Manganese and iron interactions on their uptake and distribution in soybean (Glycine max (L.) Merr.)

Summary The uptake and distribution of iron and manganese were studied in a manganese-sensitive soybean cultivar (‘Bragg’) grown over a range of supply levels of these nutrients in solution culture. At high (90 and 275 μM) manganese levels, increasing the iron concentration in solution from 2 to 100 μM partially overcame the effects of manganese toxicity. Interactions between manganese and iron occurred for dry matter yields, rate of Mn absorption by the roots, and the proportions of manganese and iron transported to the tops. No interaction was observed for the rate of root absorption of iron. The percentage distribution of manganese in the plant top increased with increasing iron, despite a reduced rate of Mn uptake. On the other hand, iron uptake was independent of solution Mn concentration and increased with increasing solution Fe. Also more iron was retained in the roots at high Mn and/or Fe levels in solution. Concentrations of manganese and iron in roots, stems and individual leaves were affected independently by the manganese and iron supplyi.e. without any interaction occurring between the two elements. In general, the concentration in a plant part was related directly to the solution concentration. Symptoms resembling iron deficiency correlated poorly with leaf Fe concentrations whereas high levels of manganese were found in leaves displaying Mn toxicity symptoms.     

Role of sulphur availability on cadmium-induced changes of nitrogen and sulphur metabolism in maize (Zea mays L.) leaves

The interactions between sulphur nutrition and Cd exposure were investigated in maize (Zea mays L.) plants. Plants were grown for 12 days in nutrient solution with or without sulphate. Half of the plants of each treatment were then supplied with 100 microM Cd. Leaves were collected 0, 1, 2, 3, 4 and 5 days from the beginning of Cd application and used for chemical analysis and enzyme assays. Cd exposure produced symptoms of toxicity (leaf chlorosis, growth reduction) and induced a noticeable accumulation of non-protein SH compounds. As phytochelatins are glutamate- and cysteine-rich peptides, the effect of cadmium on some enzyme activities involved in N and S metabolism of maize leaves was studied in relation to the plant sulphur supply. In vivo Cd application to S-sufficient plants resulted in a drop of all measured enzyme activities. On the other hand, S-deficient plants showed a decrease in nitrate reductase (NR; EC 1.6.6.1) and glutamine synthetase (GS; EC 6.3.1.2) activity, and an increase in NAD-dependent glutamate dehydrogenase (GDH; EC 1.4.1.2) and phosphoenolpyruvate carboxylase (PEPc; EC 4.1.1.31) activity as a result of the Cd treatment. Furthermore, in the same plants ATP sulphurylase (ATPs; EC 2.7.7.4) and O-acetylserine sulphydrylase (OASs; EC 4.2.99.8) showed a particular pattern as both enzymes exhibited a transient maximum value of activity after 4 days from the beginning of Cd exposure. Results provide evidence that the increase of ATPs, OASs, GDH and PEPc activities, observed exclusively in S-deficient Cd-treated plants, may be part of the defence mechanism based on the production of phytochelatins.     

A non-destructive field assay for soybean nitrogen fixation by acetylene reduction

Summary A system for employing open-ended root chambers to measurein situ acetylene reduction rates under field conditions is described. Gas mixtures containing about 2 mbar acetylene were continuously flowed through the chambers providing a continuous record of acetylene reduction. These chambers have been used to measure acetylene reduction rates of soybeans during three growing seasons. The system has proved to be reliable with a high degree of precision. The large amount of plant-to-plant variability observed in N₂ fixation research has been confirmed by the data collected with this system. However, such variability in physiological studies can be reduced by using a non-destructive system to compare the response of an individual plant with its rates before treatment.     

Effect of Na/Ca and Na/K ratios in saline culture solution on the growth and mineral nutrition of rice (Oryza sativa L.)

