Seaweed aquaculture is rapidly expanding, yet the reliable supply of high-quality seedstock remains a key bottleneck. Germplasm banks of kelp species, based on the long-term maintenance of gametophytes, represent a promising solution by decoupling seedstock availability from seasonal reproduction. However, their success depends on understanding how intrinsic (genetic origin, sex) and extrinsic (temperature) drivers interact to shape gametophyte performance under culture conditions. Here, we evaluated the specific growth rate (% day -1 ) and health status (%) of Macrocystis pyrifera gametophytes isolated from nine populations nested within three genetic clusters along the Chilean coast, and cultured under four temperatures (9º, 12º, 15º, and 18 °C) for four months, after more than one year of storage in a germplasm bank. Generalized linear mixed models revealed strong interactions between genetic clusters, sex, population, and temperature. Southern populations displayed higher specific growth rates at cooler conditions, consistent with local adaptation to cold environments, whereas northern females showed reduced growth at 12º and 18ºC, but performed better at 9º and 15ºC. Across treatments, males generally exhibited faster growth at intermediate to warm temperatures, while females remained healthier under stress. These results highlight that genetic background and sex jointly determine culture performance, and that their effects are modulated by temperature. From an applied perspective, our findings underscore the need to incorporate both biological and environmental variation into germplasm banking strategies. Maintaining genetic and sexual diversity and aligning culture conditions with population-specific optima will improve the reliability of kelp seedstock production. By linking experimental performance data with applied biobanking practices, this study provides a framework to strengthen selective breeding programs and enhance the sustainability of kelp aquaculture under climate change.
Camus et al. (Mon,) studied this question.