Persistence of GR7 and Striga germination stimulant(s) from Euphorbia aegyptiaca Boiss. in soils and in solutions

Xie

Pest Management Science

et al. 2009

163

118

Strigolactones released from plant roots induce seed germination of root parasitic weeds, witchweeds (Striga spp.) and broomrapes (Orobanche spp.), and hyphal branching of symbiotic arbuscular mycorrhizal (AM) fungi. In addition to these functions in the rhizosphere, strigolactones have recently been shown to be a novel class of plant hormones regulating shoot outgrowth. The natural strigolactones identified so far have the common C-D ring moiety, which is thought to be the essential structure for exhibiting biological activity. The introduction of substitutions on the A-B ring moiety of 5-deoxystrigol, the basic strigolactone, affords various strigolactones, e.g. hydroxylation on C-4, C-5 and C-9 leads to orobanchol, strigol and sorgomol respectively. Then, acetylation and probably other derivatisations of these hydroxy-strigolactones would occur. Although the C-2'-(R) stereochemistry was thought to be an important structural feature for potent germination stimulation activity, 2'-epi-strigolactones were found in root exudates of tobacco, rice, pea and other plant species, indicating that at least some plants produce both epimers.

Section: Biological Activity Of Strigolactonesmentioning

confidence: 99%

Strigolactones: structures and biological activities

Xie

Pest Management Science

et al. 2009

163

118

“…These more stable SLs might be involved in the germination stimulation of Striga seeds in alkaline soils that are common in Sub-Saharan Africa. 24) The low germination-stimulating activity of 7-oxoorobanchol is attributable to its instability, as discussed before. Accordingly, the germination-stimulating activity of naturally occurring SLs on O. minor seeds was found to depend on the lipophilicity of SL molecules, and their stability also influenced activity.…”

Section: )mentioning

confidence: 86%

Structure-activity relationship of naturally occurring strigolactones in Orobanche minor seed germination stimulation

et al. 2010

Eleven naturally occurring strigolactones (SLs) were examined for their germination-stimulating activity on the seeds of a root parasitic plant Orobanche minor Sm. Based on their activity, SLs are classified into 3 groups (A-C). Group A, the most active germination stimulant, consists of 3 monohydroxy-SLs, orobanchol, 2Ј-epiorobanchol, and sorgomol, inducing Ͼ80% germination of O. minor seeds at 10 pM. Group B includes 5 SLs, which were ca. 10-fold less active than those in group A. The 3 least active SLs in group C were either more lipophilic or probably less stable than SLs in groups A and B. These results indicate that the germination-stimulating activity of SLs depends on the lipophilicity of the SL molecules and their stability also influences activity. Other structural features for germination-stimulating activity are also discussed.

“…GR 7 and an extract of Euphorbia aegyptiaca Boiss containing natural germination stimulants were investigated using soils of varying types, collected from five different locations in Sudan. Adequate persistence (6–8 days) of GR 24 was observed in acidic soils (pH 5.0–6.3), whereas it was short (1–3 days) in alkaline soils (Babiker et al. , 1988).…”

Section: Introductionmentioning

confidence: 94%

Strigolactone analogues induce suicidal seed germination of Striga spp. in soil

et al. 2012

Striga hermonthica and Striga asiatica are obligate root parasites that cause serious problems in the production of staple cereal crops in Africa. Because of the high levels of infestation, there is an urgent need to control these weeds. A potentially useful control option is depletion of the soil seed bank by suicidal germination, which involves germination of the seeds in the absence of host plants. Suicidal germination is often mentioned in the literature, but not considered realistic, because of the alleged untimely decomposition of the stimulants in the soil, despite the fact that some encouraging results were reported around 1980. The alleged instability has prevented active research in this direction for the past 20-25 years. Five newly designed synthetic germination stimulants were investigated as candidates for suicidal germination. An important issue is the persistence of these stimulants in soil. Packets with Striga spp. seeds were put in pots with soil and then treated with aqueous solutions of the stimulants. All five compounds induced germination under these conditions, with percentages varying between 18% and 98% depending on stimulant and species. There were no noticeable signs of decomposition of the stimulants. The best performing stimulant is derived from 1-tetralone. We conclude that synthetic strigolactones analogues have excellent prospects for use in combating parasitic weeds. Further testing will be needed to evaluate whether such prospects can be realised in the field.