Fe Deficiency Stress Research Articles

Overcoming Fe deficiency by a transgenic approach in rice

Iron (Fe) is an essential microelement for plant growth. Fe availability is particularly limited on calcareous soils, which have high pH. Approximately 30% of the world's soils are considered calcareous with low Fe availability, which results in extensive areas of Fe deficiency in plants. Some graminaceous plants are known to secrete high amounts of mugineic acid family phytosiderophores (MAs) under Fe deficiency. This Fe acquisition system is called the Strategy-II mechanism. Tolerance to Fe deficiency in graminaceous plants is thought to depend on the quantity of MAs secreted by plants under Fe deficiency stress. This system was utilized to enhance the tolerance of rice to low Fe availability. Transgenic rice expressing the barley naat genes, one of the genes for the enzymes on the biosynthetic pathway of MAs, showed tolerance to low Fe availability when grown in a calcareous soil.

EFFECT OF IRON DEFICIENCY STRESS ON IRON-REDUCTASE ACTIVITY AT PLASMALEMMA OF APPLE ROOT CELLS

ABSTRACT Using two phase systems, plasma membrane (PM) of root cells was separated and purified from Malus xiaojinensis Cheng et Jiang, and iron (Fe)-reductase activities on PM analyzed, under conditions of both the normal Fe level (+Fe) and the Fe deficiency stress (−Fe) were compared. The results showed that FeCN-reductase on PM depended on NADH as the electron donor. The FeCN-reductase activity was 2.66 μmol L−1 mg−1 min−1 at +Fe, while the reductase activity was 4.92 μmol L−1 mg−1 min−1 at −Fe. Fe-EDTA-reductase could depend on either NADH or NADPH as the electron donor. There were no differences in Fe-EDTA-reductase activities on PM at either +Fe or −Fe, when the electron donor was NADPH. NADH being as the electron donor, however, the Fe-EDTA-reductase activity was 4.06 μmol L−1 mg−1 min−1 at −Fe, while the reductase activity was 2.73 μmol L−1 mg−1 min−1 at +Fe. Therefore, Fe3+ reduction on PM by Fe-reductase systems could be induced and also enhanced in M. xiaojinensis by Fe deficiency stress, which indicated that M. xiaojinensis had a stronger Fe deficiency stress response, and it was an Fe-efficient fruit genotype.

GENOTYPIC DIFFERENCE IN SEED IRON CONTENT AND EARLY RESPONSES TO IRON DEFICIENCY IN WHEAT

ABSTRACT Wheat plants were grown in nutrient solution with or without 100 ÂμM iron (Fe) under controlled environmental conditions. Two wheat genotypes were chosen as two extremes in seed Fe content (Z181 with 1.18 Âμg Fe seed−1 and N85021 with 2.21 Âμg Fe seed−1) from a field screening-experiment that showed a significant difference in seed Fe contents among 26 wheat cultivars. Under 0 ÂμM Fe supply, N85021 showed better seedling vigor, and had greater dry matter production-dates printpubdate="07/01/2002" in root and shoot, chlorophyll concentration in fresh fully expanded leaves and Fe uptake in both root and shoot in comparison with Z181. However, there was no significant difference for the two genotypes when 100 ÂμM Fe was supplied. For the 0 ÂμM Fe treatment, the genotype N85021 with high seed Fe had a higher Fe concentration in plants than Z181. Most of seed Fe was transported into the seedling tissues due to the absence of external Fe supply. The difference in Fe concentration between the two genotypes was greater in roots than shoots. On day 13 after germination, the percentage of Fe translocated from seed to plant was 82% for N85021 and 86% for Z181. The rate of phytosiderophore release was higher for Z181 than N85021 only on day 5 after germination due to Z181 being more sensitive to Fe deficiency stress than N85021. The release of phytosiderophores by N85021 increased sharply with the duration of treatment and surpassed Z181 after day 6. The highest release of phytosiderophores by wheat plants was observed on day 11 for Z181 and day 12 for N85021. Compared with Z181, N85021 exuded a higher amount of phytosiderophores under Fe deficiency till day 17 after treatment. N85021 had higher chlorosis resistance than Z181; this genotypic difference in Fe efficiency between N85021 and Z181 could have resulted from both a higher rate of phytosiderophore release and a higher seed Fe content. The pattern of phytosiderophore release, as an important factor related to tolerance to Fe deficiency was mainly controlled by the genotype, while seed Fe content showed only a modifying effect via changing the dynamics of phytosiderophore release over time. The higher Fe content in seed may also be an important factor related to chlorosis resistance in wheat because it improves the early establishment of seedlings. Sowing high-Fe seed combined with growing Fe-efficient genotypes may be an effective measure to solve the Fe-deficiency-related chlorosis in wheat. Thus, the effect of seed Fe content should be taken into account when comparing genotypes for resistance to Fe deficiency

CDNA microarray analysis of gene expression during Fe-deficiency stress in barley suggests that polar transport of vesicles is implicated in phytosiderophore secretion in Fe-deficient barley roots.

