Journal of Experimental Botany, Vol. 52, No. 358, pp. 1093±1099, May 2001 Phytosiderophore release in Aegilops tauschii and Triticum species under zinc and iron deficiencies I. Tolay1, B. Erenoglu1,2,V.RoÈ mheld2, H.J. Braun3 and I. Cakmak4,5 1 Cukurova University, Department of Soil Science and Plant Nutrition, 01330 Adana, Turkey 2 UniversitaÈ t Hohenheim, Institut fuÈ r PflanzenernaÈ hrung %330), 70593 Stuttgart, Germany 3 CIMMYT, POB 39, Emek 06511, Ankara, Turkey 4 Sabanci University, Faculty of Engineering and Natural Sciences, 81474 Tuzla, Istanbul, Turkey Received 2 August 2000; Accepted 27 November 2000 Abstract of PS release was around 14 mmol *30 plants)À1 *3 h)À1. Diploid wheats and Ae. tauschii accessions Using three diploid *Triticum monococcum, AA), behaved similarly in their capacity to release PS three tetraploid *Triticum turgidum, BBAA), two hexa- and intermediate between tetraploid and hexa- ploid *Triticum aestivum and Triticum compactum, ploid wheats regarding the PS release capacity. All BBAADD) wheats and two Aegilops tauschii *DD) Triticum and Aegilops species released more PS genotypes, experiments were carried out under under Fe than Zn deficiency, particularly when the controlled environmental conditions in nutrient solu- rate of PS release was expressed per unit dry weight tion *i) to study the relationships between the rates of roots. On average, the rates of PS release under Fe of phytosiderophore *PS) release from the roots and deficiency were 3.0, 5.7, 8.4, and 16 mmol *30 plants)À1 the tolerance of diploid, tetraploid, and hexaploid *3 h)À1 for Ae. tauschii, diploid, tetraploid and wheats and Ae. tauschii to zinc *Zn) and iron *Fe) hexaploid wheats, respectively. The results of the deficiencies, and *ii) to assess the role of different present study show that the PS release mechanism in genomes in PS release from roots under different wheat is expressed effectively when three genomes, regimes of Zn and Fe supply. Phytosiderophores A, B and D, come together, indicating complementary released from roots were determined both by meas- action of the corresponding genes from A, B and D urement of Cu mobilized from a Cu-loaded resin genomes to activate biosynthesis and release of PS. and identification by using HPLC analysis. Com- pared to tetraploid wheats, diploid and hexaploid Key words: Aegilops tauschii, iron deficiency, phyto- wheats were less affected by Zn deficiency as judged siderophores, Triticum monococcum, Triticum dicoccum, from the severity of leaf symptoms. Aegilops Triticum aestivum, zinc deficiency. tauschii showed very slight Zn deficiency symptoms possibly due to its slower growth rate. Under Fe-deficient conditions, all wheat genotypes used were similarly chlorotic; however, development of chlorosis was first observed in tetraploid wheats. Introduction Correlation between PS release rate determined by Zinc and Fe de®ciencies are common micronutrient de®- Cu-mobilization test and HPLC analysis was highly ciencies in calcareous soils, and adversely affect crop pro- significant. According to HPLC analysis, all geno- duction SillanpaÈaÈ, 1982; Vose, 1982; White and Zasoski, types of Triticum and Ae. tauschii species released 1999). Zinc de®ciency is a particular micronutrient only one PS, 29-deoxymugineic acid, both under de®ciency problem in cereal-growing areas causing large Fe and Zn deficiency. Under Zn deficiency, rates of decreases in grain yield and quality, for example in PS release in tetraploid wheats averaged 1 mmol Australia Graham et al., 1992), Turkey Cakmak et al., *30 plants)À1 *3 h)À1, while in hexaploid wheats rate 1996a, 1999a) and India Takkar et al., 1989). 5 To whom correspondence should be addressed. Fax: q90 216 4839550. E-mail: [email protected] ß Society for Experimental Biology 2001 1094 Tolay et al. There is substantial variation in tolerance to Zn or Fe grown in Zn-de®cient calcareous soils Cakmak et al., de®ciency within and among cereal species. Possibly, the 1999b). This may suggest a role of the A genome in release of phytosiderophores PS) non-protein amino the synthesis and release of PS. Aegilops tauschii DD) is acids) from roots in response to Fe or Zn de®ciencies is the donor of the D genome in hexaploid wheat Kerby an important factor affecting genotypic variation in the and Kuspira, 1987; Miller, 1987), and there is a high tolerance to Zn and Fe de®ciencies. Phytosiderophores variation in tolerance to Zn de®ciency between the are highly effective in solubilization and mobilization accessions of Ae. tauschii Cakmak et al., 1999c). Using of Zn and Fe in calcareous soils Treeby et al., 1989) and only one genotype from each wheat species, it was are involved in the uptake of these nutrients by roots recently shown Ma et al., 1999) that diploid AA), tetra- RoÈmheld and Marschner, 1990; von Wiren et al., 1995). ploid BBAA) and hexaploid