Potential role of transposable elements to differentiate tuna and xoconostle Opuntia varieties

Abstract

Opuntia, an important horticultural crop in Mexico, is cultivated mainly for its two fruits
variants: sweet fruits or prickly pears (tunas) and acidic fruits (xoconostles). The interretrotransposon
amplified polymorphism (IRAP) technique was applied to evaluate genetic
diversity of Opuntia varieties and to differentiate xoconostle fruits from tunas. Five IRAP
primers previously described for other plant species and classified into three retrotransposon
families, namely Copia, Gypsy and TRIM, were analysed in 43 Opuntia varieties (eight
xoconostles and 35 tunas). The five individual IRAP primers generated a total of 264
fragments, where 64.8 % of them were polymorphics. The retrotransposon of the Gypsy
family (60 fragments) was more represented than Copia (average of 52 fragments) or TRIM
(48 fragments) families. Moreover, the percentage of polymorphic fragments was higher (61.9
%) in xoconostles than in tunas (56.5 %). A larger number of total amplified fragments (262)
was found among tunas, compared to those amplified from xoconostle varieties (257
fragments). In contrast, a lower number of polymorphic bands were counted among tunas
(148) than among xoconostle varieties (159). Unlike the UPGMA analysis, where three of the
xoconostle-producing varieties were grouped with other tunas, the PCoA analysis allowed a
better separation of all xoconostle varieties. These results suggest a potential role of the
transposable elements in genetic divergence within the Opuntia genus.