To acquire Fe from soil, graminaceous plants secrete mugineic acid family phytosiderophores (MAs) from their roots. The secretion of MAs increases in response to Fe deficiency, and shows a distinct diurnal rhythm. We used a microarray that included 8987 cDNAs of rice EST clones to examine gene expression profiles in barley roots during Fe-deficiency stress. Approximately 200 clones were identified as Fe-deficiency-inducible genes, of which seven had been identified previously. In order to meet the increased demand for methionine to produce MAs, Fe-deficiency enhances the expression of genes that participate in methionine synthesis, as well as recycling methionine through the Yang cycle. Of these 200 genes, approximately 50 exhibited different transcription levels in Fe-deficient roots at noon and at night. Northern blot analysis of time course experiments confirmed that five of these genes exhibited a diurnal change in their level of expression. The diurnal changes in the expression of these genes suggest that polar vesicle transport is involved in the diurnal secretion of MAs.

Phytosiderophore release from nodal, primary, and complete root systems in maize

Some maize (Zea mays L.) hybrids grown in high pH soil in Nebraska suffer from severely reduced yields caused by iron (Fe) deficiency chlorosis. Hybrids which recover from early season Fe-deficiency chlorosis and yield well are termed Fe-efficient or tolerant. Most Fe-efficient gramineous species respond to Fe-deficiency stress by releasing phytosiderophores (mugineic acid and its derivatives) into the rhizosphere, thereby increasing Fe availability and uptake of the Fe 3+ -phytosiderophore complex via a high affinity uptake system. Field-grown Fe-efficient maize recovers from Fe-deficiency chlorosis at a stage when nodal roots have become the dominant root system. Quantifying phytosiderophore release from hydroponically grown plants has been proposed as a viable alternative to time-consuming and variable field trials and has been used successfully to delineate among Fe-efficient and Fe-inefficient lines of oat (Avena sativa L.) and wheat (Triticum aestivum L.). Our objectives were (1) to determine if phytosiderophore release differed between nodal- and primary-root systems of maize. and (2) to compare phytosiderophore release from 12 hybrids. Root exudates secreted during daily 4-h collections were analyzed for their Fe-solubilizing ability, which was equated to phytosiderophore release. Nodal root systems released significantly more phytosiderophore than primary- or complete-root systems. In early experiments, an Fe-efficient hybrid (P3279) released more phytosiderophore from nodal roots than an Fe-inefficient hybrid (P3489). Tests of an additional 10 hybrids showed that phytosiderophore release varied significantly among the cultivars but did not clearly distinguish between hybrids classified as Fe-efficient or Fe-inefficient in individual company trials. We recommend using nodal roots when studying Fe-stress response mechanisms in maize.

Photodegradation of FeDTPA in Nutrient Solutions. II. Effects on Root Physiology and Foliar Fe and Mn Levels in Marigold

Marigold (Tagetes erecta L.) grown hydroponically in an irradiated nutrient solution containing FeDTPA had root ferric reductase activity 120% greater, foliar Fe level 33% less, and foliar Mn level 90% greater than did plants grown in an identical, nonirradiated solution, indicating that the plants growing in the irradiated solution were responding to Fe-deficiency stress with physiological reactions associated with Fe efficiency. The youngest leaves of plants grown in the irradiated solution had symptoms of Mn toxicity (interveinal chlorosis, shiny-bronze necrotic spots, and leaf deformation). Plants grown in irradiated solution in which the precipitated Fe was replaced with fresh Fechelate were, in general, no different from those grown in the nonirradiated solution. Chemical name used: ferric diethylenetriaminepentaacetic acid (FeDTPA).

