Levent Ozturk

Biofortification and localization of zinc in wheat grain.

Zinc (Zn) deficiency associated with low dietary intake is a well-documented public health problem, resulting in serious health and socioeconomic problems. Field experiments were conducted with wheat to test the role of both soil and foliar application of ZnSO4 in Zn concentration of whole grain and grain fractions (e.g., bran, embryo and endosperm) in 3 locations. Foliar application of ZnSO4 was realized at different growth stages (e.g., stem elongation, boot, milk, dough stages) to study the effect of timing of foliar Zn application on grain Zn concentration. The rate of foliar Zn application at each growth stage was 4 kg of ZnSO4·7H2O ha(-1). Laser ablation (LA)-ICP-MS was used to follow the localization of Zn within grain. Soil Zn application at a rate of 50 kg of ZnSO4·7H2O ha(-1) was effective in increasing grain Zn concentration in the Zn-deficient location, but not in the locations without soil Zn deficiency. In all locations, foliar application of Zn significantly increased Zn concentration in whole grain and in each grain fraction, particularly in the case of high soil N fertilization. In Zn-deficient location, grain Zn concentration increased from 11 mg kg(-1) to 22 mg kg(-1) with foliar Zn application and to 27 mg kg(-1) with a combined application of ZnSO4 to soil and foliar. In locations without soil Zn deficiency, combination of high N application with two times foliar Zn application (e.g., at the booting and milk stages) increased grain Zn concentration, on average, from 28 mg kg(-1) to 58 mg kg(-1). Both ICP-OES and LA-ICP-MS data showed that the increase in Zn concentration of whole grain and grain fractions was pronounced when Zn was sprayed at the late growth stage (e.g., milk and dough). LA-ICP-MS data also indicated that Zn was transported into endosperm through the crease phloem. To our knowledge, this is the first study to show that the timing of foliar Zn application is of great importance in increasing grain Zn in wheat, especially in the endosperm part that is the predominant grain fraction consumed in many countries. Providing a large pool of Zn in vegetative tissues during the grain filling (e.g., via foliar Zn spray) is an important practice to increase grain Zn and contribute to human nutrition.

Biofortification of Durum Wheat with Zinc Through Soil and Foliar Applications of Nitrogen

ABSTRACT Increasing zinc (Zn) concentration of cereal grains is a global challenge to alleviate Zn deficiency-related health problems in humans caused by low dietary Zn intake. This study investigated the effects of soil- and foliar-applied nitrogen (N) and Zn fertilizers on grain Zn accumulation of durum wheat (Triticum durum) grown on a Zn-deficient soil. In addition, localization of Zn and protein within durum wheat grain was studied by using Bradford reagent for protein and dithizone (diphenyl thiocarbazone) for Zn. Grain Zn concentration was greatly enhanced by soil or foliar applications of Zn. When Zn supply was adequately high, both soil and foliar N applications improved grain Zn concentration. Consequently, there was a significant positive correlation between grain concentrations of Zn and N, when Zn supply was not limiting. Protein and Zn staining studies showed co-localization of Zn and protein within grain, particularly in the embryo and aleurone. Results indicate that N and Zn fertilization ...

Morphological and physiological differences in the response of cereals to zinc deficiency

Greenhouse and growth chamber experiments were carried out using seven bread wheat (Triticum aestivum), three durum wheat (T durum), two rye (Secale cereale), three barley (Hordeum vulgare), two triticale (x Triticosecale Wittmack) and one oat (Avena sativa) cultivars to study response to zinc (Zn) deficiency and Zn fertilisation in nutrient solution and in a severely Zn deficient calcareous soil. Visual Zn deficiency symptoms, such as whitish-brown necrotic patches on leaf blades, developed rapidly and severely in the durum wheat and oat cultivars. Bread wheat showed great genotypic differences in sensitivity to Zn deficiency. In triticale and rye, visual deficiency symptoms were either absent or appeared only slightly, while barley showed a moderate sensitivity. When grown in soil, average decreases in shoot dry matter production due to Zn deficiency were 15% for rye, 25% for triticale, 34% for barley, 42% for bread wheat, 63% for oat and 65% for durum wheat. Differential Zn efficiency among and within cereal species was better related to the total amount of Zn per shoot, but not to the Zn concentration in the shoot dry matter. However, in leaves of Zn efficient rye and bread wheat cultivars, the activity of Zn-containing Superoxide dismutase was greater than in Zn inefficient bread and durum wheat cultivars, suggesting higher amounts of physiologically active Zn in leaf tissue of efficient genotypes. When grown in nutrient solution, there was a poor relationship between Zn efficiency and release rate of Zn-chelating phytosiderophores from roots, but uptake of labelled Zn (65Zn) and its translocation to the shoot was higher in the Zn efficient rye and bread wheat cultivars than in inefficient bread and durum wheat cultivars. The results demonstrate that susceptibility of cereals to Zn deficiency decline in the order durum wheat > oat > bread wheat > barley > triticale > rye. The results also show that expression of high Zn efficiency in cereals was causally related to enhanced capability of genotypes to take up Zn from soils and use it efficiently in tissues.

