In recent decades, wild stocks of eastern oyster Crassostrea virginica have suffered major declines across most of the species’ range including in the Gulf of Mexico, the largest producing region in the US. In 2019, the SALT consortium initiated a breeding program to support the developing industry in the Gulf of Mexico with oysters bred for improved performance in different salinity environments. The program is evaluating the effectiveness of a family selection approach where families are mixed at fertilization and reared communally until phenotyping. The research team works in collaboration with a business advisory council to discuss objectives of the program and orient activities to meet the demand of the industry.
The first generation was produced by crossing 102 males and 102 females collected from 17 natural reefs across the northern Gulf of Mexico between San Antonio Bay (Texas), and Cedar Key (Florida). Founders were bred according to 51 non-overlapping 2 males x 2 females mini-factorial crosses to produce 204 families. Crosses were produced between August 31 and September 3 2020 by strip spawning and in vitro fertilization. Families produced on the same day were pooled after fertilization for larval culture. Eyed larvae from each group were harvested over a 4-day period and set separately set on microcultch to produce single-seed oysters. All groups were pooled for common garden culture on October 10 (38-41 days post fertilization). Random samples of the pool were deployed in April 2021 on 7 growout sites expected to experience different salinity conditions. Four of the sites were selected at the end of the growout period based on the salinity conditions recorded during the growing season. Oysters from these four sites were retrieved between mid-October and early November 2021. Most of the harvests were frozen until measurements (shell height, length, width, and scoring of back-bend deformity) and tissue sampling for genotyping and parentage assignment. A sub-sample (600 specimens per site) was kept alive as candidate broodstock for the second generation. The candidate oysters were individually tagged with Passive Integrated Transponders (PIT-Tags) and a non-lethal biopsy was taken for genotyping. Parents and all offspring are being genotyped at 192 Single Nucleotide Polymorphism markers. Pedigrees will be reconstructed using a likelihood ratio approach. The dataset will be used to estimate genetic parameters for growth and conformation traits for each salinity environment, genetic correlation across environments, and breeding values of candidate broodstock. Future development of the program including assessment of additional traits and incorporation of genomic information will be discussed.