Main drivers of broomrape regulation. A review

Abstract

Orobanchaceae-broomrapes-are a family of parasitic plants that represent an ecological and agronomic challenge because some of them cause significant damage to many monocots or dicots. Weedy broomrapes infest different crops in the Mediterranean basin, leading to substantial yield losses. Besides, they quickly adapt to new host plants, so that new crops are more and more under threat. Control methods are lacking because as plant parasites they cannot be considered as a common weed in agriculture. It is therefore important to characterize the main drivers of their regulation to identify sustainable management strategies.We reviewed all the possible interactions of Orobanchaceae species with surrounding organisms in an agricultural landscape, with a focus on the Orobanche and Phelipanche genera. Our main findings are that (1) broomrapes successfully co-evolve with their host through tight interactions ranging from the molecular to the tissue level, resulting in a unique strategy in their interactions with their host; (2) broomrapes have to face natural regulatory mechanisms such as host plant defenses, allelopathic interferences, and pest attacks from both the rhizosphere and phyllosphere; (3) alternative methods combining these natural mechanisms with existing conventional methods should be used to control broomrape. Conventional methods have shown limited results with parasitic weeds. By considering their life cycle and biotic and abiotic environment, management methods will target their weak point(s). Combining different control methods needs to be considered in an integrated weed management system. Furthermore, future studies on biocontrol will bring out new products to be used in addition to cultural techniques. Modeling approaches would help predict the evolution of broomrape-infested plots and the available potential management strategies.

Inhibition of broomrape germination by 2,4-diacetylphloroglucinol produced by environmentalPseudomonas

“…This lag phase could be interpreted as the time needed for the bacterial inoculant to establish itself within the soil and/or root microbiome, and/or to produce DAPG in sufficient amounts. Bacteria can exert, as well, an indirect positive activity on oilseed rape leading to a decreased sensitivity to broomrape infection as cited previously by Cartry et al [5]. Moreover, several reports showed that DAPG act as a signaling molecule inducing the plant systemic resistance [32] or the expression of its own biosynthetic genes [26].…”

“…The survival of the seeds depends on various abiotic factors (pH, humidity, climate) [9] and biotic factors (host plants, soil and rhizosphere microbiota; [6,[10][11][12]. Different agricultural strategies attempt to regulate broomrape populations in agroecosystems, such as crop rotation, triggering the suicidal-germination of the plant parasitic seeds or the use of resistant host plant varieties or chemical herbicides [5]. However, biological control solutions are emerging to limit broomrape infestation, including the use of microorganisms [5,13].…”

“…These parasitic plants are obligate root holoparasites, entirely dependent on their host plant to survive as they are not capable of photosynthesis [4]. Indeed, these parasitic plants obtain all the resources they need while maintaining their host alive for accomplishing their entire life cycle [5, 6]. The seed germination and haustorium formation are specifically induced by allelochemical signals such as strigolactones released from the host roots [7].…”

“…The seed germination and haustorium formation are specifically induced by allelochemical signals such as strigolactones released from the host roots [7]. The activity spectrum of these parasitic plants can be either specific (e.g., Orobanche cumana which can only parasitize sunflower) or generalist (e.g., Phelipanche ramosa able to parasitize hemp ( Cannabis sativa ), tobacco ( Nicotiana tabacum ), and oilseed rape ( Brassica napus )) [1, 5]. Broomrapes produce a large number of small seeds (less than 3 mm) that can survive in soil for several decades.…”

“…Different agricultural strategies attempt to regulate broomrape populations in agroecosystems, such as crop rotation, triggering the suicidal-germination of the plant parasitic seeds or the use of resistant host plant varieties or chemical herbicides [5]. However, biological control solutions are emerging to limit broomrape infestation, including the use of microorganisms [5, 13]. Indeed, several microorganisms inhibit the germination of different broomrape species, including, among others, Fusarium oxysporum [14], Azospirillum brasilense [15] or Pseudomonas fluorescens [16].…”