Manganese uptake and Mn efficiency of wheat cultivars are related to Mn‐uptake kinetics and root growth

Wheat cultivars differ widely in manganese (Mn) efficiency. To investigate the reasons for different Mn efficiencies, a pot experiment with soil, a solution‐culture experiment, and model calculations were carried out. The pot experiment was conducted with wheat (Triticum aestivum L. cvs. PBW 373, PBW 154, PBW 343, PBW 138, and Triticum durum L. cvs. PBW 34 and PDW 233) grown in a screen house in India. The soil was a loamy sand with pH 8.1, DTPA‐extractable Mn 1.62 mg (kg soil)^–1, and initial soil solution Mn concentration (C_Li) of 0.19 μM. When fertilized with 50 mg Mn (kg soil)^–1, C_Li increased to 0.32 μM. At C_Li 0.19 μM, wheat cv. PBW 373 produced 74% of its maximum shoot dry weight (SDW) with 64% of its maximum root length (RL), while cv. PDW 233 produced only 25% of its maximum SDW with 11% of its maximum RL. The other wheat cultivars were between these extremes. Manganese deficiency caused a reduction in shoot growth, but more strongly reduced root growth. The low Mn efficiency of T. durum cv. PDW 233 was related to a strong depression of its root growth. Manganese influx was similar for all cultivars. In solution culture below 1 μM Mn, under controlled climate‐chamber conditions, Mn influx was linearly related to Mn concentration. Both the efficient cv. PBW 343 and the inefficient cv. PDW 233 had a similar influx. Uptake kinetic parameters from the solution experiment together with soil and plant parameters from the pot experiment were used in a mechanistic nutrient‐uptake model. Calculated values of Mn influx for wheat grown in soil were 55% to 74% of measured values. A sensitivity analysis showed that increasing C_Li or the slope of the uptake isotherm by about 30% would be enough to reach the observed influx. The results of this research indicate that an increase of Mn solubility by microbial or chemical mobilization would increase Mn uptake. But on the other hand, no chemical mobilization would be required to increase Mn uptake if the plant improved its uptake kinetics. Low Mn efficiency of some wheat cultivars was related to their reduced root growth at low soil Mn supply.     

Differences in manganese efficiency of wheat (Triticum aestivum L.) and raya (Brassica juncea L.) as related to root‐shoot relations and manganese influx

Manganese efficiency is a term used to describe the ability of plants to obtain higher relative yields at low Mn supply compared to other species. To evaluate Mn efficiency of wheat (Triticum aestivum L.) and raya (Brassica juncea L.), a greenhouse pot experiment was conducted using Mn deficient Typic Ustochrept loamy sand soil, treated with 0, 50, and 100 mg Mn (kg soil)^–1. In the no‐Mn treatment, wheat had produced only 30 % of its maximum dry matter yield (DMY) with a shoot concentration of 10.8 mg Mn (kg DM)^–1 after 51 days of growth, while raya had produced 65 % of its maximum DMY with 13.0 mg Mn (kg DM)^–1. Taking relative shoot yield as a measure of Mn efficiency, raya was more efficient than wheat. Both crops produced the maximum DMY with 50 mg Mn (kg soil)^–1. Even though raya had a lower root length : DMY ratio and a higher shoot growth rate, it acquired higher Mn concentrations in the shoot than wheat under similar soil conditions, because of a 2.5 times higher Mn influx. Model calculations were used to calculate the difference of Mn solution concentration (ΔC_L) between the bulk soil (C_Li) and the root surface (C_L0) that is needed to drive the flux by diffusion equal to the measured influx. The results showed that ΔC_L was smaller than C_Li, which indicates that chemical mobilization of Mn was not needed to explain the observed Mn uptake even for raya. According to these calculations, the higher Mn influx of raya was caused by more efficient uptake kinetics, allowing for a 4.5 times higher Mn influx at the same Mn concentration at the root surface.     

