Abstract:In this paper, a crossing-experiment between Pyropia radi from India and Pyropia haitanenesis from China was done for breeding of improved strains with obvious hybrid recombinant advantages.The male parent was the wild-type strain(Pr-WT01)of P.radi, which was characterized by thick blade, slow growing, good toughness and high production of conchospores, and the female parent was the mutation strain(Ph-HMC5)of P.haitanensis, which was characterized by thin blade, fast growing, poor toughness and low production of conchospores.At first, four improved strains with obvious hybrid recombinant advantages were obtained from the F1 color-sectored blades, and finally the most improved strain(HR-6)was selected from them.The maximum of absolute growth rate of the male and female parents were 0.39 and 5.24 cm/d, respectively, while that of HR-6 strain was 9.27 cm/d and its absolute growth rate was greater than the maximum growth rate of the female parent during 30-50 days in culture.After 60 days in culture, the mean length of F1 blades of the male and female parents were 13.18 cm and 85.67 cm, respectively, while that of HR-6 strain was 218.57 cm which was 2.55 times that of the female parent and 16.58 times that of the male parent, respectively.The contents of Chl.a in the 35-day-old blades of HR-6 strain was 9.43 mg/g, increasing by 50% and 20% in contrast with that of the male parent and the female parent, respectively.The content of phycobiliprotein of HR-6 strain was 99.62 mg/g, which was 1.74 times that of the female parent and 2.18 times that of the male parent, respectively.The mean thickness of the 35-day-old blades of HR-6 strain was 26.22 μm, decreasing by 37% in contrast with that of the male parent and increasing by 30% in contrast with that of the female parent, and the toughness of the F1 blades of HR-6 strain increased significantly.The total number of conchospores released from HR-6 strain was 167.72×104, which was 2.65 times that of the female parent and 1.13 times that of the male parent, respectively.The above results confirmed that HR-6 was characterized by fast growth, high quality, large amount of conchospores, having excellent production applicability.