Chlorosis correction and agronomic biofortification in field peas through foliar application of iron fertilizers under Fe deficiency

Effectiveness of different iron (Fe) foliar sprays for leaf chlorosis correction and grain Fe boosting was studied in field peas under Fe deficiency. No chlorophyll reduction was observed in Fe deficient plants treated with foliar sprays. EDDHA [ethylenediamine-N,N′-bis(2-hydroxyphenylacetic acid)] followed by FeSO₄ (73.7?mg/l Fe) treated at the start of flowering was most responsive in correcting chlorosis and increasing shoot dry biomass in peas. Inductively coupled plasma-atomic emission spectroscopy data showed significant increase of Fe in grains while treated with all foliar sprays at the time of grain filling in Fe-deficient plants. Among them, FeSO₄ (73.7?mg/l Fe) was the most efficient in biofortifying Fe in mature grain under Fe deficiency in peas. Results also pinpoint that flowering is a suitable time for applying foliar sprays to boost Fe in mature grains. Taken together, application of Fe foliar sprays facilitated both chlorosis correction and Fe boosting in peas and can be further used by breeders and farmers.     

Foliar fertilization to control iron chlorosis in pear (Pyrus communis L.) trees

The effectiveness of foliar fertilization to re-green chlorotic leaves in iron-deficient pear trees has been studied. Trials were made to assess the influence of (i) the level of Fe deficiency, (ii) the leaf surface treated (adaxial or abaxial), and (iii) two different surfactants, L-77 and Mistol. Treatments were ferrous sulphate alone, ascorbic, citric and sulphuric acids, applied either alone or in combination with ferrous sulphate, Fe-DTPA and water as a control. Solutions were applied with a brush and leaves were treated twice each year. None of the treatments caused a full recovery from Fe deficiency chlorosis. Treatments containing Fe caused the largest re-greening effects, and FeSO₄ had a similar re-greening effect to Fe(III)-DTPA. Increases in leaf Chl were more pronounced with abaxial leaf surface applications and in severely deficient leaves. Using Fe(III)-DTPA in foliar sprays does not seem to be justified, since their effects are not better than those of FeSO₄. The joint use of Fe(III)-DTPA and L-77 and that of FeSO₄ and citric acid do not seem to be suitable. With a single foliar application, FeSO₄ combined with acids gave slightly better results than FeSO₄ alone. Acidic solution applications without Fe may be effective in alleviating chlorosis in some cases, especially in the case of citric acid. In the current state of knowledge, foliar fertilization cannot offer yet a good alternative for full control of Fe chlorosis, although its low environmental impact and cost make this technique a good complementary measure to soil Fe-chelate applications and other chlorosis alleviation management techniques. Abbreviations: Chl – chlorophyll; EDDCHA – ethylenediamine di(5-carboxy-2-hydroxyphenylacetic) acid; EDDHA – ethylenediamine di(o-hydroxyphenylacetic) acid; EDDHMA – ethylenediamine di(o-hydroxy-p-methylphenylacetic) acid; EDDHSA – ethylenediamine di(2-hydroxy-5-sulfophenylacetic) acid     

Correcting iron deficiencies in annual and perennial plants: Present technologies and future prospects

Correction of Fe chlorosis is done mainly by foliar sprays because soil applications generally are ineffective, especially for annual crops. Inorganic Fe sources applied to soils react rapidly to forms which are not as available to plants; ferrous Fe is oxidized to the ferric form in well-aerated soils, especially as soil pH increases. Several synthetic chelates and organic complexes have been used with varying success, depending upon Fe source and rate, application method, plant species, and weather and soil conditions. Use of Fe-efficient cultivars is one method of counteracting Fe deficiencies in some species. Future prospects for improving control of Fe chlorosis lie more with development of Fe-efficient cultivars of Fe-sensitive species than with development of improved Fe fertilizers and methods of application. The techniques of molecular biology should be applicable to help solve this important plant nutrition problem, but priority has not been given to conduct this research at this time.     

