GENETIC IMPROVEMENT PRACTICES ON SMALL ABALONE Haliotis diversicolor TO ENHANCE SURVIVAL AND GROWTH IN SOUTHERN CHINA  

China is the most important abalone producing countries, while the abalone cultured production reached to 110,380 tons in 2013, which covered more than 80% of the whole production in the world. Genetic improvement plays an important place in the development of abalone industry in the past decade. Small abalone (H. diversicolor) is commercially important species cultured along the coast of Southern China. Genetic breeding project has been conducted since 2003. Different geographical population were collected or introduced to establish the abundant germplasm banks, and genetic background were analysed by molecular markers. Then pedigree based inbred lines were built and divergent selection were conducted for several generations. In the other way, complete diallel cross were conducted among intraspecies abalone. At last, intraspecies hybridization between two inbred lines of small abalone, which originated from Japan population and Taiwan population, showed exciting heterosis on disease-resistant ability "Dongyou I" small abalone was conferred for "new species certificate" by Ministry of Agriculture and now are large-scale cultured in China.  

"Dongyou I " was backcrossed with Japan and Taiwan population, respectively. Growth and survival for reciprocal backcross progenies were significantly different. Japan population was then selected as recurrent parents for grading cross with Taiwan population. Survival rate of F3 (83.4%) progenies were higher than that of F2 (77.6%) and F1 (71.4%) at grow-out stage. Genetic variation for backcross progenies from different populations were also studied by microsatellite markers.

Studying on the growth-related genes, analyzing the expression patterns of these genes and identification of growth traits-associated SNPs would benefit our understanding in the molecular mechanisms underlying growth traits, and also provide useful information for breeding fast growth abalone new variety. Three growth-related candidate genes were cloned and function of the 3 genes were studied by real-time qRT-PCR and the whole mount in situ hybridization. The single nucleotide polymorphisms (SNPs) in the 3 genes were screened through high-throughput sequencing and genotyped. The association of these SNPs with growth traits and gene expression levels were analyzed. This study will provide important information to our understanding of marker-assisted selection breeding in H. diversicolor.