Development and cultivation of F2 hybrid between Undariopsis peterseniana and Undaria pinnatifida for abalone feed and commercial mariculture in Korea

The kelp Undariopsis peterseniana (Kjellman) Miyabe et Okamura is warm water tolerant and consequently there is currently considerable interest in developing commercial cultivation techniques for this species in Korea. Undaria is an important species for both the abalone industry and for commercial seaweed mariculture. In an attempt to extend the culture period of Undaria we bred and cultured hybrid kelp that is a cross between free-living gametophytes of U. peterseniana and Undariopsis pinnatifida. The morphological characteristics of the F-1 hybrid sporophytes were intermediate between those of the parent plants having shallow pinnated blades and forming both sorus and sporophyll. A F-2 generation was produced by isolating zoospores from sorus and sporophyll separately from a F-1 hybrid thallus. Using free-living gametophyte seeding and standard on-growing techniques, F-0 (female U. pinnatifida and male U. peterseniana), F-1, and F-2 gametophytes were cultured from December 2011 to May 2013. The morphological differences between the F-1 and F-2 generations were assessed. The F-2 hybrids were found to have longer pinnate blades and narrower midribs than the F-1 hybrid and only formed sporophylls. Growth and morphology of F-2 hybrids originating from the sporophyll or sorus of the F-1 hybrids were not morphologically different from each other. Both of the F-2 hybrids exhibited late maturation, with the early stages of sporophylls appearing in April. This late maturation of F-2 hybrids is beneficial in the development of hybrid strains that extend the period of availability of Undaria for abalone feed and cultivation in Korea.