Importance of iron use‐efficiency of nodules in common bean (Phaseolus vulgaris L.) for iron deficiency chlorosis resistance

Several studies suggest that the Fabaceae‐Rhizobium symbiosis is particularly sensitive to iron (Fe) deficiency with respect to NO₃^–‐dependent plants. The aim of this study, which is part of a screening program for common bean tolerance to Fe deficiency, was to study genotypical differences in Fe requirement and Fe use‐efficiency of common bean cultivars depending on symbiotic nitrogen fixation (SNF). Results show that ARA14 produces more whole plant dry matter and particularly more nodule biomass than Coco blanc. ARA14 is characterized by a high capacity of nitrogen fixation and a better Fe use‐efficiency for the growth and the function of the nodules.     

Inheritance of iron deficiency chlorosis resistance in groundnut (Arachis hypogaea L.)

Iron-deficiency chlorosis (IDC) is an important abiotic constraint affecting the growth and yield of groundnut in calcareous and alkaline soils worldwide. The present study investigated the inheritance of IDC resistance among four straight crosses of groundnut involving four IDC susceptible cultivars as females and a common IDC resistant male parent. The F₁'s of all the four crosses were resistant to IDC indicating the dominant nature of IDC resistance. The F₂'s of all the four crosses showed a good fit to the ratio of 15 (IDC resistant): 1 (IDC susceptible) and their behavior among the F₃'s was as per the expected ratio of 7:4:4:1. The IDC resistance in groundnut is under the control of duplicate dominant genes wherein, the presence of a dominant allele at either of the loci results in IDC resistance, while duplicate recessive results in IDC susceptibility. This information would facilitate development of IDC resistant cultivars of groundnut.     

Soybean genotype evaluation for iron deficiency chlorosis using sodium bicarbonate and tissue culture

The evaluation of soybean genotypes for resistance to iron deficiency through field experiments is complicated by variation in symptom expression. The objective of this study was to develop a tissue culture technique that could distinguish between Fe‐efficient and Fe‐inefficient genotypes. Ten soybean genotypes varying in sensitivity to iron deficiency were planted at 5 locations and rated based on chlorosis expression. For the lab evaluation, friable callus of the ten genotypes was placed on a 4MSII medium amended with 10 mM NaHCO₃. Callus growth reduction relative to a control medium without NaHCO₃ was recorded. Callus weight of all cultivars was affected by the addition of NaHCO₃ however, significant differences in growth reduction among genotypes was observed. The high correlation between callus growth reduction and field chlorosis ratings observed (r²=0.92) and the fact that the expiant source plant can be grown to produce seed indicates that this technique would be useful in a soybean breeding program.     

Differential responses of soybean and dry bean to zinc deficiency 1

Whether a legume obtains its nitrogen (N) from the air, through dinitrogen fixation, or from the soil, as nitrate (NO₃), may influence its susceptibility to zinc (Zn) deficiency. The influence of N source [potassium nitrate (KNO₃)+ native soil N versus rhizobium‐inoculated seed + native soil N] and phosphorus (P) (0 and 200 mg P/kg), and Zn fertilizers (0, 1, and 8 mg Zn/kg) on growth and nutrient composition of soybean (Glycine max L. cv. McCall) and navy bean (Phaseolus vulgaris L. cv. Seafarer) grown on a calcareous soil were studied under greenhouse conditions. Inoculated plants, but not their KNO₃‐treated counterparts, had root nodules. However, due to N deficiency resulting from suboptimal N fixation, growth of these inoculated plants, especially of navy bean, was poorer than that of similarly treated KNO₃‐fed plants. As a consequence of this restricted growth, responses to P and Zn fertilizers were generally greater in KNO₃‐treated plants. Added P decreased the yield of KNO₃‐treated navy bean in the absence of added Zn, but P‐induced Zn deficiency had little effect on the growth of similarly treated inoculated plants. Plant excess bases (EB)/total plant N ratios [EB = 1/2 Ca + l/2Mg + Na + K ‐ Cl ‐ total S (S = divalent) ‐ total P (P = monovalent)] were less in KNO₃‐treated soybean than in correspondingly treated navy bean. Therefore, rhizosphere pH values around navy bean roots were probably less than those around soybean roots. Despite the hypothesized lower rhizosphere pH values, KNO₃‐treated navy bean was more susceptible to Zn deficiency than soybean. This greater susceptibility of navy bean to Zn deficiency was apparently at least partly due to poor translocation of Zn from the roots to the tops.     

