Fe Deficiency Chlorosis Research Articles

Effects of bicarbonate and iron supply on Fe(III) reducing capacity of roots and leaf chlorosis of the susceptible peach rootstock “Nemaguard”

Peach varieties grafted on the rootstock “Nemaguard” (Prunus persica (L.) Batsch) usually show chlorosis when grown in calcareous soils. This chlorosis can be corrected by applying iron chelates to the soil. In this work we present results on the behavior of “Nemaguard” seedlings grown in nutrient solutions with different concentrations of bicarbonate and Fe as FeEDDHA. Chlorosis degree was increased by either increasing bicarbonate (0–15 mM) or decreasing Fe (100–0 μM). Shoot dry weight was decreased in chlorotic plants, but also in green plants grown with bicarbonate (15 mM) and high Fe (100 μM). This indicates that the growth decrease caused by bicarbonate is not only related to Fe deficiency chlorosis. When plants were grown with 10 mM bicarbonate and 2.5 μM Fe and showed clear chlorosis symptoms, they were transferred to a similar nutrient solution but with 100 μM Fe. After one week plant regreening was appreciable, in particular in the youngest leaves. The root Fe(III) reducing capacity was measured in a medium with absence of bicarbonate and in the presence of 10 mM MES, at pH 5.0, for 2h and 30 min. In the treatment with 10 mM bicarbonate and 2.5 μM Fe, roots had a very low reducing capacity and plants became chlorotic. However, these plants markedly increased their reducing capacity just one day after transferring them to a similar nutrient solution but with 100 μM Fe, despite they were still very chlorotic. These results show that bicarbonate inhibits the development of reducing capacity under low Fe conditions but not at higher Fe levels. It is assumed that under field conditions both the induction of chlorosis and the regreening process may be partly consequence of changes in the reducing capacity.

Effect of bicarbonate on uptake and translocation of 59 Fe in two grapevine rootstocks differing in their resistance to Fe deficiency chlorosis

In order to study the effect of high bicarbonate concentration in the root medium on root Fe III reduction, Fe uptake and its translocation to the leaves, two rootstocks ( Vitis riparia Michx., susceptible, and 41 B ( Vitis vinifera L. cv. Chasselas x Vitis berlandieri Planch.), resistant to Fe deficiency chlorosis) were pre-cultivated in nutrient solutions with high and low Fe supply. After three weeks of preculture at low Fe, chlorosis symptoms occurred in both, Fe-resistant and Fe-susceptible genotypes. The Fe III reducing capacity by roots was enhanced at Fe deficiency in both genotypes, which was consistent with the increase of subsequent root uptake and translocation rates of 59 Fe. In the presence of bicarbonate in the solutions the Fe III reducing capacity, 59 Fe uptake and translocation rate decreased in both genotypes precultured with low re supply. The 59 Fe uptake and translocation rate, however, were significantly higher in the Fe chlorosis-resistant rootstock 41 B. These results clearly indicate that bicarbonate-induced Fe chlorosis in grapevine rootstocks is obviously caused by an inhibition of Fe uptake and translocation due to an inhibition of Fe III reduction by root cells. The fact that these processes were less inhibited in the chlorosis-resistant rootstock hints to genotypical differences in Fe acquisition by roots at high bicarbonate levels. These differences might be used in breeding programs to identify Fe chlorosis-resistant rootstocks.

