Date: 08 Jun 2011

Vasconcellea

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Abstract

Vasconcellea, comprising 21 species, is the largest genus of the Caricaceae, best known for the monotypic genus Carica, including papaya (C. papaya), one of the most important tropical fruit crops. It is distributed from Mexico to Chile, with the center of diversity in Ecuador and Colombia. Because of their preference for higher altitudes, most Vasconcellea species are referred to as highland or mountain papayas. Currently, five of them are threatened and red-listed and four are not found in protected areas, while none of them are currently present in seed collections, raising questions on their conservation and urging for rapid action. Some Vasconcellea species have potential as novel tropical fruits, particularly V. × heilbornii, V. cundinamarcensis, and V. goudotiana, which are being used for a growing (niche) market for new exotic products. As a source of papain, several Vasconcellea species show proteolytic activity up to 17 times as high as that of papaya. Others are being used as a source of new genes for papaya breeding, particularly for disease resistance (especially against papaya ringspot virus), cold tolerance, and specific organoleptic traits. Optimal use of Vasconcellea genetic resources requires a better understanding of its genetic potential, as well as the development of technologies to create intergeneric hybrids with papaya, as conventional breeding faces significant barriers. Cytogenetic and molecular studies, based on AFLP, PCR-RFLP, and SRR analysis, have allowed a better understanding of the evolution of the main Vasconcellea species, indicating complex hybridization and introgression processes among multiple species, which contrasts with the straightforward domestication of the common papaya. Genomic research in Vasconcellea has been limited to the sequencing of some gene fragments and the development of BAC libraries for a few species. Recent progress on papaya genomics, the development of a high-density genetic map, and the sequencing of the genome will help in the identification of genes of interest in Vasconcellea, either for papaya breeding or for the development of Vasconcellea species as new crops.