The effect of high pH and P on the development of lime-chlorosis in two seedling populations ofEucalyptus obliqua L'Hérit

Summary Glasshouse experiments have shown that the application of an acidulating agent to a calcareous soil can increase growth and alleviate severe chlorosis in an acidic population ofE. obliqua. In contrast, a calcareous population showed only a slight response to this treatment and maintained adequate growth and a low frequency of chlorosis on both control and treated calcareous soils. Foliar analyses of seedlings of the acidic population showed that alleviation of chlorosis was concomitant with a reduction in the levels of P, Ca and K, and an increase in uptake of Fe. However, the total Fe content of foliage was poorly correlated with the occurrence of severe chlorosis. Although this evidence suggested that the differential susceptibility ofE. obliqua to lime-chlorosis can be reduced by increasing the availability of Fe, the greater concentration of Fe in chlorotic seedlings indicated that lime-chlorosis may also be due to an inactivation of Fe within the plant (i.e. by P). This hypothesis was partly confirmed by a water culture experiment which showed that a combination of relatively high pH and high external levels of P could induce severe chlorosis in seedlings of the acidic population. In contrast, it appears that the calcareous population has a more efficient mechanism for absorbing Fe and holding it in an available form, even when external concentrations of P are high. It is suggested that plants which have an efficient mechanism for the uptake of Fe at relatively high pH and are less susceptible to the detrimental effects of P have been selected for on these alkaline calcareous soils.     

Using iron fertilizer to control Cd accumulation in rice plants: A new promising technology

Effects of two kinds of iron fertilizer, FeSO4 and EDTA·Na2Fe were studied on cadmium accumulation in rice plants with two rice genotypes, Zhongzao 22 and Zhongjiazao 02, with soil culture systems. The results showed that application of iron fertilizers could hardly make adverse effects on plant growth and rice grain yield. Soil application of EDTA·Na2Fe significantly reduced the Cd accumulation in rice roots, shoots and rice grain. Cd concentration in white rice of both rice genotypes in the treatment of soil application of EDTA·Na2Fe was much lower than 0.2 mg/kg, the maximal Cd permission concentra- tion in cereal crop foods in State standard. However, soil application of FeSO4 or foliar application of FeSO4 or EDTA·Na2Fe resulted in the significant increase of Cd accumulation in rice plants including rice grain compared with the control. The results also showed iron fertilizers increased the concentra- tion of iron, copper and manganese element in rice grain and also affected zinc concentration in plants. It may be a new promising way to regulate Cd accumulation in rice grain in rice production through soil application of EDTA·Na2Fe fertilizers to maintain higher content of available iron and ferrous iron in soils.     

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

The objective of this study was to evaluate the growth and nutrient-uptake characteristics of Fe-deficiency resistant and susceptible subclover (Trifolium subterraneum L., T. yanninicum Katzn. and Morley, T. brachcalycinum Katzn. and Morley) cultivars on a calcareous soil. Ten subclover cultivars showing varying susceptibilities to Fe-deficiency chlorosis (Karridale, Nangeela, Geraldton, Mt. Barker, Woogenellup, Larisa, Trikkala, Rosedale, Koala and Clare) were grown on a low-Fe, calcareous soil (Petrocalcic Paleustoll) under moist (18% water content, 85% of water holding capacity) and water-saturated conditions using a Cone-tainer^® culture system. Chlorosis and its correlation with growth traits and mineral nutrition of the 10 cultivars were examined. The Fe-deficiency susceptibilities of the 10 cultivars decreased in the above order under the moist condition, but in slightly different order under the saturated condition. Shoot and root dry weights, total dry weight, and root-to-shoot ratio were each negatively correlated with chlorosis under both soil-moisture conditions, as was total shoot content of P, Ca, Fe, Mn and Zn. Shoot P and Fe concentrations were each positively correlated with chlorosis under the moist soil condition. Iron and Cu utilization efficiencies (biomass per unit weight of nutrient) in the shoot were each negatively correlated with chlorosis under the moist soil condition. These results suggest that there may be several characteristics of Fe-deficiency chlorosis resistance in subclovers, such as a more effective soil-Fe mobilizing mechanism(s), more balanced nutrition, lower required Fe concentration in the shoot, higher shoot-Fe utilization efficiency, and higher root/shoot ratio under Fe-deficiency stress conditions.     

