Allelopathic Effect of Quercetin, a Flavonoid from Fagopyrum esculentum Roots in the Radicle Growth of Phelipanche ramosa: Quercetin Natural and Semisynthetic Analogues Were Used for a Structure-Activity Relationship Investigation.

Mónica Fernández-Aparicio,Alessio Cimmino,Marco Masi,Antonio Evidente,Susana Vilariño

doi:10.3390/plants10030543

Abstract

Allelopathic potential of buckwheat roots on the radicle growth of the broomrape weed species Orobanche cumana and Phelipanche ramosa was studied. Buckwheat root exudates induced a significant growth inhibition in P. ramosa radicles but radicles of O. cumana were not affected. Among the metabolites present in the root organic extract we identified the flavonol quercetin and the stilbene p-coumaric acid methyl ester with only quercetin showing inhibitory effect on P. ramosa. The activity of quercetin was compared with other two similar flavanoids, the flavone apigenin and the dihydroflavanol 3-O-acetylpadmatin extracted respectively from Lavandula stoechas and Dittrichia viscosa plants. In this comparative assay only 3-O-acetylpadmatin besides quercetin, showed inhibition activity of radicle growth while apigenin was inactive. These results indicated that the presence of two ortho-free hydroxy groups of C ring, like catechol, could be an important feature to impart activity while the carbon skeleton of B ring and substituents of both A and B rings are not essential. Besides reduction of radicle growth, haustorium induction was observed at the tip of P. ramosa radicles treated with quercetin which swelled and a layer of papillae was formed. Activity of quercetin on haustorium induction in P. ramosa was assayed in comparison with the known haustorium-inducing factor 2,6-dimethoxy-p-benzoquinone (DMBQ) and a three partial methyl ether derivatives semisynthetized from quercetin. Results indicated that P. ramosa haustorium was induced by DMBQ at concentrations of 1–0.5 mM and quercetin and its derivatives at concentration range 0.1–0.05 mM.

Highlights

The parasitic broomrape weeds (Orobanche and Phelipanche species) have not functional roots nor photosynthetic activity obtaining all nutrients and water from the crop root by haustorial connections with the vascular system [1]
Allelopathic potential of buckwheat root exudates was assayed on radicle development of two broomrape species P. ramosa and O. cumana and the effect of buckwheat compared with the effect of two sunflower cultivars NR5 and P96 and the negative control GR24
Growth of O. cumana radicles treated with a combination of buckwheat root exudates and GR24 was not significantly different from the growth of GR24-treated O. cumana control radicles nor the growth of radicles treated with combination of sunflower root exudates and GR24

Summary

Introduction

The parasitic broomrape weeds (Orobanche and Phelipanche species) have not functional roots nor photosynthetic activity obtaining all nutrients and water from the crop root by haustorial connections with the vascular system [1]. Their expansion in Mediterranean Basin and Asia is uncontrolled infecting crops in the Apiaceae, Asteraceae, Brassicaceae, Fabaceae or Solanaceae becoming a threat to food security [1,2]. Due to the undesirable effects of herbicides, the number of old herbicides authorized are in constant decline with few novel herbicides in development [5,6] which prompt the need for the development of novel nature-inspired bioherbicides containing either microbial strains or toxins from microbial or plant origin. In many cases the natural herbicidal substances lack appropriate physicochemical properties for field application and their use in agriculture depends on the development of formulations that increase the solubility in water [16,17] or the development of strategies for the application of the whole organic extract of allelopathic plants or incorporating them into biofilms [18]

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