Release of phytosiderophores from roots of wheat and triticale under nickel‐deficient conditions

Despite numerous studies on phytosiderophores (PS) there is still an open question whether nickel (Ni) deficiency induces release of PS from graminaceous plant roots. Seedlings of two wheat cultivars (Triticum aestivum L. cvs. Rushan and Kavir) and a triticale cultivar (X. triticosecale) were grown in Ni‐free nutrient solution (Ni‐deficient, Ni–) and with 10 µM NiSO₄ (Ni‐sufficient, Ni+, control). Root exudates were collected weekly for 4 weeks and the amount of PS in the root exudates was measured. The response to Ni deficiency on the release of PS differed between species. Roots of Rushan and triticale exuded higher PS in response to Ni‐deficient conditions. Nickel deficiency significantly enhanced shoot Fe and Zn concentrations in wheat, while it decreased shoot Fe and Zn concentrations in triticale. In Kavir, PS exudation was decreased by Ni deficiency at weeks 3 and 4 and the reduced release of PS from roots of Kavir was accompanied by lower concentrations of Fe and Zn in plant roots but higher Fe and Zn concentrations in shoot tissue. The PS release by Kavir was triggered by a Ni‐induced Zn deficiency particularly in the shoots. According to the results, it is suggested that in the studies concerning the phytosiderophore release under Ni deficiency, special attention should be given to different responses among and within cereals and to the plant Zn or Fe nutritional status.     

Doybean growth and composition as affected by K,Ca, and Mg rates and corn rotation

Abstract

Different rates of K, Ca, and Mg were applied to bulklots of Decatur clay loam (pH 5.8) which had been collected from an area under natural vegetation. Nitrogen and P were each applied at the rate of 100 ppm. Soybean (Glycine max L.) and corn (Zea mays L.) were planted to pots in four replications of each treatment. Plants were grown for 6 weeks and subsequently all the pots were re‐planted to soybeans. This crop rotation was repeated until six crops had been harvested from each pot.

Potassium fertilization did not affect soybean growth but increased the dry matter of corn plants. Calcium application affected the growth of neither crop, but Mg addition to the soil reduced the growth of both crops. The composition of the plants generally reflected the available amounts of each nutrient. Additionally, Mg consistently decreased K in soybeans but increased Mn in the two crops. The inclusion of corn in rotation with soybeans resulted in the following effects on the succeeding soybean harvests: more tolerance to high Mg, greater reduction of plant Ca and Mg caused by K application, and lower levels of available K and Ma in soils and soybeans. However, the greater rate of depletion of soil K and Mn under corn rotation did not appear Co affect the dry matter yields of the following soybean plants relative to the plants under the continuous soybean cropping system.     

Phosphorus Nutrition of Upland Rice,Dry Bean,Soybean, and Corn Grown on an Oxisol

Rice, dry bean, corn, and soybean are important food crops. Phosphorus (P) deficiency is one of the most yield-limiting factors for these crops grown on highly weathered Brazilian Oxisols. Four greenhouse experiments were conducted to determine P requirements of these four crops. The P levels used were 0, 50, 100, 200, and 400 mg kg^?1. Growth, yield, and yield components evaluated of four crop species were significantly increased with the application of P fertilization. Most of the responses were quadratic in fashion when the P was applied in the range of 0 to 400 mg kg^?1. Maximum grain yield of upland rice was obtained with the application of 238 mg P kg^?1 of soil, maximum dry bean grain yield was obtained with the application of 227 mg P kg^?1 of soil, and maximum grain yield of soybean was obtained with the application of 224 mg P kg^?1 of soil. Maximum shoot growth of corn was obtained with the addition of 323 mg P kg^?1 of soil. Most of the growth and yield components had significant positive association with grain yield or shoot dry weight. Phosphorus concentration and uptake were greater in the grain compared to straw in upland rice and dry bean plants. Overall, P-use efficiencies decreased with increasing P rates.     