Role of exogenous nitric oxide in alleviating iron deficiency-induced peanut chlorosis on calcareous soil

This study examined the effects of exogenous nitric oxide (NO) on physiological characteristics of peanut (Arachis hypogaea L.) growing on calcareous soil. Sodium nitroprusside (SNP), a NO donor, was root application (directly; slow-release bag; slow-release capsule; slow-release particle) and foliar application. The results showed that SNP application alleviated iron (Fe) deficiency-induced chlorosis, increased the yield of peanut and increased the Fe concentration in peanut grain. SNP, especially supplied by slow-release particle improved the available Fe in soil by reducing pH of soil and increasing available Fe of soil. Furthermore, SNP application significantly increased the H⁺-ATPase and Fe³⁺ reductase activities and increased the total Fe concentration in the leaves. Meanwhile, SNP application, especially foliar application enhanced the availability of Fe in the plant by significantly increasing the active Fe content and chlorophyll content in the leaves. In addition, SNP also increased the antioxidant activities, but decreased the superoxide anion (O₂^??) generation rate and malondialdehyde content, which protected peanut against the Fe deficiency-induced oxidative stress. Therefore, these results support a physiological action of SNP on the availability, uptake and transport of Fe in the plant and foliar application SNP had the best effects in leaves and SNP supplied by slow-release particle had the best effects in roots. In addition, on the whole, the effects of SNP supplied by slow-release ways were better than directly supplied into the soil.     

Trifluralin-induced chlorosis in soybeans (Glycine max (L.) Merr.) grown on clayey,high pH soils

Summary The cause of leaf chlorosis, frequently observed on soybeans (Glycine max (L.) Merr.) grown on high pH soils of the Mississippi Blackland Prairie, is thought to be low Fe availability and restricted rooting. Three greenhouse experiments were conducted using two soils, Sumter, a Rendollic Eutrocrept and Okolona, a Typic Chromudert; nine soybean cultivars differing in Feefficiency; and trifluralin (α-α-α-trifluoro-2,6-dinitro-N, N-di-propyl-p-toludine). Trifluralin at rates greater than 0.56 kg/ha caused chlorosis which was more severe on the Sumter, a soil low in available Fe. Fe-efficient cultivars were more resistant to the chlorosis induced by trifluralin than the Fe-inefficient cultivars. It was concluded that the chlorosis is an Fe deficiency caused by reduced uptake. The herbicide-induced chlorosis can be avoided by proper dosage and placement of the herbicide.     

Effect of soil and foliar application of ferrous sulphate and of acidulation of soil on iron chlorosis of paddy seedlings ingoradu soil nurseries in India

Summary Nursery experiments were conducted to determine the cause for the chronic problem of chlorosis in paddy seedlings raised ongoradu soil nurseries of Anand area of Kheda district of Gujarat State and to find out remedial measures for it. The findings are (i) the chlorosis is due to high bicarbonate content of the soil (ii) application of ferrous sulphate to soil at 40 kg Fe/ha increased the survival period of the seedling but did not quite control the chlorosis (iii) spray of 0.4% ferrous sulphate solution twice a week was helpful in partial recovery of the seedlings from chlorosis (iv) acidulation of soil with sulphuric acid about ten days prior to sowing produced very healthy, vigorous and green seedlings of paddy which did not show any signs of chlorosis at all and (v) total and IN HCl-soluble iron content of the shoots did not at all reflect the degree of chlorosis of the paddy seedlings. These results are discussed in the light of current theories of absorption and translocation of iron in plant system and the iron-chlorosis of paddy seedlings ingoradu soils is attributed to both soil and plant factors.     