花生缺铁黄化的敏感时期及耐低铁品种的筛选指标

采用盆栽试验,系统研究了石灰性土壤上16个花生品种在各个生育时期新叶的黄化度、叶绿素值、活性铁含量的差异及其动态变化。结果表明,缺铁胁迫下花生耐低铁和铁敏感品种间叶片的黄化程度存在着显著差异,大多数铁敏感品种在出苗后50～65 d时黄化度最高。供试16个品种顶部新展开叶片的叶绿素值（SPAD值）和活性铁含量在整个生育期的变幅分别为4.5～34.6和8.0～36.3 mg/kg, FW,随生长时间的延长两者均呈高―低―高的动态变化趋势。在生长前期,耐低铁品种新叶的叶绿素值和活性铁含量均显著高于铁敏感品种;开花期是花生对缺铁胁迫最为敏感的时期,此阶段黄化现象最严重、各品种新叶的叶绿素值和活性铁含量最低。相关分析表明,在生长前期叶绿素值与黄化度、活性铁及荚果产量之间均呈极显著的相关关系。新叶叶绿素值可作为花生耐低铁品种筛选的一可靠指标。     

Evaluating grain sorghum hybrids for tolerance to iron chlorosis

Grain sorghum production in calcareous soils is frequently affected by iron (Fe) chlorosis. Greenhouse experiments were conducted to screen sorghum hybrids for their tolerance to iron deficiency chlorosis (IDC) and evaluate the effectiveness of Fe chelate application in alleviating IDC. Treatments in Exp. 1 were a factorial combination of 14 sorghum hybrids and three Fe chelate application rates (0, 3.4 and 6.8?kg product ha^?1) applied in-furrow with the seed at the time of planting. Exp. 2 evaluated two sorghum hybrids (85Y40 and NK5418) and three Fe chelate rates (0 and 3.4?kg product ha^?1) at planting, and a split treatment of 3.4?kg ha^?1. Results showed iron chelate application suppressed IDC and increased leaf chlorophyll content and grain yield in susceptible hybrids. Split application of Fe chelate suppressed IDC and increased grain yield. Our results indicate sorghum hybrids G8G08, 86G32 and 87P06 showed promise for tolerance to IDC.     

铁肥根系输液矫正苹果缺铁失绿症效果及其机理

根系输液条件下,Ｎ－Ｆｅ能够在短时间内有效地矫正苹果缺铁失绿症,ＥＤＴＡ－Ｆｅ容易产生肥害,柠檬酸铁效果居中。红色邻二氮杂菲铁示踪结果表明：二价铁肥根系输处理时仍以二价态由根被动吸收,运输到根、茎、叶和主脉内,运输部位都是靠近形成层的木质部,运输速度每小时可达数十厘米。室内营养液培养的八棱海棠苗用＾５９Ｆｅ示踪结果表明,断根中分配的＾５９Ｆｅ为１９．３％,叶中分配的＾５９Ｆｅ占７０．９％,八棱海棠     

树干高压注射铁肥矫正苹果失绿症及其机理

利用N-Fe、邻二氮杂菲铁和.59Fe作为铁源,以3-8年生富士／八棱海棠为试材进行主干强力高压注射试验。结果表明,铁肥树干强力高压注射,主要以二价铁(Fe2+)沿中央木质部的导管运输,大部分向下运输,使铁在根中大量贮存;向上运输较少,运输速度为每小时数百厘米,矫正缺铁失绿症的速度比根系输液慢,但由于根中贮存大量的铁,持效期较长。主干强力高压注射产生肥害的机理是先使吸收根中毒,然后导致叶片枯萎,提高注射部位,提高注射液浓度和减少注射的用药量,可以防止或减轻肥害的产生。     