Manganese efficiency and maganese‐uptake kinetics of raya (Brassica juncea), wheat (Triticum aestivum), and oat (Avena sativa) grown in nutrient solution and soil

Manganese (Mn) deficiency is reported worldwide and often decreases crop yield. However, plant species differ in their susceptibility to Mn deficiency. Poaceae are often inefficient, whereas Brassicaceae seem to be efficient in Mn uptake. The objective of this paper was to determine the relevance of Mn‐uptake kinetics, root‐system size, and Mn mobilization for differences in Mn efficiency of wheat, oat, and raya. To determine Mn‐uptake kinetics, wheat (Triticum aestivum L. cv. PBW 343), raya (Brassica juncea L. cv. RLM 619), and oat (Avena sativa L. cv. Aragon) were grown in a growth chamber together in complete nutrient solution having an average Mn concentration of 90, 180, 360, 910, and 2270 nmol L^–1. For determining Mn efficiency of the three species in soil, the plants were grown for 22 d in pots filled with 3 kg of a loamy soil low in Mn availability (pH (CaCl₂) 7.4; DTPA‐extractable Mn: 3.5 mg (kg soil)^–1). The soil was fertilized with 0, 1, 2, 4, and 8 mmol Mn (kg soil)^–1 resulting in Mn soil‐solution concentrations ranging from 40 to 90 nmol L^–1, hence lower than in the solution experiment. In order to determine Mn soil‐solution concentration close to the root surface, the root length density was increased by growing two plants of raya and four plants of wheat in only 250 mL soil columns for 25 d. In solution culture at high concentrations, raya showed a higher Mn uptake compared to wheat and oat. However, at low Mn supply, all three species were comparably Mn‐efficient, i.e., plant growth was similar, and also the uptake was similar. In soil, the highest yield was achieved for raya in the unfertilized treatment whereas the Poaceae needed at least a fertilization of 1 mmol Mn (kg soil)^–1. The Poaceae showed a yield reduction of about 40% in the unfertilized treatment. Manganese concentration in the shoot dry weight was always higher in raya than in wheat or oat. This was due to a higher Mn uptake whereas relative shoot‐growth rate and root‐to‐shoot ratio were similar among the species. The higher Mn uptake of raya in soil was in contradiction to the comparable Mn‐uptake kinetics of the three crops at low Mn concentration in solution. This points to plant differences in their ability to affect Mn availability in the rhizosphere. In the bulk soil, all the crops decreased Mn solution concentration, but this effect was somewhat less for raya. But in the rhizosphere, raya increased Mn soil‐solution concentration significantly to 58 nmol L^–1, as compared to 37 nmol L^–1 of the unplanted control soil. In contrast, wheat showed a Mn solution concentration of 25 nmol L^–1 which was not significantly different from the control. The results indicate that differences in Mn efficiency among the crops studied are related to their ability to affect the solubility of Mn in the rhizosphere.     

Contribution of Post-Anthesis Growth and Manganese Dynamics to Differential Grain Yield in Different Wheat Species

Manganese (Mn) deficiency has become a serious nutritional problem for wheat grown in alkaline coarse textured soil. The study aimed to investigate post-anthesis Mn partitioning in different wheat species. Cultivars of bread wheat (‘PBW509’, ‘DBW17’, ‘PBW550’ and ‘PBW636’); durum wheat (‘PDW291’) and triticale (‘TL2908’) were grown in 6.5 L pots with two treatments of Mn (0 and 50 mg Mn kg^?1 soil) in screen house and harvested at anthesis, 18- days post-anthesis, and maturity to record Mn uptake. Durum cv. ‘PDW291’ retained highest proportion of Mn in its vegetative parts under Mn deficiency resulting into lowest partitioning to the grain and had the lowest grain yield. All bread wheat cv. facilitated superior Mn partitioning to the grain, lesser retention in vegetative organs and higher Mn utilization efficiency, than triticale and durum wheat species. Cultivars producing higher yield on Mn deficit soils are viable alternative to foliar application of Mn.     

Variation in Selenium Tolerance,Accumulation, and Growth Parameters of Different Wheat Cultivars

In a greenhouse experiment, wheat cultivars PDW 291, PBW 550, and TL 2908 were grown in alkaline sandy-loam soil treated with sodium selenate at 0, 2, and 4 mg selenium (Se) kg^?1 soil. Selenate-treated wheat plants accumulated greater Se in roots, stems, leaves, and grains and showed growth retardation, snow-white chlorosis, decreased shoot length and chlorophyll, and reduced leaf area and produced less number of grains as compared to control plants. Maximum reduction in these parameters was observed in selenate-treated TL 2908 plants and most of the plants died before maturity with almost no grain formation with 4 mg Se kg^?1 soil. Selenium accumulation resulted in decreased reducing sugar, starch, and protein contents in grains whereas total free amino acids increased significantly in all the three cultivars. Selenium accumulation in wheat showed metabolic disturbances and its accumulation in grains was beyond toxic levels, thus making it unfit for consumption.     

