Journal of Taiwan Agricultural Research

Author:Chi-Ni Hsia*, Uei-Chern Chen, Chin-Yi Tsao, Yi-Mei Chou, and Tzu-Kai Lin

Abstract:

    Brassica oleracea var. botrytis is one of the most important vegetables in the world. However, very few studies on cauliflower microspore culture were conducted in Taiwan. The objective of this study was to establish a microspore culture system- an efficient technique to produce inbred lines for breeding elite F₁ hybrids, starting from cultivar screening for embryogenesis and followed by modifying conditions for germination of microspore-derived embryos. Microspores were inoculated with 4 × 104 microspores mL^-1 in a NLN-13 medium, then incubated at 32℃ for 1- or 3-day. A total of 8 commercial F₁ hybrids were surveyed. Among them, ‘Chinglong S-65’ and ‘Known-you Farmers extra early’ had the highest embryogenesis response. However, there were 3 cultivars were found without any embryo. A multiple factor experiment using two culture media in combination with three duration treatments at 32℃ was further conducted using ‘Known-you Farmers extra early’. The effect of 32℃ treated duration, medium salt strength, and their interactions were all significant (P < 0.01) on embryogenesis. Among six treatments, 1/2 NLN medium in combination with 1-day culturing at 32℃ had the highest embryogenesis with 12.0 embryos/petri dish. Low germination rates of 2.1% and 4.0% for ‘Known-you Farmers extra early’ and ‘Chinglong S-65’ were obtained, respectively, from microspore-derived embryos cultured directly on a hormone-free B5 medium for 4-week. Various types of tissues derived from cotyledonary embryos were subcultured consistently on a BA containing medium for 1-week preculture before on the hormone-free medium for another 5 weeks culturing. Higher shoot germination rates of 66.7% and 86.9% for ‘Known-you Farmers extra early’ and ‘Chinglong S-65’ were observed, respectively, from the particular type of explant-elongated hypocotyl tissues with secondary organogenesis. Ploidy level of regenerated plants from ‘Known-you Farmers extra early’ and ‘Chinglong S-65’ were analyzed using flow cytometer, and diploid rate of 58.8% and 56.3% were obtained, respectively.

Key words:Cauliflower, Microspore, Doubled haploid

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