IRON EFFICIENCY IN KENTUCKY BLUEGRASS NOT RELATED TO PHYTOSIDEROPHORE RELEASE

Some Kentucky bluegrass (KBG; Poa pratensis L.) is susceptible to iron (Fe)-deficiency chlorosis. Under Fe-deficiency stress, phytosiderophore is produced and released by the roots of many grasses to solubilize soil Fe and enhance uptake. In other species, quantifying phytosiderophore screens for Fe-deficiency resistant cultivars. A hydroponic study was conducted at 1 and 10 μM solution Fe to variously stress ‘Baron’, ‘Award’, ‘Limousine’, and ‘Rugby II’ KBG cultivars. One μM Fe solution produced more Fe-deficiency stress in all cultivars compared to 10 μM, resulting in greater chlorosis and phytosiderophore release but reduced shoot and root Fe concentrations and shoot weight. Of the four cultivars, Baron was the most susceptible to Fe deficiency and exhibited severe Fe chlorosis and low shoot Fe but, surprisingly, produced the most phytosiderophore. These results imply that Fe-deficiency susceptibility in KBG may be less related to phytosiderophore release and more related to inefficient uptake or utilization mechanisms.     

PHOSPHORUS UPTAKE AND USE EFFICIENCY IN FIELD CROPS

Phosphorus (P) is required by crop plants for many physiological and biochemical functions. Knowledge of phosphorus uptake and its use by crop plants is essential for adequate management of this essential nutrient. A field experiment was conducted during four consecutive years to determine P uptake and use efficiency by upland rice, dry bean, corn and soybean grown in rotation on a Brazilian Oxisol. Plant samples were taken at different growth stages during the growth cycle of each crop for phosphorus analysis. Phosphorus concentration (content per unit dry matter) significantly decreased in a quadratic fashion with the advancement of plant age in four crop species. Phosphorus concentration was higher in legumes compared to cereals. Phosphorus uptake in shoot, however, significantly increased in an exponential quadratic fashion with the advancement of plant age of crop species. At harvest, P uptake was higher in grain compared to shoot, indicating importance of this element in improving crop yields. Phosphorus use efficiency (grain or straw yield per unit P uptake) was higher in cereals compared to legumes. The P use efficiency for grain production was 465 kg kg^?1 for upland rice, 492 kg kg^?1 for corn, 229 kg kg^?1 for dry bean and 280 kg kg^?1 for soybean. The higher P use efficiency in cereals was associated with higher yield of cereals compared to legume species.     

Root and Leaf Ferric Chelate Reductase Activity in Pond Apple and Soursop

Abstract

Root and leaf ferric chelate reductase (FCR) activity in Annona glabra L. (pond apple), native to subtropical wetland habitats and Annona muricata L. (soursop), native to nonwetland tropical habitats, was determined under iron (Fe)-sufficient and Fe-deficient conditions. One-year-old seedlings of each species were grown with 2, 22.5, or 45 µM Fe in a nutrient solution. The degree of tolerance of Fe deficiency was evaluated by determining root and leaf FCR activity, leaf chlorophyll index, Fe concentration in recently mature leaves, and plant growth. Root FCR activity was generally lower in soursop than in pond apple. Eighty days after plants were put in nutrient solutions, leaf FCR activity of each species was lower in plants grown with low Fe concentrations (2 µM) than in plants grown with high (22.5 or 45 µM) Fe concentrations in the nutrient solution. Leaves of pond apple grown without Fe became chlorotic within 6 weeks. The Fe level in the nutrient solution had no effect on fresh and dry weights of soursop. Lack of Fe decreased the leaf chlorophyll index and Fe concentration in recently matured leaves less in soursop than in pond apple. The rapid development of leaf chlorosis in low Fe conditions and low root and leaf FCR activities of pond apple are probably related to its native origin in wetland areas, where there is sufficient soluble Fe for adequate plant growth and development. The higher leaf FCR activity and slower growth rate of soursop compared to pond apple may explain why soursop did not exhibit leaf chlorosis even under low Fe conditions.     

Growth and Zinc Uptake and Use Efficiency in Food Crops

Zinc (Zn) deficiency in annual crops is very common in Brazilian Oxisols. Data are limited on Zn uptake and use efficiency during crop growth cycles. A field experiment was conducted during two consecutive years with the objective to determine shoot dry weight and Zn uptake and use efficiency in upland rice, dry bean, corn, and soybean during growth cycles. Shoot dry weight of four crops was significantly increased in an exponential quadratic fashion with increasing plant age. Rice and corn had higher shoot dry weights and grain yields than dry bean and soybean. Zinc concentration in rice and corn decreased in a quadratic fashion with increasing plant age. However, in dry bean and soybean, Zn concentration had a quadratic increase. Zinc uptake followed an exponential quadratic response in four crops, and it was higher in corn and upland rice than in dry bean and soybean. Zinc use efficiency in shoot dry‐weight production had significant quadratic responses in upland rice and soybean with increasing plant age. In corn, Zn use efficiency for shoot dry‐weight production was linear as a function of plant age. Zinc use efficiency for grain production was maximum for corn and minimum for soybean. Hence, cereals had higher Zn use efficiency than legumes.

