The influence of different factors on microspore embryogenesis in Chinese cabbage (B. rapa ssp. chinensis) was studied. A genotype dependence for embryo formation was observed. The majority of embryos and plants were obtained from microspores isolated from flower buds (2-2.9 mm in length) and cultured in the NLN liquid medium with 13% sucrose (w/v) supplemented with 24 epibrassinolide and 1% activated charcoal. Embryos cultured on the 1/2 Murashige Skoog culture medium with 2% sucrose (w/v), 0.1 mg/L benzylaminopurine, and 3 g/L Phytagel stimulated the formation of secondary embryos that resulted in development of large number of doubled haploid plants.
Antibiotics are widely applied for plant cultivation in vitro to eliminate bacterial contamination. However, they can have both positive and negative effects on the cells of cultivated plants, and these effects largely depend on the type antibiotic used and its concentration. The objective of the present study was to estimate the effect of β-lactam antibiotics ampicillin (Amp) and cefotaxime (Cef) on microspore embryogenesis induction in vitro in the Brassica species. The performed experiments confirmed cefotaxime inhibits microspores in B. napus and B. oleracea, even in concentrations as low as 50 mg/L. The highest embryo yield was obtained for B. napus in the NLN-13 medium with added ampicillin in concentrations of 50–100 mg/L as an antimicrobial agent. This embryo yield was significantly higher than that obtained in a medium without supplemented antibiotics and two times higher than in the medium with added cefotaxime. Analogous results were obtained for B. oleracea and B. rapa.
A b s t r a c tPresently, cabbage breeding is mainly focused on F 1 hybrids necessitating constant parental lines to be obtained. Doubled haploid (DH) technology based on isolated microspore in vitro culture is widely used to produce pure lines of brassica crops. This method allows us to rapidly develop homozygous lines, in contrast to time-consuming traditional breeding for heterosis in cross-pollinating crops which takes 7 to 10 years for annuals and 14 to 20 years for biennial plants. One of the objectives of DH technology is to provide the all possible number of doubled haploid plants that allows more fully encompass the spectrum of genetic recombination, including the recessive locus. The aim of our study was to evaluate economically important traits in white cabbage (Brassica oleracea L. convar. capitata var. alba DC) constant doubled haploid lines of late ripening and to improve the technology for producing DH based F 1 hybrids. Eleven breeding lines of late ripening cabbage were used to obtain doubled haploid lines from microspore in vitro culture. Of the obtained lines, twelve doubled haploid genotypes were selected for further use based on evaluation of ploidy and combining ability. Seed progeny was reproduced by hybridization of regenerated plants in a climatic chamber (2014)(2015). We used the schemes of creating self-incompatible lines and two-line-based hybrids. In the field trials (Moscow region, 2014(Moscow region, -2015, the doubled haploids and their hybrid combinations were compared to the standard (Severyanka F 1 ) for the main valuable characteristics (i.e. the content of dry matter, nitrates, and vitamin C). The field resistance to Fusarium wilt, alternariosis, and pest damage were determined at cabbagehead technical maturity. The resistance to clubroot was assessed under artificial infection. There was a direct relationship of the average number of chromosomes to the number of chloroplasts in the stomata guard cells and the length of guard cells. The frequency of spontaneous doubling of the chromosomes numbers varied from 50.0 % to 87.5 % in different geotypes. A total of 11 to 73 % produced lines were high self-incompatible. Their geitonogamic pollination in the topcrosses resulted in 42 hybrid combinations. The model of F 1 hybrid most fully responding to consumer market demands was developed. Ten promising hybrid combinations which matched the model parameters in two-year field testing were recommended for variety testing. Hybrids were characterized by uniformity, high biochemical quality, the resistance to major diseases and pests and the yield of 104.60±8.27 t/ha. The dry matter content reached to 10.5 %, the sugar content was about 4.21-5.10 %, and ascorbic acid level ranged from 21.12 to 38.70 mg%. Both the highest level of ascorbic acid (92.0 mg%) and the smallest nitrate accumulation (33 mg/kg) were characteristic of one hybrid combination.Keywords: white cabbage, Brassica oleracea L., doubled haploid lines, heterosis F 1 hybrids, in vitro isolated microspore culture, self-incomp...
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