Response of wild and weedy broomrapes to synthetic strigolactone analogue GR24

Abstract

Parasitic plants of genera Orobanche and Phelipanche germinate after exposition to chemical signals exuded by roots of the host plants. The most studied germination stimulants belong to strigolactones (SLs), the newly discovered plant hormones which are stimulating hyphal branching of arbuscular mycorrhizal fungi and are involved in regulation of shoot and root architecture of plants. However, little is known about the effect of strigolactones on germination of non-weedy broomrapes. The objective of our study was to investigate the sensitivity of seeds of non-weedy broomrapes to synthetic analogue of SLs, GR24.

Differences in seed germination response of two populations of Phelipanche ramosa (L.) Pomel to a set of GR24 concentrations and durations of stimulation

“…For high GR24 concentrations, the germination percentage was around 90%. These results are in accordance with previous dose-response studies showing that P. ramosa seeds reach a higher asymptote, frequently higher than 90%, in response to GR24 (Gibot-Leclerc et al, 2004; Matusova et al, 2014; Huet et al, 2020). For low GR24 concentrations, the maximum germination rate was lower, to be compared to a viability of seed lots ranging from 87 to 97% in our study, suggesting that the remaining viable seeds are no longer stimulated by GR24.…”

“…No germination of P. ramosa seeds was observed either in the absence, or at too low concentrations of the germination stimulant, confirming that the induction of seed germination of this parasitic plant requires a minimum concentration of stimulant, in accordance with previous studies (Gibot-Leclerc et al, 2004; Fernández-Aparicio et al, 2011; Matusova et al, 2014; Huet et al, 2020). In our study, following a conditioning period, the germination of P. ramosa seeds was induced by concentrations of GR24 as low as 10 −6 mg l −1 , comparable to GR24 concentrations observed in other studies (Fernández-Aparicio et al, 2011; Matusova et al, 2014), although lower concentrations can also induce germination (Huet et al, 2020). Moreover, we highlighted a marked difference in sensitivity to the germination stimulant between the two P. ramosa populations studied, the P. ramosa seeds of the R (oilseed rape) population appearing more sensitive to GR24 than the P. ramosa seeds of the T (tobacco) population by a factor 10 4 .…”

“…Moreover, the maximum germination can greatly differ between the two P. ramosa populations for a similar GR24 concentration, for example from 33% for population T to 96% for population R at 0.01 mg l −1 . These differences were also observed by Matusova et al (2014) between two geographically distinct P. ramosa populations harvested from different host crops. Our observations of a higher asymptote ( G max ) differing between concentrations of the germination stimulant for the same P. ramosa population, or between P. ramosa populations for a same GR24 concentration, suggest a response to a limiting factor for which the minimum level to reach a high maximum germination rate is variable between populations.…”