Zinc concentration in grain of dry bean and soybean was higher than in upland rice and corn, which is a desirable quality factor for human consumption so as to avoid Zn deficiency.     

EFFECT OF CADMIUM ON PHYSIOLOGICAL RESPONSES OF WHEAT AND CORN TO IRON DEFICIENCY

This work evaluated the effect of cadmium (Cd) on the physiological responses of corn (Zea Mays L.) and wheat (Triticum aestivum L.) to iron (Fe) deficiency. For this purpose, seedlings of corn and wheat were cultivated under controlled conditions, plants were grown in different strength Hoagland's solutions for one month. In the fifth week, some seedlings were still in full strength Hoagland's solution (+Fe) and others were in full strength Hoagland's solutions without iron (?Fe). The plants were exposed to different cadmium (Cd) concentrations for four days. The plant chlorophyll content of young leaves, Fe and Cd content in shoots and roots, biomass production, and phytosiderophores (PS) release by roots were assessed. Results showed that Cd decreased the chlorophyll content of young leaves, accompanied by a significant shoot and root biomass reduction for Fe-deficient and Fe-sufficient wheat and corn across all Cd treatments. However, chlorophyll content and shoot and root biomass of Fe-deficient wheat and corn were lower than Fe-sufficient plants at different Cd concentrations. Iron-deficiency induced Cd accumulation compared to Fe-sufficient in wheat and corn; however, a depressive effect of Cd on iron acquisition in shoots and roots of Fe-deficient and Fe-sufficient wheat and corn across all Cd treatments was observed. Cadmium also inhibited PS release in Fe-deficient and Fe-sufficient wheat and corn. Iron-deficient PS release was higher than Fe-sufficient corn and wheat across all Cd treatments. These results suggested that Cd might reduce capacity of plants to acquire iron from solution by inhibiting PS release.     

Uptake and Translocation of Copper in Brassicaceae

Abstract

Ten cvs. of four Brassicaceae species were tested to evaluate their copper (Cu) uptake and translocation. Germination and root length tests indicated that Brassica juncea cv. Aurea and Raphanus sativus cvs. Rimbo and Saxa were the species with the highest germinability and longest roots at Cu concentrations ranging from 25 up to 200 µM. Raphanus sativus cv. Rimbo grown in hydroponic culture at increasing Cu concentrations (from 0.12 up to 40 µM) for 10 days produced a relatively high biomass (17.2 mg plant^?1) at the highest concentration and had a more efficient Cu translocation (17.8%) in comparison with cvs. Aurea and Saxa. The potential of cv. Rimbo for Cu uptake was then followed for 28 days at 5, 10, and 15 µM Cu. In comparison with the control, after 28 days of growth the 15 µM Cu‐treated plants showed a reduction in the tolerance index (?40%) and in the above‐ground dry biomass (?19%). On the contrary, an increase in the below‐ground dry weight was observed (+35%). Copper accumulated during the growth period both in the below‐ and above‐ground parts (about 14 and 4 µg plant^?1 at 10 and 15 µM Cu, respectively), but the translocation decreased from 50 to 30% in the last week at all the concentrations used. In addition, cv. Rimbo grown in a multiple element [cadmium (Cd), chromium (Cr), Cu, lead (Pb), and zinc (Zn)] naturally‐contaminated site accumulated all elements in the above‐ground part in a range from 5 to 62 µg plant^?1.     

Varietal tolerance to Zinc deficiency in wheat and barley grown in chelatorbuffered nutrient solution and its effect on uptake of Cu,Fe, and Mn

Tolerance to zinc (Zn) deficiency was examined for three wheat (Triticum aestivum L.) and three barley (Hordeum vulgare L.) varieties grown in chelator‐buffered nutrient solution. Four indices were chosen to characterize tolerance to Zn deficiency: (1) relative shoot weight at low compared to high Zn supply (“Zn efficiency index”), (2) relative shoot to root ratio at low compared to high Zn supply, (3) total shoot uptake of Zn under deficient conditions, and (4) shoot dry weight under deficient conditions. Barley and wheat exhibited different tolerance to Zn deficiency, with barley being consistently more tolerant than wheat as assessed by all four indices. The tolerance to Zn deficiency in the barley varieties was in the order Thule=Tyra>Kinnan, and that of wheat in the order Bastian=Avle>Vinjett. The less tolerant varieties of both species accumulated more P in the shoots than the more tolerant varieties. For all varieties, the concentrations of Mn, Fe, Cu, and P in shoot tissue were negatively correlated with Zn supply. This antagonism was more pronounced for Mn and P than for Cu and Fe. Accumulation of Cu in barley roots was extremely high under Zn‐deficient conditions, an effect not so clearly indicated in wheat.     

