Intraspecific crossing of Saccharina japonica using distantly related unialgal gametophytes benefits kelp farming by improving blade quality and productivity at Sanggou Bay, China

Abstract

When cultivating the kelp, Saccharina japonica, in China, one of the causes leading to degeneration in blade quality and productivity has been thought to be inbreeding caused by the use of limited numbers of sorus-bearing individuals that are continuously used over generations to produce large numbers of offspring. One of the effective solutions is to use intraspecific hybrid vigor to produce new cultivars or to recreate the original agronomic features of the older cultivars. This study produced a sporophytic B013 (cultivar code) by crossing a pair of distantly related unialgal male and female gametophyte clones. The male was isolated from an individual collected from a farmed population at Rongcheng, China, while the female came from a Korean wild individual sporophyte. In comparison with four controls, the B013 sporophytic offspring demonstrated excellent blade quality (entirely dark green in the dried product), high alginate (29.7-32.9 %) and iodine (0.29-0.31 mg g −1 ) contents in the dried product, the lowest fresh weight/sun-dried weight (FW/DW) ratio and the smallest coefficients of variation for total length (7.4 %), width (6.9 %), and biomass output (14.6 %). In addition, this cultivar remained in a vegetative state from June to August, greatly reducing the biomass loss during the hot summer season. In comparison with seeding zoospores for seedling production, seeding a selected pair of unialgal gametophytes had apparent advantages in effectively preventing inbreeding depression, which gave rise to a uniformed product and provided new cultivars for large-scale farming.

Overview of 3 year precommercial seafarming of Macrocystis pyrifera along the Chilean coast

“…; Zhao et al . ), and it is beginning to be developed in Europe (Peteiro & Freire ; Peteiro et al . ).…”

“…Therefore, understanding the predomestication processes, which traits and which environmental factors of the cultivation system are involved, may allow maximizing the process itself and may be a cornerstone for future sustainability of seaweed aquaculture (Loureiro et al 2015, Valero et al in press). There is an urgent need to develop macroalgal germplasms, as it has been proposed for the giant kelp (Barrento et al 2016), what has been done with commercial kelps in Asia (Pang et al 1997;Shan et al 2016;Zhao et al 2016), and it is beginning to be developed in Europe (Peteiro & Freire 2014;Peteiro et al 2016). These initiatives will allow the conservation of the genetic diversity of the species selected for domestication.…”

“…Current practices of kelp cultivation in Asia, and mainly in China, have suffered a rapid evolution due to technological developments such as artificial seedling rearing and floating raft cultivation (Pereira & Yarish 2008;Titlyanov & Titlyanova 2010;Liu et al 2014). Also, they have increased their production by focusing on the development of elite cultivars of important species, for example Undaria variety 'Haibao No1' , Saccharina variety 'Huangguan No1' (Liu et al 2014) and 'Dongfang 2, Dongfang 3, Dongfang 6' (Li et al 2007(Li et al , 2008 with a production primarily oriented to human consumption, which includes specific texture of blades, taste and form Zhao et al 2016).…”

Genetic diversity and population structure among cultivars of Saccharina japonica currently farmed in northern China

“…During cultivation, it has been observed that some cultivars steadily lost their productivity, as reflected by a decrease of biomass or worsening of the quality of harvested blades, which may be caused by inbreeding due to the limited number of parental plants used (Zhao et al ). Moreover, in some circumstances, it is difficult to recognize the specific cultivars unambiguously based on finite morphological characteristics that are susceptible to environmental factors (Ravishankar et al ).…”

“…The cultivars were produced in large quantities, each with 2–5 hundred million individuals each year. During seedling production, hundreds of well‐matured parental plants are selected to release spores for seedling production (Zhao et al ). In the following year, the same number of well‐matured parental plants is selected from farmed populations and used to produce seedlings again.…”