Physiological basis of iron chlorosis tolerance in rice (Oryza sativa) in relation to the root exudation capacity

Micronutrient deficiency in cultivable soil, particularly that of iron (Fe) and zinc (Zn), is a major productivity constraint in the world. Low Fe availability due to the low solubility of the oxidized ferric forms is a challenge. An experiment was, thus, executed to assess the performance of eight genetically diverse rice genotypes on Fe-sufficient (100 µM) and Fe-deficient (1 µM) nutrient solution, and their ability to recover from Fe deficiency was measured. Fe efficiency under Fe deficiency in terms of biomass production showed a significant positive correlation with the root release of phytosiderophore (PS) (R² = 0.62*). This study shows that the Fe deficiency tolerance of Pusa 33 was related to both a high release of PS by the root and an efficient translocation of Fe from the root to the shoot as the Fe–PS complex, which could be useful for improving the Fe nutrition of rice particularly under aerobic conditions.     

花生耐低铁性的基因型差异及其生理特性研究

通过田间试验对16个花生品种在石灰性土壤上的耐低铁性进行了评价。不同花生品种耐低铁能力存在显著的基因型差异,这种差异表现在生长过程中叶片活性铁含量、叶绿素含量以及最终的荚果产量上。溶液培养试验结果表明,根系Fe3+还原力提高是抗缺铁花生品种适应缺铁胁迫的主要机制,抗缺铁品种铁还原力高峰出现期早于铁敏感品种,且峰值远高于铁敏感品种。同时缺铁胁迫下介质pH值、新叶过氧化氢酶活性也存在显著的基因型差异。     

Breeding soybean for resistance to iron-deficiency chlorosis and soybean cyst nematode

Abstract

Iron-deficiency chlorosis (IDC) and soybean cyst nematode (SCN) result in yield and income losses for soybean growers in the U.S. Breeding programs are identifying soybean genotypes with resistance to IDC using calcareous soils infested with SCN, where SCN might interfere with evaluation. Our first objective was to examine whether associations could be established for chlorosis symptoms with SCN infestation of soybean grown on SCN-infested calcareous soils. Two breeding populations, their parents, and five SCN-susceptible, IDC-control genotypes (IDC controls) were evaluated for IDC symptoms on SCN-infested calcareous soils in 2000 and 2001. In general, no significant correlations were detected between chlorosis expression and SCN infestation in either year, although a negative correlation (r = ?0.93, p ≤ 0.05) was observed for the IDC controls in 2001. For our second objective, we examined the relationship between genotype resistance to SCN and IDC. Although IDC controls were all equally susceptible to SCN and chlorosis observed in the field and nutrient solution was similar, SCN-resistant genotypes expressed resistance to IDC in the field, but severe susceptibility to IDC in nutrient solution. Our third objective was to investigate the value of calcareous soil properties to predict IDC in soybean grown on SCN-infested calcareous soils. For one breeding population in 2001, positive correlations (p ≤ 0.05) were detected for chlorosis with calcium carbonate (r = 0.62) and electrical conductivity (r = 0.59), and a negative correlation (r = –0.41) with soil Fe-DTPA-TEA. No significant correlations were observed for the remaining genotypes. Our study indicated that associations between IDC, SCN, and calcareous soil properties are dependent on genotype and environment. In addition, our study demonstrated a potential association between plant health and SCN reproduction in SCN-susceptible genotypes, the possibility that SCNresistant genotypes may be sensitive to iron availability, and the importance of genotype on the detection of associations between IDC expression and SCN infestation.     

