Inhibition of Orobanche crenata Seed Germination and Radicle Growth by Allelochemicals Identified in Cereals

Orobanche crenata is a parasitic weed that causes severe yield losses in important grain and forage legume crops. Cereals have been reported to inhibit O. crenata parasitism when grown intercropped with susceptible legumes, but the responsible metabolites have not been identified. A number of metabolites have been reported in cereals that have allelopathic properties against weeds, pests, and pathogens. We tested the effect of several allelochemicals identified in cereals on O. crenata seed germination and radicle development. We found that 2-benzoxazolinone, its derivative 6-chloroacetyl-2-benzoxazolinone, and scopoletin significantly inhibited O. crenata seed germination. Benzoxazolinones, l-tryptophan, and coumalic acid caused the stronger inhibition of radicle growth. Also, other metabolites reduced radicle length, this inhibition being dose-dependent. Only scopoletin caused cell necrotic-like darkening in the young radicles. Prospects for their application to parasitic weed management are discussed. © 2013 American Chemical Society.This research is supported by projects FP7-ARIMNet-MEDILEG and AGL2011-22524 (cofinanced by FEDER funds).Peer Reviewe

Characterisation of resistance to branched broomrape, Phelipanche ramosa, in winter oilseed rape

a b s t r a c t Over the past decade, Phelipanche ramosa, a weedy parasitic plant (broomrape), has been increasingly infesting winter oilseed rape (WOSR) fields in France. Elite WOSR lines have shown different responses in P. ramosa infested fields, suggesting that genetic variability might be available for breeding programmes targeting broomrape resistance. Ten WOSR genotypes selected for their contrasting response in field experiments were analysed using mini-rhizotron and greenhouse co-culture experiments to determine the components of resistance to broomrape. Partial resistance was revealed at three developmental stages of the parasitic plant. First, at the germination stage, parasite attachment to the roots of some WOSR lines was limited and associated with a low rate of parasite seed germination. This mechanism of parasite avoidance could nevertheless be suppressed under high infestation in mini-rhizotron and greenhouse conditions. Second, at the root attachment stage, limited parasite attachment was observed in mini-rhizotron conditions under low and high infestation, and in greenhouse conditions. Third, after successful parasite attachment, some WOSR genotypes retarded and even disturbed the growth of tubercles, minimising and delaying parasite emergence from the soil. Although the exact mechanisms limiting parasite attachment and tubercle development require further investigation, our findings suggest that, by cumulating various resistance traits in new genotypes to enhance effectiveness and potential durability of resistance, breeding could be a promising control strategy in WOSR

Characterisation of resistance to branched broomrape, Phelipanche ramosa, in winter oilseed rape

International audienceOver the past decade, Phelipanche ramosa, a weedy parasitic plant (broomrape), has been increasingly infesting winter oilseed rape (WOSR) fields in France. Elite WOSR lines have shown different responses in P. ramosa infested fields, suggesting that genetic variability might be available for breeding programmes targeting broomrape resistance. Ten WOSR genotypes selected for their contrasting response in field experiments were analysed using mini-rhizotron and greenhouse co-culture experiments to determine the components of resistance to broomrape. Partial resistance was revealed at three developmental stages of the parasitic plant. First, at the germination stage, parasite attachment to the roots of some WOSR lines was limited and associated with a low rate of parasite seed germination. This mechanism of parasite avoidance could nevertheless be suppressed under high infestation in mini-rhizotron and greenhouse conditions. Second, at the root attachment stage, limited parasite attachment was observed in mini-rhizotron conditions under low and high infestation, and in greenhouse conditions. Third, after successful parasite attachment, some WOSR genotypes retarded and even disturbed the growth of tubercles, minimising and delaying parasite emergence from the soil. Although the exact mechanisms limiting parasite attachment and tubercle development require further investigation, our findings suggest that, by cumulating various resistance traits in new genotypes to enhance effectiveness and potential durability of resistance, breeding could be a promising control strategy in WOSR. (C) 2012 Elsevier Ltd. All rights reserved