Polymorphism of leaf turnip Brassica rapa L. doubled haploid lines produced in isolated microspore in vitro culture

Background. The development of high-yielding and nutritious cultivars of leaf turnip Brassica rapa L. using traditional breeding methods is a lengthy process. The application of biotechnological methods, particularly the production of doubled haploid (DH) lines in vitro, significantly accelerates the creation of homozygous forms and unlocks the genetic potential of hybrids. The aim of the research was to evaluate DH-lines of leaf turnip, produced from the F₁ Torazirok hybrid, for a set of economically important morphological and biochemical traits. Materials and methods. The object of the study was the leaf turnip F₁ Torazirok hybrid (k-330, Japan) and 15 DH lines derived from it through in vitro isolated microspore culture. Plants were grown under controlled conditions in a climate chamber. The plants were described morphologically, and biochemical analysis of the content of photosynthetic pigments chlorophylls a, b, carotenoids, and β-carotene was performed by spectrophotometry. Results and discussion. Significant polymorphism has been revealed between the DH lines and the F₁ hybrid. The duration of the vegetative period varied from 41 to 52 days. Rosette diameter ranged from 20.5 to 40.3 cm, and the above-ground plant mass from 0.15 to 0.33 kg. β-carotene content fluctuated from 2.6 to 6.3 mg/100 g of fresh weight. The lines that were found to significantly surpass the original hybrid in key traits were DH 8 – in productivity with the mass of 0.33 kg and β-carotene content (6.3 mg/100 g); DH 4 – in rosette diameter (40.3 cm) and the mass of 0.31 kg; DH 2 and DH 5 – in β-carotene content (5.6 and 5.2 mg/100 g, respectively). The DH 2 line combines early maturity (41 days), high productivity, and maximum carotenoid content. Conclusions. The isolated microspore culture method is effective for the rapid creation of genetically diverse and homozygous leaf turnip breeding material. The obtained range of DH-lines is a valuable source for breeding. Promising donor lines have been identified: DH 2 and DH 8 – for early maturity and increased β-carotene content; DH 4 and DH 8 – for high productivity. The results confirm that the haploid technology allows not only for the fixation but also for the enhancement of economically important traits, providing ready-made material for genetic research and the creation of new cultivars.

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