Genetic and environmental influence on triploid Crassostrea virginica grown in Chesapeake Bay: Growth

Abstract

Aquaculture of triploid Crassostreavirginica in the Chesapeake Bay, USA is popular with the majority of growers raising mostly triploids. This choice stems from improved growth and survival relative to diploids. Triploids are made commercially by crossing tetraploid males and diploid females, thus either or both parent could influence the performance of the triploid. We examined the influence of the female (diploid) parent in an experiment comparing nine diploid (2n×2n) and nine triploid (4n×2n) crosses across three environments. The diploid genotypes consisted of wild populations and selectively bred lines and the environments ranged from low salinity with no disease pressure to higher salinity with consistent disease pressure. Growth metrics (shell height and wet tissue weight) are reported. In the low salinity environment, triploidy seemed disadvantageous for any genotype at least when gauged by final tissue weight. In moderate salinity with low disease pressure, selectively bred diploids performed equivalently to their triploid counterparts showing that breeding efforts can improve diploid field performance to rival triploids. In high salinity with constant disease pressure, triploids offered the greatest advantage for growth. Genotype×environmental response of triploids indicates that breeders may have to tailor crosses to suit particular areas interested in using triploids. Statement of relevanceWe address factors of commercial triploid oyster performance.