Growth Performance and Pathological Responses of Tissue Culture and Local Kappaphycus alvarezii Seedlings in Marine Waters of Punti Village, Bima Bay, Indonesia

Kappaphycus alvarezii is an economically important carrageenan-producing red alga, and tissue culture has been promoted as a means of improving seedling quality and field growth performance in Indonesian seaweed farming; however, field-based evidence comparing tissue-culture and conventional (local) seedlings under commercial cultivation conditions remains limited. This study therefore compared the growth performance and disease susceptibility of tissue-culture-derived and local Kappaphycus alvarezii seedlings cultivated using the longline method in the marine waters of Punti Village, Bima Bay, West Nusa Tenggara, Indonesia, over a 45-day period. Environmental conditions remained stable and within the tolerance range reported for the species, with temperature ranging from 27–30°C, salinity from 31–33 ppt, and pH from 7.5–8.1. Tissue-culture seedlings recorded a numerically higher biomass increase (70.1%) and specific growth rate (1.18% day⁻¹) than local seedlings (68.6% and 1.17% day⁻¹, respectively); however, independent-samples t-tests showed no statistically significant difference between the two seedling types (p > 0.05). In contrast, the seedling types differed markedly in disease response: tissue-culture seedlings exhibited pronounced susceptibility to ice-ice disease, marked by thallus structural damage and characteristic white discoloration, whereas local seedlings retained comparatively higher disease resistance. These results indicate that, under field conditions, propagation method had little influence on short-term growth but a substantial influence on disease susceptibility, suggesting that seedling resilience—rather than growth rate alone—should guide cultivation strategy in ice-ice-prone waters such as Bima Bay.