Abstract
The root parasitic weed broomrapes, Phelipanche spp., cause severe damage to agriculture all over the world. They have a special host-dependent lifecycle and their seeds can germinate only when they receive chemical signals released from host roots. Our previous study demonstrated that 2-phenylethyl isothiocyanate is an active germination stimulant for P. ramosa in root exudates of oilseed rape. In the present study, 21 commercially available ITCs were examined for P. ramosa seed germination stimulation, and some important structural features of ITCs for exhibiting P. ramosa seed germination stimulation have been uncovered. Structural optimization of ITC for germination stimulation resulted in ITCs that are highly active to P. ramosa. Interestingly, these ITCs induced germination of P. aegyptiaca but not Orobanche minor or Striga hermonthica. P. aegyptiaca seeds collected from mature plants parasitizing different hosts responded to these ITCs with different levels of sensitivity. ITCs have the potential to be used as inducers of suicidal germination of Phelipanche seeds.
Highlights
Broomrapes (Orobanche and Phelipanche spp.) in the family Orobanchaceae are devastating obligate root parasitic weeds damaging crop production all over the world [1,2]
The germination stimulation activity of 3-phenylpropyl, 4-phenylbutyl, and 5-phenylpentyl ITCs were compared with GR24 at ≤10−9 M, and 5-phenylbutyl ITC appeared to be the most active eliciting about 20% germination even at 10−15 M (Figure 3)
None of the ITCs examined in this study induced seed germination of O. minor or S. hermonthica. These results demonstrate that ITCs are important germination stimulants for Phelipanche spp. which have developed a special seed germination strategy to parasitize Brassica spp., non-host plants of arbuscular mycorrhizal (AM) fungi which exude only small amounts of SLs [15]
Summary
Broomrapes (Orobanche and Phelipanche spp.) in the family Orobanchaceae are devastating obligate root parasitic weeds damaging crop production all over the world [1,2]. The seeds of root parasitic weeds can germinate only when they receive host-derived chemical-germination stimulants. This is a sophisticated strategy for survival of the root parasites, since germinated seeds with limited food stock should attach to the host roots within a couple of days, otherwise they will die. Only the parasite seeds in the rhizosphere of host plants will germinate by sensing host-derived stimulants [5]. In severely infested soils, one potentially effective control method for root parasitic weeds is to induce seed germination of the parasites in the absence of host plants, termed ‘suicidal germination’ [6]. Suicidal germination contributes to reduce the parasite seed bank
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