Isolation and characterization of a heat‐resistant strain derived from interspecific crosses between Pyropia haitanensis and ( P. haitanensis × Pyropia radi )

SUMMARY Pyropia haitanensis is a vital economically cultivated seaweed in China. However, the frequent occurrence of extreme high‐temperature events has posed a severe threat to its industrial sustainability. To develop new heat‐resistant strains of Pyropia , this study conducted a crossing experiment using genetically distinct parental strains. The female parent was the mutant strain ( SH‐3 ) of P. haitanensis . The male parent ( HR‐6 ) was an interspecific hybrid between P. haitanensis and Pyropia radi . From the F 1 blades derived from heterozygous conchocelis, a heat‐resistant strain named Ph‐c‐2 was successfully isolated. When conchospores of the three strains were subjected to high‐temperature culture at 30°C for 14 days, the survival rate of Ph‐c‐2 conchospore germlings reached 46.1%, which was 1.2‐fold and 3.1‐fold that of SH‐3 and HR‐6 , respectively. After being cultured for 30 days at a suitable temperature (25°C), the mean length of Ph‐c‐2 blades was 22.0 cm, comparable to HR‐6 but 3.1‐fold longer than SH‐3 . At 60 days of culture, Ph‐c‐2 blades exhibited a mean length of 184.3 cm, which was 1.4‐fold and 2.8‐fold longer than SH‐3 and HR‐6 , respectively. The contents of pigments and pigment proteins in 45‐day‐old blades of Ph‐c‐2 were significantly higher than those in both parental strains. When blades cultured at 25°C for 30 days were further cultured at 30°C for 30 days, HR‐6 blades showed massive cell death, chromatophore morphology shifting from star‐shaped to diffused, and growth stopped. In contrast, SH‐3 and Ph‐c‐2 blades exhibited extremely few dead cells and maintained relatively rapid growth rates. In summary, compared with the two parental strains, the hybrid recombinant strain ( Ph‐c‐2 ) showed greater advantages in terms of growth rate, pigment protein content, and heat resistance of conchospores and young blades, etc. It is expected to be cultivated into a new variety for production applications.