Iron resupply-mediated deactivation of Fe-deficiency stress responses in roots of sugar beet

Different root zones with or without increased Fe-reducing activities have been studied in Fe-deficient sugar beet (Beta vulgaris L.) plants after Fe resupply to the nutrient solution. The subapical regions of roots from Fe-deficient plants decreased by 19 and 88% their capacity to reduce ferric chelates after 24 and 96 h of Fe resupply, respectively. Iron resupply caused 52 and 96% decreases in phosphoenolpyruvate carboxylase activity in root extracts after 24 and 96 h, respectively, and also caused general decreases in other enzyme activities involved in carboxylic acid metabolism. The large pools of carboxylic acids in Fe-deficient roots decreased by 9 and 48% after 24 and 96 h of Fe resupply, respectively. The activities of pyruvate decarboxylase and lactate dehydrogenase, enzymes related to anaerobic metabolism, decreased by 88% after 24 h of Fe resupply. The mitochondrial quinone and pyridine nucleotide pools became more oxidised in the Fe-deficient root tips after Fe resupply. Iron resupply caused a 70% decrease in root oxygen consumption rates 96 h after Fe resupply. Results indicate that deactivation of the Fe deficiency stress responses of sugar beet roots upon Fe resupply occurs in a progressive manner in a time scale of several days.

Significance of root exudates in acquisition of heavy metals from a contaminated calcareous soil by graminaceous species

Graminaceous species release phytosiderophores for mobilization of iron (Fe) under Fe deficiency stress. In this study the possible risk that these root exudates might also enhance the uptake of toxic heavy metals from contaminated soils, was investigated. For this purpose wheat (Triticum aestivum L. cv. Piko) and sorghum (Sorghum bicolor (L.) Moench cv. E‐610), differing in release of phytosiderophores were precultured with roots in nylon bags in a sand culture system for low and high Fe nutritional status (+/‐Fe supply) for two weeks. After this preculture the nylon bags were brought in contact with a sewage sludge or heavy metal salt‐contaminated calcareous soil in a climate chamber for an additional 8 days growth period. At harvest the concentration of Fe, Zn, Ni and Cd in roots and shoots were analysed. The results clearly show that both plant species have mobilized Fe and heavy metals from the contaminated soil. Plants precultured for low Fe nutritional status had a higher uptake of Fe, Zn, Ni and Cd (up to 200%) than control plants with adequate Fe nutritional status. This enhanced acquisition of heavy metals was particularly expressed in wheat as an Fe efficient graminaceous species with corresponding higher release of phytosiderophores under Fe deficiency stress than sorghum.

Hormones induce an Fe-deficiency-like root epidermal cell pattern in the Fe-inefficient tomato mutantfer

The tomato mutantfer (Lycopersion esculentum L. T3238fer) displayed a chlorotic phenotype at normal external Fe levels. Root cells of the mutant are incompetent to take up iron in adequate amounts and are incapable to induce any of the known responses to Fe deficiency stress. We report here that the ethylene precursor 1-aminocyclopropane-l-carboxylic acid and the auxin analog 2,4-dichlorophenoxyacetic acid induce the formation of extra root hairs and transfer cells in the epidermis, thus mimicking the root-morphological Fe stress responses. In contrast, the physiological reactions involved in iron acquisition are not affected by the hormone treatment. These results indicate that ethylene is essential for transducing environmental signals into adaptive changes in root morphology. The data further suggest that the mutation does not affect necessary steps in the differentiation processes of epidermal cells. TheFER gene appears to control sensing of iron levels and/or the regulation of mechanisms involved in iron uptake.

Ethylene production, cluster root formation, and localization of iron(III) reducing capacity in Fe deficient squash roots.

Dicots and non-graminaceous monocots have the ability to increase root iron(III) reducing capacity in response to iron (Fe) deficiency stress. In squash (Cucurbita pepo L.) seedlings, Fe(III) reducing capacity was quantified during early vegetative growth. When plants were grown in Fe-free solution, the Fe(III) reducing capacity was greatly elevated, reached peak activity on day 4, then declined through day 6. Root ethylene production exhibited a temporal pattern that closely matched that of Fe(III) reducing capacity through day 6. On the 7th day of Fe deficiency, cluster root morphology developed, which coincided with a sharp increase in the root Fe(III) reducing capacity, although ethylene production decreased. Localization of Fe(III) reducing capacity activity was observed during the onset of Fe deficiency and through the development of the root clusters. It was noted that localization shifted from an initial pattern which occurred along the main and primary lateral root axes, excluding the apex, to a final localization pattern in which the reductase appeared only on secondary laterals and cluster rootlets.