Iron deficiency in lentil: Yield loss and geographic distribution in a germplasm collection

Iron deficiency symptoms are observed on some genotypes of lentil (Lens culinaris Medikus) grown in calcareous soil. A germplasm collection of 3512 accessions originating from 18 countries was characterized for iron deficiency in a Calcic Rhodoxeralf soil at ICARDA, Tel Hadya, Syria in the 1979/80 season. At 105 days after sowing, 592 accessions, representing 16.9% of the collection, showed chlorosis symptoms characteristic of iron (Fe) deficiency. The Fe deficiency was verified by foliar application of Fe-chelate. Germplasm from different countries showed differences in iron deficiency, with those accessions exhibiting symptoms of iron deficiency mostly originating from relatively warm climates such as India (37.5% accessions showing Fe deficiency) and Ethiopia (30%). Populations from those Mediterranean countries where lentil originated (Syria and Turkey) exhibited Fe-deficiency symptoms only at very low frequencies. Fe-deficiency induced chlorosis was positively correlated with cold susceptibility. Fe chlorosis was transient, the deficiency symptoms largely disappearing during reproductive growth at a time, coinciding with increases in soil temperature and daylength-conditions favorable for plant growth. In Indian germplasm, mild deficiency symptoms did not lead to reduced seed yield, but there was a major yield reduction of 47% in those accessions with the most severe symptoms. Straw yields was reduced commensurately with the severity of symptoms. ei]Section editor: B G Rolfe     

The effects of nutrient supply,predominantly addition of iron,and rhizobial inoculation on the tolerance of Lupinus pilosus genotypes to a calcareous soil

Two glasshouse experiments were conducted to examine the effects of nutrient supply and rhizobial inoculation on the performance of Lupinus pilosus genotypes differing in tolerance to calcareous soils. In experiment 1, plants were grown for 84 days in a calcareous soil (50% CaCO₃; soil water content 90% of field capacity) at four nutrient treatments (no-added nutrients, added nutrients without Fe, added nutrients with soil applied FeEDDHA, added nutrients with foliar applied FeSO₄). In experiment 2, plants were grown for 28 days with supply of NH₄NO₃ without inoculation or inoculated with Bradyrhizobium sp. (Lupinus). Chlorosis in the youngest leaves was a good indicator of the relative tolerance of the genotypes to the calcareous soil in both experiments, except the treatment with FeEDDHA at 5 mg kg^–1 soil which was toxic to all genotypes. Chlorosis scores correlated with chlorophyll meter readings and chlorophyll concentrations. The foliar application of FeSO₄ did not fully alleviate chlorotic symptoms despite concentrations of active or total Fe in the youngest leaves being increased. Adding nutrients and chemical nitrogen did not change the severity of chlorosis or improve the growth of the plant. The nutrient supply did not alter the ranking of tolerance of genotypes to the calcareous soil. The results suggest that nutrient deficiency or poor nodulation was not a major cause of poor plant growth on calcareous soils and that bicarbonate may exert a direct effect on chlorophyll synthesis. The mechanism for tolerance is likely to be related to an ability to exclude bicarbonate or prevent its transport to the leaves.     

Using iron fertilizer to control Cd accumulation in rice plants: A new promising technology

Effects of two kinds of iron fertilizer, FeSO₄ and EDTA·Na₂Fe were studied on cadmium accumulation in rice plants with two rice genotypes, Zhongzao 22 and Zhongjiazao 02, with soil culture systems. The results showed that application of iron fertilizers could hardly make adverse effects on plant growth and rice grain yield. Soil application of EDTA·Na₂Fe significantly reduced the Cd accumulation in rice roots, shoots and rice grain. Cd concentration in white rice of both rice genotypes in the treatment of soil application of EDTA·Na₂Fe was much lower than 0.2 mg/kg, the maximal Cd permission concentration in cereal crop foods in State standard. However, soil application of FeSO₄ or foliar application of FeSO₄ or EDTA·Na₂Fe resulted in the significant increase of Cd accumulation in rice plants including rice grain compared with the control. The results also showed iron fertilizers increased the concentration of iron, copper and manganese element in rice grain and also affected zinc concentration in plants. It may be a new promising way to regulate Cd accumulation in rice grain in rice production through soil application of EDTA·Na₂Fe fertilizers to maintain higher content of available iron and ferrous iron in soils.     

