Reduced Germination of Orobanche cumana Seeds in the Presence of Arbuscular Mycorrhizal Fungi or Their Exudates

Abstract

Broomrapes (Orobanche and Phelipanche spp) are parasitic plants responsible for important crop losses, and efficient procedures to control these pests are scarce. Biological control is one of the possible strategies to tackle these pests. Arbuscular Mycorrhizal (AM) fungi are widespread soil microorganisms that live symbiotically with the roots of most plant species, and they have already been tested on sorghum for their ability to reduce infestation by witchweeds, another kind of parasitic plants. In this work AM fungi were evaluated as potential biocontrol agents against Orobanche cumana, a broomrape species that specifically attacks sunflower. When inoculated simultaneously with O. cumana seeds, AM fungi could offer a moderate level of protection against the broomrape. Interestingly, this protection did not only rely on a reduced production of parasitic seed germination stimulants, as was proposed in previous studies. Rather, mycorrhizal root exudates had a negative impact on the germination of O. cumana induced by germination stimulants. A similar effect could be obtained with AM spore exudates, establishing the fungal origin of at least part of the active compounds. Together, our results demonstrate that AM fungi themselves can lead to a reduced rate of parasitic seed germination, in addition to possible effects mediated by the mycorrhizal plant. Combined with the other benefits of AM symbiosis, these effects make AM fungi an attractive option for biological control of O. cumana.

Linking agricultural practices, mycorrhizal fungi, and traits mediating plant–insect interactions

“…Inoculum from one organic farm completely prevented seed germination, demonstrating that this pattern could be important in some agricultural settings. We are unaware of a mechanism that could explain these results, although a recent report that AMF spore exudates suppress seed germination of a parasitic plant (Louarn et al 2012) suggests further studies of this phenomenon are warranted.…”

Distribution Rules of Nutrients in Orobanche Aegyptiaca-Tomato Parasitic System

“…Researchers also tried to eliminate Orobanche aegyptiaca through different methods mainly including hand weeding, adjustment of the sowing dates of main crops, application of chemical herbicides and biological herbicides, selection and breeding of Orobanche-resistant crop cultivars and elimination of the Orobanche seed bank in soil based on crop induction, etc., (Parker and Riches 1993;Dhanapal, et al, 1996;Louarn, et al, 2012;Ma, et al, 2013).…”

Changes at the Rhizosphere Microbiota of the Sunflower – Orobanche cumana Wallr Pathosystem

“…Some degree of reduction germination of O. cumana Wallr., seeds in the presence of AMF and their exudates have been found. Besides a lower production of germination stimulants was also marked antagonism between the AMF and the parasite (Louarn, 2012). The most recent research has shown that not only strigolactones stimulate the germination of seeds of broomrapes, but a several substances of other classes metabolites have been identified (Cordozo et al, 2011;FernandezAparicio et al, 2011;Raupp et al, 2013).…”