Summary A study was conducted to evaluate the effect of manganese on accumulation of Zn, Fe, Cu, and B by different soybean genotypes under varying soil pH conditions, in view of determining tolerance towards extremes in soil pH and mineral toxicities. Enon sandy loam soil was used for the investigation in a greenhouse. Manganese rates were 0, 10, and 20 kg/ha. The pH levels were 5.3, 6.3, and 7.0. The soybean genotypes tested were PI 159319, PI 324924, PI 960895, and L-76-0132. Results indicate that Zn concentration in the genotypes leaf and seed was not affected by Mn application whereas the Cu concentration in the leaf was affected. In general, there was an increase in concentration of Fe in the genotypes seed with Mn application. Boron concentration in the genotypes leaf and seed was unaffected by Mn application. The effect of soil pH on Zn, Fe, Cu, and B in the genotypes tissue was significant. This did not result in toxic levels of the elements in the tissues.Contribution of the Department of Plant Science and Technology, North Carolina Agricultural and Technical State University, Greensboro, N.C. 27411, and Agronomic Division, North Carolina Department of Agriculture, Raleigh, NC 27611, USA     

Proton efflux and transfer cell formation as responses to Fe deficiency of soybean in nutrient solution culture

Hydroponically grown Hawkeye soybeans with N supplied as NO ₃ ^– did not show any measurable pH decrease of the nutrient solution during the first week of Fe deficiency as has been observed for other Fe-efficient dicotyledonous species. Only after prolonged Fe stress with no renewal of the nutrient solution could an unspecific pH reduction be measured as a consequence of a decrease in the NO ₃ ^– content of the solution. On the other hand, Fe stress induced H⁺ efflux could be localized at the root tip region by day foru of-Fe treatment when intact plants were transferred from the nutrient solution to agar medium containing the pH indicator dye bromocresol purple. However, the activity of this H⁺ pump obviously was too weak to neutralize HCO₃-ions simultaneously excreted from older root parts and to acidify the bulk nutrient solution. Thus no remobilization of iron precipitated on older parts of the roots occurred and the plants remained chlorotic.Electron microscopy of the H⁺ extruding zone revealed hypodermal transfer cells with wall protuberances surrounded by cytoplasm especially rich in mitochondria. No transfer cells occurred in the rhizodermis as seen in other Fe-efficient dicots. Some cortical cells also showed transfer cell features with wall protuberances in the intercellular spaces. Often wall ingrowths were surrounded by a periplasmic space which reduced the potential surface amplification of the plasma membrane. It is concluded that the weak capacity of Hawkeye soybeans for Fe stress-induced H⁺ extrusion correlates with their less intense wall labyrinth formation as compared with other dicotyledonous species with higher Fe efficiency.     

The frequency of polyembryonic seedlings and polyploids from ms1 soybean

Summary Seed from homozygous recessivems ₁ genetic male-sterile soybean (Glycine max (L.) Merr.) plants was studied for frequencies of polyembryonic seedlings and different levels of polyploidy among abnormal seedlings from six different source populations: Amesms ₁ (Ams), North Carolinams ₁ (NCms), Tonicams ₁ (Tms), Urbanams ₁ (Ums), and F₄ generation seed obtained from crosses ofms ₁ to two chromosome interchange lines (Ams x Clark T/T and Ums x KS-172-11-3). Frequencies of polyembryony observed in Tms, Ums, Ams, NCms, F₄ seed from Ams x Clark T/T, and F₄ seed from Ums x KS-172-11-3 were 3.6%, 2.4%, 3.1%, 2.5%, 2.2% and 0.1%, respectively. Frequencies of abnormal seedlings from these six sources varied from 1.7% (Ums X KS-172-11-3) to 16.8% (Ams X Clark T/T). Frequencies of polyploids among the abnormal seedlings ranged from 6.8% in Ums x Ks-172-11-3 to 66.7% in Tms. On average, the frequency of polyploid individuals from monoembryonic seedlings was 1.22%. Chromosome number of these seedlings varied from 20 to 200. Variation of the frequencies of polyembryonic seedlings and polyploid progeny among abnormal seedlings suggested that the mechanism(s) controlling the characters of polyembryony and formation of polyploids was associated with thems ₁ gene and was affected by other gene(s) or environmental factors.Joint contribution: Agricultural Research Service, US Department of Agriculture, and Journal Paper No. J-11255 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IA 50011, USA. Project 2471     

