Taura syndrome virus resistance in pacific white shrimp, penaeus (litopenaeus) vannamei : estimation of genetic parameters relevent to selective breeding

Date
2013-08
Authors
Moss, Dustin Robert
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Publisher
[Honolulu] : [University of Hawaii at Manoa], [August 2013]
Abstract
Taura syndrome virus (TSV) is an economically important pathogen of Pacific white shrimp, Penaeus (Litopenaeus) vannamei. TSV is highly virulent and TSV-associated mortalities in unselected, naïve populations of P. vannamei range from 40-95%. TSV-associated crops losses are estimated to be >$1 billion USD. Selective breeding of P. vannamei for TSV resistance began in the mid-1990s and several breeding programs have developed lines of shrimp which exhibit varying degrees of TSV resistance. Despite long-standing breeding efforts, several important aspects of TSV resistance have yet to be properly studied. In this dissertation, I conducted four studies to address key knowledge gaps in breeding P. vannamei for TSV resistance. The first study investigated the effects of inbreeding on TSV resistance. Inbreeding was found to have moderate to severe effects on TSV survival and the effects of inbreeding appeared worsen as environmental quality decreased. The second study focused on the estimation of genetic correlations for shrimp survival to a genetically, diverse suite of TSV isolates and the estimation of genetic correlations between TSV survival and growout performance traits. Genetic correlations for shrimp survival among TSV isolates were generally high, suggesting that breeding for resistance to a single TSV isolate should result in increased resistance to other tested isolates. Genetic correlations among TSV survival and growout performance traits were generally low and suggest that there are no major impediments to simultaneous genetic improvement of these traits. The objective of the third study was to estimate correlations and heritability for TSV survival in two size-classes (2.5 g and 8.0 g) of shrimp. Heritabilities were similar between size-classes and genetic and phenotypic correlations were high. These results show that the common practice of challenging small juveniles (1-3 g) to TSV and using this data to select for TSV resistance is likely effective in improving farm survival during TSV epizootics. The final study investigated the effects of viral load on TSV survival. Survivors were found to generally have lower viral loads compared to moribund shrimp. This finding suggests that immune mechanism(s) that suppress viral load are important to a shrimp's ability to survive TSV infection. iv
Description
Ph.D. University of Hawaii at Manoa 2013.
Includes bibliographical references.
Keywords
shrimp
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