Modern wheat cultivars have greater root nitrogen uptake efficiency than old cultivars

The availability of nitrogen (N) contained in crop residues for a following crop may vary with cultivar, depending on root traits and the interaction between roots and soil. We used a pot experiment to investigate the effects of six spring wheat (Triticum aestivum L.) cultivars (three old varieties introduced before mid last century and three modern varieties) and N fertilization on the ability of wheat to acquire N from maize (Zea mays L.) straw added to soil. Wheat was grown in a soil where ¹⁵N‐labeled maize straw had been incorporated with or without N fertilization. Higher grain yield in three modern and one old cultivar was ascribed to preferred allocation of photosynthate to aboveground plant parts and from vegetative organs to grains. Root biomass, root length density and root surface area were all smaller in modern than in old cultivars at both anthesis and maturity. Root mean diameter was generally similar between modern and old cultivars at anthesis but was greater in modern than in old cultivars at maturity. There were cultivar differences in N uptake from incorporated maize straw and the other N sources (soil and fertilizer). However, these differences were not related to variation in the measured root parameters among the six cultivars. At anthesis, total N uptake efficiencies by roots (total N uptake per root weight or root length) were greater in modern than in old cultivars within each fertilization level. At maturity, averaged over fertilization levels, the total N uptake efficiencies by roots were 292?336 mg N g^?1 roots or 3.2?4.0 mg N m^?1 roots for three modern cultivars, in contrast to 132?213 mg N g^?1 roots or 0.93?1.6 mg N m^?1 roots for three old cultivars. Fertilization enhanced the utilization of N from maize straw by all cultivars, but root N uptake efficiencies were less affected. We concluded that modern spring wheat cultivars had higher root N uptake efficiency than old cultivars.     

Evaluation of Different Mn Efficiency Indices and their Relation to Morphophysiological Traits in Diverse Wheat Genotypes

Wheat genotypes display differential tolerance to manganese (Mn) deficiency. Growing Mn-efficient cultivars in Mn deficient soil could be effective in improving yields. A pot experiment was conducted with eight genotypes grown in Mn deficient soil treated with 0 (no Mn fertilizer) and 50 ppm (50 mg Mn kg^?1soil applied as mangansese sulfate monohydrate (MnSO₄.H₂O) Mn. The genotypes were classified on the basis of grain yield and grain physiological efficiency as efficient and responsive (SAMNYT 410, GLUPRO 200, PBW 621, and BW 9178), efficient and nonresponsive, inefficient and responsive (HD 2967), and inefficient and nonresponsive (PDW 314, PDW 291, and PBW 636). The genotypes in different groups differed in morphophysiological characteristics; efficient and responsive genotypes recorded more leaf area, higher SPAD index, higher Fv/Fm ratio, and longer roots than inefficient and nonresponsive. Efficient and responsive genotypes are desirable by farmers, whereas inefficient and responsive genotypes in a breeding program for their Mn-responsive characteristics.     

Seedling vigor and nitrogen use efficiency of Moroccan wheat as influenced by level of soil nitrogen

Abstract

One of the characteristics that can help wheat (Triticum aestivum L.) plants escape late season drought in the semiarid areas of Morocco is early stand establishment and adequate vigor. Little is known about the effect of nitrogen (N) on early seedling vigor in wheat. The objective of this study was to determine how N supply affects early root and shoot growth, N partitioning between the two parts and N use efficiency of seedlings. To reach this objective, three spring wheat cultivars were grown in pots in a growth chamber under N conditions which were low, adequate and high. Data showed that optimum N rates increased shoot and root growth but high N concentrations reduced their dry matter accumulation and inhibited root elongation. The cultivars tested behaved differently. ‘Nesma’, an older cultivar, produced 60% more dry matter and accumulated 93% more N in the shoot and root than the newer cultivars ‘Merchouch 8’ and ‘Saada’. Because of its high N uptake, ‘Nesma’ probably reduced soil N concentration at the root zone and avoided the negative effect of high N concentration on root growth. Although, ‘Nesma’ performed better and produced more dry matter, it used N less efficiently than the other two cultivars.

