Breeding of an elite Laminaria variety 90-1 through inter-specific gametophyte crossing

Abstract

Laminaria longissima and ZaohouchengNo.1 (a commercial variety selected from Laminaria japonica) differ to a certain extent in their morphological characteristics and biological habits. It was assumed that varieties bred through their hybridization should exhibit high yield potential and tolerate relatively high seawater temperatures. Female gametophyte clones isolated from L. longissima were crossed with male clones isolated from Zaohoucheng No.1. Laminaria variety 90-1 was obtained after gametophyte crossing, continuous self-crossing and selection. This variety was genetically homozygous; the indices of variation of blade length, width and thickness of the final two selection cycles were 7-8%; i.e., not different significantly. Variety 90-1 grew faster, lost less tissue and had higher yield potential than two widely used commercial varieties of L. japonica (all commercial varieties currently used in China originate from this latter species). The blade of variety 90-1 increased 3.71 cm day −1 on average during the whole period of cultivation, almost twofold that of two controls, and growth was maintained even when seawater temperature was higher than 18°C -3°C higher than the temperature tolerated by other Laminaria varieties. Variety 90-1 increased yield by more than 70% over two controls and also synthesized desirable amounts of iodine, mannitol and algin. In blade length, variety 90-1 was more similar to L. longissima than to L. japonica, but more similar to L. japonica in blade width and thickness. Since the adoption of variety 90-1 in 1999, its culturing area has increased each year to reach its current area of 7,000 ha, i.e., almost one-third of the total cultivation acreage of Laminaria in China. Breeding of variety 90-1 has demonstrated that it is feasible to develop elite Laminaria varieties by crossing gametophytes from different Laminaria species in combination with successive self-crossing and selection.

Towards domestication of giant kelp (Macrocystis pyrifera) in Chile: selection of haploid parent genotypes, outbreeding, and heterosis

“…Due to the dominant diploid state combined with obligatory sexual reproduction and dioecism, the occurrence of heterosis in kelps is not surprising, and a first case has been reported for Undaria by Hara and Akiyama (1985). Heterosis breeding strategies are presently applied in Laminaria mariculture in China, using intraspecific matings between Laminaria japonica cultivars (Li et al 2008) and reciprocal crosses between cultivars of L. japonica and L. longissima (Li et al 2007;Zhang et al 2007). …”

Seaweed aquaculture in Norway: recent industrial developments and future perspectives

“…Commercial varieties of Saccharina japonica (Zhang et al 2007) as well as eucheumoid species like Kappaphycus alvarezii and Eucheuma denticulatum (Ask and Azanza 2002) illustrate successful efforts towards seaweed crop improvement. However, crop selection and the use of the selected varieties on a large scale may lead to gene swamping, where genetic material from cultivated crops is introduced to wild populations (Snow et al 2010).…”

An AFLP-based survey of genetic diversity and relationships of major farmed cultivars and geographically isolated wild populations of Saccharina japonica (Phaeophyta) along the northwest coasts of the Pacific

“…As such, a cultivar may lose the initial agronomical characteristics after a few years of repeated use in practical farming. One of the examples of such degeneration and contamination is the well-known elite cultivar recently used in China, i.e., cultivar 90-1 (Xia et al 2005;Zhang et al 2007a). One solution to solve the aforementioned degeneration and contamination problem in application of a selected cultivar is the use of vegetative gametophytes which was termed 'free-living technique' when first applied in mass cultivation of another brown alga, i.e., Undaria pinnatifida (Harvey) Suringar (Perèz et al 1992;Pang and Wu 1996;Pang et al 1997).…”