Studies on the improvement in iron nutrition of peanut by intercropping with maize on a calcareous soil

Both rhizobox and field experiments were conducted to investigate nutritional interactions between peanut and maize in intercropping systems for Fe acquistion. Field observations indicated that Fe deficiency chlorosis symptoms in peanut grown in monoculture were more severe and widespread compared to those of peanuts intercropped with maize. This indicated a marked improvement in the iron nutrition of peanut intercropped with maize in the field and was further studied. In experiments with rhizoboxes, roots of maize and peanut were either allowed to interact with each other or prevented from making contact by inserting a solid plate between the root systems of the two species. A field experiment for four cropping treatments were examined: peanut grown separately in monoculture, normal peanut/maize intercropping, peanut/maize intercropping with solid plates between the root systems of the two crop species and peanut/maize intercropping with 30 μm nylon nets between the root systems. The results show that the chlorophyll and HCl-extractable Fe concentrations in young leaves of peanut in the intercropping system with unrestricted interactions of the roots of both plant species were much higher than those of peanut in monoculture. In the nylon mesh treatment, the beneficial effects of the maize extended to row 3. The improvement of Fe nutrition in the intercropping system got reduced but not diminished completely in the treatment with nylon net. It is suggested that the improvement in the Fe nutrition of peanut intercropped with maize was mainly caused by rhizosphere interactions between peanut and maize.

Mechanism of Fe uptake by the leaf symplast: Is Fe inactivation in leaf a cause of Fe deficiency chlorosis?

The mechanism of iron (Fe) uptake from the leaf apoplast into leaf mesophyll cells was studied to evaluate the putative Fe inactivation as a possible cause of Fe deficiency chlorosis. For this purpose, sunflower (Helianthus annuus L.) and faba bean plants (Vicia faba L.) were precultured with varied Fe and bicarbonate (HCO 3 - ) supply in nutrient solution. After 2–3 weeks preculture, FeIII reduction and 59Fe uptake by leaf discs were measured in solutions with Fe supplied as citrate or synthetic chelates in darkness. The data clearly indicate that FeIII reduction is a prerequisite for Fe uptake into leaf cells and that the Fe nutritional status of plants does not affect either process. In addition, varied supply of Fe and HCO 3 - to the root medium during preculture had no effect on pH of the xylem sap and leaf apoplastic fluid. A varied pH of the incubation solution had no significant effect on FeIII reduction and Fe uptake by leaf discs in the physiologically relevant pH range of 5.0–6.0 as measured in the apoplastic leaf fluid. It is concluded that Fe inactivation in the leaf apoplast is not a primary cause of Fe deficiency chlorosis induced by bicarbonate.

By-product Iron-humate Increases Tree Growth and Fruit Production of Orange and Grapefruit

Citrus trees planted in alkaline soils typically show iron (Fe) deficiency chlorosis. Currently, Fe-EDDHA (ethylenediiminobis-2-hydroxyphenyl acetic acid) chelate is the most effective source of Fe for high pH soils. Iron humate (FeH), a by-product of the drinking water decolorization process, was compared with Fe-EDDHA for Fe deficiency correction on nonbearing `Ambersweet' orange and `Ruby Red' grapefruit Citrus paradisi Macf., and bearing `Hamlin' orange Citrus sinensis and `Flame' grapefruit trees, all on Swingle citrumelo rootstock, planted on high pH (>7.6) soils. Iron humate was applied under the tree canopy in spring at rates from 2 to 200 g Fe (nonbearing trees), or 22 to 352 g Fe (bearing trees) per tree per year. Application of FeH to nonbearing trees decreased twig dieback rating and increased flush growth, flush color rating, tree size, and leaf Fe concentration. Addition of urea or ammonium nitrate to FeH did not increase Fe availability. Iron amendments (22 g Fe per tree per year) increased fruit yield after the 1st year of application. Further increases in the rate of Fe, from 22 to 352 g Fe per tree per year as FeH, did not significantly increase tree growth, fruit yield, or fruit quality. This study demonstrated that FeH was an effective Fe source for citrus trees planted on alkaline soils.