铁肥虹吸输液对缺铁失绿苹果叶片光合生理指标和荧光参数的影响

为了进一步探索矫正苹果缺铁失绿症途径,采用铁肥虹吸输液方法,研究了铁肥虹吸输液对缺铁黄化叶片复绿,叶片解剖结构、 色素含量、 光合生理指标和叶绿素荧光参数的影响。结果表明,虹吸输液处理的复绿苹果叶片单个细胞叶绿体数目比对照增加了3.6个,淀粉粒有所减少;叶绿体内基粒结构更清晰、 垛叠增多;线粒体内嵴数量增多、 清晰度提高;叶绿体和线粒体的被膜结构得到修复。虹吸输铁后失绿程度由2.00级恢复到0.49级;铁肥虹吸输液显著提高了叶片的光合速率、 气孔导度,降低了细胞间隙的CO2浓度。输铁处理其PSⅡ原初光能转化效率（Fv/Fm）和PSⅡ潜在活性（Fv/Fo）均为最高。缺铁失绿苹果叶片叶绿素a、 叶绿素b含量分别比未输液对照增加2.97倍和3.18 倍。说明采取铁肥虹吸输液的方法能够矫正苹果缺铁失绿症。     

Determination of iron chlorosis with extractable iron analysis in peach leaves

Iron (Fe) though indispensable for the biosynthesis of chlorophyll, but its total content in the plant was not associated with the occurrence of chlorosis. Iron, which is the ferrous‐iron (Fe²⁺) form—termed “active”; Fe— and extracted with weak acids and some chelating agents, has been closely related to Fe chlorosis. In this study, three different methods were tested in order to determine suitable methods for extractable‐Fe analysis in a Dixired peach cultivar. In the first two methods, o‐phenantroline (o‐Ph) and 1N hydrochloric acid (HCl) were used to extract Fe²⁺ from fresh leaves. In the third method, 1N HCl were used as an extractant on dried leaf samples. The relationship between chlorophyll content of the leaves and Fe extracted by the three methods, was statistically significant. Hydrochloric acid extraction with dried leaves which gave the highest significant correlation (r = 0.930) with chlorophyll content, can be used for the determination of Fe²⁺ ("active”; Fe) status in peach trees.     

Depressed growth of non‐chlorotic vine grown in calcareous soil is an iron deficiency symptom prior to leaf chlorosis

The development of iron deficiency symptoms (growth depression and yellowing of the youngest leaves) and the distribution of iron between roots and leaves were investigated in different vine cultivars (Silvaner, Riparia 1G and SO4) grown in calcareous soils. As a control treatment all cultivars were also grown in an acidic soil. Only the cultivars Silvaner and Riparia 1G showed yellowing of the youngest leaves under calcareous soil conditions at the end of the cultivation period. All cultivars including SO4 showed severe shoot growth depression, by 50 % and higher, before yellowing started or without leaf yellowing in the cultivar SO4. Depression of shoot growth occurred independently from that of root growth. In a further treatment the effect of Fe‐EDDHA spraying onto the shoot growth of the cultivar Silvaner after cultivation in calcareous soil was investigated. Prior to Fe application plants were non‐chlorotic, but showed pronounced shoot growth depression. Spraying led to a significant increase in shoot length, though leaf growth was not increased. Accordingly, depression of shoot growth of non‐chlorotic plants under calcareous soil conditions and with ample supply of nutrients and water has been evidenced to be at least partly an iron deficiency symptom. We suggest that plant growth only partially recovered because of dramatic apoplastic leaf Fe inactivation and/ or a high apoplastic pH which may directly impair growth. Since growth was impaired before the youngest leaves showed chlorosis we assume that meristematic growth is more sensitively affected by Fe deficiency than is chlorophyll synthesis and chloroplast development. In spite of high Fe concentrations in roots and leaves of the vines grown in calcareous soils plants suffered from Fe deficiency. The finding of high Fe concentrations also in young, but growth retarded green leaves is a further indication that iron deficiency chlorosis in calcareous soils is caused by primary leaf Fe inactivation. However, in future, only a rigorous study of the dynamic changes of iron and chlorophyll concentration, leaf growth and apoplastic pH at the cellular level during leaf development and yellowing will provide causal insights between leaf iron inactivation, growth depression, and leaf chlorosis.<?show $6#>     

Mechanisms of exogenous nitric oxide and 24-epibrassinolide alleviating chlorosis of peanut plants under iron deficiency