Growth and Iron Uptake of Lowland and Aerobic Rice Genotypes under Flooded and Aerobic Cultivation

With increasing water shortages in China, rice (Oryza sativa L.) cultivation is gradually shifting away from continuously flooded conditions to partly or even completely aerobic conditions. The effects of this shift on the growth and iron (Fe) nutrition of different aerobic and lowland rice genotypes are poorly understood. A field experiment was conducted to determine the effects of cultivation system (aerobic vs. flooded), genotype (five aerobic rice varieties and one lowland rice variety), and Fe fertilization [no Fe and 30 kg ha^?1 ferrous sulfate (FeSO₄·7H₂O] on rice grain yield and Fe nutrition. Plants were sampled at tillering and physiological maturity. In both aerobic and flooded plots, Fe application significantly increased shoot dry weight, shoot Fe concentration, and shoot Fe content at tillering but not physiological maturity. At physiological maturity, grain yield and Fe and grain harvest indices were significantly lower in aerobic than in flooded plots. Shoot dry weight and shoot Fe content differed among genotypes at tillering and at physiological maturity. The grain harvest index of aerobic rice genotype 89B-271-17(hun) was significantly greater than that of the other five genotypes when no Fe was applied. Because soil Fe fertilization did not improve the Fe nutrition of rice in aerobic plots, the results indicate that the shift from flooded to aerobic cultivation will increase Fe deficiency in rice and will increase the problem of Fe deficiency in humans who depend on rice for nutrition.     

Factors related to iron uptake by dicotyledonous and monocotyledonous plants. I. pH and reductant

Some plants respond to Fe‐deficiency stress by inducing Fe‐solubilizing reactions at or near the root surface. In their ability to solubilize Fe, dicotyledonous plants are more effective than monocotyledonous plants. In this study we determined how representative plants differ in their response when subjected to Fe‐deficiency stress in a calcareous soil and in nutrient solutions. Iron‐inefficient genotypes of tomato, soybean, oats, and corn all developed Fe chlorosis when grown in soil, whereas Fe‐efficient genotypes of these same species remained green. The same genotypes were grown in complete nutrient solutions and then transferred to nutrient solutions containing N (as NO₃ ^‐) and no Fe.

The T3238 FER tomato (Lycopersican esculentum Mill.) Fe‐efficient) was the only genotype that released significant amounts of H from the roots (the pH was lowered to 3.9) and concomitantly released reductants. Under similar conditions, Hawkeye soyhean [Glycine max (L.) Merr.] released reductants but the solution pH was not lowered. Both Fe‐inefficient and Fe‐efficient genotypes of oats (Avena sativa L.) and corn (Zea mays L.) released insufficient H or reductant from their roots to solubilize Fe; as a result, each of these genotypes developed Fe‐deficiency (chlorosis).

The marked differences observed among these genotypes illustrate the genetic variability inherent within many plant species. A given species or genotype may accordingly not be adapted to a particular soil. Conversely, a given species or genotype may be found (or developed) that is precisely suited for a particular soil. In this event, the need for soil amendments may be reduced or eliminated.     

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.     

MAIZE HYBRIDS DIFFER IN THEIR 24-H PATTERNS OF PHYTOSIDEROPHORE RELEASE

Iron (Fe) chlorosis tolerant gramineous species respond to Fe-deficiency stress by releasing phytosiderophores. The objective of this study was to characterize the diurnal pattern of phytosiderophore release from Fe-chlorosis tolerant and susceptible maize (Zea mays L.) hybrids. Phytosiderophore was collected from individual, Fe-deficient maize plants in 10 mg L^?1 Micropur solution during 4-h collection periods. The diurnal pattern of phytosiderophore release differed among maize hybrids. Similar levels of phytosiderophore were released during light and dark conditions for three hybrids. Greater phytosiderophore release was measured from a fourth hybrid when the collection procedure began 2-h after the initiation of light compared to 2-h before the initiation of dark. When a single plant was used for six consecutive collection periods, phytosiderophore release declined during the final 8- to 12-h of collection. The decline in phytosiderophore release was attributed to dissolution of apoplastic Fe and deactivation of the Fe-stress response mechanism.     