wheats BBAADD) and The existence of large differences in tolerance to Fe Ae. tauschii DD) are able to release PS under Fe de®ciency between various cereal species correlated de®ciency. In this study Ma et al., 1999), the highest well with the release rate of PS from roots Marschner and lowest amounts of PS release were found in hexaploid et al., 1986; Kawai et al., 1988; RoÈmheld and Marschner, and diploid wheats, respectively. In the present study, 1990). Similarly, differences in tolerance to Zn de®ciency using three diploid AA), three tetraploid BBAA) and between sorghum, wheat and corn correlate well with the two hexaploid BBAADD) wheats and two Ae. tauschii amounts of PS released from roots Hopkins et al., 1998). DD) accessions experiments were carried out to study Wild grasses, adapted to severely Zn-de®cient calcareous the role of different genomes on the release of PS under soils, released high amounts of PS when grown under Zn Fe and Zn de®ciencies. Among the species studied, de®ciency Cakmak et al., 1996c). Bread wheat cultivars the diploid and hexaploid wheat genotypes are known to show greater tolerance to Zn de®ciency than durum be tolerant to Zn de®ciency, and tetraploid wheats and wheat cultivars, and this difference in tolerance correlated Ae. tauschii accessions show high and moderate sensitivity with differences in the release rate of phytosiderophores to Zn de®ciency when grown on a severely Zn-de®cient Cakmak et al., 1994; Walter et al., 1994; Rengel et al., soil, respectively Cakmak et al., 1999b, c). 1998). However, when genotypes of a given cereal species were compared, tolerance to Zn or Fe de®ciencies and the rate of PS release were not always well correlated, as Materials and methods shown in oat for Fe de®ciency Hansen and Jolley, 1995) and wheat for Zn de®ciency Erenoglu et al., 1996). Plant growth Little information is available about the genetic con- Two separate experiments were carried out to study the effects trol of PS release from roots. Since both the concentra- of genomes of the Ae. tauschii and Triticum species on PS release under Zn experiment I) and Fe experiment II) de®ciencies. tions in roots and the amounts released from roots of PS The genotypes of Ae. tauschii and Triticum species used in the are much lower in tetraploid BBAA) than hexaploid present work are presented in Table 1. Seeds from Germany wheats BBAADD) under Fe and especially Zn de®ciency were provided by Dr CI Kling University of Hohenheim- Cakmak et al., 1994, 1996b; Rengel and Romheld, Stuttgart). Seeds, surface-sterilized by 1% vuv) sodium hypo- 2000a), it can be assumed that the D genome possibly chlorite for 20 min, were germinated in quartz sand moistened with saturated CaSO4 solution. After 4 or 5 d the seedlings were affects the biosynthesis and release of PS. Recently, it has transferred to 2.5 l plastic pots 30 seedlings per pot) containing been shown that diploid wheats AA), like hexaploid the following continuously aerated nutrient solution: 0.88 mM wheats, possess very high tolerance to Zn de®ciency when K2SO4, 2.0 mM CaNO3)2, 0.25 mM KH2PO4, 1.0 mM MgSO4, Table 1. Diploid, tetraploid and hexaploid wheats used in the study, and their genotypes and sources Species Accessions or cultivars Seed source Classi®cation Diploid T. monococcum AA) ssp. monococcum FAL-67 Germany Primitive ssp. monococcum FAL-43 Germany Primitive ssp. monococcum FAL-30 Germany Primitive Tetraploid T. turgidum BBAA) ssp. dicoccum FAL-21 Germany Primitive ssp. dicoccum FAL-02 Germany Primitive ssp. dicoccum FAL-13 Germany Primitive Hexaploid T. aestivum BBAADD) ssp. compactum Stammbaum Germany Primitive ssp. aestivum Bezostaja Turkey Modern Aegilops tauschii DD) 400682 ICARDA Wild Aegilops tauschii DD) 400630 ICARDA Wild Aegilops tauschii DD) 400356 ICARDA Wild Phytosiderophore release in wild wheats 1095 0.1 mM KCl, 1 mMH3BO4, 0.5 mM MnSO4, and 0.02 mM was dissolved in 3.3% vuv) HCl, and Zn and Fe concentrations NH4)6Mo7O24. In the experiment dealing with Zn de®ciency no were determined by atomic absorption spectrometry. Zn, but 0.1 mM Fe-EDTA was added, and in the experiment with Fe de®ciency, plants were supplied with 1 mM Fe-EDTA and 1 mM ZnSO4. Due to a limited number of seeds, experi- ments were carried out only under Zn- and Fe-de®cient con- Results ditions with three replications for each genotype. Plants were Plant growth and PS release under Zn deficiency grown for 21 d Zn-de®cient plants) and 13 d Fe-de®cient plants) in nutrient solution under controlled climatic conditions Average shoot dry weights of hexaploid and tetraploid lightudark regimes of 16u18 h, temperature 24u20 8C and photo- wheats were very similar under Zn de®ciency Table 2). synthetic photon ¯ux of 350 mmol mÀ2 sÀ1 at plant height provided by Osram Sylvania cool white FR 96 T12 tubes, However, the genotypes within each species showed Ontario-Canada).