Embryogenesis induction of carrot (Daucus carota L.) in isolated microspore culture

Haploid technologies are used to create homozygous lines for accelerated breeding. We aimed to optimize the technology for using the isolated microspore culture in vitro to obtain doubled haploids of the carrot (Daucus carota L.). We studied two carrot varieties with different responsiveness to embryogenesis, Altajskaya lakomka and Breeding line 17. Carrot microspores were isolated from buds and cultivated in liquid nutrient media supplemented with an antibiotic and activated carbon in vitro. They were exposed to different thermal treatments. The experiment showed the benefits of combining cold pre-treatment of buds (5°C for 1 day) with heat shock of isolated microspores in vitro (32°C for 2 days). The induction of embryogenesis on the NLN-13 medium was twice as high as on the MSm-13 medium. The use of 1% activated carbon in 0.5% agarose increased the yield of embryoids by more than 1.5 times. 100 mg/L of ampicillin was found to be the most efficient concentration. After 30 days of cultivation under optimized conditions, the yield was 161.3 and 44.0 embryoids per Petri dish for the cultivar Altajskaya lakomka and Breeding line 17, respectively. The induction of carrot embryogenesis is determined by the type and duration of thermal stress, the composition of the nutrient medium, the use of activated carbon as a sorbent, the addition of β-lactam antibiotics, and the type of explant exposed to thermal treatment. Our technology enabled us to obtain homozygous doubled haploid lines of carrots during a year, and these lines were included in the breeding process to create F1 hybrids.