Grain zinc, iron and protein concentrations and zinc-efficiency in wild emmer wheat under contrasting irrigation regimes

Micronutrient malnutrition, and particularly deficiency in zinc (Zn) and iron (Fe), afflicts over three billion people worldwide, and nearly half of the world’s cereal-growing area is affected by soil Zn deficiency. Wild emmer wheat [Triticum turgidum ssp. dicoccoides (Körn.) Thell.], the progenitor of domesticated durum wheat and bread wheat, offers a valuable source of economically important genetic diversity including grain mineral concentrations. Twenty two wild emmer wheat accessions, representing a wide range of drought resistance capacity, as well as two durum wheat cultivars were examined under two contrasting irrigation regimes (well-watered control and water-limited), for grain yield, total biomass production and grain Zn, Fe and protein concentrations. The wild emmer accessions exhibited high genetic diversity for yield and grain Zn, Fe and protein concentrations under both irrigation regimes, with a considerable potential for improvement of the cultivated wheat. Grain Zn, Fe and protein concentrations were positively correlated with one another. Although irrigation regime significantly affected ranking of genotypes, a few wild emmer accessions were identified for their advantage over durum wheat, having consistently higher grain Zn (e.g., 125 mg kg^?1), Fe (85 mg kg^?1) and protein (250 g kg^?1) concentrations and high yield capacity. Plants grown from seeds originated from both irrigation regimes were also examined for Zn efficiency (Zn deficiency tolerance) on a Zn-deficient calcareous soil. Zinc efficiency, expressed as the ratio of shoot dry matter production under Zn deficiency to Zn fertilization, showed large genetic variation among the genotypes tested. The source of seeds from maternal plants grown under both irrigation regimes had very little effect on Zn efficiency. Several wild emmer accessions revealed combination of high Zn efficiency and drought stress resistance. The results indicate high genetic potential of wild emmer wheat to improve grain Zn, Fe and protein concentrations, Zn deficiency tolerance and drought resistance in cultivated wheat.     

Enrichment of fertilizers with zinc: An excellent investment for humanity and crop production in India

Micronutrient malnutrition is a growing concern in the developing world, resulting in diverse health and social problems, such as mental retardations, impairments of the immune system and overall poor health. In recent years, the zinc (Zn) deficiency problem has received increasing attention and appears to be the most serious micronutrient deficiency together with vitamin A deficiency. Zinc deficiency is particularly widespread among children and represents a major cause of child death in the world. In countries where Zn deficiency is well documented as an important public health problem, cereal-based foods are the predominant source of daily calorie and protein intake. Because the concentration of Zn in cereal crops is inherently very low, growing cereals on potentially Zn-deficient soils further decreases grain Zn concentrations. It is, therefore, not surprising that high Zn deficiency incidence in humans occurs predominantly on areas where soils are deficient in plant-available Zn, as shown in many Southeast Asian countries. India has some of the most Zn-deficient soils in the world. Nearly 50% of cultivated soils in India are low in plant-available Zn; these soils are under intensive cultivation of wheat and rice with no or little application of Zn fertilizers. Consequently, cereal crops grown on such Zn-deficient soils contribute only marginally to daily Zn intake. In the rural areas of India, rice and wheat contributes nearly 75% of the daily calorie intake. These facts clearly point to an urgent need for improved Zn concentration of cereal grains in India. Recent calculations indicate that biofortification (enrichment) of rice and wheat grain with Zn, for example by breeding, may save lives of up to 48,000 children in India annually. Breeding new cereal genotypes for high grain Zn concentration is the most realistic and cost-effective strategy to address the problem. However, this strategy is a long-term one, and the size of plant-available Zn pools in soils may greatly affect the capacity of Zn-efficient (biofortified) cultivars to take up Zn and accumulate it in grains. Therefore, application of Zn-containing fertilizers represents a quick and effective approach to biofortifying cereal grains with Zn, thus being an excellent complementary tool to the breeding strategy for successful biofortification of cereals with Zn. Increasing evidence is available from field trials showing that soil and/or foliar application of Zn fertilizers improves grain Zn concentration up to 2- or 3-fold. In the countries where Zn deficiency is both a public health issue and an important soil constraint to crop production, like in India, enrichment of widely applied fertilizers with Zn would be an excellent investment for improving grain Zn while contributing to increased crop production. Recent work by the scientists of the Indian Agricultural Research Institute indicates that the use of Zn-enriched urea in rice and wheat significantly improves both grain Zn concentration and grain yield. It is obvious that enrichment of widely applied fertilizers with Zn and/or foliar application of Zn fertilizers appear to be a high priority with the strongest potential to alleviate Zn deficiency-related problems in India. A Government action and policy plan for enrichment of selected major fertilizers with Zn is required urgently.     

