Nitrogen deficiency as well as phosphorus deficiency in sorghum promotes the production and exudation of 5-deoxystrigol, the host recognition signal for arbuscular mycorrhizal fungi and root parasites.
ABSTRACT Strigolactones released from plant roots induce hyphal branching of symbiotic arbuscular mycorrhizal (AM) fungi and germination of root parasitic weeds, Striga and Orobanche spp. We already demonstrated that, in red clover plants (Trifolium pratense L.), a host for both AM fungi and the root holoparasitic plant Orobanche minor Sm., reduced supply of phosphorus (P) but not of other elements examined (N, K, Ca, Mg) in the culture medium significantly promoted the secretion of a strigolactone, orobanchol, by the roots of this plant. Here we show that in the case of sorghum [Sorghum bicolor (L.) Moench], a host of both the root hemiparasitic plant Striga hermonthica and AM fungi, N deficiency as well as P deficiency markedly enhanced the secretion of a strigolactone, 5-deoxystrigol. The 5-deoxystrigol content in sorghum root tissues also increased under both N deficiency and P deficiency, comparable to the increase in the root exudates. These results suggest that strigolactones may be rapidly released after their production in the roots. Unlike the situation in the roots, neither N nor P deficiency affected the low content of 5-deoxystrigol in sorghum shoot tissues.
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ABSTRACT: Five Glomus species (G. intraradices, G. albidum, G. mosseae, G. fasciculatum, and G. etunicatum) were compared against a check [without arbuscular mycorrhizal (AM) fungi, plus Striga] and control (without AM fungi or Striga) treatments for the control of Striga in a tolerant sorghum variety (War-wara bashi) in an experiment carried out in 12-cm-diameter clay pots. The experiment was carried out in a controlled growth chamber. G. mosseae significantly reduced the number of Striga emerging per plant, increased plant growth, shoot and total dry matter yield of sorghum, did not affect the root dry matter compared with the other AM fungi species, but had a comparable effect to the control treatment. All the AM fungi except G. mosseae, and also the Striga-infested treatment, increased the root:shoot ratio compared to the control treatment. The percent reduction (62%) of Striga emergence after G. mosseae inoculation resulted in about a 30% increase in total dry matter yield of sorghum over the control, while the total loss in dry matter yield of sorghum due to Striga infestation was 36%. Root colonization of sorghum by AM fungi was highest for G. mosseae (44%) followed by G. intraradices (24%) and G. albidum (23%) then G. fasciculatum (18%), with the lowest recorded for G. etunicatum (14%). No colonization of Striga roots was observed. The potential of AM fungi to reduce or to compensate for Striga infestation could be important for soil management, especially in the tropics, and for the reduction of Striga-resistant varieties of sorghum which are mycorrhiza-responsive.Mycorrhiza 11/2003; 13(5):277-81. · 2.96 Impact Factor
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ABSTRACT: A crystalline germination stimulant (trivial name strigol) for the rootparasite, witchweed (Striga lutea Lour.), has been isolated from cotton rootexudates and characterized as a C(19)H(22)O(6) compound. Although apparently different from known plant hormones, the stimulant is active at hormonal levels, causing germination at concentrations less than 1O(-5) part per million.Science 01/1967; 154(3753):1189-90. · 31.03 Impact Factor
Article: Plastic plants and patchy soils.[show abstract] [hide abstract]
ABSTRACT: Soil nutrients are distributed in a non-uniform or 'patchy' manner. It is well established that the modular nature of root systems allows them to show both morphological and/or physiological plasticity upon encountering nutrient-rich patches. These plastic responses are widely believed to be foraging mechanisms by the plant to enhance nutrient resource capture. Although morphological plasticity has traditionally been viewed as the more expensive option as it requires new root construction, more recent evidence suggests this may not necessarily be the case. Moreover, plants may be able to recapture most of the initial outlay involved in new root construction, again lowering the overall cost to the plant. Under natural conditions the roots of most plant species have an additional nutrient acquisition mechanism namely mycorrhizal symbiosis. However, the impact of these important symbiotic associations upon the host plant's response to nutrient patches has received relatively little attention. The mycorrhizal fungal symbiont should, in theory, be better able to compete directly with the rest of the microbial community for the nutrients in the patch. This could potentially be important to the host plant, as generally, root proliferation responses are more important for interspecific plant, than plant-microbial, competition.Journal of Experimental Botany 02/2006; 57(2):401-11. · 5.24 Impact Factor