Contrasting response of <i>Gracilaria chilensis</i> (Gracilariales, Rhodophyta) life cycle stages to epiphyte infection
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Date
2023
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Abstract
The red seaweed Gracilaria chilensis, a species extensively cultivated in Chile for agar extraction, was subjected to a bioassay to determine the susceptibility of tetrasporophytes, female and male gametophytes collected from natural and cultivated populations, to the red epiphyte Acrochaetium sp. and the brown epiphyte Ectocarpus sp. The settlement, attachment and germination of epiphytic algal spores on G. chilensis thalli were evaluated, and the photosynthetic responses and the concentration of total phenolic compounds were determined as a possible response of G. chilensis to biotic stress. The results showed that when the thalli were exposed to Acrochaetium infection, female individuals had a significantly lower percentage of germinated spores than other phases of the life cycle. After infection with Ectocarpus spores, males showed the highest % germination of the epiphyte. For both epiphytes, the response of tetrasporophytes from natural and cultivated populations shows a similar trend. The total content of phenolic compounds showed that, in general, the individuals infected with Acrochaetium had a higher defense capacity, whereas the infection with the brown alga did not induce a significant release of phenolic compounds. Despite the heterogeneous results observed for photosynthetic activity, a higher photoinhibition of the maximum fluorescence quantum yield (F-v/F-m) was observed in thalli with the Acrochaetium epiphyte, confirming that G. chilensis was subjected to stress after infection. Taken together, these observations may suggest that the cultivation of females could be of long-term benefit to farms by reducing biomass losses under stressful conditions and epiphyte invasions on farms.
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Epiphytes, Gracilariales, Rhodophyta, Life cycle, Photosynthetic activity, Phenolic compounds