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 fruitsvariants: sweet fruits or prickly pears (tunas) and acidic fruits (xoconostles). The interretrotransposonamplified polymorphism (IRAP) technique was applied to evaluate geneticdiversity of Opuntia varieties and to differentiate xoconostle fruits from tunas. Five IRAPprimers previously described for other plant species and classified into three retrotransposonfamilies, namely Copia, Gypsy and TRIM, were analysed in 43 Opuntia varieties (eightxoconostles and 35 tunas). The five individual IRAP primers generated a total of 264fragments, where 64.8 % of them were polymorphics. The retrotransposon of the Gypsyfamily (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 (257fragments). 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 thexoconostle-producing varieties were grouped with other tunas, the PCoA analysis allowed abetter separation of all xoconostle varieties. These results suggest a potential role of thetransposable elements in genetic divergence within the Opuntia genus.