Screening for resistance to iron deficiency chlorosis in dry bean using iron reduction capacity

Identifying cultivars resistant to iron (Fe) deficiency chlorosis so prevalent in calcareous soils is a more economical solution than fertilizer application in field crops. The current method of screening for resistance using chlorosis ratings in field trials is time consuming and highly variable. Root Fe reduction successfully separated cultivars or rootstocks, varying widely in resistance, of soybean (Glycine max L.), peach (Prunus persica L.), and grape (Vitis spp.), but was unsuccessful in sub‐clover (Trifolium subterraneum L.). Dry bean (Phaseolus vulgaris L.) exhibits Fe deficiency chlorosis in calcareous soils and initiates Fe reduction by the roots in response to such stress. The resistance of 24 dry bean cultivars to Fe deficiency chlorosis was assessed by measuring and summing daily Fe reduction by the roots. The cultivars were grown both hydroponically in an environmental chamber in low Fe solutions (0.05 mg‐L‐1) and at three field sites in both 1995 and 1996. A significant relationship (P<0.01) between field chlorosis scores made 36 days after planting and root Fe reduction summations was observed for all sites in 1995 and 1996 (r = ‐0.42 to ‐0.71). The variability of chlorosis scores among sites, especially in 1996, points out the difficulty of using field chlorosis scores for screening. These results indicate that measurements of root Fe reduction can be used to predict resistance to Fe deficiency chlorosis in dry bean. Successful implementation of this technique should reduce if not eliminate field trials for screening resistance to Fe deficiency chlorosis.

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.

Competition between micro-organisms and roots of barley and sorghum for iron accumulated in the root apoplasm.

Graminaceous plant species respond to iron (Fe)-deficiency stress by enhancing the release of phytosiderophores from the roots and the uptake of Fe-phytosiderophores. For studying the mobilization and uptake of apoplasmic root Fe by barley (inherently high phytosiderophore release) and sorghum (inherently low phytosiderophore release) in axenic and nonaxenic (inoculated) nutrient solution, Fe pools in the root apoplasm were loaded during plant preculture with 10-4 M Fe(III)-EDTA. After 27 d growth in Fe-deficient nutrient solution, inoculated barley plants developed moderate Fe-deficiency chlorosis compared with the less chlorotic axenic plants. In inoculated plants, recovery of phytosiderophores and mobilization of apoplasmic root Fe tended to be slightly lower than in axenic plants, and in both treatments apoplasmic root Fe was completely depleted at harvest. As determined by the nonsoluble Fe fraction (> 0·2 μm) in the nutrient solution and at the rhizoplane, the microbial uptake and immobilization of apoplasmic root Fe was estimated at about 3% of the total amount of apoplasmic root Fe after preculture and at less than 10% of plant Fe uptake. Under axenic conditions, Fe-deficient sorghum also depleted apoplasmic root Fe and developed moderate Fe-deficiency chlorosis, although phytosiderophore recovery was 5-10-fold lower than in barley. By contrast, in inoculated sorghum plants, phytosiderophore recovery and Fe mobilization were extremely low. At harvest, in inoculated sorghum plants apoplasmic Fe pools were still considerably loaded and plant Fe uptake was c. 60% lower than that of axenic plants, resulting in severe Fe-deficiency chlorosis. Thus, in Fe-deficient sorghum plants, the lower rate of phytosiderophore release and its degradation restricted an efficient mobilization of apoplasmic root Fe in the presence of micro-organisms. In barley, however, the higher rate of phytosiderophore release allowed a complete mobilization of apoplasmic root Fe even in inoculated nutrient solution. Furthermore, the results show that the dominating effect of micro-organisms in their competition with barley and sorghum for apoplasmic root Fe is the degradation of phytosiderophores rather than the immobilization or uptake of Fe.