Dry matter and nitrogen accumulation and partitioning in selected soybean genotypes of different derivation

Summary Experiments were conducted to determine if changes in the accumulation and partitioning of dry matter (DM) and nitrogen (N) in soybean [Glycine max (L.) Merr.] were associated with agronomic improvements and to assess the degree of genetic variation present for these traits. Fifteen maturity group II soybean genotypes including three ancestral cultivars, three modern cultivars, and nine agronomically superior plant introductions (PI's) were grown in replicated tests at four locations in the eastern U.S. The DM and N of stems, pod walls, and seeds were determined at maturity, and the apparent harvest indices (HI) and the apparent nitrogen harvest indices (NHI) were calculated. Pod DM partitioning was calculated as the ratio of seed DM to total pod DM and pod N partitioning was the ratio of seed N to total pod N. The mean DM accumulation of the modern cultivars was significantly greater than that of the ancestral cultivars and PI's. The apparent HI and the pod DM partitioning of both the modern and ancestral cultivars were significantly higher than that of the PI's. The three modern cultivars demonstrated the highest N accumulation. As a group, the modern cultivars consistently showed maximal accumulation and partitioning of DM and N suggesting that these physiological traits are associated with agronomic improvement. No individual PI was found to possess DM or N accumulation or partitioning which significantly exceeded the best modern cultivar or ancestral cultivar, indicating that genotypes with accumulation or partitioning characteristics which exceed available germplasm may be difficult to identify. Seed yield was correlated (P<0.05) with both DM (r=0.61) and N (r=0.57) accumulation.     

Development of a highly efficient, repetitive system of organogenesis in soybean (Glycine max (L.) Merr).

A highly efficient, repetitive system of organogenesis was developed in soybean. Seeds of soybean cv. White hilum pretreated with TDZ formed multiple bud tissue(s) (MBT) at the cotyledonary nodes. MBT initiation occurred only if the axillary buds were not removed from the cotyledonary node. The best MBT formation was achieved by pretreating the seeds for 1 week on medium supplemented with 0.1 mg/l TDZ, followed by culture of the cotyledonary node on medium supplemented with 0.5 mg/l BA for 4 weeks. Culture of the MBT on medium supplemented with 0.1 mg/l TDZ resulted in the proliferation of MBT. MBT was maintained in this way for 12 months. Three hundred thirty six shoots were obtained when 1 g of MBT was subcultured on medium supplemented with 0.5 mg/l BA. Plants were rooted on medium without growth regulators. The regenerated plants grew normally in the greenhouse. Unfortunately, they did not set seeds because of the long-day conditions during growth. This system was successfully applied in three other genotypes.     

Characterization of soybean vegetative storage proteins and genes

Summary Soybean vegetative storage proteins (VSPs) were purified and characterized. Anion exchange HPLC resolved partially purified VSPs into fractions containing 27-kD/27-kD and 29-kD/29-kD homodimers and 27-kD/29-kD heterodimers. Reversed-phase HPLC resolved partially purified VSPs into three fractions. One fraction contained only 27-kD VSP and the other two contained 29-kD VSP. The two 29-kD VSP fractions differed with respect to their cyanogen bromide cleavage patterns, an observation that indicated the 29-kD VSPs were heterogeneous. Genomic clones that contained 29-kD VSP genes were also isolated and characterized. One genomic clone contained a complete 29-kD VSP gene and was sequenced. The coding region in the clone contained two introns whose borders had regulatory sequences typical of other eukaryotic genes. Putative polyadenlyation signals were present in the 3-flanking region of the gene, while putative TATA, CAAT, and enhancer core sequences were found in the 5-flanking regions. A second genomic clone that was studied contained the 5 regions of two partial 29-kD VSP genes in an inverted linkage. Genomic DNA gel blots showed that the two genes were organized in the same arrangement in the soybean genome.Cooperative research between USDA/Agricultural Research Service and the Indiana Agricultural Experiment Station. Journal Paper No. 12,192 from the Indiana Agricultural Experiment Station     

