Effects of domesticated-to-wild gene flow on the genetic structure and diversity of wild papaya (Carica papaya L.) in its Mesoamerican diversity area.

Abstract

Due to the increase in demand for food production worldwide, the cultivation of improved varieties is used as a strategy in order to maximize production. The improved Maradol papaya variety was introduced to the Yucatan Peninsula (YP), Mexico, the Mesoamerican diversity area of papaya, in the 1990s. The domesticated and wild papaya belong to the same species (Carica papaya L.), which promotes gene flow from crops to their wild relatives, threatening the genetic diversity of wild papaya populations in the region. In this study, we used a population genomic approach to evaluate the impact of domesticated-to-wild gene flow on the genetic structure and diversity of wild papaya in the YP. We used 2054 SNP markers for 227 wild individuals from 15 collection sites and 127 domesticated individuals from 13 Maradol papaya plantations. We found, (a) the presence of individuals that may be the result of a hybridization process between wild and domesticated papaya; (b) a higher genetic diversity in the wild group (H_E = 0.18) in comparison to the domesticated group (H_E = 0.09); and (c) low migration rates from domesticated to wild plants (m = 0.005). The domesticated-to-wild gene flow in C. papaya can have a negative effect on the genetic diversity and adaptive potential of wild populations from this region. The conservation of crop wild relatives should be a priority since they are part of various ecological processes and are considered natural reservoirs of genetic diversity for crops.