From this study, we can conclude that use of optimum N rates at time of seeing will result in quicker establishment and higher vigor of wheat seedlings. However, excessive N supply may retard seedling growth. The cultivars that produce more seedling dry matter with greater N accumulation are not necessarily the ones that use N more efficiently.     

Zinc biofortification of bread wheat,triticale, and durum wheat cultivars by foliar zinc fertilization

Poor zinc (Zn) nutrition of wheat is one of the main causes of poor human health in developing countries. A field experiment with no zinc and foliar zinc application (0.5% ZnSO₄.7H₂O) on bread wheat (8), durum wheat (3), and triticale (4) cultivars was conducted in a randomized block design with three replications in 2 years. The experimental soil texture was loamy sand with slightly alkalinity. The grain yields of bread wheat, triticale, and durum wheat cultivars increased from 43.6 to 56.4, 46.5 to 51.6, and 49.4 to 53.5 t ha^?1, respectively, with foliar application of 0.5% ZnSO₄.7H₂O. The highest grain yield was recorded by PBW 550 (wheat), TL 2942 (triticale), and PDW 291 (durum), which was 5.22, 4.24, and 4.56% and significantly higher over no zinc. Foliar zinc application increased zinc in bread wheat, triticale, and durum wheat cultivars grains varying from 31.0 to 63.0, 29.3 to 61.8, and 30.2 to 62.4?mg kg^?1, respectively. So, agronomic biofortification is the best way which enriching the wheat grains with zinc for human consumption.     

Response of Cotton and Wheat Cultivars to Soil-applied Boron in a Boron-deficient,Noncalcareous Typic Ustochrept

Field experiments were conducted to study the response of cotton genotypes (G. arboreum Bt cv. RCH 650 BGII; non-Bt cv. F 2228; G. herbaceum cv. FDK 124) and wheat and triticale genotypes (T. aestivum cv. PBW 622; T. durum cv. PDW 314; triticale cv. TL 2908) to direct and residual B application (0, 0.5, 1.0, and 2.0 kg B ha^?1 as borax) using a Typic Ustrochrept, neutral, noncalcareous, loamy sand and B-deficient soil. A significant response of 218 and 231 kg ha^?1 in seed cotton yield was recorded with an application of 1.0 kg B ha^?1 to cotton and 2.0 kg B ha^?1 to wheat. A significant response of 152 kg ha^?1 grain yield of wheat was observed with the application of 0.5 kg B ha^?1 to wheat, while no residual effect of B was observed when B was applied to cotton. On the basis of agronomic and B uptake efficiency, genotypes of cotton (RCH 650 BG II > FDK 124 > F 2228) and wheat (PDW 314> TL 2908> PBW 621) responded differentially to B application, thus indicating that yield of Bt cotton and durum wheat will be reduced more than the other cultivars under B deficiency.     

Manganese seed content and take‐all of cereals 1

Manganese (Mn) is a critical regulator of many physiological defense reactions of plants to disease; and the severity of take‐all root, crown, and foot rot of cereals has been correlated with such cultural practices as form of nitrogen (N), pH adjustment, and crop rotation which all influence the availability of Mn. This study was initiated to determine if the content of Mn in seed influences the severity of take‐all. Five cultivars of soft red winter wheat (Triticum aestivum L.) were grown under two widely different ecological conditions (alkaline, low Mn soil and Mn sufficient soil) to modify their Mn seed content Four cultivars (Cardinal, Lincoln, Steele, and Twain) differed by 10 to 18 μg g^‐1 in Mn seed content (0.33 to 60 ug seed^‐1) while the Mn seed content of one cultivar (Caldwell) was similar from both locations. All cultivars were grown at three field locations in Indiana with natural infestations of Gaeumannomyces graminis var. tritici (Ggt). Under these moderately‐severe to severe disease conditions, plants from seed with the higher Mn seed content were generally more vigorous, had an average of 11% less take‐all (white heads), and yielded an average of 165 kg/ha more grain than plants from seed of the same cultivar with a lower Mn content No significant differences in vigor, yield, or take‐all severity were observed with either source of the cultivar grown from seed produced under widely different environments unless there was a significant difference in Mn seed content.     

