Preliminary study on genetic diversity of endemic and threatened species of Petunia (Solanaceae)

Abstract

Rare and narrowly endemic species are more vulnerable to extinction due to their restricted geographical distribution. the genus Petunia has 14 species and most of them are endemic to a restricted area. Four Petunia species that grow in Southern Brazil were studied: P. bonjardinensis, P. reitzii, P. integrifolia subsp. depauperata, and P. exserta. We presented a preliminary study on the genetic diversity of five populations of Petunia, using allozyme markers. For the genetic analyses, allozyme electrophoresis was carried out and eight enzyme systems were reliably scored. Standard measures of allozyme diversity were calculated. The highest genetic diversity and the highest fixation index was found in the two studied populations of P. bonjardinensis (P = 90, Â_p= 2.2 and 1.9, Ĥ_e= 0.33 and 0.30, F = 0.31 and 0.27); this species occurs in small isolated patches, that may restrict gene flow among populations. Petunia reitzii showed the second highest genetic diversity values (P = 78, Â_p= 1.78, Ĥ_e= 0.28), and Petunia integrifolia subsp. depauperata showed moderate values (P = 40, Â_p= 1.4 and Ĥ_e= 0.11). Petunia exserta did not show any polymorphic locus. Our results show the urgency of preserving the studied population of P. exserta that did not show any allozyme variation and occurs in a very particular and threatened habitat.