Rational approaches to control of iron deficiency other than plant breeding and choice of resistant cultivars

Satisfactory progress has been made in recent years in preventing and correcting Fe deficiency in plants, and more can be expected in the future. Important advances include uses of acid- and Fe-fortified organic wastes and use of amended sulfur-pyrite mixes in soil. Three different approaches with organics are as an acidified matrix with Fe, as a means of chelating Fe, and as a carrier of acidifiers. Several procedures can help minimize Fe deficiency. (1) Avoid mis-management of soil physical properties and overirrigation. (2) Avoid nutrient imbalance, such as excess P or excess micronutrients. (3) Use preplant application of mildly acid-organic matter-Fe-sulfur or pyrite mixes worked into zones of soil or banded into seed rows. It is important that small bands or spots in soil be completely neutralized of CaCO₃. (4) Where foliar sprays can or need be used, especially to correct mild chlorosis, use ferrous compounds prepared to be delivered at pH 3± so that the Fe does not easily oxidize or precipitate in the solution. (5) For established trees that have become Fe deficient, inject, via slant drilling of small holes in tree trunks, dilute ferric ammonium citrate sufficient to supply not more than 100 mg kg^-1 Fe to leaves (dry weight basis). Most but not all species will respond. Procedure may be repeated in two or three weeks if necessary. (6) Iron chelates may be used in drip irrigation. If soil is sandy, soil pH not over 7.2, FeDTPA may be used; otherwise, FeEDDHA should be used. If the Fe is supplied with no other nutrients, pH may be at 4 and some FeSO₄ included to recycle the chelating agents. If Fe is used without chelating agents, the pH may be 1.0 or less and other nutrients included. (7) Urea-acid sulfate-Fe sulfate may be irrigated into soil around plants, especially if soil was polymer treated. (8) Efficiency of use of Fe chelates may be increased by making them slow release or by applying with seeds.     

Evaluation of 59Fe-lignosulfonates complexes as Fe-sources for plants

Iron chlorosis is a wide-spread limiting factor of production in agriculture. To cope with this problem, synthetic chelates (like EDTA or EDDHA) of Fe are used in foliar-spray or in soil treatments; however, these products are very expensive. Therefore paper-production byproducts, like Lignosulfonates (LS), with varying content of carboxylate and sulfonate groups, were tested with respect to their ability to maintain Fe in the solution of soils and to feed plants grown in hydroponics with Fe through foliar sprays or application to the nutrient solution. Results show that LS had a low capability to solubilize ⁵⁹Fe-hydroxide and that preformed ⁵⁹Fe(III)-LS complexes had poor mobility through a soil column (pH 7.5) and scarce stability when interacting with soils compared to ⁵⁹Fe(III)-EDDHA. However when ⁵⁹Fe(III)-LS were supplied to roots in a hydroponic system, they demonstrated an even higher capability to fed Fe-deficient tomato plants than ⁵⁹Fe(III)-EDDHA. Hence, data here presented indicate that the low Fe use efficiency from Fe-LS observed in soil-applications is due to interactions of these Fe-sources with soil colloids rather than to the low capability of roots to use them. Foliar application experiments of ⁵⁹Fe(III)-LS or ⁵⁹Fe(III)-EDTA to Fe-deficient cucumber plants show that uptake and reduction rates of Fe were similar between all these complexes; on the other hand, when ⁵⁹Fe(III)-LS were sprayed on Fe-deficient tomato leaves, they showed a lower uptake rate, but a similar reduction rate, than ⁵⁹Fe(III)-EDTA did. In conclusion, Fe-LS may be a valid, eco-compatible and cheap alternative to synthetic chelates in dealing with Fe chlorosis when applied foliarly or in the nutrient solution of hydroponically grown plants.     