Iron(Fe) is a crucial transition metal for all living organisms including plants; however, Fe deficiency frequently occurs in plant because only a small portion of Fe is bioavailable in soil in recent years. To cope with Fe deficiency, plants have evolved a wide range of adaptive responses from changes in morphology to altered physiology. To understand the role of nitric oxide(NO) and 24-epibrassinolide(EBR) in alleviating chlorosis induced by Fe deficiency in peanut(Arachis hypogaea L.) plants, we determined the concentration of chlorophylls, the activation, uptake, and translocation of Fe, the activities of key enzymes, such as ferric-chelate reductase(FCR),proton-translocating adenosine triphosphatase(H~+-ATPase), and antioxidant enzymes, and the accumulation of reactive oxygen species(ROS) and malondialdehyde(MDA) of peanut plants under Fe sufficiency(100 μmol L~(-1)ethylenediaminetetraacetic acid(EDTA)-Fe) and Fe deficiency(0 μmol L~(-1)EDTA-Fe). We also investigated the production of NO in peanut plants subjected to Fe deficiency with foliar application of sodium nitroprusside(SNP), a donor of NO, and/or EBR. The results showed that Fe deficiency resulted in severe chlorosis and oxidative stress, significantly decreased the concentration of chlorophylls and active Fe, and significantly increased NO production. Foliar application of NO and/or EBR increased the activity of antioxidant enzymes, superoxide dismutase,peroxidase, and catalase, and decreased the ROS and MDA concentrations, thus enhancing the resistance of plants to oxidative stress.Application of NO also significantly increased Fe translocation from the roots to the shoots and enhanced the transfer of Fe from the cell wall fraction to the cell organelle and soluble fractions. Consequently, the concentrations of available Fe and chlorophylls in the leaves were elevated. Furthermore, the activities of H~+-ATPase and FCR were enhanced in the Fe-deficient plants. Simultaneously,there was a significant increase in NO production, especially in the plants that received NO, regardless of Fe supply. These suggest that NO or EBR, and, especially, their combination are effective in alleviating plant chlorosis induced by Fe deficiency.     

Evaluation of world collection of kabuli chickpea for resistance to iron-deficiency chlorosis

Summary Iron-deficiency chlorosis is often seen in chickpea (Cicer arietinum L.) fields in the Mediterranean region and is particularly severe in fields where iron-deficiency susceptible cultivars are sown. Therefore, ICARDA's breeding programme field evaluated 6224 kabuli chickpea germplasm accessions for iron-deficiency chlorosis on a high pH Calcic Rhodoxeralf soil (pH 8.5, 20–25% calcium carbonate) at Tel Hadya, Syria during the winter and spring of 1987/88. Two resistant and 17 susceptible lines were grown during autumn, winter and spring of 1988/89 to examine the effect of sowing time on the appearance of the deficiency. About 99% of accessions showed no iron-deficiency symptoms. Evaluation of susceptible accessions during autumn, winter, and spring sowing revealed that iron-deficiency chlorosis was more pronounced during winter sowing. There were also significant genotype x season interactions, indicating differential responses of genotypes to time of sowing. Since the iron-deficiency chlorosis character is controlled by recessive genes, a negative selection to discard the susceptible lines from breeding material is recommended as an effective breeding strategy.Joint contribution from ICARDA and ICRISAT (International Crops Research Institute for Semi-Arid Tropics), Patancheru P.O., A. P. 502 324, India.     

铁肥根系输液矫正果树缺铁失绿症机理

邻二氮杂啡铁示踪结果表明 ,铁肥根系输液处理时铁以二价态由根被动吸收 ,并运输到根、茎、和叶的主脉内。运输部位都是靠近形成层的木质部 ,运输速度每小时可达数十厘米。室内营养液培养的八棱海棠苗用59Fe示踪结果表明 ,断根中分配的59Fe为 18.1% ,叶中分配的59Fe占 70 .9% ;断 1、2、3条根的植株59Fe在叶中的分配比例分别为 57.9%、63.6 %、68.0 %。     

