Abstract
The current study aimed to assess the allelopathic effect of Rosmarinus officinalis L. essential oils (EOs) to define the potent effect against weed species, by exploring distinct chemotypes and their main compounds. The EOs from eight accessions were characterized. Their components were identified by gas chromatography, and four chemotypes were defined; C1 (α-pinene), C2 (camphor), C3 (α-pinene/1,8-cineole), and C4 (α-pinene/1,8-cineole/camphor). Four concentrations of the EOs (400, 800, 1200, and 2400 μL/L) and the main compounds of each chemotype were tested in a laboratory assay against Amaranthus retroflexus L. and Lolium perenne L. in pre- and post-germination. The results showed that the EOs significantly affected all the tested parameters (germination, early growth, and physiological and histological parameters of the weeds under study) in a dose, chemotype, and species dependent manner. A. retroflexus was more sensitive than L. perenne at germination level being significantly inhibited at the lowest dose of all the chemotypes. The latter all exhibited significant effects but with a higher potency of C2 (camphor chemotype) and C3 (α-pinene/1,8-cineole chemotype), as well qualitative differences in the induced damage. Our results thus increase knowledge about the role of the monoterpene composition in bio-herbicidal effect, which can help in the development of EO based bio-herbicides.
Highlights
In all farming systems, weeds account for the most expensive pest to manage causing up to 30% of total potential losses from all pests [1]
No clear trend was visible following an increase in the dose. These results suggested a lower sensitivity of A. retroflexus root membrane integrity to the essential oils (EOs), or indicate the sensitivity of its root tissue to the Trypan blue stain, which is reported to be cytotoxic and can induce damage to cells [40]
As for root staining with Trypan blue, the results showed a difference in sensitivity between the species, since all the treatments had comparable staining expressed by similar pixel intensity
Summary
Weeds account for the most expensive pest to manage causing up to 30% of total potential losses from all pests [1]. As weed management can reach up to 50% of the total production cost, notably in intensive organic horticulture [3] This higher complexity is mainly related to the restriction of the use of synthetic herbicides and the lack of potent alternatives under allowed natural herbicides [4]. The latter class is available to organic farmers currently in very few options and at a high cost for the necessary rates [5,6]. Much attention is being given, in that sense, to the utilization of the allelopathic potential in plants as an ecologically based
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