Quantitative trait loci conferring grain mineral nutrient concentrations in durum wheat × wild emmer wheat RIL population

Mineral nutrient malnutrition, and particularly deficiency in zinc and iron, afflicts over 3 billion people worldwide. Wild emmer wheat, Triticum turgidum ssp. dicoccoides, genepool harbors a rich allelic repertoire for mineral nutrients in the grain. The genetic and physiological basis of grain protein, micronutrients (zinc, iron, copper and manganese) and macronutrients (calcium, magnesium, potassium, phosphorus and sulfur) concentration was studied in tetraploid wheat population of 152 recombinant inbred lines (RILs), derived from a cross between durum wheat (cv. Langdon) and wild emmer (accession G18-16). Wide genetic variation was found among the RILs for all grain minerals, with considerable transgressive effect. A total of 82 QTLs were mapped for 10 minerals with LOD score range of 3.2–16.7. Most QTLs were in favor of the wild allele (50 QTLs). Fourteen pairs of QTLs for the same trait were mapped to seemingly homoeologous positions, reflecting synteny between the A and B genomes. Significant positive correlation was found between grain protein concentration (GPC), Zn, Fe and Cu, which was supported by significant overlap between the respective QTLs, suggesting common physiological and/or genetic factors controlling the concentrations of these mineral nutrients. Few genomic regions (chromosomes 2A, 5A, 6B and 7A) were found to harbor clusters of QTLs for GPC and other nutrients. These identified QTLs may facilitate the use of wild alleles for improving grain nutritional quality of elite wheat cultivars, especially in terms of protein, Zn and Fe.     

Optimized potassium nutrition improves plant-water-relations of barley under PEG-induced osmotic stress

Aims

Water use efficiency (WUE) of crop plants is an important plant trait for maintaining high yield in water limited areas. By influencing osmoregulation of plants, potassium (K) plays a critical role in stress avoidance and adaptation. However, whole plant physiological mechanisms modulated by K supply in respect of plant drought tolerance and water use efficiency are not well understood. In the present study, growth, development and transpiration dynamics of two barley cultivars were evaluated with and without PEG-induced osmotic stress using an automated balance system and image based leaf area determination.

Methods

Experiments were conducted to study the effects of varied K supply under different osmotic stress treatments on a wide range of morphological, biochemical and physiological characteristics of barley plants such as leaf area development, daily whole plant transpiration rate (DTR), stomatal conductance (g_s), assimilation rate (A_N), biomass and leaf water use efficiency (WUE) as well as foliar abscisic acid (ABA) concentrations. Two barley cultivars (cv. Sahin-91 and cv. Milford) were treated with two K supply levels (0.04 and 0.8 mM K) and osmotic stress induced by polyethylene glycol 6000 (PEG) for a period of 9 days (in total 48 days experiment) in the hydroponic plant culture (non-PEG and + 20% PEG ).

Results

Without PEG, low-K supply depressed dry matter (DM) by almost 60% averaged across both cultivars. Under osmotic stress (+PEG), total leaf area was reduced by almost 70% in low-K compared to adequate-K plants. Low K concentration under PEG stress was correlated with higher ABA concentration and was correlated with lower leaf- and whole plant transpiration rate. Biomass-WUE under low K supply decreased significantly in both barley cultivars, to a greater extent in cv. Milford under osmotic stress. However, leaf-WUE was not affected by K supply in the absence of osmotic stress.