Concentration of zinc and activity of copper/zinc-superoxide dismutase in leaves of rye and wheat cultivars differing in sensitivity to zinc deficiency

Summary Two bread wheat ( Triticum aestivum L. cvs. Bezostaja-1 and BDME-10), two durum wheat ( Triticum durum L. cvs. Kunduru-1149 and Kiziltan-91) and one rye ( Secale cereale L. cv. Ashm) cultivars differing in sensitivity to zinc (Zn) deficiency were grown under controlled environmental conditions for 21 days in a Zn deficient soil to compare severity of Zn deficiency symptoms with the concentration of total Zn and activities of total superoxide dismutase (SOD), copper (Cu) and Zn containing SOD (Cu/Zn-SOD) and manganese (Mn) containing SOD (Mn-SOD) in leaves. Visual Zn deficiency symptoms such as development of whitish-brown necrotic patches on leaf blades appeared rapidly and were severe in bread wheat cultivar BDME-10 and particularly in both durum wheat cultivars, while Bezostaja-1 was much less affected by Zn deficiency. In the case of rye, the leaf symptoms were either absent or only slightly developed. The effect of Zn deficiency on shoot dry matter production was very similar to the effect on leaf symptoms. Decreases in shoot dry matter production as a result of Zn deficiency were about 16 % in Ashm (rye) and Bezostaja-1, 36 % in BDME-10 and 47% in durum wheats. Despite of such marked differences in sensitivity to Zn deficiency, concentrations of Zn in leaf dry matter were not different between the cultivars under Zn deficiency. However, activities of Cu/Zn-SOD and, in part, total SOD, but not Mn-SOD were very closely related with the sensitivity of cultivars to Zn deficiency. Under Zn deficiency, rye showing a high resistance to Zn deficiency had the greatest activity of Cu/Zn-SOD. Among the wheat cultivars, Bezostaja-1 with less sensivity to Zn deficiency showed higher activity of Cu/Zn-SOD than other wheat cultivars. The results suggested that Zn efficient cereal genotypes possess higher amounts of physiologically active Zn in leaves and that activity of Cu/Zn-SOD is a better indicator of Zn nutritional status of plants than Zn concentration alone. An efficient utilization of Zn at the cellular level seems to be a major factor determining expression of Zn efficiency in cereals growing under deficient supply of Zn.

Zinc‐efficient wild grasses enhance release of phytosiderophores under zinc deficiency

Abstract The effect of the zinc (Zn) nutritional status on the rate of phyto‐siderophore release was studied in three wild grass species (Hordeum murinum, Agropyron orientale, and Secale cereale) grown in nutrient solution under co‐trolled environmental conditions. These wild grasses are highly “Zn‐efficient”; and grow well on severely Zn‐deficient calcareous soils in Turkey (DTPA‐extractable Zn was 0.12 mg/kg soil and CaCO3 was 37%). In all wild grasses studied, Zn deficiency reduced shoot growth but had no effect on root growth. Low amounts of phytosiderophores were released from roots of all wild grasses adequately supplied with Zn. In plants grown without Zn, release of phytosiderophores progressively increased with the onset of visual Zn deficiency symptoms, such as inhibition of shoot elongation and appearance of chlorotic and necrotic patches on leaves. Compared to Zn‐sufficient plants, phytosiderophore release increased 18–20‐fold in deficient plants. HPLC analysis of root exudates showed that the...

