Document Type : Original Article

Authors

• Marzieh Salari ¹
• Ali Kazemipour ²
• Mehrnaz Kashigarzadeh ¹
• Soraya Pourtabrizi ¹
• MohamadGhader Ghaderi ³
• Roohollah Abdolshahi ⁴

¹ MSc students of Plant Breeding, Shahid Bahonar University of Kerman, Kerman, Iran

² Assistant Professor, Department of Plant Genetics and Production Engineering, Shahid Bahonahr University of Kerman, Kerman, Iran

³ Assistant Professor, Department of Agronomy and Plant Breeding, University of Birjand, Birjand, Iran

⁴ Associate Professor, Department of Plant Genetics and Production engineering, Shahid Bahonahr University of Kerman. Iran

Abstract

Introduction
Green Revolution which occurred by introducing dwarfing genes into bread wheat varieties had a great impact on the global wheat production. Nevertheless, these genes decrease grain yield under rain-fed conditions. In general, semi-dwarf genes may not have any advantage in heat and drought stress conditions. In rain-fed conditions, the combination of Rht-D1b and Rht-B1b genes causes a decrease in the grain yield and coleoptile length. It should be noted that the genes Rht4, Rht5, Rht7, Rht8, Rht9, Rht12, Rht13 and Rht14, which are sensitive to gibberellic acid, do not affect coleoptile length.
Materials and methods
In the present research, wild type genes which cause higher plant height were transferred from Roshan to Excalibur variety using backcrossing. Similarly, in the F3 generation of a cross between Roshan and Mahdavi, a semi-dwarf plant was observed. This plant was backcrossed with Roshan to have semi-dwarf isogenic lines of this cultivar. Development of isogenic lines for plant height in two genetic backgrounds made it possible to study the effect of the plant height on yield and yield components. Isogenic lines and their parents were evaluated in two successive years (2020-2021 and 2021-2022) under Sepidan rain-fed conditions.
Results and discussion
On average, plant height of Roshan and its semi-dwarf isogenic lines were 90.84 and 51.22 cm, respectively. Also, the average plant height of Excalibur and its tall isogenic line were 47.61 and 65.36 cm, respectively. Results showed that breeding for higher plant height had a positive and significant effect on wheat grain yield under rain-fed conditions. On average, tallness increased grain yield by 375.43 and 177.94 kg.ha in Roshan and Excalibur genetic backgrounds, respectively. In addition, the effect of plant height on yield components under rain-fed conditions was investigated. The findings of this research show that breeding for higher plant height indirectly increase grains number per spike and 1000 grain weight to improve grain yield. While, spikes number per meter square was not affected with plant height. Considering the high heritability of plant height and its significant correlation with grain yield, it is suggested that this trait be considered in breeding programs under rain-fed conditions.
Conclusion
In the present research, it was found that tallness improve grains yield of bread wheat under rain-fed conditions via increasing grains number per spike. Two other yield components were also investigated and it was found that the plant height had no effect on spikes number per meter square. 1000-grains weight did not affected by plant height in the first year, although in the second year, the taller genotypes had higher 1000-grains weight. Considering that plant height has high heritability and response to selection, it is recommended to pay special attention to this trait in breeding programs for rain-fed conditions. It should be mentioned that as narrow sense heritability of plant height is very high, selection for this trait based on single plant is very effective. Consequently, selection for plant height in backcrossing and pedigree breeding methods could be extremely successful.

Keywords

• Backcrossing
• Drought stress
• Grains number per spike
• Isogenic lines
• Tallness

Main Subjects

• Breeding plants for stress conditions