Helichrysum (family Asteraceae) is a large, heterogeneous and polyphyletic genus. Most of the Helichrysum species have ornamental and medicinal values. Helicrysum leucocephalum Boiss., has wide geographical distribution in Iran and forms several local populations. The present investigation was performed to study inter populations , genetic, cytogenetic and morphological diversity of this medicinal species. The AMOVA test showed significant genetic difference among the studied populations but the Mantel test did not show correlation between the genetic distance and geographical distance of these populations. STRUCTURE and reticulation analyses showed some degree of genetic admixture and gene exchange among the studied populations. These populations had different chromosome numbers and also differed significantly in the size of their chromosomes.
Morphological characteristics as well as inter-simple sequence repeats (ISSR) molecular markers were used to study the species relationship in Onosma species (Boraginaceae) in Iran. Principal component analysis (PCA) showed that morphological characters like caule leaf size and shape, bract shape, corolla shape, nutlet length, venation and corolla teeth size and anther length are the most variable morphological characters among Onosma species studied. Out of 17 ISSR primers used, 6 primers produced 41 polymorphic and reproducible bands. Few specific ISSR bands were obtained for the species studied which show genetic material change during species diversification. Such bands may be used in the species identification too. Morphological and molecular trees obtained partly agreed with each other. In both trees, Onosma dasytrichum and Onosma microcarpum are placed close to each other, Onosma procerum and Onosma pachypodum show affinity to each other and Onosma araraticum, Onosma bodeanum, Onosma bistonensis, Onosma stenosiphon and Onosma bulbotrichum are placed close to each other while, Onosma rostellatum stands far from the other species. The combined morphological and ISSR tree obtained separated the members of three sections of Onosma, Podnosma and Protonosma from each other. Moreover, almost a good separation of different subsections in the section Onosma was observed in the combined tree.
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