Germplasm variation among wild populations of the southernmost highland papayas (Vasconcellea quercifolia and V. glandulosa): implications for conservation

Abstract Species of Vasconcellea are promising for the agricultural industry as a source of genes for papaya improvement because many of them have edible fruits with favorable organoleptic properties. Vasconcellea quercifolia and V. glandulosa are the southernmost species and have recently been categorized as species of high conservation priority in Argentina. Although seeds of both species can be stored in genebanks, no specific studies have been conducted on their germplasm variation, which is a key aspect to designing a conservation strategy. In this work, we assess morphological, physiological, and biochemical variability at the species and population levels and propose a conservation strategy. In four wild populations of each species located at different elevations in northwest Argentina, vegetative and reproductive material was collected from 110 individuals of V. glandulosa and 70 of V. quercifolia. Twenty-seven morphological, two biochemical and four physiological descriptors were determined to characterize each species. Then, variance decomposition, differences between populations (with ANOVA) and a principal component analysis were performed using morphological quantitative fruit and seed data, to assess variability between populations. Although both species showed a wide range of phenotypic variability, it was higher in V. quercifolia than in V. glandulosa and within each population than between them. Leaves, female flowers and physiological descriptors were the most variable, while seed morphological descriptors were the least variable. Variance analysis revealed differences between populations in the majority of morphological descriptors. We recommend collecting germplasm from the entire natural distribution range of each species and from many individuals in each population.