Meng Lin

Ocean University of China

Abstract: Gracilaria lemaneiformis is a large algae in the genus Rhodophyta. It has a high growth rate under artificial culture conditions, and has good quality of agar, and is widely used, and it is a species for industrialization and high value development and utilization. With the continuous development of the cultivation industry of the longxucai, its high temperature resistance, growth rate and agar content still need to be improved, so as to expand its cultivation area and extend the cultivation time, and further improve the product yield and quality. Therefore, the basic research on genetic improvement of the existing varieties of longxucai has very important theoretical and practical significance, so as to select new varieties with more application value.

In this experiment, the breeding method of combining nitroguanidine mutation with hydroxyproline resistant screening was applied to the genetic breeding of longxucai. The breeding effect of 60co- γ ray and high temperature screening was also discussed.

Through the observation and breeding of the mutant algae strains, the aim is to select new strains of longiflower with excellent characters, and to explore the screening method of high temperature resistant strains suitable for longiflower, which provides experimental basis for further selection of high yield and anti-counterfeiting strains of important economic seaweed longiflower.

The results show that:

(1) The results showed that the mutant strain 07-2 had more branches, uniform color and rapid growth after 30mg/l MNNG was used to mutate for 30min, and then the second screening was conducted under the stress pressure of 2mmol/l hydroxyproline. But the breeding method combining 60co- γ ray and high temperature screening did not screen out the mutant algae with growth advantage.

(2) The new line 07-2 was superior in growth rate, and the growth speed on line was 17% higher than 981, about 50% in diameter, 36% in branch number, and higher than 981 in a-galactosidase activity.

(3) The heat resistance of the spinach was determined by survival rate, growth volume, membrane permeability and antioxidant enzyme activity. From these indexes, the new strain 07-2 of the spinach was screened in this experiment had lower relative electrolyte exudation rate, MDA content, higher Pro content and antioxidant enzyme activity under heat stress. These indicators indirectly reflect that 07-2 has strong heat resistance.

(4) The results showed that the average daily growth rate of 07-2 was higher than 981 in the cultivation experiments of Nan'ao Island and Rongcheng, Shandong Province, and 143% of 981 after 42d. The agar characteristics of 2 strains were analyzed and compared. The results showed that the agar content and gel strength of 07-2 increased to 981 compared with that of gelatin, and the transparency of agar was higher. It shows that 07-2 has the advantages of fast growth rate and high quality of agar compared with 981.