Genetic diversity for grain nutrients in wild emmer wheat: potential for wheat improvement

BACKGROUND AND AIMS Micronutrient malnutrition, particularly zinc and iron deficiency, afflicts over three billion people worldwide due to low dietary intake. In the current study, wild emmer wheat (Triticum turgidum ssp. dicoccoides), the progenitor of domesticated wheat, was tested for (1) genetic diversity in grain nutrient concentrations, (2) associations among grain nutrients and their relationships with plant productivity, and (3) the association of grain nutrients with the eco-geographical origin of wild emmer accessions. METHODS A total of 154 genotypes, including wild emmer accessions from across the Near Eastern Fertile Crescent and diverse wheat cultivars, were characterized in this 2-year field study for grain protein, micronutrient (zinc, iron, copper and manganese) and macronutrient (calcium, magnesium, potassium, phosphorus and sulphur) concentrations. KEY RESULTS Wide genetic diversity was found among the wild emmer accessions for all grain nutrients. The concentrations of grain zinc, iron and protein in wild accessions were about two-fold greater than in the domesticated genotypes. Concentrations of these compounds were positively correlated with one another, with no clear association with plant productivity, suggesting that all three nutrients can be improved concurrently with no yield penalty. A subset of 12 populations revealed significant genetic variation between and within populations for all minerals. Association between soil characteristics at the site of collection and grain nutrient concentrations showed negative associations between soil clay content and grain protein and between soil-extractable zinc and grain zinc, the latter suggesting that the greatest potential for grain nutrient minerals lies in populations from micronutrient-deficient soils. CONCLUSIONS Wild emmer wheat germplasm offers unique opportunities to exploit favourable alleles for grain nutrient properties that were excluded from the domesticated wheat gene pool.

Biofortification of wheat with iron through soil and foliar application of nitrogen and iron fertilizers

Increasing iron (Fe) concentration in food crops is an important global challenge due to high incidence of Fe deficiency in human populations. Evidence is available showing that nitrogen (N) fertilization increases Fe concentration in wheat grain. This positive impact of N on grain Fe was, however, not studied under varied soil and foliar applications of Fe. Greenhouse experiments were conducted to investigate a role of soil- and foliar-applied Fe fertilizers in improving shoot and grain Fe concentration in durum wheat (Triticum durum) grown under increasing N supply as Ca-nitrate. Additionally, an effect of foliar Fe fertilizers on grain Fe was tested with and without urea in the spray solution. Application of various soil or foliar Fe fertilizers had either a little positive effect or remained ineffective on shoot or grain Fe. By contrast, at a given Fe treatment, raising N supply substantially enhanced shoot and grain concentrations of Fe and Zn. Improving N status of plants from low to sufficient resulted in a 3-fold increase in shoot Fe content (e.g., total Fe accumulated), whereas this increase was only 42% for total shoot dry weight. Inclusion of urea in foliar Fe fertilizers had a positive impact on grain Fe concentration. Nitrogen fertilization represents an important agronomic practice in increasing grain Fe. Therefore, the plant N status deserves special attention in biofortification of food crops with Fe.

Shoot biomass and zinc/cadmium uptake for hyperaccumulator and non-accumulator Thlaspi species in response to growth on a zinc-deficient calcareous soil

