Abstract
The co-evolution of Orobanche spp. and their hosts within the same environment has resulted in a high degree of adaptation and effective parasitism whereby the host releases parasite germination stimulants, which are likely to be unstable in the soil. Our objective was to investigate whether extracts from non-host plants, specifically, Chinese medicinal plants, could stimulate germination of Orobanche spp. Samples of 606 Chinese medicinal herb species were extracted with deionized water and methanol. The extracts were used to induce germination of three Orobanche species; Orobanche minor, Orobanche cumana, and Orobanche aegyptiaca. O. minor exhibited a wide range of germination responses to the various herbal extracts. O. cumana and O. aegyptiaca exhibited an intermediate germination response to the herbal extracts. O. minor, which has a narrow host spectrum, showed higher germination rates in response to different herbal extracts compared with those of O. cumana and O. aegyptiaca, which have a broader host spectrum. Methanolic extracts of many Chinese herbal species effectively stimulated seed germination among the Orobanche spp., even though they were not the typical hosts. The effective herbs represent interesting examples of potential trap crops. Different countries can also screen extracts from indigenous herbaceous plants for their ability to induce germination of Orobanche spp. seeds. The use of such species as trap plants could diminish the global soil seed bank of Orobanche.
Highlights
The co-evolution of Orobanche spp. and their hosts within the same environment has resulted in a high degree of adaptation and effective parasitism whereby the host releases parasite germination stimulants, which are likely to be unstable in the soil
It is widely believed that seeds of Orobanche spp. require a conditioning period of several days under suitable temperature and moisture conditions before germinating in response to germination stimulants [1,25 27]
We found that O. minor seeds required a conditioning period before responding to germination stimulants
Summary
The co-evolution of Orobanche spp. and their hosts within the same environment has resulted in a high degree of adaptation and effective parasitism whereby the host releases parasite germination stimulants, which are likely to be unstable in the soil. Methanolic extracts of many Chinese herbal species effectively stimulated seed germination among the Orobanche spp., even though they were not the typical hosts. Different countries can screen extracts from indigenous herbaceous plants for their ability to induce germination of Orobanche spp. seeds The use of such species as trap plants could diminish the global soil seed bank of Orobanche. The depletion of its soil seed bank by inducing “suicidal germination” would be an efficient way to control Orobanche Investigations into another parasitic weed, Striga, have advanced research on Orobanche seed germination stimulants. Evidente et al [17] reported the isolation of two strigolactone-like compounds (peagol and peagoldione) from pea root exudates Both compounds showed selective stimulation of Orobanche seed germination
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