313 Iron-chelate Photodegradation in Lab-prepared Nutrient Solutions Alters Root Physiology and Causes Mn Toxicity in Marigold

Our objective was to determine the effects on plant growth and physiology that a photodegraded Fe-chelate containing lab-prepared nutrient solution would have when used in plant culture. Plants grown hydroponically in the irradiated Fe-DTPA containing nutrient solution had ferric reductase activity 2.2 times greater, foliar Fe level 0.77 times less, and foliar Mn level 1.9 times greater than in plants grown in an identical but non-irradiated solution, indicating that plants growing in the irradiated solution were responding to Fe deficiency stress with physiological reactions associated with Fe efficiency. The youngest leaves of plants that were grown in the irradiated solution had symptoms of Mn toxicity. Restoration of the irradiated solution by removing the precipitated Fe by centrifugation and adding fresh Fe-chelate resulted in plants that were, in general, not different from those grown in the non-irradiated solution (control).

Iron Deficiency Induced Changes in Ascorbate Content and Enzyme Activities Related to Ascorbate Metabolism in Cucumber Roots

Ascorbate content and the activities of ascorbate free-radical reductase (AFR-R) and ascorbate peroxidase (APX) were investigated in order to determine whether they are affected under Fe deficiency. Plasma membrane vesicles, cell wall and cytosolic fractions were isolated from the roots of cucumber (Cucumis sativus L.) plants grown in the absence or in the presence of Fe. Plasma membrane vesicles showed NADH-dependent reducing activities with Fe3+-citrate, ferricyanide and AFR as electron acceptors. Only AFR-R activity was stimulated ca. 3-fold in Fe deficient plasma membranes. No significant change in cytosolic AFR-R activity was induced by Fe depletion, while the activity of cytosolic APX was more than twice that of the non-deficient control. Furthermore, the content of ascorbate (AA) was enhanced ca. 1.7-fold in Fe deficient roots. These results indicate that metabolic changes resulting in enhanced AA levels and activities of AFR-R and APX in the roots could be related to plant responses to Fe deficiency stress.

Ethylene Production by Fe-deficient Roots and its Involvement in the Regulation of Fe-deficiency Stress Responses by Strategy I Plants

Species that showed marked morphological and physiological responses by their roots to Fe-deficiency (Strategy I plants) were compared with others that do not exhibit these responses (Strategy II plants). Roots from Fe-deficient cucumber (Cucumis sativusL. ‘Ashley’), tomato (Lycopersicon esculentumMill. T3238FER) and pea (Pisum sativumL. ‘Sparkle’) plants produced more ethylene than those of Fe-sufficient plants. The higher production of ethylene in Fe-deficient cucumber and pea plants occurred before Fe-deficient plants showed chlorosis symptoms and was parallel to the occurrence of Fe-deficiency stress responses. The addition of either the ethylene precursor ACC, 1-aminocyclopropane-1-carboxylic acid, or the ethylene releasing substance, Ethephon, to several Fe-sufficient Strategy I plants [cucumber, tomato, pea, sugar beet (Beta vulgarisL.),Arabidopsis (Arabidopsis thaliana(L.) Heynh ‘Columbia’), plantago (Plantago lanceolataL.)] promoted some of their Fe-deficiency stress responses: enhanced root ferric-reducing capacity and swollen root tips. By contrast, Fe-deficient roots from several Strategy II plants [maize (Zea maysL. ‘Funo’), wheat (Triticum aestivumL. ‘Yécora’), barley (Hordeum vulgareL. ‘Barbarrosa’)] did not produce more ethylene than the Fe-sufficient ones. Furthermore, ACC had no effect on the reducing capacity of these Strategy II plants and, except in barley, did not promote swelling of root tips. In conclusion, results suggest that ethylene is involved in the regulation of Fe-deficiency stress responses by Strategy I plants.