Iron nutrition of cucumber and maize: Effect of Pseudomonas putida YC 3 and its siderophore

Long-term experiments were made to study the effects of root inoculation with Pseudomonas putida and various other microorganisms on the ability of cucumber ( Cucumis sativus L.) and maize ( Zea mays L.) plants to acquire Fe from inorganic solid phase Fe (autoclaved soil) supplied in nutrient solution. Cucumber plants with autoclaved soil as the sole Fe source showed severe Fe-deficiency chlorosis, and there was no beneficial effect of inoculation with siderophore-producing (pyoverdine) P. putida YC 3 in comparison with the siderophore-negative mutant P. putida MN 22, the siderophore-auxotroph Arthrobacter flavescens JG 9, or with a soil microorganism mixture. In contrast to cucumber, maize plants supplied with autoclaved soil remained green in all treatments, except when inoculated with the soil microorganism mixture. No beneficial or detrimental effects on Fe nutrition were observed for inoculation with P. putida YC 3 or MN 22, or with A. flavescens JG 9. However, inoculation with the soil microorganism mixture resulted in the development of severe Fe-deficiency chlorosis. This mixture was also very effective in degradation of the plant-borne phytosiderophores released into the nutrient solution by Fe-deficient maize. In short-term experiments Fe uptake from 59Fe-pyoverdine was compared with 59FeEDTA by cucumber and 59Fe-phytosiderophores by maize. Results with Fe-deficient plants showed that ferrated pyoverdine was a relatively poor Fe source for either maize or cucumber; supplying Fe to cucumber at a rate 40 times lower than 59FeEDTA and to maize 665 times lower than 59Fe-phytosiderophores. In cucumber the low uptake rate from 59Fe-pyoverdine was correlated with a very low reduction rate of ferrated pyoverdine. The results do not support the view of an important direct role of pyoverdine-producing P. putida in the Fe nutrition of plants, although in soil-grown plants, Fe acquisition may be indirectly affected, for example, by increasing the extracellular supply of Fe at the root surface.

Effect of manganese deficiency on seed yield of soybean cultivars

Abstract Manganese (Mn) deficiency is a problem in soybeans grown on high pH soils, which to date can only be controlled by chemical fertilizers. In view of the success of genetic resistance in reducing yield losses associated with iron (Fe) deficiency chlorosis, a one year study was initiated to determine whether genetic resistance could be used to control Mn deficiency related yield losses. For this study, twenty soybean genotypes ranging from Group I maturity to Group III maturity were planted at five locations which had previously exhibited symptoms of Mn deficiency. Individual plots were rated for Mn‐deficiency symptoms on a 1–5 scale (1 = no yellowing to 5 = severe yellowing with some necrosis) at the Rl growth stage and plants in the center rows were harvested for yield. The mean Mn‐deficiency rating was 2.8 with a range from 1.8 for NKS 23–03 and P9181 to a 3.9 for A3205. The mean yield was 3059.3 kg/ha with a range from 3670.6 for A3205 to 2567.5 kg/ha for Chapman. The correlation between Mn‐defi...

Plant growth and nutrient uptake characteristics of Fe-deficiency chlorosis susceptible and resistant subclovers

Plant growth and nutrient uptake characteristics of Fe-deficiency chlorosis susceptible and resistant subclovers

Iron deficiency in lentils in the mediterranean region and its control through resistant genotypes and nutrient application1

Abstract Iron (Fe)‐deficiency symptoms are observed on some genotypes of lentil (Lens culinaris Medikus) grown on high pH and calcareous soils. Ten lentil cultivars/lines differing in response to Fe‐deficiency chlorosis (FeDC) were grown on a high pH (8.0), calcareous (38% calcium carbonate equivalent in surface 20 cm) and silty clay soil in the field (Beka'a Valley), to determine the effects of FeDC on seed and straw yield of cultivars/lines sprayed with Fe. A significant interaction (P<0.05) between cultivars/lines and Fe‐spray treatment was noted for visual FeDC ratings, and no significant interactions for these treatments were noted for seed and straw yields. Sprayed cultivarsAines generally produced higher straw yields than unsprayed ones. Overall increases were 38%. Even though only slight FeDC was noted on some cultivars/lines receiving no‐Fe spray, straw yields were significantly increased when sprayed with Fe. Spraying cultivars/lines with Fe did not show a significant increases in seed yield. In...

