Trait evaluation and trial cultivation of Dongfang No. 2, the hybrid of a male gametophyte clone of Laminaria longissima (Laminariales, Phaeophyta) and a female one of L. japonica

Abstract

Direct cultivation of the first filial generation of gametophyte clones from different Laminaria species is a highly effective way of utilizing kelp heterozygous vigor (heterosis). A male gametophyte clone of L. longissima Miyabe and a female one of L. japonica Areschoug were hybridized, generating Dongfang No. 2 hybrid kelp. This hybrid kelp was used directly in trial cultivation, and its agronomical traits were evaluated. L. longissima and L. japonica are obviously different and complement each other in their morphological characteristics and ecological performances. The hybrid of their gametophyte clones, Dongfang No. 2, showed 56.8% heterozygous vigor in yield. It also showed increased yields of 41.0 and 76.4% compared to the widely used commercial kelps Variety 1 and Variety 2, respectively. In largescale cultivation trials at different locations and in different years, Dongfang No. 2 attained significantly higher yields than Varieties 1 and 2, increasing yield by 26.4% on average over Variety 1 and by 65.0% over the other. Dongfang No. 2 has a robust holdfast and a wide, long and deep-brown uniform blade, which shows a distinct middle groove. In addition to yield, Dongfang No. 2 also demonstrates obvious heterozygous vigor in other agronomic traits. It is resistant to strong irradiance, as the two commercial varieties are, has an appropriate vegetative maturation time, and adapts well to a range of different culture conditions. The parentage analysis using AFLP of total DNA and SNP of the ITS region of ribosomal RNA transcription unit showed that Dongfang No. 2 is the real hybrid of L. japonica and L. longissima.

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). …”

Offshore and Multi-Use Aquaculture with Extractive Species: Seaweeds and Bivalves

“…Selective breeding and intensive selection of kelp strains in Asia, however, have reduced the genetic diversity and narrowed the germplasm base of the varieties in cultivation. This has led to decreased adaptability of these varieties to environmental changes and jeopardizes the industry expansion in Asia (Kawashima and Tokuda 1993;Li et al 2009;Robinson et al 2013). In North America and Europe, strain development will be a challenge.…”

Macrocystis mariculture in Chile: growth performance of heterosis genotype constructs under field conditions

“…More recently, closely related Laminaria species were crossed in order to produce superior genotypes in China Li et al 2007). Li et al (2008) used molecular techniques to correlate genetic distances between Lami naria parent lines and economically interesting characters of their heterosis products.…”