Mineral Nutrient Limitations of Calcifuge Plants in Phosphate Sufficient Limestone Soil

Twelve species of calcifuge plants were grown in an Ordovician-limestone soil with and without phosphate amendment, as well as in an acid silicate soil of their natural habitat. Phosphate treatment of the limestone soil raised the P concentrations of the plant biomasses to levels within sufficiency ranges reported for cultivated plants and productivity usually increased two- to five-fold. Out of twelve species studied,Scleranthus perenniswas unable to survive in the limestone soil unless treated with phosphate, whereas growth and general performance ofGalium saxatilewas impaired by phosphate additions. Biomass dilution effects on micro-nutrients, but usually not on macronutrients, were recorded as a result of the phosphate treatment. Dilution of Mn was most distinct and Fe was least distinct. However, no foliar symptoms clearly assignable to Mn deficiency were observed. Symptoms of foliar chlorosis, reminiscent of Fe deficiency, developed inGalium saxatile, Carex piluliferaandVeronica officinalis. InC.pilulifera, but not inV.officinalis, chlorosis was accompanied by decreasing foliar Fe concentrations.     

The effect of soil moisture on the tolerance of Lupinus pilosus genotypes to a calcareous soil

Commercial narrow-leafed lupins (Lupinus angustifolius L.) grown on calcareous soils commonly display chlorotic symptoms resembling Fe deficiency. The severity of chlorosis increases with concurrent increases in soil moisture content. Our research has indicated that the rough-seeded lupin species, Lupinus pilosus Murr., has a range of adaptation to calcareous soils, from tolerant to intolerant. A pot experiment was conducted comparing a tolerant, a moderately tolerant and a moderately intolerant genotype of L. pilosus. Plants were grown for 35 days in a calcareous soil (50% CaCO₃) at three moisture contents (80%, 100% and 120% of field capacity); the growth was compared with that on a fertile black cracking clay control soil at 70% of field capacity. Visual chlorosis score, chlorophyll meter readings, number of leaves and shoot dry weights were recorded at 14, 21, 28 and 35 days after sowing. Concentrations of chlorophyll, active Fe and nutrients in the youngest fully expanded leaves were also measured. Results showed that increased soil moisture increased the severity of chlorotic symptoms (increased chlorosis score) in all genotypes. The tolerant genotype showed significantly less symptoms than other genotypes at all moisture contents. All genotypes were able to recover from chlorosis symptoms at 80% moisture in the calcareous soil. Chlorosis score negatively correlated with chlorophyll meter readings, chlorophyll concentration and foliar active and total Fe, and Mn concentrations. Visual chlorosis score appeared to be a cost effective, accurate and efficient method enabling classification of the tolerance of genotypes. The chlorotic symptoms were likely to be due to HCO₃ ^- induced nutrient deficiencies or a direct effect of HCO₃ ^- on chlorophyll synthesis. This study indicates that the most probable mechanism of tolerance is related to an ability to prevent uptake of HCO₃ ^- or efficiently sequester it once inside the root which prevents increases in internal pH and transport to the shoots.     

Rapid elicitation of second messengers by nanomolar doses of triacontanol and octacosanol

Triacontanol (TRIA) increases the dry weight and alters the metabolism of rice (Oryza sativa L.) seedlings within 10 min of application to either the shoots or roots. This activity is prevented if octacosanol (OCTA, C₂₈ primary alcohol) is applied with the TRIA on the roots or shoots. Triacontanol activity is also stopped if the OCTA is applied at least 1 min before the TRIA on the opposite part of the seedling.Triacontanol rapidly elicits a second messenger that moves rapidly throughout the plant resulting in stimulation of growth (dry-weight increase) and water uptake. Octacosanol also produces a second messenger that inhibits TRIA activity. We have named the putative secondary messengers elicited by TRIA and OCTA, TRIM and OCTAM, respectively. The water-soluble TRIM extracted from plants treated with TRIA increases the growth of rice seedlings about 50% more than extracts from untreated plants, within 24 h of application. Both OCTAM and OCTA inhibit the activity of TRIA but not of TRIM.The TRIA messenger was isolated from rice roots within 1 min of a foliar application of TRIA. The TRIM elicited by TRIA will pass through a 4-mm column of water connecting cut rice shoots with their roots and can also be recovered from water in which cut stems of TRIA-treated plants have been immersed. Triacontanol applied to oat (Avena sativa L.) or tomato (Lycopersicon esculentum Mill.) shoots connected to rice roots by a 4-mm water column also results in the appearance of TRIM in rice roots.Abbreviations OCTA octacosanol - OCTAM second messenger elicited by OCTA - TAS tallow alkyl sulfate - TRIA triacontanol - TRIM second messenger elicited by TRIA Michigan Agricultural Experiment Station Journal Article No. 12001     

