semi-tall Excalibur line was earlier-maturing compared to the control cultivars in Dashtkar, Negar, and Sepidan, but this difference was not significant in Orzueeyeh. In Kazerun, it was earlier-maturing than the Kalheydari cultivar. Increased plant height in Orzueeyeh reduced the number of spikes per square meter, but this reduction was not significant in Negar and Dashtkar. In Kazerun, increased plant height had no significant effect on spike density, whereas in Sepidan, it decreased the number of spikes. Under both well-watered and rain-fed conditions, no significant difference was observed between the semi-tall Excalibur line and the Excalibur cultivar in terms of grains per spike. This result indicates that, in this study, increased plant height had no effect on the number of grains per spike. Increased plant height in the Orzueeyeh, Negar, and Sepidan regions led to a higher thousand-grain weight whereas this increase was not significant in the Dashtkar and Kazerun regions. It can be inferred that higher plant height enhances biomass production and photosynthetic activity, thereby increasing the thousand-grain weight in some regions. In the Orzueeyeh region, the semi-tall Excalibur line had lower grain yield compared to the parent Excalibur, while this yield reduction was not significant in the Negar and Dashtkar regions. In Orzueeyeh, due to the region's high winds, extreme heat, and low humidity, wheat shedding is very high, and the semi-tall Excalibur line experienced significant shedding in this area. The grain yield of the semi-tall Excalibur line was lower than that of the control cultivars in the Dashtkar and Negar regions. In Orzueeyeh, it showed no difference with the Setare cultivar but was lower than the Sirvan cultivar. Therefore, it can be concluded that the semi-tall Excalibur line is not suitable for cultivation in the Dashtkar and Negar regions. However, in Orzueeyeh, due to its higher straw production compared to the Setare cultivar, it could serve as a replacement for Setare. In the Kazerun region, no significant difference in grain yield was observed between the semi-tall Excalibur line and the Excalibur cultivar. However, in the Sepidan region, a decrease in grain yield was observed due to increasing plant height. Unlike Kazerun, plants in Sepidan faced severe stress by the end of the growing season. In other words, rainfall distribution was much better in Kazerun than in Sepidan. Regarding grain yield in Sepidan, the semi-tall Excalibur line was lower than the Baran and Kalheydari cultivars but showed no difference with the Mahdavi cultivar. In Kazerun, it did not differ from the Karim and Koohdasht cultivars but was higher than Kalheydari. Therefore, this line could be a suitable replacement for the Kalheydari cultivar in the Kazerun region.
 
Conclusion
It can be concluded that selecting for tallness under rain-fed conditions can be a beneficial and suitable approach in breeding programs to improve yield in bread wheat. Conversely, under well-watered conditions, selecting for dwarfism is recommended.

Keywords

Main Subjects

References

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Volume 17, Issue 2
February 2026
Pages 101-114

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