Changes in nutritional homeostasis of Poncirus trifoliata and Ceratonia siliqua as a response to different iron levels in nutrient solution

Abstract

Iron (Fe) deficiency is a nutritional disorder in plants. Poncirus trifoliata is susceptible to Fe deficiency, but symptoms of Fe deficiency are rare in Ceratonia siliqua, a slow-growing species. Specimens of the two species were grown in nutrient solutions containing three Fe concentrations: without Fe (0?µM), 1?µM Fe, and either 10?µM Fe (for Ceratonia) or 40?µM Fe (for P. trifoliata). Growth, the degree of chlorosis, the plant mineral composition, and the activity of the root ferric chelate-reductase (FCR) were assessed. Ceratonia plants exposed to 1?µM Fe were efficient at using Fe in the synthesis of chlorophyll. The activity of FCR was enhanced in the total absence of Fe. In Poncirus a low activity of the FCR was observed in plants with no Fe. The balance between micronutrients in the Ceratonia roots was not affected with 1?µM Fe compared with the higher Fe concentration treatments.     

Manganese deficiency in wheat genotypes: Physiological responses and manganese deficiency tolerance index

Manganese (Mn) deficiency limits wheat productivity on sandy loam, calcareous and alkaline soils cropped with rice. Variation of wheat genotypes to sustain production and Mn use from Mn deficient condition was investigated to screen efficient genotypes. Forty-seven diverse wheat genotypes were evaluated on Mn sufficient (0.195 µM) and Mn deficient (0 µM) nutrient solution to elucidate physiological basis of Mn deficiency tolerance and to develop manganese deficiency tolerance index (MDTI). Shoot dry weight and mean Mn accumulation was 136.7% and 76.5% enhanced when Mn nutrition was improved, respectively. Efficient genotypes under limited Mn had lower root length/shoot weight ratio but higher relative shoot growth rate with higher shoot demand on root which reflected higher Mn influx. Genotypes were classified as tolerant (>0.66), semi-tolerant (0.33–0.66) and sensitive (<0.33) on the basis of MDTI (0–1 scale). Manganese efficient genotypes are most desirable for sustainable production of wheat under low Mn.     

NITROGEN USE EFFICIENCY IN DRY BEAN GENOTYPES

Dry bean is an important legume crop for Latin American people and nitrogen is one of the most yields limiting nutrients for bean crop. A greenhouse experiment was conducted to evaluate nitrogen (N) use efficiency of 20 dry bean genotypes. Genotypes were grown on an Oxisol and two N levels used were without N application (low level) and an application of 400 mg N kg^?1 (high level). Shoot dry weight, grain yield and yield components, N concentration and uptake in shoot and grain were significantly affected by N and genotype treatments. Grain yield had a highly significant (P < 0.01) association with shoot dry weight, pod number, grains per pod and 100 grain weight. Among the 20 genotypes tested, Perola, CNFR 7847, CNFR 7865, CNFP 7777 and CNFM 6911 were found to produce reasonably good yield at low N rate as well as responded well to applied N. Whereas, some genotypes like BRS Radiante, CNFP 7624, CNFM 7875, CNFM 7886, CNFC 7813, CNFC 7827, CNFP 7677 and CNFP 7775 produced very good yields at higher N rate but very low yields at lower N rate. Hence, these genotypes are good for farmers using higher technology. Nitrogen concentration and uptake were higher in dry bean grains compared with shoot and 63% of N accumulated at zero N rate and 75% N accumulated at 400 mg N rate were translocated to grain across 20 genotypes. Nitrogen uptake efficiencies were having highly significant (P < 0.01) quadratic relationship with grain yield. This indicates that improving N uptake in dry bean plants can increase grain yield.     

