Abstract
The phytotoxic potential of the legume shrubs Ulex europaeus L. (gorse) and Cytisus scoparius (L.) Link. (Scotch broom) is studied in this work for the first time. On the basis of their richness in active principles, the previous evidence of biological activity, and the abundance of biomass in their native range and invaded areas, a question arose: can U. europaeus and C. scoparius be considered as potential sources of natural herbicides for sustainable agriculture? By means of volatile bioassays, the flowering fresh plant material of both shrub species was shown to produce and emit volatile organic compounds (VOCs) able to inhibit the germination and/or early growth of two agricultural weeds: Amaranthus retroflexus and Digitaria sanguinalis. Novel complete VOCs profiles from the volatile extracts of the shrub species were obtained by GC and GC/MS. A total of 20 compounds were identified from U. europaeus flowering biomass, theaspirane and eugenol, among others, being described in gorse for the first instance. The chemical profile of C. scoparius yielded 28 compounds and was rich in oxygenated monoterpenes such as terpinen-4-ol, verbenol, α-terpineol, and verbenone, which were also identified in this species for the first time. Using dose-response bioassays with pure compounds, these VOCs were argued to be involved in the phytotoxicity observed for the plant materials, even at very low concentrations. The phytotoxic effects were predominantly irreversible, particularly for D. sanguinalis, since the seeds exposed to the VOCs produced damaged seedlings, were unable to recover germination capacity after removing the phytotoxin or, when recovered, produced unviable seedlings. Our results extend the interest of the abundant U. europaeus and C. scoparius for the obtention of natural products with bioherbicide potential, or to be used as allelopathic biomass in the development of new sustainable agricultural practices.
Highlights
Legume species have major relevance in agriculture and agroforestry worldwide
From the analysis of variance, root and shoot lengths of A. retroflexus were very significantly affected (P 0.01) by the volatile organic compounds (VOCs) emitted from the flowering branches and the flowers of U. europaeus, achieving inhibitions up to ca. 40% (Fig 1C) and ca. 30% (Fig 1D) of control, respectively
Identification of VOCs from flowering branches and flowers of gorse and Scotch broom The extraction of volatile compounds from fresh plant material of the shrub species rendered a yellowish liquid with fresh, light liquorice odour, obtained at a mean yield of 0.06% (w/w, on a fresh mass basis) with a mean density of 0.85 g mL-1
Summary
Legume species have major relevance in agriculture and agroforestry worldwide. They are vital components in ecosystems for their role as atmospheric nitrogen fixers through their association with Rhizobium bacteria. (Scotch broom) are native to the Atlantic region. Gorse is native to the western coast of continental Europe and the British Isles, whereas Scotch broom is widely distributed all across Europe. The Atlantic shrubland is dominant in the native range [1,2,3]. Outside their natural distribution range, U. europaeus and C. scoparius are considered highly invasive weeds [4,5,6]. Gorse is considered one of the 100 worst invasive species in the world [7]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
