Collaboration boosts South American breeding programs

Genetics study focused on developing more disease-resistant Pacu species
Colin Ley
March 29, 2019
By Colin Ley
Vito Mastrochirico (left, seated) and Ross Houston (center, standing) with the research team at Roslin Institute in Edinburgh, Scotland.
Vito Mastrochirico (left, seated) and Ross Houston (center, standing) with the research team at Roslin Institute in Edinburgh, Scotland.
Fish breeders in Brazil stand to benefit from a recent collaboration between the Aquaculture Centre of Sao Paulo State University and a genetics-based research group at Roslin Institute in Edinburgh, Scotland.  

Vito Mastrochirico Filho, a PhD student at the Aquaculture Centre, visited the Scottish capital in February last year to work with Roslin’s Professor of Aquaculture Genetics, Ross Houston, and his genetics group, with the aim of helping to develop a new set of breeding tools for use in the improvement of native fish species in Brazil.

 The key focus of the collaboration was Piaractus mesopotamicus, a Brazilian freshwater species which is popularly known in South America as ‘Pacu,’ a name best translated as ‘fast eater fish'.

 One of the most important freshwater species in the region, mainly because of its size, reaching up to 40 inches long and weighing up to 40 lbs., Pacu has become a victim of over-fishing in recent years. This has, in turn, prompted an increased requirement for aquaculture to supply animal protein to the population in a sustainable and profitable way, and to play a part in helping to restore species numbers.

Due to a lack of biological information relating to Pacu, coupled with little understanding of the species’ susceptibility to bacteria under stressful conditions and immunity factors when cultured in intensive production systems, farming Pacu has so far resulted in high mortality rates. This was largely due to bacterial diseases, such as aeromoniosis.  

Better genes
Almost as important as the mortality issue, the task of farming Pacu successfully also involved the marked use of antibiotics or bactericides, a requirement which it’s hoped the genetic improvement of the species can reduce.

 Filho’s time at Roslin was spent seeking to apply the genetics knowledge and expertise, already developed by Houston and his group, to the farming problems surrounding Pacu. A particular focus was on applying modern genomic tools to the species, especially as they relate to resistance against bacterial infections.

 These tools, which were already developed and well understood at Roslin, relate to how to acquire genomic knowledge about the immune system of an individual species and how to apply such immunity factors within future breeding programs.

To address the circumstances surrounding Pacu, in particular, the joint Brazil/Scotland study was designed to genetically characterize the species according to its resistance to the bacteria Aeromonas hydrophila.

This involved the characterization of immune system genes of both susceptible and resistant individuals which were challenged with A. hydrophila infection. Work was also done to identify regions of the Pacu’s genome associated with resistance to A. hydrophila, also known as QTL (Quantitative Trait Locus) analysis.

This was the context in which Filho worked with Roslin’s Dr. Carolina Peñaloza, Dr. Diego Robledo and Dr. Alejandro Gutierrez, seeking to generate a genomic profile of the host response to A. hydrophila infection in Pacu. The ultimate aim was to establish genetic markers for use in the development of future breeding programs which specifically tackle disease issues surrounding the species.

This was the first research of its type to be performed on a Brazilian native fish species and, as such, could become the cornerstone for the development of genomic resources for other South American species, potentially leading to the integration of genomic tools to improve selective breeding across Brazilian aquaculture.

“The accomplishment of our analyses will generate results that can be applied in the development of Brazilian native species production,” said Filho. “This is particularly the case in issues related to fish mortality in aquaculture.”

Houston was similarly positive, adding that the collaboration has helped Roslin's genetics group to develop a set of genomic tools and techniques that could potentially be used to study the genetics of new aquaculture species.

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