657 PB 063 IRON DEFICIENCY IN POTATO IN THE MEDITERRANEAN REGION AND ITS CONTROL THROUGH RESISTANT GENOTYPES AND NUTRIENT APPLICATION

Iron-deficiency symptoms are observed on some genotypes of potato (Solanum tuberosum L.) grown on high-pH and calcareous soils. seven potato cultivars differing in response to iron deficiency chlorosis (FeDC) were grown on high-pH (8.1), calcareous (38% calcium carbonate equivalent in surface 20 cm) and silty clay soil in the field (Beka'a Valley, Lebanon), to determine the effects of FeDC on tuber yield of cultivars sprayed with Fe. A significant interactions between cultivars and Fe spray treatment were noted for visual FeDC ratings and tuber yield. Even though only slight FeDC was noted on some cultivars receiving no Fe spray, tuber yields were significantly increased when sprayed with Fe. Some cultivars with moderate FeDC ratings did not show a significant increase in yield when sprayed with Fe while other cultivars did. Sprayed cultivars generally produced higher tube; yields than unsprayed ones. Indicating that Fe-deficiency chlorosis in the Mediterranean region may be a serious limitation to potato tuber yield.

Greenhouse Screening of Citrus Rootstock for Tolerance to Bicarbonate-induced Iron Chlorosis

Eighteen citrus rootstock seedling lines were tested for their tolerance to Fe chlorosis using sand culture. Potassium carbonate was used to induce Fe-deficiency chlorosis. Chlorosis was quantified by 1) visual ratings, 2) SPAD-502 chlorophyll meter readings, 3) leaf chlorophyll concentration, 4) leaf active Fe, and 5) leaf total Fe. The first four criteria were well correlated among each other but not with leaf total Fe. Although any of the first four measurements could be used to quantify chlorosis, visual ratings and SPAD-502 readings were more convenient. The rootstock that have been reported to be tolerant or very susceptible to Fe chlorosis in calcareous soils were rated similarly for tolerance to bicarbonate-induced Fe chlorosis. Nontrifoliate types such as Texas sour orange (C. aurantium L.), Cleopatra mandarin (C. reticulata Blanco), Vangasay lemon (C. limon Burro.), and Ridge pineapple x Milam 1578-201 (C. sinensis L. Osbeck x C. jambhiri) were tolerant to moderately tolerant. Although most of the trifoliate hybrids tested were moderately susceptible to very susceptible, Smooth Seville x Argentine trifoliate {[C. grands (L.) Osbeck x C. aurantium] x Poncirus trifoliata (L.) Raf.} and F-81-12 citrange (C. sinensis x P. trifoliata) exhibited relatively high tolerance to lime-induced Fe chlorosis.

Yield of iron‐sprayed and non‐sprayed strawberry cultivars grown on high ph calcareous soil

Abstract Iron (Fe) deficiency chlorosis (FeDC) results in extensive reduction in yield of strawberry (Fragaria x ananassa Duch.) grown on high pH calcareous soils. Three cultivars differing in response to FeDC were grown on a high pH (8.2) calcareous soil (25.4% calcium carbonate equivalent in surface 20 cm) in the field (Choueifat, coastal area of Lebanon) to determine the effects of FeDC on fruit yield of cultivars sprayed with FeEDDHA [ferric ethylene‐diiminobis (2‐hydroxyphenyl) acetate]. The unsprayed plots were used as a control. No significant interaction (P<0.05) between cultivars x FeEDDHA spray treatment, and no significant differences (P<0.05) between one and two FeEDDHA spray(s)/week treatment was noted for visual FeDC, fruit number, and fruit yield. Sprayed cultivars once a week produced higher yields than unsprayed ones; overall increases were 33% (13% for ‘Motto’, 30% for ‘Chandler’, and 56% for ‘Douglas'). Even though only slight FeDC was noted on the ‘Motto’ cultivar receiving no Fe EDDHA...