Conclusions

It was suggested that reduced biomass-WUE in low-K treated barley plants was not related to inefficient stomatal control under K deficiency, but instead due to reduced assimilation rate. It was further hypothesized that under low K supply, a number of energy consuming activities reduce biomass-WUE, which are not distinguished by measuring leaf-WUE. This study showed that low K supply under osmotic stress increases foliar ABA concentration thereby decreasing plant transpiration.

     

Maternal care,larviparous and oviparous reproduction of <Emphasis Type="Italic">Hypoaspis larvicolus</Emphasis> (Acari: Laelapidae) feeding on astigmatid mites

Hypoaspis larvicolus (Acari: Laelapidae) (first report from Turkey) occurred together with Sancassania polyphyllae (Acari: Acaridae) on the larvae of the scarab beetle, Polyphylla fullo (Coleoptera: Scarabaeidae), that were feeding on the roots of strawberry in Aydin, Turkey. Laboratory studies were conducted to (1) observe whether H. larvicolus feeds and completes its life cycle on the various stages of S. polyphyllae or other astigmatid mites, such as Acarus siro, Carpoglyphus lactis and Tyrophagus putrescentiae (Acaridae), and to determine its population growth when feeding on these prey, and (2) to determine development periods, longevity and fecundity of H. larvicolus feeding on C. lactis. Hypoaspis larvicolus females did not feed on S. polyphyllae, but fed, developed and reproduced when A. siro, C. lactis or T. putrescentiae were provided as prey. Hypoaspis larvicolus is larviparous as well as oviparous. The female lays eggs or gives birth to larvae. If a female gives birth to a larva, it is attached under the female’s venter for 1–2 days, a phenomenon recorded for the first time in Hypoaspis; in fact, for the first time in mites. The results of the population growth experiments revealed that H. larvicolus feeding on C. lactis produced the highest number of eggs, juveniles and adults. The developmental periods of H. larvicolus feeding on C. lactis at life-cycle path I (larva to adult) and II (egg to adult) were 12.2?±?0.3 and 15.6?±?0.6 days (females) and 19.5?±?0.2 and 20.9?±?0.4 days (males), respectively. Longevity of females versus males of H. larvicolus was 120.6?±?7.2 versus 91.6?±?13.1 days (life cycle I) and 110.0?±?27.7 versus 118.3?±?10.9 days (life cycle II), respectively.     

Zinc deficiency as a critical problem in wheat production in Central Anatolia

In a soil and plant survey, and in field and greenhouse experiments the nutritional status of wheat plants was evaluated for Zn, Fe, Mn and Cu in Central Anatolia, a semi-arid region and the major wheat growing area of Turkey.All 76 soils sampled in Central Anatolia were highly alkaline with an average pH of 7. 9. More than 90% of soils contained less than 0.5 mg kg^-1 DTPA-extractable Zn, which is widely considered to be the critical deficiency concentration of Zn for plants grown on calcareous soils. About 25% of soils contained less than 2.5 mg kg^-1 DTPA-extractable Fe which is considered to be the critical deficiency concentration of Fe for plants. The concentrations of DTPA-extractable Mn and Cu were in the sufficiency range. Also the Zn concentrations in leaves were very low. More than 80% of the 136 leaf samples contained less than 10 mg Zn kg^–1. By contrast, concentrations of Fe, Mn and Cu in leaves were in the sufficient range.In the field experiments at six locations, application of 23 kg Zn ha^-1 increased grain yield in all locations. Relative increases in grain yield resulting from Zn application ranged between 5% to 554% with a mean of 43%. Significant increases in grain yield (more than 31%) as a result of Zn application were found for the locations where soils contained less than 0.15 mg kg^-1 DTPA-extractable Zn.In pot experirnents with two bread (Triticum aestivum, cvs. Gerek-79 and Kirac-66) and two durum wheats (Triticum durum, cvs. Kiziltan-91 and Kunduru-1149), an application of 10 mg Zn kg^-1 soil enhanced shoot dry matter production by about 3.5-fold in soils containing 0.11 mg kg^-1 and 0.15 mg kg^-1 DTPA-extractable Zn. Results from both field observations and greenhouse experiments showed that durum wheats were more susceptible to Zn deficiency than the bread wheats. On Zn deficient soils, durum wheats as compared to bread wheats developed deficiency symptoms in shoots earlier and to a greater extent, and had lower Zn concentration in shoot tissue and lower Zn content per shoot than the bread wheats.The results presented in this paper demonstrate that (i) Zn deficiency is a critical nutritional problem in Central Anatolia substantially limiting wheat production, (ii) durum wheats possess higher sensitivity to Zn deficient conditions than bread wheats, and (iii) wheat plants grown in calcareous soils containing less than 0.2 mg kg^-1 DTPA-extractable Zn significantly respond to soil Zn applications. The results also indicate that low levels of Zn in soils and plant materials (i.e. grains) could be a major contributing factor for widespread occurrence of Zn deficiency in children in Turkey, whose diets are dominated by cereal-based foods.     