Genetic variation for quantitative traits in soybean lines derived from tissue culture

Tissue culture may generate useful genetic variation for quantitative traits. The objective of this study was to analyze genetic variation for ten quantitative traits of soybean [Glycine max (L.) Merr.] among lines derived from the tissue culture of three cultivars. The three cultivars used to obtain R0 plants from tissue culture were BSR 101, Hodgson 78, and Jilin 3. A total of 63 R0-derived lines of BSR 101, eight of Hodgson 78, and 42 of Jilin 3 was planted with the untreated controls in row plots in a randomized complete-block design with three replications at two locations for each of 2 years. The traits evaluated were days to beginning bloom (R1), beginning seed (R5), beginning maturity (R7), full maturity (R8), height, lodging, seed yield, seed weight, protein content, and oil content. Significant (P < 0.05) variation was observed among lines for each of the ten quantitative traits. There was 57.1% of the BSR 101 lines, 87.5% of the Hodgson 78 lines, and 76.2% of the Jilin 3 lines that were significantly different from the controls for at least one trait. The percentages of lines that were significantly different from the control for an individual trait ranged from 2.7% for oil content to 25.7% for R7. The magnitude of the changes was relatively small. Although this genetic variation may be useful for cultivar development, greater variability at less expense would be expected with conventional artificial hybridization.Journal Paper No. J-14958 of the Iowa Agriculture and Home Economics Experiment Station, Ames, IOWA, USA Project No. 2475.     

Agronomic evaluation of tissue-culture-derived soybean plants

Summary Genetic alterations of regenerated plants based on the tissue culture process (somaclonal variation) have become common for many plant species including soybean [Glycine max (L.) Merr.]. The objective of this study was to test for the presence of tissue-culture-derived genetic variation in eight agronomic traits in homozygous progeny regenerated by organogenesis using the commercially important cultivar Asgrow A3127. A total of 86 lines derived by repeated self-pollination of nine regenerated plants was grown in two locations for 2 years. When compared to the unregenerated parent, statistically significant variation (P<0.05) was found for maturity, lodging, height, seed protein and oil, but not for seed quality, seed weight, or seed yield. All of the variation noted was beneficial and did not involve decreased yield. Since the differences were not large, the results indicate that the tissue culture process is not necessarily detrimental to plant performance, which is an important consideration since tissue culture techniques are used in many genetic engineering methods.     

Iron-deficiency chlorosis evaluation of soybean with tissue culture

Summary The objectives of this study were: (i) to develop a tissue culture technique for the evaluation of Fe efficiency in soybean, and (ii) to compare the laboratory technique with field Fe chlorosis scores. Nineteen genotypes that had low and high levels of Fe efficiency were evaluated in the laboratory and at five field locations. Friable callus was induced from epicotyl sections, weighed, and placed on two different modified Murashige and Skoog media; one low in -naphthaleneacetic acid and the other low in Fe. Callus growth was rated as lack of growth compared to respective controls. As an example, Fe-inefficient cultivars (Asgrow A3205 and Pride B216) had significantly reduced growth compared to Fe-efficient germ plasm lines (All and A14). Correlation between the laboratory and field chlorosis rating was highest for the low auxin medium (r ² = 0.78), although correlation for the low Fe medium was also significant (r ² = 0.72). These results show that in vitro evaluation for Fe efficiency can be a useful tool for plant breeders.     