Amino acid sequence of proteins induced in Fe-deficient stressed alfalfa (Medicago sativa L.) roots

Alfalfa (Medicago sativa L.) grows well in soils with a moderately high pH and dissolves insoluble iron in the rhizosphere. We have investigated active uptake mechanisms under Fe-deficient nutrient conditions and the effects of Fe-deficiency on plants. Previously, we observed that Fe-deficient alfalfa roots exuded many compounds (Masaoka et al. 1993) such as fiavonoids. We also identified a new compound “alfafuran” which is a phenol compound and is different from organic acids or phytosiderophore-type amino acid derivatives exuded by Fe-deficient plant roots. This compound is also very effective in dissolving ferric phosphate (Noguchi et al. 1994), suggesting that alfalfa may have developed several strategies against Fe-deficient stress including the exudation of organic compounds like alfafuran which accelerate the Fe3+-reducing activity on the root cell membrane to dissolve insoluble iron compounds. Suzuki et al. (1995, 1997) observed that in barley several peptide spots obtained by electrophoresis were induced under Fe-deficient stress when mugineic acid-family phytosiderophores were secreted from the roots. They suggested that these peptides control the mugineic acid synthesis and secretion. We examined the peptides induced in Fe-deficient alfalfa roots.

A Selection Procedure for Iron-deficiency Stress Tolerance among Warm-season Turfgrasses Using Ferrihydrite-amended Growth Media

Iron-deficiency (Fe-deficiency) stress, characterized by chlorosis of leaf tissue, is a major limiting factor in turfgrass production on calcareous soils. The objectives of this study were to: 1) evaluate ferrihydrite-amended growth media and the threshold amount of Fe initially added for use in a whole-plant screening procedure for selecting cultivars that are tolerant to Fe-deficiency stress conditions; 2) measure and evaluate whole-plant growth characteristics that could be an index of Fe deficiency stress; and 3) assess the potential of using a synthetically produced Fe oxide, ferrihydrite, as a slow-release Fe fertilizer source. Iron-stress sensitive `Raleigh' St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] and Fe-stress tolerant `Tifway' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Davy] cultivars were grown under glasshouse conditions in a medium consisting of quartz sand, 5% (m/m) CaCO,, and a ferrihydrite amendment providing Fe in concentrations of 0, 15, 30, 46, or 120 mg·kg-1 media, (equivalent to 2, 3, 4, 5, or 10 mg DTPA-extractable Fe/kg media). There also was a nonlimiting iron control. St. Augustinegrass was first rated for iron chlorosis 83 days after planting (DAP) while bermudagrass was first rated at 294 DAP. Initial Fe levels equivalent to 5 mg DTPA-extractable Fe/kg media showed potential for screening genotypes. Visual estimates of iron chlorosis and chlorophyll contents of leaves were the best indicators of low soil Fe availability. A single ferrihydrite soil amendment at 10 mg DTPA-extractable Fe/kg media was adequate in preventing chlorosis for the duration of the study (174 and 509 days for St. Augustinegrass and bermudagrass, respectively). Chemical name used: Diethylenetriaminepentaacetic acid (DTPA).

Iron assimilation in Chlamydomonas reinhardtii involves ferric reduction and is similar to Strategy I higher plants

The mechanism of adaptation to Fe-deficiency stress was investigated in the unicellular green alga, Chlamydomonas reinhardtii. Upon removal of nutri- Introduction tional Fe, the activity of a cell surface Fe(III)-chelate For higher plants Fe is an essential nutritional element reductase was increased by at least 15-fold within that is required in micromolar concentrations. In spite of 24 h. This increase was negatively correlated with the its widespread abundance in the Earth’s crust, Fe is Fe concentration in the growth media. Incubation poorly available in an oxidizing environment, which of cells in the presence of the Fe2+-specific chela- favours the formation of poorly soluble Fe(III )-oxides tor, bathophenanthrolinedisulphonic acid, led to an and -hydroxides at pH values above neutral. Nevertheless, increased Fe3+ reductase activity, even when suffi- excess Fe is toxic to the cells due to its ability to catalyse cient Fe was present. Growth of cells in Cu-free media the formation of reactive oxygen species such as superfor 48 h led to no statistically significant increase in oxide anions and hydroxyl radicals (Halliwell and Fe3+ reductase activity. The Fe(III)-chelate reductase Gutteridge, 1989). activity in Fe-starved cells was saturable with an In higher plants, two basic strategies for iron acquisiapparent K m of 31 mM and was inhibited by uncouplers tion have been observed (reviewed in Guerinot and Yi, of the transmembrane proton gradient but not by 1994). In grasses (Strategy II plants), Fe is taken up as SH-specific reagents.