NITROGEN SOURCE AND MANGANESE APPLICATION EFFECTS ON MANGANESE DYNAMICS IN THE RHIZOSPHERE OF WHEAT CULTIVARS GROWN ON MANGANESE-DEFICIENT SOILS

To study the effect of two different nitrogen (N) sources and manganese application on root-shoot relations and manganese (Mn) dynamics in the rhizosphere of two wheat cultivars, a screen house experiment was conducted using manganese-deficient soil. Significantly higher root length (RL), root surface area, shoot dry weight (SDW), root length density, and manganese uptake were recorded in calcium nitrate supplied plants of cultivar ‘WH 542’ when applied with calcium nitrate along with manganese rather than ammonium sulfate. Cultivar ‘PD W274’ produced 72% of the maximum RL and 77% of the maximum SDW under similar conditions. Results indicated that cultivar ‘WH 542’ was more manganese efficient than ‘PD W274’ and calcium nitrate was a better source of nitrogen than ammonium sulfate. However, maximum shoot manganese content was recorded in ammonium sulfate supplied plants, which was due to depletion of manganese at root surface to a lower value, causing higher concentration gradient and hence higher manganese influx to root.     

小麦品种的耐盐性变化：甜菜碱和乙烯的作用

Four wheat (Triticum aestivum L.) cultivars 711, PBW343, 3765 and WH542 were screened for studying variations in glycinebetaine (GB) content and plant dry mass under 100 mmol L-1 NaCl stress. A tolerance index was calculated using plant dry mass data to select salt-tolerant and salt-sensitive types and find association between tolerance index and GB content. Tolerance index has been used as a good criterion to select the tolerant types under high salinity stress. Further, physiological differences in salt-tolerant cultivar 711 and salt-sensitive cultivar WH542 were examined. The salt-tolerant cultivar exhibited greater GB content, which was found correlative with ethylene. The cultivar also showed higher nitrogen (N) content and nitrate reductase activity, reduced glutathione and higher redox state resulting in maximal protection of plant dry mass than the salt-sensitive type. Thus, the content of GB may be considered as important physiological criteria for selecting salt-tolerant wheat types.     

Performance of Some Wheat Cultivars Under Saline Irrigation Water in Field Conditions

Most of the crop salt tolerance studies are often conducted in a glasshouse and are limited under field conditions. Therefore, the present research study was conducted under field conditions to evaluate the performance of six wheat cultivars at five salinity levels (EC 0, 3, 6, 9, and 12 dS m^?1) in split plot design with three replications. Increasing salinity significantly increased soil pH, electrical conductivity (EC), and sodium adsorption ratio (SAR). Yield parameters of different cultivars were affected more at higher salinity levels than lower in two years. Data over two years revealed that up to EC 9 dS m^?1 cultivars PBW 658 and HD 2967 performed ???better on the absolute yield basis but PBW 621 produced ?higher relative yield. At EC 12 dS m^?1, PBW 658 produced significantly higher grain yield (4.23 t ha^?1) than cultivars HD 2967 (4.11 t ha^?1) and PBW 621 (3.99 t ha^?1); therefore, should be preferred at salinity more than 9 dS m^?1.     

Effect of seed phosphorus concentration on nodulation and growth of three common bean cultivars

Abstract

An experiment was conducted in the greenhouse to evaluate the effects of seed phosphorus (P) concentration on growth, nodulation, and nitrogen (N) and P accumulation of three common bean (Phaseolus vulgaris L.) cultivars. Seeds were produced under low or high soil P levels, and soaked, or not, in 200 mM KH₂PO₄ solution. The experiment had a 3×3×2×2 factorial block design: three cultivars (ICA Col 10103, Carioca and Honduras 35), three levels of applied P (15, 30 and 45 mg P kg^?1 soil), two native seed P concentrations, and two seed soaking treatments. Plants were harvested at flowering. Soaked seeds increased the number, dry mass and P content of nodules, but did not affect plant growth. Plants originated from seeds with high native P concentration presented higher shoot dry mass and nodule number and mass at every soil P level, and were less responsive to increased soil P supply, than plants from low seed P. In plants from seeds with high P, soil P levels did not alter significantly root dry mass, while in plants from seeds with low P bean cultivars expressed wider differences in root dry mass. The genotypic variability of nodulation was influenced by soil P levels and seed P concentration. Both higher soil or seed P supply enhanced N and P accumulation in shoots. These results indicate that a high seed P concentration produces plants less dependent on soil P supply, and can enhance nodulation and N₂ fixation of common bean. Seed P supply affected the cultivar performance, and should be considered in evaluation of bean genotypes.     

