Body color selection of domesticated carp (Cyprinus carpio) in traditional agricultural systems: Insight provided by growth performance, nutritional quality, and genetic diversity

Abstract

The body color retention of domesticated organisms in traditional agricultural systems results from long-term natural selection and human intervention, which usually encompasses the local understanding and management experience of the species. Exploiting the body color trait advantage and genetic potential of domesticated animals will help to select breeding stock, improve farmers' economic income, and provide insight into future sustainable agriculture design to utilize locally appropriate populations. In this study, the rice-fish coculture system, a Global Important Agriculture Heritage System (GIAHS) in Qingtian County, Zhejiang Province, China, was selected as the representative research system. Four body color (red, red-black, bronze and cyan) of the indigenous species Qingtian paddy field carp (Cyprinus carpio) were selected to compare the economic trait advantages such as the growth performance, nutritional quality of the fish, and the rice yield cocultured with the carp. Besides, the genetic resources and population structure of different body colors were also examined through mitochondrial D-loop gene. Our results show that there are two subgroups of the four populations (K = 2). Among them, the bronze-colored group occupied one subgroup with a large number of unique haplotypes, showing great genetic differentiation from other body color groups. The red and the red-black-colored groups have higher genetic diversity and more frequent gene flow between each other. The genetic diversity of the cyan and the bronze-colored groups were relatively low with more regionally restricted. Three economic indexes showed that the nutritive values of the carps with the four body colors were relatively similar and had no effect on rice yield under the same feeding conditions. Among them, the red-black-colored group had the best specific growth rate (SGR, P < 0.01), weight gain rate (WGR, P < 0.01) and linoleic acid content (P < 0.05). The cyan-colored group had the lowest WGR and SGR, but had the strongest paddy field survival ability (P < 0.01). In summary, the red-black-colored group are rich in genetic diversity and have the best breeding potential and environmental adaptability, which is the most suitable body color for paddy field cultivation.