Physiological responses of grapevine callus cultures to iron deficiency

Grapevine is considered a ‘Strategy I’ plant because it performs some peculiar biochemical and physiological responses when grown under iron (Fe) deficiency stress conditions. Callus cultures were started from leaf and internode cuts of micropropagated plantlets of two grapevine genotypes well known for their Fe‐chlorosis characteristic: Vitis riparia a very susceptible genotype and Vitis berlandieri a resistant one. Modification of NADH: ferric (Fe3+) reductase activity was spectrophotometrically evaluated by following the formation of the complex ferrous (Fe2+)‐(BPDS)3, while the malic and citric acid production were determined in callus cultures grown both in the presence (+Fe) and absence (‐Fe) of Fe. Moreover, a microsomal fraction was isolated from the calli to evaluate the H+‐ATPase and the Fe3+‐EDTA reductase activities. As expected, calli of the Fe‐efficient genotype (V. berlandieri) was able to enhance Fe3+‐EDTA reductase activity when growing under Fe deficiency while the Fe‐chlorosis susceptible V. riparia could not or did it with lower efficiency. Therefore, the H+‐ATPase assay showed a higher enzymatic activity in the microsomal fraction isolated from Vitis berlandieri grown without Fe with respect to its control (+Fe). Organic acid determination gave quite contradictory results, specially regarding malic acid which, under our study conditions, seemed not to be linked with the strategies of response to Fe deficiency.

In-vitro-cultured subclover root can develop Fe-deficiency stress response

In-vitro-cultured subclover root can develop Fe-deficiency stress response

Fe-deficiency stress response in Fe-deficiency resistant and susceptible subterranean clover: importance of induced H+release

Plants can exhibit Fe-deficiency stress response when they are exposed to Fe-deficiency conditions. The relative importance of the individual Fe-deficiency stress-response reactions, for example, increased release of H+ from roots, enhanced root plasma membrane-bound Fe3+ -reductase activity, and release of reductant, in Fe-deficiency resistance is not understood. To address this problem, the Fe-deficiency stress response of two cultivars of subterranean clover (subclover), Koala (Trifolium brachycalycinum Katzn. and Morley) (Fe-deficiency resistant) and Karridale (T. subterraneum L.) (Fe-deficiency susceptible), were evaluated. The plants were cultured hydroponically at 0 (−Fe) and 30 (+Fe) μM Fe3+ EDTA conditions. After 6 d Fe treatment, the −Fe Koala and Karridale decreased the pH of the nutrient solution by 1.83 and 0.79 units, respectively, while the +Fe plants increased the pH of the nutrient solution. The H+ -release rate of the −Fe Koala determined 7 d after Fe treatment initiation was more than three times higher than that of the −Fe Karridale. The −Fe plants had a significantly enhanced Fe3+ -reduction rate compared with the +Fe plants for each cultivar, but the resistant cultivar did not exhibit a higher root Fe3+ -reduction rate than the susceptible cultivar at each Fe treatment. Reductant release from the roots of subclover was negligible. These results indicate that Fe-deficiency-induced H+ release may be the predominant factor influencing Fe-deficiency resistance in subclover.

Phytosiderophore Release Related to Susceptibility of Wheat to Iron Deficiency

Some wheat (Triticum aestivum L. emend. Thell.) genotypes when grazed by livestock and subsequently used for grain production develop Fe deficiency chlorosis and decline in grain yield. Wheat is known to release phytosiderophores (compounds involved in Fe mobilization and uptake) in response to Fe deficiency stress. These studies conducted in environmental growth chambers correlated the release of phytosiderophore from the roots of eight wheat genotypes with field chlorosis scores from Oklahoma grazing trials. Plants were grown hydroponically in low Fe nutrient solutions and phytosiderophore release was measured with an Fe‐binding assay. Since grazing exacerbates Fe deficiency chlorosis development, the eight genotypes were tested both with and without clipping. Phytosiderophore release with time was summed to improve correlation compared with individual daily measurements. The field chlorosis scores and the sum of the first six phytosiderophore release measurements (Days 6 to 11 after imposition of low Fe treatment) from unclipped wheat were not correlated (r = −0.17, P = 0.70), but the sum of the last five days (13 to 17) was highly correlated with field chlorosis scores (r = −0.82, P = 0.01). Clipping did not greatly improve the relationship (r = −0.83, P = 0.008). Correlation coefficients were more consistent for individual days when plants were clipped. Three‐day sums of phytosiderophore release provided good correlations when data were collected in the latter stages of Fe deficiency development (Day 11). Identification of chlorosis resistant lines by monitoring phytosiderophore release will by‐pass years of field trials and should be implemented by plant breeders where wheat is managed concurrently for forage and grain production on calcareous soils.