Phytosiderophore release in bread and durum wheat genotypes differing in zinc efficiency

The effect of the zinc (Zn) nutritional status on the rate of phytosiderophore release was studied in nutrient solution over 20 days in four bread wheat (Triticum aestivum cvs. Kiraç-66, Gerek-79, Aroona and Kirkpinar) and four durum wheat (Triticum durum cvs. BDMM-19, Kunduru-1149, Kiziltan-91 and Durati) genotypes differing in Zn efficiency.Visual Zn deficiency symptoms, such as whitish-brown necrosis on leaves and reduction in plant height appeared first and more severe in Zn-inefficient durum wheat genotypes Kiziltan-91, Durati and Kunduru-1149. Compared to the bread wheat genotypes, all durum wheat genotypes were more sensitive to Zn deficiency. BDMM-19 was the least affected durum wheat genotype. Among the bread wheat genotypes, Kirkpinar was the most sensitive genotype. In all genotypes well supplied with Zn, the rate of phytosiderophore release was very low and did not exceed 1 mol 32 plants^-1 3h^-1, or 0.5 mol g^-1 root dry wt 3h^-1. However, under Zn deficiency, with the onset of visual Zn deficiency symptoms, the release of phytosiderophores was enhanced in bread wheat genotypes up to 7.5 mol 32 plants^-1 3h^-1, or 9 mol g^-1 root dry wt 3h^-1, particularly in Zn-efficient Kiraç-66, Gerek-79 and Aroona. In contrast to bread wheat genotypes, phytosiderophore release in Zn-deficient durum wheat genotypes remained at a very low rate. Among the durum wheat genotypes BDMM-19 had highest rate of phytosiderophore release. HPLC analysis of root exudates showed that 2-deoxymugineic acid (DMA) is the dominating phytosiderophore released from roots of Zn-efficient genotypes. In root extracts concentration of DMA was also much higher in Zn-efficient than in inefficient genotypes. The results demonstrate that enhanced synthesis and release of phytosiderophores at deficient Zn supply is involved in Zn efficiency in wheat genotypes. It is suggested that the expression of Zn efficiency mechanism is causally related to phytosiderophore-mediated enhanced mobilization of Zn from sparingly soluble Zn pools and from adsorption sites, both in the rhizosphere and plants.     