Influence of microorganisms on iron acquisition in maize

Graminaceous species can enhance acquisition of iron (Fe) by release of phytosiderophores mainly from apical root zones. However, phytosiderophores are readily degradable by microorganisms. To study the effect of rhizosphere microorganisms in Fe acquisition, maize plants were grown axenically or inoculated with a mixture of microorganisms in a limestone substrate supplemented with a small amount of Fe III-oxide. Axenic plants grew well without Fe deficiency symptoms and released considerable amounts of phytosiderophores. In contrast, inoculated plants showed severe symptoms of Fe deficiency chlorosis and much less phytosiderophores were detectable in the substrate. The severity of Fe deficiency chlorosis was strongly influenced by the mode of water supply either continuously by glass fibre wicks or by periodic short-term flooding. Inoculated plants became more chlorotic, when watered by flooding than plants watered by glass fibre wicks. This was suggested to be due to greater microbial degradation of phytosiderophores as a consequence of higher microbial population density in apical root zones, the sites of phytosiderophore release. To prove this hypothesis maize plants were grown in a silty loam soil. Short-term periodic flooding resulted in a uniform distribution pattern of rhizosphere microorganisms along the root axis, whereas in non-flooded plants the number of rhizosphere microorganisms was lower in apical root zones and increased sharply from 0–20 to 20–40 mm distance from the root apex. It is concluded, that in solid substrates a low population density of rhizosphere microorganisms in the apical root zone is of particular importance for efficient Fe acquisition by phytosiderophores in graminaceous species like maize.

Effects of soil water levels on solution bicarbonate, chlorosis and growth of sorghum

Abstract Relationships between solution HCO3‐ and Fe deficiency chlorosis have been demonstrated with certain dicotyledonous plants grown with high soil moisture and poor aeration. This study was conducted to determine the influence of soil moisture on solution HCO3‐ at depths to 1 meter in a calcareous soil and determine the influence of moisture regime and length of pre‐plant wetting on sorghum (Sorghum bicolor (L.) Moench, cv. G‐522DR) growth. The effects of three soil moisture regimes and three pre‐plant wetting periods on sorghum growth were examined utilizing a randomized complete block, factorial design with three replications. A Clare ville clay loam (Pechic Argiustoll) was reconstructed in 0.102 m diameter pipe 1 meter in length with sorghum being grown in a greenhouse for eight weeks. Soil solution HCO3‐ concentration increased with increasing soil moisture, with a positive linear relationship being found at depths > 0.2 m. Even though solution HCO3‐ concentrations > 8 mM were found in the wette...

Relationship between Chlorophyll Concentration and Iron Chlorosis in Grain Sorghum

Grain sorghum, Sorghum bicolor (L.) Moench, is susceptible to Fe chlorosis when grown on many calcareous soils. Cultivars that are high yielding and resist Fe chlorosis can be developed only after methods for identifying sources of Fe chlorosis resistance are obtained. This study was conducted to examine the relationship between leaf chlorophyll and visual scoring of Fe deficiency symptoms and to compare the effectiveness of these methods for classifying sorghum response to Fe deficiency. Sorghum cultivars and hybrids were planted in two tests at Berclair, TX, on a Weesatche fine sandy loam (fineloamy, mixed, hyperthermic Typic Argiustoll) in single‐row plots and replicated twice with each entry adjacent to the resistant and susceptible check. Chlorophyll a, b, and a + b (Chla, Chlb, and Chla+b) classified entries for resistance or susceptibility as well as visual scoring. Resistant entries identified by Chla+b included IS12684C, IS7273C, IS12682C, IS12678C, and IS7367C. Visual scoring identified IS12684C and IS7273C as being significantly superior to the resistant check and experimental entries for each measure of chlorophyll. Significant (P&lt; 0.01) negative correlations, each greater than −0.809, existed between visual scoring and the three measures of chlorophyll. Using visual scoring and analysis of covariance resulted in a coefficient of variation of 15 for the cultivar test and 17 for the hybrid test compared with a range of 42 to 59 for the chlorophyll measurements in each test. None of the four evaluation methods was superior to another for identification of cultivars with resistance to Fe deficiency chlorosis.

