Genetic diversity and relationships among Nopalea sp. and Opuntia spp. accessions revealed by RAPD, ISSR and ITS molecular markers

Background: Dactylopius opuntiae (Cockerell) (carmine cochineal) is an insect pest highly noxious that has spread through cactus pear crops in the Brazilian semiarid region. Knowledge of diversity and genetic relationships of the cactus pear accessions is fundamental to create new varieties resistance to carmine cochineal. Therefore, this investigation was undertaken to assess the genetic diversity and genetic relationships that existed among cactus pear accessions of Nopalea sp. and Opuntia spp. with contrasting resistance to D. opuntiae.

Methods and results: We conducted a molecular analysis in seven cactus pear accessions from the "reference collection" of the Agronomic Institute of Pernambuco, Brazil using RAPD, ISSR and ITS molecular markers. A total of 242 bands were detected from 26 polymorphic primers. The high percentage of polymorphism by RAPD (89.8%), ISSR (81.2%) and ITS (75%) markers suggests that the cactus pear accessions have high genetic diversity. The combined analysis of markers systems enabled the accessions discrimination of about the genus and ploidy, but were incongruous in relation to resistance level to D. opuntiae.

Conclusions: Genetic diversity, discrimination of about the genus and ploidy was confirmed by merging information from ISSR, RAPD and ITS markers systems. The IPA-200016, IPA-200149, IPA-100004, IPA-200205 accessions are genetically divergent, therefore could be potentially incorporated into any further breeding programs directed to create new varieties of cactus pear resistant to D. opuntiae.