Gracilaria/Gracilariopsis lemaneiformis is the second largest cultivated alga in China, with economic valuerelated to agar production and bioremediation potential by eliminating eutrophication. It is important to establish a geneticbreeding system for Gracilaria/Gracilariopsis lemaneiformis (GL) to promote sustainable development of themariculture industry. In the present study, 3 productive characters of the F1 generation of GL gametophytes, includinglinear growth rate, branch number, and central base diameter, were analyzed and evaluated using the DTOPSIS comprehensiveevaluation method to convert qualitative comprehensive traits of F1 gametophytes to quantitative indicatorsof Ci value, which is necessary to determine an ideal solution to improve breeding. Thus, characters of all strains werecomprehensively analyzed and provided evidence for future cultivar hybridization and selection.

Among the 100 individuals tested, the linear growth rate ranged from 2.0%/d to 7.3%/d, with an average of4.76%/d (standard deviation, 1.28). Its variable coefficient was 26.79%, and that the difference among individuals wassignificant. Branch number was unevenly distributed with extremely substantial variation. The mean value was 1.93with a range from 1 to 5, standard deviation of 0.8, and variable coefficient of 41.17%; this was the most substantialvariation and a relatively large variation range. The average central base diameter was 1.8 mm, with a range from 1.4 mm to2.2 mm, and standard deviation of 0.18. Its variable coefficient, 9.87%, had the lowest variation range and least variancedifference among the three productive characters. All of the above three characters had normal distributions: Mostof the linear growth rates of F1 gametophytes distributed between 3.0%/d and 6.0%/d; 40% of individuals had 2branches after 28 days of culturing; and central base diameter mostly distributed between 1.6 mm and 2.1 mm. Standarddeviation analysis revealed large variation in the range of characters of the F1 generation of these gametophyte plants.Based on DTOPSIS comprehensive analysis, three productive characters of F1 generation gametophytes were comprehensivelyevaluated, and 100 strains were ranked based on their Ci value. The results showed that strains 20, 47, 93, 6,and 31 were superior to the others because they had higher Ci values, which indicates that they have a balance of advantageousgrowth rate, branch number, and central base diameter. These strains could be exploited for genetics-basedbreeding before they reach maturity. In addition, adjacent strains ranked by DTOPSIS analysis had similar Ci values,whereas strains at either extreme showed substantial difference, which was consistent with the normal distribution.

The large variation among F1 GL gametophytes of the three productive characters indicates that strains with substantialcharacter differences can be chosen as parents for hybridization to obtain improved varieties. DTOPSIS analysisintuitively measured comprehensive traits of F1 gametophytes, which provides a theoretical basis for subsequent researchon strain selection and further construction of a Gracilaria/Gracilariopsis lemaneiformis genetic breeding system.