Abstract
The holoparasitic broomrapes, Orobanche spp. and Phelipanche spp. (Orobanchaceae), are root parasites that completely depend on a host plant for survival and reproduction. There is considerable controversy on the taxonomy of this biologically and agronomically important family. Flowers of over 25 parasitic Orobanchaceae and a number of close, parasitic and non-parasitic, relatives emitted a complex blend of volatile organic compounds (VOCs), consisting of over 130 VOCs per species. Floral VOC blend-based phylogeny supported the known taxonomy in internal taxonomic grouping of genus and eliminated the uncertainty in some taxonomical groups. Moreover, phylogenetic analysis suggested separation of the broomrapes into two main groups parasitizing annual and perennial hosts, and for the annual hosts, into weedy and non-weedy broomrapes. We conclude that floral VOCs are a significant tool in species identification and possibly even in defining new species and can help to improve controversial taxonomy in the Orobanchaceae.
Highlights
Just as humans and other animals use sound to communicate with organisms in their environment, flowering plants have a sophisticated language for communication, floral scents or floral volatile organic compounds (VOCs)
For four Orobanche spp. (O. alba, O. elatior/Figure 1A/, O. flava, and O. reticulata), two Phelipanche spp. (Ph. aegyptiaca and Ph. ramosa/Figure 1F/) and two outgroup species (Mimulus luteus and Paulownia tomentosa) a detailed annotation of the floral VOCs is shown in Supplementary Table S2
393 VOCs could be tentatively identified, and each species was characterized by a different VOC composition, there was considerable overlap (Supplementary Table S2)
Summary
Just as humans and other animals use sound to communicate with organisms in their environment, flowering plants have a sophisticated language for communication, floral scents or floral volatile organic compounds (VOCs). Flowers often emit hundreds of different VOCs and there are large differences between species (Pichersky and Gershenzon, 2002; Raguso, 2008a). These complex blends present a detailed language for communication with other organisms (Dudareva et al, 2006). Over 1700 compounds have been identified in floral blends (Knudsen et al, 2006) and one species may emit from one to over a hundred different compounds (Knudsen and Gershenzon, 2006) This implies that the flower VOC blend contains an enormous amount of information (Dudareva and Pichersky, 2006), potentially on taxonomic relationships.
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