Morphological and genetic analyses of the current major cultivars of Undaria pinnatifida at Lvshun, Dalian, the principal farming region in North China

Close to 66% of the annual national production of the brown alga Undaria pinnatifida, about 115 thousand tonnes (fresh weight), is produced through farming in Liaoning Province in north China. To clarify the agronomic characters and genetic differences of currently farmed U. pinnatifida, we investigated three major farmed cultivars in combination with other traditional ones focusing specially on sporophylls, one of the principal end products in a typical farm at Lvshun, Dalian city. Results showed that these cultivars differ in timing of maturation and are arranged to be harvested in sequence in the farm to diversify the periods of harvesting and processing. Sporophyll fresh weight and the stipe width are positively correlated with the growth of the plant. Ten neutral microsatellite markers were used to assess relationships among major farmed cultivars. Both genetic distance and Bayesian model-based analyses showed that there was genetic differentiation among C1, C2, and other traditional cultivars. C3 showed the highest genetic variations in major farmed cultivars, with three private alleles and a mean expected heterozygosity of 0.817. In general, prominent genetic divergences were found among different cultivars confirming the effect of consecutive selection, while weak relationships were observed between sporophyll forms and genotypes.