Phytosiderophore release by Sorghum,wheat, and corn under zinc deficiency 1

Zinc (Zn) deficiency is more common in corn (Zea mays L.) than in sorghum [Sorghum bicolor (L.) Moench] or wheat (Triticum sp.). The ability of wheat to withstand low soil Zn conditions is related to increased release of phytosiderophore from its roots. The reasons for sorghum's ability and corn's inability to utilize low levels of soil Zn have not been explored adequately. The objectives of this research were to 1) ascertain if Zn deficiency could be induced in sorghum, wheat, and corn grown in a chelator‐buffered nutrient solution and 2) determine relative releases of phytosiderophore from roots of sorghum, wheat, and/or corn under Zn‐deficiency conditions. Sorghum, wheat, and corn were grown hydroponically in the greenhouse with a chelator‐buffered nutrient solution designed to induce Zn deficiency, while supplying adequate amounts of other nutrients. Root exudates were collected over time to measure phytosiderophore release. Shoot Zn concentrations and shoot and root dry matter yields were determined also. The technique was effective for inducing Zn deficiency in sorghum, wheat, and corn, as evidenced by reduced shoot and root dry matter yields, shortened internodes, reduced shoot Zn concentrations, and plant Zn concentrations below the suggested critical values for these species. Sorghum and wheat plants increased the release of phytosiderophore in response to Zn deficiency, but com did not. The total amount of phytosiderophore released by the roots was in the order wheat>sorghum>corn. The absence of a “phytosiderophore”; response to Zn deficiency of corn, coupled with the evidence that this species requires, or at least accumulates, more Zn than wheat or sorghum, provides an explanation as to why Zn deficiencies are more prevalent for corn than wheat or sorghum under field conditions.     

Genetic Differences in Resistance to Iron Deficiency Chlorosis in Peanut

Iron (Fe) deficiency has been a widespread problem in peanut (Arachis hypogaea L.) grown on calcareous soils of northern China and has resulted in significant yield losses. Field observations showed considerable variability in visual chlorosis symptoms among peanut cultivars in the same soil. The objective of this study was to confirm the genetic differences in resistance to Fe-deficiency chlorosis in peanut and to identify feasible indicators for screening Fe-efficient genotypes. Resistance to Fe chlorosis of sixteen peanut cultivars grown on calcareous soil was evaluated in the field and physiological responses to Fe-deficiency stress were studied in nutrient solution. There were significant differences in resistance to Fe-deficiency chlorosis among the sixteen peanut cultivars tested, which was identified with SPAD readings, active Fe concentrations in young leaves in the early growth stages, and the pod yield. For Fe-resistant peanut cultivars, Fe-reduction capacity and quality of releasing hydrogen ions from roots increased under Fe-deficiency stress. Highly correlated relationships were observed between the summation of root Fe reduction and field chlorosis scores for sixteen cultivars (r² = 0.79). It was concluded that Fe-reduction capacity was a better physiological indicator for screening Fe-efficient peanut genotypes of the mechanisms measured.     

Zinc nutrition effect on the tolerance of wheat genotypes to Fusarium root-rot disease in a solution culture experiment

Abstract

Zinc (Zn) nutrition and plant genotype are two factors that may affect the tolerance of wheat to root-rot diseases. The aim of the present study was to determine the effect of Zn on shoot yield, root permeability and infection by Fusarium solani in six wheat genotypes with different Zn efficiency. A greenhouse (solution culture) experiment was carried out in which five bread wheat genotypes (Triticum aestivum L. cvs Rushan, Kavir, Cross, Pishtaz and Falat) and one durum wheat genotype (Triticum durum L. cv. Yav79), which are common in Zn-deficient soils of Iran and were exposed to two levels of Zn (0 and 1?μmol?L^–1?Zn?kg^?1, as ZnSO₄.7H₂O) and two F. solani infection levels (0 and 10⁶?spore?mL^?1). Zinc deficiency significantly decreased shoot dry matter in five of the genotypes (Yav79, Kavir, Rushan, Cross and Falat), but had no effect on shoot growth in Pishtaz. Infection with F. solani significantly decreased the shoot dry matter in Yav79, but did not affect the shoot dry weight of the other wheat genotypes. Root membrane permeability was lower in the Zn treatments than in the Zn-free treatments. Zinc deficiency caused a decrease in root reactive sulfhydryl (SH) groups, particularly in the Cross genotype. Root sulfhydryl groups decreased with Fusarium infection. Zinc application sharply increased the Zn content and decreased the Mn content of the shoots. Application of Zn had a positive effect on the tolerance of wheat to F. solani root rot. The relationship between Zn nutrition and disease tolerance suggests that Zn deficiency should be treated before evaluating the cost-effectiveness of fungicides. No correlation was found between the Zn efficiency of the wheat genotypes and Fusarium root-rot disease severity in this solution culture experiment.