Comparative investigation on the susceptibility of faba bean (Vicia faba L.) and sunflower (Helianthus annuus L.) to iron chlorosis

Comparative physiological studies on iron (Fe) chlorosis of Vicia faba L. and Helianthus annuus L. were carried out. High internal Fe contents in Vicia cotyledons (16–37 μg) were completely used for plant growth and Fe chlorosis was not inducible by the application of nitrate (with or without bicarbonate). In Helianthus, low quantities of Fe in the seeds (4 μg) were insufficient for normal growth and without Fe in the nutrient solution, Fe chlorosis was obtained in all treatments. This chlorosis was an absolute Fe deficiency. Also, the treatment with 1 μM Fe in the nutrient solution and nitrate (with or without bicarbonate) led to severe chlorotic symptoms associated with low leaf Fe concentrations and high Fe concentrations in the roots. In contrast, Helianthus grown with NH₄NO₃ and 1 μM Fe had green leaves and high leaf Fe concentrations. However, with NO₃ supply (with or without bicarbonate), Fe translocation from the roots to the upper plant parts was restricted and leaves were chlorotic. Chlorotic and green sunflower leaves may have the same Fe concentrations, leaf Fe concentration being dependent on Fe translocation into the leaf at the various pH levels in the nutrient solution. At low external pH levels (controlled conditions) more Fe was translocated into the leaf leading to similar leaf Fe concentrations with higher chlorophyll concentrations (NH₄NO₃) and with lower chlorophyll concentrations (NO₃). This indicates a lower utilization of leaf Fe of NO₃ grown sunflower plants. Utilization of Fe in faba bean leaves is presumably higher than in sunflower leaves. In Vicia xylem sap pH was not affected by nitrate. In contrast, the xylem sap pH in Helianthus was permanently increased by about 0.4 pH units when fed with nitrate (with or without bicarbonate) compared with NH₄NO₃ nutrition. The xylem sap pH is indicative of leaf apoplast pH. From our earlier work (Mengel et al., 1994; Kosegarten und Englisch, 1994) we therefore suppose that in Helianthus, Fe immobilization occurs in the leaf apoplast due to high pH levels when grown with nitrate (with or without bicarbonate).     

Screening of iron bioavailability patterns in eight bean (Phaseolus vulgaris L.) genotypes using the Caco-2 cell in vitro model

The common bean ( Phaseolus vulgaris) is an important staple plant food in the diets of people of Latin America, East Africa,and other regions of the developing world. It is also a major source of dietary iron. The primary goal of this research was to use an in vitro digestion/Caco-2 model to study iron bioavailability in eight genotypes (three Mesoamerican and five Andean) that represent the diversity of grain types in this crop. Complementing this goal, we measured the distribution of both iron and phytate in different bean grain tissues (cotyledon, seed coats, and embryos). Seed coats were confirmed to be the exclusive tissue containing polyphenols. The removal of the seed coat and associated polyphenols improved Caco-2 iron bioavailability, and significant differences were observed between genotypes. The addition of ascorbate enhanced iron bioavailability and exposed additional differences in Fe availability among the genotypes. These results indicate that iron accumulation and in vitro iron bioavailability vary among bean genotypes and that polyphenols had greater inhibitory effects on Caco-2 iron bioavailability as compared to phytate.     

Timing and rate of iron chelate application to correct chlorosis of peanut

The timing and rate of application of iron (Fe) chelates (seques‐trene 138 Fe) to correct Fe chlorosis of peanut grown on calcareous soils was studied for three seasons (1985–87) in seven experiments. It was found that the biological yield of peanut increased up to the highest rate of chelate used (8 g/m²). However, under the existing prices of the chelate and peanuts, application is financially untenable above 4 g/m². The time of chelate application should not be at sowing, but after the crop becomes chlorotic. Even though the yield differences between early application at branching, 25 to 30 days after emergence, and an application at anthesis, 45 to 50 days after emergence, was small, the trend in yield and size of nuts favored the earlier application. Therefore, it is recommended that the application of the Fe chelate be at the early stages of plant development, particularly in cases of severe chlorosis.