Reproductive Biology and Novel Cultivar Development of the Eucheumatoid Kappaphycus alvarezii

Kappaphycus species are globally cultivated in tropical waters as a major source of k-carrageenan. Since the early 1970s, Kappaphycus farming, through clonal propagation, has been confined to a few good-quality commercial strains of unknown ploidy and/or life history phase. After five decades of successful cultivation, the productivity of Kappaphycus spp. has continually declined. This has been attributed to low genetic variability, making the >50-year-old cultivars more susceptible to environmental stressors, pests, and diseases. Hence, the establishment of new cultivars with unique genetic makeup and corresponding desirable traits can provide alternative seedstocks from the currently cultivated strains. Cultivar development includes the collection of wild individuals, both vegetative and reproductive materials, for culture collection and biobanking, spore release and cultivation, selection, and breeding. Moreover, the distinction of specific life history phases, sex, and ploidy among the established cultivars can be tested for specific traits, such as vigor and fitness, productivity, and biochemistry. This initiative can avoid repeated crop failure associated with old and fatigued strains and conduct targeted farming of specific cultivars with corresponding known traits. Understanding their ecological tolerance to different abiotic factors can also mitigate risks in seaweed farming in relation to climate change. Continuous cultivar development is necessary for future crop domestication and improvement programs to sustain the livelihoods of thousands of small-scale farmers and the multi-million-dollar seaweed industry.