Ferulic acid uptake by soybean root in nutrient culture

Ferulic acid uptake by soybean root in nutrient culture was investigated by the depletion method at different concentrations, temperatures and pH. Results showed that soybean roots absorbed this compound at greater rates in the concentrations between 0.05-mM and 1.0-mM and it was concentration dependent. Ferulic acid uptake was unaffected at pH 4.5 or 6.0 but reduced at pH 7.0. At pH 6.0, uptake rates decreased significantly with increasing temperature of nutrient solution.     

Yield and composition of soybean seed as a function of potassium supply

Summary A reduction in K supply to soybean plants to deficiency levels during both vegetative and reproductive development resulted in reductions not only in yield, but also in oil and K concentrations in the seed and a concomittant increase in seed protein concentration. Correlations between mean fruit yield and oil, protein and K concentrations, over a wide range of K regimes, were 0.97, −0.94 and 0.98, respectively. When K supply was increased well above the level necessary to produce maximum yields,i.e. luxury consumption, there was no significant change in K concentration in the seed, indicating a high degree of control in the movement of K to the developing seed under high K regimes. When the K supply to the plant was limiting, the rate of accumulation of oil and carbohydrate fractions, but not of seed protein, declined during the latter part of podfilling. This resulted in a fall in the C/N ratio in the non-structural seed components during this part of seed development. Depriving plants of K only during seed development had no effect on seed composition or yield, whereas resupplying K to deficient plants after anthesis resulted in almost the same seed composition and yield as that which occurred with control plants. Possible mechanisms whereby K deficiency influences soybean seed composition and yield are discussed in terms of movement of carbohydrate and nitrogen to the seed. We suggest that potassium-deficient soils are likely to produce crops with low yields and low seed oil levels; the crop may respond to K fertilizers as late as anthesis.     

Effects of phosphorus and iron fertilizers on the growth of two soybean varieties at two soil temperatures

The influence of FeEDDHA (0, 0.2 and 2 μg Fe g⁻¹ soil) and NaH₂PO₄·H₂O (0 and 120 μg Pg⁻¹ soil) on the growth of two Fe-ineffective soybean (Glycine max L. Merr.) varieties (anoka and T203) on a calcareous soil at two soil temperatures (16 and 24°C) was compared under greenhouse conditions. The two soybean varieties differed in the following respects: (a) T203 accumulated smaller concentrations of Fe in washed tops than Anoka under comparable conditions; (b) T203 was more susceptible to Fe deficiency and its accentuation by high levels of fertilizer P than Anoka; (c) T203 accumulated lower quantities of Mn in tops than Anoka under comparable conditions; (d) T203, but not Anoka, developed Mn deficiency symptoms when treated with P and 2 μg Fe g⁻¹ at 16°C. Fe deficiency was more severe in both varieties at the higher soil temperature due apparently to: (a) greater plant concentration of P in tops at 24°C; and/or (b) an increased rate of plant growth and greater dilution of Fe in young tissue at 24°C. Foliar P concentration was increased much more than foliar Fe concentration by an increase in soil temperature. Severely Fe deficient T203 plants grown without FeEDDHA at 24°C accumulated less foliar Mn than their FeEDDHA counterparts. Comparisons of Fe effectiveness of various soybean cultivars based on relative responses to FeEDDHA can be influenced by differential effects on Mn nutrition.     

Inheritance of two independent isozyme variants in soybean plants derived from tissue culture

