Construction of a genetic linkage map in Pyropia yezoensis (Bangiales, Rhodophyta) and QTL analysis of several economic traits of blades

Pyropia yezoensis is an important economic seaweed, to construct a genetic linkage map and analyze the quantitative trait loci (QTLs) of blades, a doubled haploid (DH) population containing 148 DH strains established from the intraspecific hybridization between two strains with different colors was used in the present study and genotyped using 79 pairs of polymorphic sequence-related amplified polymorphism (SRAP) markers labeled with 5'-HEX and capillary electrophoresis. A chi-square test for significance of deviations from the expected ratio (1:1) on the loci which were polymorphic between parents and segregated in mapping population identified 301 loci with normal segregation (P ≥ 0.01) and 96 loci (24.18%) with low-level skewed segregation (0.001 ≤ P < 0.01). The map was constructed using JoinMap software after a total of 92 loci were assembled into three linkage groups. The map spanned 557.36 cM covering 93.71% of the estimated genome, with a mean interlocus space of 6.23 cM. Kolmogorov-Smirnov test (α=5%) of the marker positions along each LG showed a uniform distribution. After that, 10 QTLs associated with five economic traits of blades were detected, among which one QTL was for length, one for width, two for fresh weight, two for specific growth rate of length and four for specific growth rate of fresh weight. These QTLs could explain 2.29-7.87% of the trait variations, indicating that their effects were all minor. The results will serve as a framework for future marker-assisted breeding in P. yezoensis.