نوع مقاله : مقاله پژوهشی
نویسندگان
1 استاد، موسسه تحقیقات اصلاح و تهیه نهال و بذر، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرج، ایران.
2 کارشناس، موسسه تحقیقات اصلاح و تهیه نهال و بذر، سازمان تحقیقات، آموزش و ترویج کشاورزی، کرج، ایران.
چکیده
کلیدواژه‌ها
عنوان مقاله [English]
نویسندگان [English]
This research was carried out to introduce single seed descent as an applied wheat breeding for accelerating the development of pure lines. Twenty five crosses between durum wheat cultivars and landraces and four crosses between bread wheat cultivars were performed and F1 and F2 generations were produced under field conditions in 2021-2022 and 2022-2023 cropping cycles. Ninety populations of durum wheat and four population of bread wheat, in total 23 populations, were used for producing seed of F2 segregating populations, which led to pure lines using the single seed descent (SSD) method in controlled conditions in greenhouse. Each generation cycle was approximately 70–80 days. To maintain and transfer genetic variation between and within generations, a single seed was harvested from each spike in the F₂, F₃, and F₄ generations and replanted to produce the subsequent generation. In the F₅ generation, all seeds from each spike were harvested separately, and stored in individual envelopes and considered as F₆ pure lines. At the conclusion of the three-year study, a total of 1,456 F6 pure lines were developed from the 23 successful wheat crossing programs.
Keywords: Wheat, hybridization, segregating generations, desirable traits, seed number.
Introduction
Recently, speed breeding has emerged as a novel strategy to shorten the time required to achieve pure lines and develop new crop varieties. In this method, plants are grown in controlled growth chambers or greenhouses under optimized light intensity, quality, photoperiod, and temperature, accelerating physiological processes such as photosynthesis and flowering, thereby reducing the seed-to-seed cycle. Researchers have introduced speed breeding as a powerful method to accelerate cultivar development in crop plant breeding programs (Watson et al., 2018; Hickey et al. 2019; Jin-Kyung et al., 2023). Among speed breeding techniques, the single seed descent (SSD) method has proven highly effective. In SSD method, a single seed is harvested from each self-pollinated plant per generation. This approach not only reduces generational turnover time but also minimizes inter-plant competition and natural selection pressures, thereby preserving maximal genetic diversity until homozygous purity is achieved (Watson et al., 2018). The present research was designed and implemented in greenhouse conditions with the aim of reducing the time required to develop and release of durum and bread wheat cultivars resulting from different crosses using the single seed descent breeding method.
Materials and Methods
In this research, 25 crosses were made between durum wheat and four crosses between bread wheat cultivars. The F₁ and F₂ generations were produced under field conditions in 2021-2022 and 2022-2023 crop seasons, respectively. From the F₂ populations, 19 durum wheat and four bread wheat populations, totally 23 segregating populations, were kept, which led to pure lines using the single seed descent (SSD) method in controlled conditions in greenhouse. Greenhouse conditions were maintained with 22 hours of light (16,000 lux) and two hours of dark periods per day. The temperature ranged from 22–25°C during the light period and 17–18°C during the dark period. Relative humidity was maintained 60–70% in all growth stages.
Results and Discussion
In this research, 1456 pure lines were successfully developed from 23 crosses of durum and bread wheat using single seed descent (SSD) in Karaj, Iran. The process involved: 1) Crossing and F₁ seed production (Year 1), 2) Field cultivation of F₁ to generate 19 segregating F₂ populations (Years 2), 3) Handling the F3, F4, and F5 generations in the greenhouse under optimized conditions (22-hour light/2-hour dark, 23–25°C day/17–18°C night, 70% RH) to produce pure lines (Year 3). While these steps need six years in the conventional wheat breeding methods. In other words, three years were saved to produce pure lines in SSD method. No plants were removed in this method, therefore, the maximum genetic was maintained and transferred to subsequent generations. In addition, significant savings were made in irrigation water consumption, which is commonly used for managing the segregating generations in the field as well as in human resources costs in conventional wheat breeding.
Different light sources including SMD lamps with purple and yellow light with intensity of 10-13 thousand lux, LED strip lights with white, blue and purple light with intensity of 6-4 thousand lux, and conventional LED lamps with intensity of 13-16 thousand lux had no significant effect on the grain physiological maturity. However, our observation showed that the white light with an intensity of 16,000 lux led to larger wheat spikes, higher thousand-grain weight, and more grains. Also, these lamps were easier to obtain and install, and their costs was much lower than other lamps.
The pure lines produced in this research will be advanced the national wheat breeding programs for target environments in southern warm and dry and temperate agro-climatic zones. It is expected that commercial cultivars will released within the next few years.
References
Hickey, L.T., Hafeez, A.N., Robinson, H, Jackson, S.A., Leal- Bertioli S.C.M., Tester, M., Gao, C., Godwin, I.D., Hayes, B.J. and Wulff, B.B.H. 2019. Breeding crops to feed 10 billion. Nature Biotechnology, 37, pp.744–754. DOI: 038/s41587-019-0152-9
Jin-Kyung, C., Hyeonjin, P., Changhyun, C., Youngho, K., So-Myeong, L., Ki-Won, O., Jong-Min, K., Soon-Wook, K. and Jong-Hee, L. 2023. Acceleration of wheat breeding: enhancing efficiency and practical application of the speed breeding system. Plant Methods, 19(18), pp.1-9. DOI: 10.1186/s13007-023-01083-1
Watson, A., Ghosh, S., Williams, M.J., Cuddy, W. S., Simmonds, J., Rey, M.D., Md Hatta, M.A., Hinchliffe, A., Steed, A., Reynolds, D., Adamski, N.M., Breakspear, A., Korolev, A., Rayner, T., Dixon, L.E., Riaz, A., Martin, W., Ryan, M., Edwards , D., Batley, J., Raman, H., Carter, J., Rogers, C., Domoney, C., Moore, G., Harwood, W., Nicholson, P., Dieters, M. J., Lacy, I.H., Zhou, J., Uauy, C., Boden, S.A., Park, R.F., Wulff, B.H. and Hickey L.T. 2018. Speed breeding is a powerful tool to accelerate crop research and breeding. Nature Plants, 4, pp.23-29. DOI: 10.1038/s41477-017-0083-8
Yao, Y., Zhang, P., Liu, H., Lu, Z., and Yan, G. 2016. A fully in vitro protocol towards large scale production of recombinant inbred lines in wheat (Triticum aestivum L.). Plant Cell, Tissue and Organ Culture, 128, pp.655– 661. DOI: 10.1007/s11240-016-1145-8
کلیدواژه‌ها [English]
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