Screening rhizoma peanut for adaptation to calcareous soils1

Abstract Iron (Fe) deficiency chlorosis has been observed in rhizoma peanut (Arachis glabrata Benth.) under field conditions in south Texas. Calcareous soils which can induce chlorosis occur in several regions of the world where this forage legume has the potential to be grown. Twenty‐five rhizoma peanut genotypes (23 Plant Introductions plus ‘Florigraze’ and ‘Arbrook') were evaluated for Fe‐deficiency chlorosis and other agronomic characteristics in 1989–90 on a pH 8.0 Parrita sandy clay loam (clayey, mixed, hyperthermic, shallow Petrocalcic Paleustolls) in the greenhouse. Genotypes differed in chlorosis expression and were scored (1 = no chlorosis to 5 = very chlorotic) on Mar. 19 and Apr. 16, 1990. On April 16, 1990, five genotypes showed resistance to chlorosis (score ≤1.5) that was equal to, or better than Florigraze (score = 1.63, LSD .05 = 0.44). Arbrook was intermediate in susceptibility (score = 2.38) while six lines were very susceptible (score ≥ 3.0). Genotypes also varied with respect to other measurements taken. High yielding lines were Arbrook, 35, 42, and 64, while Florigraze was intermediate in dry matter production. Two genotypes averaged 26 shoots per pot, while five lines had less than 10 shoots per pot. Arbrook and line 35 measured > 20 cm tall on April 16 while eight genotypes were < 8 cm. When greenhouse chlorosis scores were compared to scores of the same genotypes grown on two different calcareous soils (pH 7.8 and 8.4) in the field (irrigated to enhance chlorosis), resulting chlorosis scores were highly correlated (r = 0.62). Results indicate that greenhouse evaluation of rhizoma peanut would be useful for screening for resistance to Fe‐deficiency chlorosis and some agronomic characteristics.

Greenhouse Evaluation of Subterranean Clover Species for Susceptibility to Iron‐Defeciency Chlorosis

Subterranean clover (subclover) is the common name for three Trifolium species (T. brachycalycinum Katzn. and Morley, T. yahninicum Katzn. and Morley, and T. subterraneum L.), which show promise for use in winter pastures in the southeastern USA. On calcareous soils in Texas, ‘Mt. Barker’ subciover (T. subterraneum) often has Fe‐deficiency chlorosis, while ‘Clare’ subclover (T. brachycalycinum) appears to be resistant. Our objective was to screen 22 available subclover cultivars in the greenhouse for susceptibility to Fe‐deficiency chlorosis. Three replications of seven plants per cultivar were grown in Conetainers ® in two calcareous soils. At 4 wk of age, the plants were subjected to high soil moisture conditions to induce the chiorosis. Two weeks later, all plants were scored and leaf samples were analyzed for total chlorophyll content. Both parameters indicated a large difference among cultivars for susceptibility to Fe‐deficiency chlorosis. Visual chiorosis scores and leaf chlorophyll contents were inversely related (r2 = 0.69). Cultivars belonging to T. brachycalycinum had no chlorosis and had high leaf chlorophyll contents (&gt; 1.2 mg g−1). Within the species T. yanninicum, three cultivars appeared to be only slightly susceptible, while ‘Yarloop’ had moderate chlorosis when grown in the Partita soil (Clayey, mixed, hyperthermic, shallow Petrocalcic Paleustoil). Cultivars of the species T. subterraneum had the greatest range of chlorosis scores. ‘Karridale’ was consistently most susceptible to Fedeficiency chlorosis, while ‘Woogenellup’ was the least susceptible. The variation among cultivars within the species T. subterraneum suggests that selection for resistance to Fe‐deficiency chlorosis maybe possible within this species.