Selection of a high-temperature resistant strain of Porphyra haitanensis (Rhodophyta)

In this paper,it was verified that the improved strain(YZ-3) of Porphyra haitanensis Chang et Zheng obtained previously in the lab is a high-temperature resistant strain.When the conchospores of the YZ-3 strains and the wild-type strain (WT) were cultured at 28 ℃ and 29 ℃,the survival rate of conchospores was 73.2% and 52.6% for YZ-3 strain,but 10.3 and 4.6% for WT strain,respectively.The division rate of conchospores at 28 ℃ and 29 ℃ was 100 and 82.8% for YZ-3 strain,and 89.7% and(65.9%) for WT strain,respectively.Both survival and division rates of conchospores of YZ-3 strain were significantly higher than those of WT strain either in culture at 28 ℃ and 29 ℃.When the conchospore germlings of YZ-3 and WT strains which have been cultured at 24 ℃ for 35 days were cultured at 24 ℃,28 ℃ and 29 ℃ for 25 days,the mean length of blades increased 33.6,23 and 15 times for YZ-3 strain,and only 7.7,1.4 and 0.9 times for WT strain compared with the original mean length,respectively.When the blades cultured at 24 ℃,28 ℃ and 29 ℃,the mean length of the blades of YZ-3 strain was 3.8,8.8 and 7.4 times as WT strain,respectively.When the blades were cultured at 28 ℃ and 29 ℃,the blades of WT strain began to decay after cultured for 15 days,however,the blades of YZ-3 strain did not decay even being cultured for 25 days.These results indicated that YZ-3 strain is strongly resistant to high temperature(28 ℃ and 29 ℃).