Boron deficiency-induced impairments of cellular functions in plants

The essentiality of B for growth and development of plants is well-known, but the primary functions of B still remain unknown. Evidence in the literature supports the idea that the major functions of B in growth and development of plants are based on its ability to form complexes with the compounds having cis-diol configurations. In this regard, the formation of B complexes with the constituents of cell walls and plasma membranes as well as with the phenolic compounds seems to be a decisive step affecting the physiological functions of B. Boron seems to be of crucial importance for the maintenance of structural integrity of plasma membranes. This function of B is mainly related to stabilisation of cell membranes by B association with membrane constituents. Possibly, B may also protect plasma membranes against peroxidative damage by toxic O₂ species. In B-deficient plants, plasma membranes are highly leaky and lose their functional integrity. Under B-deficient conditions, substantial changes in ion fluxes and proton pumping activity of the plasma membranes were noted. Impairments in phenol metabolism and increases in levels of phenolics and polyphenoloxidase activity are typical indications of B deficiency, particularly in B deficiency-sensitive plant species, such as Helianthus annuus (sunflower). Enhanced oxidation of phenols is responsible for generation of reactive quinones which subsequently produce extremely toxic O₂ species, thus resulting in the increased risk of a peroxidative damage to vital cell components such as membrane lipids and proteins. In B-deficient tissues, enhancement in levels of toxic O₂ species may also occur as a result of impairments in photosynthesis and antioxidative defence systems. Recent evidence shows that the levels of ascorbic acid, non-protein SH-compounds (mainly glutathione) and glutathione reductase, the major defence systems of cells against toxic O₂ species, are reduced in response to B deficiency. There is also increasing evidence that, in the heterocyst cells of cyanobacteria, B is involved in protection of nitrogenase activity against O₂ damage.     

Computational screening of dipeptidyl peptidase IV inhibitors from micoroalgal metabolites by pharmacophore modeling and molecular docking

Dipeptidyl peptidase IV (DPP‐IV) catalyzes conversion of GLP‐1 (glucagon like peptide 1) to inert structure, which results in insufficient secretion of insulin and increase in postprandial blood glucose level. The present study attempts to identify novel inhibitors from bioactive metabolites present in microalgae against DPP‐IV through virtual screening, molecular docking, and pharmacophore modeling for the active target. Possible binding modes of all 60 ligands against DPP‐IV receptor were constructed using MTiOpenScreen virtual screening server. Pharmacophore model was built based on identified 38 DPP‐IV test ligands by using the web‐based PharmaGist program which encompasses hydrogen‐bond acceptors, hydrophobic groups, spatial features, and aromatic rings. The pharmacophore model having highest scores was selected to screen active DPP‐IV ligands. Highest scoring model was used as a query in ZincPharmer screening. All identified ligands were filtered, based on the Lipinski's rule‐of‐five and were subjected to docking studies. In the process of docking analyses, we considered different bonding modes of one ligand with multiple active cavities of DPP‐IV with the help of AutoDock 4.0. The docking analyses indicate that the bioactive constituents, namely, β‐stigmasterol, barbamide, docosahexaenoic acid, arachidonic acid, and harman showed the best binding energies on DPP‐IV receptor and hydrogen bonding with ASP545, GLY741, TYR754, TYR666, ARG125, TYR547, SER630, and LYS554 residues. This study concludes that docosahexaenoic acid, arachidonic acid, β‐stigmasterol, barbamide, harman, ZINC58564986, ZINC56907325, ZINC69432950, ZINC69431828, ZINC73533041, ZINC84287073, ZINC69849395, and ZINC10508406 act as possible DPP‐IV inhibitors.     

Involvement of superoxide radical in extracellular ferric reduction by iron-deficient bean roots

The recent proposal of Tipton and Thowsen (Plant Physiol 79: 432-435) that iron-deficient plants reduce ferric chelates in cell walls by a system dependent on the leakage of malate from root cells was tested. Results are presented showing that this mechanism could not be responsible for the high rates of ferric reduction shown by roots of iron-deficient bean (Phaseolus vulgaris L. var Prélude) plants. The role of O₂ in the reduction of ferric chelates by roots of iron-deficient bean plants was also tested. The rate of Fe(III) reduction was the same in the presence and in the absence of O₂. However, in the presence of O₂ the reaction was partially inhibited by superoxide dismutase (SOD), which indicates a role for the superoxide radical, O₂^[unk], as a facultative intermediate electron carrier. The inhibition by SOD increased with substrate pH and with decrease in concentration of the ferrous scavenger bathophenanthroline-disulfonate. The results are consistent with a mechanism for transmembrane electron transport in which a flavin or quinone is the final electron carrier in the plasma membrane. The results are discussed in relation to the ecological importance that O₂^[unk] may have in the acquisition of ferric iron by dicotyledonous plants.