Soybean response to nodulation by bradyrhizobia differing in rhizobitoxine phenotype

Rhizobitoxine-producing (RT⁺) strains of Bradyrhizobium japonicum, differing in their abilities to induce foliar chlorosis with ‘Forrest’ soybean (Glycine max [L.] Merr.), were evaluated for effects on short term shoot productivity, nodulation, N₂ fixation, and nodule protein production under greenhouse conditions. Soybeans were singly inoculated with washed suspensions of (Group II) USDA strains 31, 46, 76, 94, 110, 123 or 130. Strains USDA 110 and USDA 123 (Group I/Ia) were included as RT-controls. The plants were cultured in the absence of combined N in horticultural-grade vermiculite for 49 days. Beginning 21 days after planting, plants were evaluated weekly for chlorophyll, leaf protein and biomass accumulation, nodular contents of leghemoglobin, soluble protein and RT, and total shoot N content. Rhizobitoxine was detected in nodules of all RT⁺ strains with the exception of USDA 31. However, only USDA 76 and USDA 94 produced both quantifiable concentrations of RT and symptoms of RT-induced chlorosis. Coincident with moderate to severe chlorosis were reductions in chlorophyll concentrations, shoot and nodule dry weight, leaf protein and total N₂ fixation. During extended periods of severe chlorosis, reductions in Lb and soluble nodular protein were observed. Based on carbon accumulation, all non-chlorotic treatments were statistically more productive than the chlorotic treatments. Similarly, non-chlorotic Group II treatments tended to fix less carbon relative to the RT-Group I/Ia controls, although these differences were not statistically significant. The results of this study suggest that, in the absence of discernable foliar chlorosis, the effect of RT⁺ (Group II) nodulation on short term soybean productivity is minimal. Published as Miscellaneous Paper No. 1439 of the Delaware Agricultural Experiment Station. Published as Miscellaneous Paper No. 1439 of the Delaware Agricultural Experiment Station.     

Methanol bioeconomy: promotion of rice crop yield in paddy fields with microbial cells prepared from natural gas-derived C1 compound

Methylotrophs, which can utilize methanol as a sole carbon source, are promising microorganisms to be exploited in a methanol-based bioeconomy, in which a variety of useful compounds are biotechnologically produced from natural gas-derived methanol. Pink-pigmented facultative methylotrophs (PPFMs) are common plant phyllospheric bacteria and are known to enhance seedling growth and total biomass of various plants. However, improvement of crop yield by inoculation of PPFMs at the field level has not been well investigated. We herein describe improvement of crop yield of several rice cultivars by foliar spraying of PPFMs. After selection of PPFM strains and rice cultivars by the in vitro seedling growth test, we further conducted paddy field experiments. The crop yield of the sake-brewing rice Oryza sativa cultivar Hakutsurunishiki was reproducibly improved in a commercial paddy field for over a 5-year period. A one-time foliar spray of PPFM cells (living or killed) or a cell wall polysaccharide fraction, after the heading date, acted in the phyllosphere and effectively improved crop yield. Our results show that the established process with PPFMs is feasible for improvement of food production in the methanol bioeconomy.     

The effect of FeEDDHA on the development of lime-chlorosis in two seedling populations ofEucalyptus obliqua L'Hérit

Summary The application of FeEDDHA to a calcareous soil significantly increased yield and alleviated severe lime-chlorosis in a genotype ofEucalyptus obliqua that is native to acidic soils. The alleviation of chlorosis brought about a significant decrease in the levels of P, Ca and K but an increase in the uptake of Fe in leaves. The total Fe content of foliage, however, was poorly coorelated with the occurrence of lime-chlorosis. It was concluded that the differential susceptibility ofE. obliqua to lime-chlorosis is related to interactions between Fe and Ca, as well as Fe and P, occurring during the absorption and translocation processes.