Application of oligoagars as elicitors for field aquaculture of Pyropia haitanensis

Oligosaccharides can elicit a defense-related response in marine algae or seaweeds. This study aimed to investigate the possible application of oligosaccharides as biological elicitors for algal farming by measuring their antirotting effects on Pyropia haitanensis. The concentration of oligoagars and the time of treatment were optimized by examining their effects on the percentage of rotting in thalli. Oxidative burst and expression of defense-related genes were examined. The optimized conditions obtained were then applied in an aquaculture setting for P. haitanensis. Elicitation with oligoagars at 100 mu g mL(-1) for 2 h produced the optimal rot resistance effect, and oligoagars delayed the severe rotting of thalli by more than 13 days. Oligoagars elicited rapid respiration in thalli. The expression levels of Phrboh and Phhsp70 genes were up-regulated whereas Phsod was down-regulated. During aquaculture, treatment with oligoagars when thalli were 30 days old and when conchospores adhered to nets improved growth, increased yield of products, and delayed the maturation of thalli. However, treatment when conchospores adhered to nets had better results and was more convenient and practical. Overall, we found that oligoagars have potential applications as elicitors for biological farming and can be applied in the aquaculture of P. haitanensis with promising results.