Diseases and pests are major limiting factors to aquaculture production, 1 including seaweeds, 2 prompting global action to improve biosecurity and knowledge of important yield-limiting pathogens affecting sustainable production, both now and in the future. 3,4 Seaweeds comprise almost 30% of global aquaculture production by volume. 5 Production of the carrageenophyte red algal genera Kappaphycus and Eucheuma (collectively known as eucheumatoids) has increased rapidly in the past decade, accounting for 33.99% of global aquatic plant cultivation in 2018. 5 Eucheumatoids are commercially cultivated for production of carrageenans, polysaccharides widely used in the pharmaceutical, cosmetic and food industries.Much of this cultivation occurs in South-East Asia, particularly
Foliose Halymenia species (Halymeniaceae, Rhodophyta) from Southeast Asia, including a new species, Halymenia malaysiana sp. nov. Abstract: Despite the large number of species discovered in Halymenia, many remain poorly known due to the scarce information available. In order to facilitate species discrimination of foliose Halymenia species in Southeast Asia, molecular analysis and morphological studies were made on Halymenia collections from Malaysia, the Philippines, and Indonesia. The rbcL phylogenetic analyses showed that there are at least six taxa of foliose Halymenia occurring in Southeast Asia. Among the six taxa, a new species, Halymenia malaysiana P.-L. Tan, P.-E. Lim, S.-M. Lin et S.-M.Phang, is proposed based on both rbcL sequence analyses and morphological observations. Halymenia malaysiana is characterized by thalli possessing oblong or suborbiculate blades with a supple cartilaginous structure and gelatinous (slimy) texture, arising from a small discoid holdfast without a stipe, abruptly expanding into a broad blade and having a smooth surface with sinusoidally undulated margins. The phylogenetic analyses also revealed that Halymenia is a polyphyletic genus, which requires further taxonomic studies.
Studies have shown that cultivars of the carrageenophytes Kappaphycus and Eucheuma are clones of a limited number of strains originally domesticated from wild populations. For the development and selection of new cultivars, it is important that a comprehensive record of available variants exists. This study was conducted to provide up-to-date analysis and compilation of the current state of cultivars as the last list of cultivars was compiled nearly a decade ago. The present study analyzed the cox2–3 spacer and cox1 (1356 bp) genetic diversity of cultivars collected from 2019 to 2020 from the east coast of Sabah where the seaweed farms are concentrated. These data were compared with cultivars reported from 2010 to 2012 to assess changes, if any, to the gene pool of farmed eucheumatoid in Malaysia. Kappaphycus alvarezii, K. striatus, and K. malesianus are currently cultivated while Eucheuma denticulatum is no longer an important cultivar compared to a decade ago, probably due to its lower price. Analysis of the cox2–3 spacer revealed a new haplotype, LBT10, and, by including published GenBank data, a further four previously unnamed haplotypes were recognized from Sabah. This study confirms that there is a limited gene pool within cultivars in Malaysia and suggests the need for new or genetically diverse cultivars which can adapt to a changing environment, to ensure a more sustainable carrageenan industry.
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