Exploiting the untapped wild resources: Developing new diploid tetrasporophyte Kappaphycus alvarezii cultivars from sporelings of wild cystocarpic parental plants

Successive clonal propagation of commercially cultivated haplotypes of Kappaphycus alvarezii from a limited gene pool over decades has plausibly led to strain fatigue and loss of vigor. Henceforth, diversifying the genetic pool of cultivated K. alvarezii became imperative to reverse these trends, and reinvigorate the productivity of the seaweed farming industry. Here, we utilized the spores from wild cystocarpic K. alvarezii to develop new cultivars that may potentially exhibit resilience to various biotic and abiotic stressors. In this study, we investigated the physiological, and biochemical performances of selected next-generation tetrasporophytes from cystocarpic parental plants of K. alvareziiof novel haplotypes, here labeled [strain (haplotype)] as, TR-C5 (KALV-D4), TR-R3(KALV-D3), TR-S8(KALV-D6), cultivated in land-based and sea-based conditions, and compared their performance to the commercially cultivated Tambalang brown strain (commercially farmed haplotype KALV-A3). Growth among the novel strains cultivated in land-based nursery conditions did not significantly vary ranging from 4.19 % day⁻¹ to 5.78 % day⁻¹. However, significant growth variability among strains was observed when cultivated in sea-based conditions ranging from 0.85 % day⁻¹ to 4.47 % day⁻¹ during D30, and 3.18 % day⁻¹ to 5.26 % day⁻¹ by D60. Moreover, susceptibility to ice-ice disease syndrome showed to be strain-specific with TR-S8 demonstrating lesser susceptibility among the novel strains. Except for the total protein, the biochemistry significantly varied among strains and between different cultivation methods (land-based hatchery vs. in situ sea-based farming). Our results further support the importance of exploring the presence of a reservoir of unutilized wild genotypes that can be used in developing new cultivars with superior traits for future domestication.