Summary Soybean [Glycine max (L.) Merr.] plants were regenerated via somatic embryogenesis from nine soybean cultivars. Our objective was to identify and characterize genetically novel mutations that would further our understanding of the soybean genome. Variant isozyme patterns were observed in two independent tissue culturederived lines. Genetic analyses were conducted on these two isozyme variants, and they were heritable. No variant isozyme patterns were evident in control (parental) soybean lines. In the cultivar BSR 101, a mutation of Aco2-b (aconitase) to a null allele was detected. The Aco2-bn mutant, Genetic Type T318, had not been previously observed in soybean. In the Chinese cultivar Jilin 3 (PI 427.099), a chlorophyll-deficient plant was identified that also lacked two mitochondrial malate-dehydrogenase (Mdh null) isozyme bands. These two mutant phenotypes, chlorophyll-deficient and Mdh null, were found to cosegregate. The Jilin 3 mutant, Mdh1-n (Ames 1) y20 (Ames 1) Genetic Type T317, was allelic to three chlorophyll-deficient, Mdh1 null mutants [Mdh1-n (Ames 2) y20 (Ames 2) (T323), Mdh1-n (Ames 3) y20 (Ames 3) (T324), and Mdh1-n (Ames 4) y20 (Ames 4) (T325)] previously identified from a transposon-containing soybean population, and to a chlorophyll-deficient, Mdh1 null mutant [Mdh1-n (Urbana) y20 (Urbana) k2, Genetic Type T253] which occurred spontaneously in soybean. The recovery of two isozyme variants from progeny of 185 soybean plants regenerated from somatic embryogenesis indicates the feasibility of selection for molecular variants.     

Carbohydrate and lipid status in soybean roots influenced by ferulic acid uptake

The objective of this research was to investigate how the allelochemical ferulic acid affects the carbohydrate and lipid contents of soybean roots cultivated in nutrient culture. The results presented revealed that ferulic acid has significant effects on carbohydrates by the increase in xylose, fructose and sucrose and decrease in glucose, after 24 h treatment of roots. Ferulic acid increased the contents of saturated and unsaturated fatty acids of the polar and non-polar lipid fractions. The results may contribute as additional data to explain allelopathic effects caused by ferulic acid.     

New disease resistance genes in soybean against Pseudomonas syringae pv glycinea: evidence that one of them interacts with a bacterial elicitor

Summary Soybean [Glycine max (L.) Merr.] cultivars Flambeau and Merit differed in their resistance to Pseudomonas syringae pv glycinea (Psg) race 4, carrying each of four different avirulence (avr) genes cloned from Psg or the related bacterium, Pseudomonas syringae pv tomato. Segregation data for F₂ and F₃ progeny of Flambeau x Merit crosses indicated that single dominant and nonallelic genes account for resistance to Psg race 4, carrying avirulence genes avrA, avrB, avrC, or avrD. Segregants were also recovered that carried all four or none of the disease resistance genes. One of the disease resistance genes (Rpg1, complementing bacterial avirulence gene B) had been described previously, but the other three genes — designated Rpg2, Rpg3, and Rpg4 — had not here to fore been defined. Rpg3 and Rpg4 are linked (40.5 ± 3.2 recombination units). Rpg4 complements avrD, cloned from Pseudomonas syringae pv tomato, but a functional copy of this avirulence gene has not thus far been observed in Pseudomonas syringae pv glycinea. Resistance gene Rpg4 therefore may account in part for the resistance of soybean to Pseudomonas syringae pv tomato and other pathogens harboring avrD.     

Effects of N-serve on soybeans and soil nitrogen transformations

Summary Plant dry weight, total N, and total Ca was increased at 0.1 and 1 ppm N-serve. At greater 10 ppm the plants showed visual symptoms of a stunted growth, stem elongation, flowers, and pods failed to form or were aborted, young leaves were curled, and roots were club shaped with many branches. These symptoms were increasingly evident with increasing N-serve application rates. The reason was attributed to an auxin effect. Dry wt and total N in the plant was less than the control at the higher N-serve applications. There was little effect on nitrogenase activity at less than 10 ppm N-serve. Nodulation tended to increase at 0.1 and 1 ppm N-serve.Nitrification was inhibited up to 104 days at 20 ppm N-serve. The soil pH of the high N-serve rates was decreased at 104 days probably due to nitrification. Generally there were little detectable differences among treatments in soil organic N. The average soil organic N from 0 to 104 days decreased by 0.01%. Average increase in total N within each pot at harvest was equivalent to about 138 kg N/ha.