DARI Speed Breeding Unit for Accelerating Cultivar Development to Climate Change Adaptation in Arid and Semi-Arid Regions of Iran

Today climate change is the main challenge for the productivity and stability of crops in arid and semi-arid areas, so it needs to increase the rate of developing high yielding and stable varieties. Generally, it takes 12-13 years to develop a new variety in which 4-5 years of that spend to develop homozygous lines following hybridization if only one crop generation is produced per year. For this reason, a speed breeding unit was established in the dryland agricultural research institute (DARI), Maragheh, Iran in the year 2018-19 to reduce the number of years required to reach homozygosity and develop a cultivar. Speed breeding is based on extending the photoperiod using supplementary lightning and controlled temperature regime, enabling rapid generation advancement in the greenhouse. This unit was equipped with light-emitting diode (LED) lights (1200 W, blue wavelength; 450-460 nm, orange-red wavelength; 640-660 nm), heating, and cooling systems with a programmable panel. Day length was set for 22 hours, and night length for 2 hours and the temperature regime was set at 20-22 °C in the day and 15-17 °C in the night. Rainfed winter and spring bread wheat, rainfed winter-facultative barley varieties, and rainfed lentil varieties were used to set up the speed breeding protocol. Four spring wheat varieties including Aftab, Gahar, Karim, and Koohdasht were planted in seedling trays and germinated and grown in the speed breeding unit. Seed to seed time for Koohdasht and Gahar was 77 days while for Karim and Aftab it was 82 days. For winter bread wheat, 26 backcrosses 1 F1 and three-way cross F1 generations were planted in seedling trays and germinated in the speed breeding unit for one week. Then they vernalized for five weeks in the cold room at -2°C, then were moved to speed breeding unit. The generation time of them ranged from 111 to 127 days. For barley, three winter-facultative barley including Artan, Ansar, and Ghaflan, also, were planted and germinated in the seedling tray for one week and then vernalized at -2°C for four weeks in the cold room. For all three barley varieties seed to seed time was 100 days. For rainfed lentil, three varieties including Precoz, Sana, Ardabil landrace were investigated in speed breeding unit and generation times for them were 74, 69, and 75 days, respectively. In general, generation time for winter bread wheat and barley is 184 and 170 days, respectively, in cold regions, for spring wheat is 110 to 140 days in warm and moderate-warm, respectively, and for lentil is 96 days in the field conditions of Iran. Using speed breeding technique, generation times were significantly reduced for winter wheat in range of 57 to 73 days, for spring wheat, 33-63 days for Gahar and Koohdasht, and 28-58 days for Karim and Aftab, for barley, 23 days and for lentil, on average 23 days in comparison to the field. Speed breeding technique provides an opportunity to increase the rate of developing new varieties by producing 3-4 generations per year in the greenhouse with supplementary lightning compared to the field. Speed breeding can also be used for crop hybridizations, gene transformation, genomic selection, plant phenotyping for traits such as plant height, disease resistance, leaf sheath glaucousness.

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