Genetic diversity in Opuntia spp. cultivated for forage production

Abstract

Opuntia genus belongs to the Cactaceae and includes a range of species from 75 to 250
originated from the Americas. Several Opuntia species represent useful sources of forage in
many arid areas, and their cultivation is drastically increasing. However the taxonomic
classification of these species is complicated by the lack of reliable morphological descriptors,
the relevant phenotypic plasticity, and the frequency of natural hybridization and of polyploidy.
In this study 31 genotypes selected for forage production including Opuntia ficus-indica and
some related species were analyzed using SSR markers to establish their genetic variability
and to elucidate phylogenetic relationships among cultivated genotypes and related species.
The analysis of six loci allowed to univocally identify most of the accessions and confirmed the
fact that their taxonomical classification is not congruent with the observed patterns of genetic
diversity. Most of the accessions selected for forage production were grouped exhibiting a
narrow genetic variation level and clustered separately from two reference O. ficus-indica
genotypes, used for fruit production in Mediterranean area. NeighbourNet analysis displayed a
low level of diversification among the forage Opuntia from Brazil suggesting they probably have
common ancestors. This information will be useful to plan future breeding strategies aimed at
the selection of improved genotypes to be cultivated in different areas.