Thlaspi caerulescens is one of the best-known heavy metal hyperaccumulating plant species. It exhibits the ability to extract metals from soils and accumulates them in shoots at extremely high concentrations, particularly zinc (Zn) and cadmium (Cd). Using T. caerulescens (J. and C. Presl, ecotype Prayon) and a closely related non-accumulator species T. arvense, greenhouse experiments were carried out to study shoot growth (dry matter production) and Zn and Cd uptake from a severely Zn-deficient calcareous soil (DTPA-Zn: 0.09 mg kg−1 soil) supplemented with increasing amounts of Zn (0, 0.05, 0.5, 5, 25 and 75 mg kg−1 soil) and Cd (0 and 25 mg kg−1 soil). Shoot dry matter production of T. caerulescens was severely depressed by Zn deficiency, while in T. arvense, Zn deficiency slightly reduced growth. At the lowest Zn supplies (0 and 0.05 mg Zn kg−1 soil), T. caerulescens showed very severe Zn deficiency symptoms, including decreased leaf size and development of chlorosis and whitish-brown necrosis on the younger leaves. These symptoms were slight in T. arvense. At the highest Zn supply, leaves of T. caerulescens did not show any symptoms, but in T. arvense there were some necrotic patches on the margins of older leaves, probably due to Zn toxicity. With increasing Zn supply from 0 to 75 mg kg−1 soil, shoot dry matter production was increased by 4-fold in T. caerulescens and only 1.3-fold in T. arvense. Supply of Cd resulted in marked decrease in shoot growth of T. arvense, particularly under low Zn supply, but had no effect on the growth of T. caerulescens. At the low soil Zn levels ( 5 mg Zn kg−1), shoot Zn concentrations were considerably higher in T. caerulescens than T. arvense. Increase in Zn supply from 0 to 75 mg kg−1 enhanced shoot Zn concentrations by 84-fold in T. caerulescens and only 8-fold in T. arvense. Shoot Zn concentrations of both species were not affected by Cd supply, while increase in Zn supply did not affect Cd concentrations in shoot of T. caerulescens, but markedly reduced them in T. arvense. The results demonstrate that T. caerulescens is extremely sensitive to Zn deficiency in soils, but tolerant to excessive accumulation of Zn and also Cd in shoot, while T. arvense is tolerant to Zn deficiency but not to accumulation of Zn and Cd in shoot. Hyperaccumulation of Zn in T. caerulescens possibly depends on the existence of high concentrations of plant-available Zn in soils, which suggests that root-based mechanisms associated with increasing metal availability in the rhizosphere (e.g., rhizosphere acidification or release of Zn-mobilizing organic compounds from roots) only play a minor role in metal hyperaccumulation by T. caerulescens. The findings also suggest that the processes causing the metal hyperaccumulation trait in T. caerulescens also cause this plant species to be sensitive to Zn deficiency stress.

Glyphosate inhibition of ferric reductase activity in iron deficient sunflower roots

Iron (Fe) deficiency is increasingly being observed in cropping systems with frequent glyphosate applications. A likely reason for this is that glyphosate interferes with root uptake of Fe by inhibiting ferric reductase in roots required for Fe acquisition by dicot and nongrass species. This study investigated the role of drift rates of glyphosate (0.32, 0.95 or 1.89 mm glyphosate corresponding to 1, 3 and 6% of the recommended herbicidal dose, respectively) on ferric reductase activity of sunflower (Helianthus annuus) roots grown under Fe deficiency conditions. Application of 1.89 mm glyphosate resulted in almost 50% inhibition of ferric reductase within 6 h and complete inhibition 24 h after the treatment. Even at lower rates of glyphosate (e.g. 0.32 mm and 0.95 mm), ferric reductase was inhibited. Soluble sugar concentration and the NAD(P)H oxidizing capacity of apical roots were not decreased by the glyphosate applications. To our knowledge, this is the first study reporting the effects of glyphosate on ferric reductase activity. The nature of the inhibitory effect of glyphosate on ferric reductase could not be identified. Impaired ferric reductase could be a major reason for the increasingly observed Fe deficiency in cropping systems associated with widespread glyphosate usage.

High phosphorus supply reduced zinc concentration of wheat in native soil but not in autoclaved soil or nutrient solution

AimsPhosphorus (P)-induced zinc (Zn) deficiency is one of the most commonly studied antagonistic interactions in plant nutrition. However, there are many controversial reports about P–Zn interaction, possibly related to growth conditions. In this study, the effects of P supply on the root uptake and tissue concentrations of Zn as well as the development of Zn deficiency were investigated in wheat (Triticum aestivum) grown in different media.MethodsPlants were grown under greenhouse and growth chamber conditions in native soil, autoclaved soil and nutrient solution with different P and Zn supplies. In the soil experiment, the shoot biomass and grain yield were measured whereas in the nutrient solution experiment, the root and shoot biomass were determined. Development of Zn deficiency symptoms was examined. Concentrations of Zn, P and other elements were measured in harvested tissues. Mycorrhizal colonization of roots was scored in soil-grown plants. Root uptake of stable Zn isotope (70Zn) was investigated at different P rates in a separate nutrient solution experiment.ResultsHigher P rates caused substantial decreases in shoot and grain Zn concentrations in native soil but not in autoclaved soil. Treatment of native soil with increasing P significantly reduced mycorrhizal colonization. At low Zn, P applications aggravated Zn deficiency symptoms in both soil and solution culture. In solution culture, root and shoot Zn concentrations were not lowered by higher P rates. Root uptake of 70Zn from nutrient solution was even depressed at low P.ConclusionsThe negative effect of increasing P supply on root Zn uptake and tissue Zn concentrations in wheat is mycorrhiza-dependent and may completely disappear in a mycorrhiza-free environment.