Aluminum tolerance associated with enhancement of plasma membrane H+-ATPase in the root apex of soybean

Abstract

Seventeen soybean cultivars were screened to discern differences in aluminum (Al) sensitivity. The Sowon (Al-tolerant) and Poongsan (Al-sensitive) cultivars were selected for further study by simple growth measurement. Aluminum-induced root growth inhibition was significantly higher in the Poongsan cultivar than in the Sowon cultivar, although the differences depended on the Al concentration (0, 25, 50, 75 or 100?μmol?L^–1) and the amount of exposure (0, 3, 6, 12 or 24?h). Damage occurred preferentially in the root apex. High-sensitivity growth measurements using India ink implicated the central elongation zone located 2–3?mm from the root apex. The Al content was lower 0–5?mm from the root apices in the Sowon cultivar than in the apices of the Poongsan cultivar when exposed to 50?μmol?L^–1 Al for 12?h. Furthermore, the citric acid exudation rate was more than twofold higher in the Sowon cultivar. Protein production of plasma membrane (PM) H⁺-ATPase from the root apices (0–5?mm) was upregulated in the presence of Al for 24?h in both cultivars. This activity, however, decreased in both cultivars treated with Al and the Poongsan cultivar was more severely affected. We propose that Al-induced growth inhibition is correlated with changes in PM H⁺-ATPase activity, which is linked to the exudation of citric acid in the root apex.     

Response of wheat cultivars to different soil nitrogen and moisture regimes: I. Dry matter partitioning and root growth 1

The balance between root and shoot growth is one of the mechanisms used by plants to adapt to a particular environment. This balance is affected by nutrient supply and water availability. The objective of this study was to understand how nitrogen (N) affects root and shoot growth of three cultivars of wheat (Triticum aestivum L.) grown under two regimes of soil moisture ('non water stressed’ and ‘stressed’ during stem elongation') in the greenhouse and growth chamber. Data showed that before stem elongation, shoot growth was less sensitive to high soil N levels than root growth. In fact, root growth was inhibited by excessive soil N concentration. The cultivar ‘Nesma’ produced more dry matter, absorbed N more rapidly and avoided the negative effect of high soil N concentrations on root growth. ‘Merchouch 8’ produced less dry matter and tolerated more water stress, and appeared to require less water. Severe water stress masked the effect of N on root and shoot growth, and the negative effect of water stress on growth was more important under high N. Plants which were water stressed during stem elongation could not fully recover when they were rewatered from boot stage to anthesis. Nitrogen application improved shoot but not root growth under this soil moisture situation. This study suggested that shoot and root growth were affected differently by N availability and that high soil N levels enhanced the negative effect of water stress on growth.     

Manganese availability and microbial populations in the rhizosphere of wheat genotypes differing in tolerance to Mn deficiency

Plant genotypes differ in their capacity to grow in soils with low manganese (Mn) availability. The physiological mechanisms underlying differential tolerance to Mn deficiency are poorly understood. To study the relationship between Mn content in soil, plant genotypes, and rhizosphere microorganisms in differential Mn efficiency, two wheat (Triticum aestivum L.) cultivars, RAC891 (tolerant to Mn deficiency) and Yanac (sensitive), were grown in a Mn‐deficient soil to which 5, 10, 20 or 40 mg Mn kg^–1 were added. The shoot dry matter of both cultivars increased with increasing Mn addition to the soil. At all soil Mn fertilizer levels, the tolerant RAC891 had a greater shoot dry matter and a higher total shoot Mn uptake than the sensitive Yanac. The concentration of DTPA‐extractable Mn in the rhizosphere soil of RAC891 at Mn20 and Mn40 was slightly lower than in the rhizosphere of Yanac. The population density of culturable microorganisms in the rhizosphere soil was low (log 6.8–6.9 cfu (g soil)^–1) in both cultivars and neither Mn oxidation nor reduction were observed in vitro. To assess the non‐culturable fraction of the soil microbial community, the ribosomal intergenetic spacer region of the bacterial DNA in the rhizosphere soil was amplified (RISA) and separated in agarose gels. The RISA banding patterns of the bacterial rhizosphere communities changed markedly with increasing soil Mn level, but there were no differences between the wheat cultivars. The bacterial community structure in the rhizosphere was significantly correlated with the concentration of DPTA‐extractable Mn in the rhizosphere, fertilizer Mn level, shoot dry matter, and total shoot Mn uptake. The results obtained by RISA indicate that differential tolerance to Mn deficiency in wheat may not be related to changes in the composition of the bacterial community in the rhizosphere.     

The influence of phosphate fertilizer application levels and cultivars on cadmium uptake by Komatsuna (Brassica rapa L. var. perviridis)

Cadmium (Cd) is a common impurity in phosphate fertilizers and application of phosphate fertilizer may contribute to soil Cd accumulation. Changes in Cd burdens to agricultural soils and the potential for plant Cd accumulation resulting from fertilizer input were investigated in this study. A field experiment was conducted on Haplaquept to investigate the influence of calcium superphosphate on extractable and total soil Cd and on growth and Cd uptake of different Komatsuna (Brassica rapa L. var. perviridis) cultivars. Four cultivars of Komatsuna were grown on the soil and harvested after 60 days. The superphosphate application increased total soil Cd from 2.51 to 2.75?mg?kg^?1, 0.1?mol?L^?1 hydrochloric acid (HCl) extractable Cd from 1.48 to 1.55?mg?kg^?1, 0.01?mol?L^?1 HCl extractable Cd from 0.043 to 0.046?mg?kg^?1 and water extractable Cd from 0.0057 to 0.0077?mg?kg^?1. Cd input reached 5.68?g?ha^–1 at a rate of 240?kg?ha^–1 superphosphate fertilizer application. Superphosphate affected dry-matter yield of leaves to different degrees in each cultivar. ‘Nakamachi’ produced the highest yield in 2008 and ‘Hamami No. 2’ in 2009. Compared with the control (no phosphate fertilizer), application of superphosphate at a rate of 240?kg?ha^–1 increased the Cd concentration in dry leaves by 0.14?mg?kg^?1 in ‘Maruha’, 1.03?mg?kg^?1 in ‘Nakamachi’, 0.63?mg?kg^?1 in ‘SC8-007’ in 2008, and by 0.19?mg?kg^?1 in Maruha’, 0.17?mg?kg^?1 in ‘Hamami No. 2’, while it decreased by 0.27?mg?kg^?1 in ‘Nakamachi’ in 2009. Field experiments in two years demonstrated that applications of different levels of calcium superphosphate did not influence Cd concentration in soil and Komatsuna significantly. However, there was a significant difference in Cd concentration of fresh and dry Komatsuna leaves among four cultivars in 2008 and 2009. The highest Cd concentration was found in the ‘Nakamachi’ cultivar (2.14?mg?kg^?1 in 2008 and 1.91?mg?kg^?1 in 2009). The lowest Cd concentration was observed in the ‘Maruha’ cultivar (1.51?mg?kg^?1?dry weight (DW)) in 2008 and in the ‘Hamami No. 2’ cultivar (1.56?mg?kg^?1?DW) in 2009. A decreasing trend in Cd concentration was found in ‘Nakamachi’, followed by ‘SC8-007’, ‘Hamami No. 2’ and ‘Maruha’ successively. It is necessary to consider a low-uptake cultivar for growing in a Cd polluted soil. In these two years’ results, ‘Maruha’ cultivar was the lowest Cd uptake cultivar compared to the others.     

Effect of soil cadmium concentration on three Chilean durum wheat cultivars in four environments

Durum wheat (Triticum turgidum L. var durum) is a species that accumulates cadmium (Cd). Durum wheat cultivars differ in their absorption ability of Cd; therefore, identifying and selecting genetic material with low Cd accumulation reduces human exposure to this toxic element. In the present study, Cd concentration was evaluated in three Chilean durum wheat cultivars (Llareta-INIA, Corcolén-INIA, and Lleuque-INIA) grown in four Chilean locations with varying concentrations of Cd in soils. The objective of this study was to evaluate the response of these durum wheat cultivars to different doses of cadmium in terms of grain yield; Cd concentration in different plant tissues (grain, straw, roots); soil Cd concentration was also evaluated. Results show that grain yield was not affected by soil Cd; differences in Cd concentration in plant tissues were generally associated with location, cultivar, and soil Cd concentration. Grain Cd concentration in all three cultivars was classified in the low accumulation category for this metal; ‘Lleuque-INIA’ noted as having a very low accumulation.