Quinclorac Resistance in Echinochloa crus-galli from China

Echinochloa crus-galli is a major weed in rice fields in China, and quinclorac has been long used for its control. Over-reliance of quinclorac has resulted in quinclorac resistance in E. crus-galli. Two resistant(R) E. crus-galli populations from Hunan, China were confirmed to be at least 78-fold more resistant to quinclorac than the susceptible(S) population. No difference in foliar uptake of 14 C-labelled quinclorac was detected between the R and S plants. However, a higher level of 14 C translocation and a lower level of quinclorac metabolism were found in the R plants. Basal and induced expression levels of β-cyanoalanine synthase(β-CAS) gene and β-CAS activity were not significantly different between the R and S plants. However, the induction expression of 1-aminocyclopropane-1-carboxylic acid oxidase(ACO1) gene by quinclorac treatment was evident in the S plants but not in the R plants. Quinclorac resistance in the two resistant E. crus-galli populations was not likely to be related to foliar uptake, translocation or metabolism of quinclorac, nor to cyanide detoxification via β-CAS. Thus, target-site based quinclorac signal reception and transduction and regulation of the ethylene synthesis pathway should be the focus for further research.     

Overexpression of the Barley Nicotianamine Synthase Gene HvNAS1 Increases Iron and Zinc Concentrations in Rice Grains

In humans, iron (Fe) and zinc (Zn) deficiencies result in major worldwide health problems. Transgenic technologies to produce Fe- and Zn-biofortified rice varieties offer a promising potential solution. Nicotianamine, the precursor of phytosiderophores, chelates Fe²⁺ and Zn²⁺ and plays an important role in transporting these metals to both vegetative and reproductive organs within the plant. Our objective was to increase Fe and Zn contents in rice grains by overexpressing the barley nicotianamine synthase gene HvNAS1. HvNAS1-overexpressing transgenic rice showed increased HvNAS1 expression and subsequent increases in endogenous nicotianamine and phytosiderophore content in shoots, roots, and seeds. Fe and Zn concentrations in polished T₁ seeds from transgenic plants increased more than three and twofold, respectively; Fe and Zn concentrations also increased in both polished and brown T₂ seeds. These results suggest that the overproduction of nicotianamine enhances the translocation of Fe and Zn into rice grains.     

Increase in Iron and Zinc Concentrations in Rice Grains Via the Introduction of Barley Genes Involved in Phytosiderophore Synthesis

Increasing the iron (Fe) and zinc (Zn) concentrations of staple foods, such as rice, could solve Fe and Zn deficiencies, which are two of the most serious nutritional problems affecting humans. Mugineic acid family phytosiderophores (MAs) play a very important role in the uptake of Fe from the soil and Fe transport within the plant in graminaceous plants. To explore the possibility of MAs increasing the Fe concentration in grains, we cultivated three transgenic rice lines possessing barley genome fragments containing genes for MAs synthesis (i.e., HvNAS1, HvNAS1, and HvNAAT-A and HvNAAT-B or IDS3) in a paddy field with Andosol soils. Polished rice seeds with IDS3 inserts had up to 1.40 and 1.35 times higher Fe and Zn concentrations, respectively, compared to non-transgenic rice seeds. Enhanced MAs production due to the introduced barley genes is suggested to be effective for increasing Fe and Zn concentrations in rice grains.     

Effects of Different Nitrogen Fertilizer Levels and Native Soil Properties on Rice Grain Fe, Zn and Protein Contents

Deposition of protein and metal ions (Fe, Zn) in rice grains is a complex polygenic trait showing considerable environmental effect. To analyze the effect of nitrogen application levels and native soil properties on rice grain protein, iron (Fe) and zinc (Zn) contents, 32 rice genotypes were grown at three different locations each under 80 and 120 kg/hm2 nitrogen fertilizer applications. In treatments with nitrogen fertilizer application, the brown rice grain protein content (GPC) increased significantly (1.1% to 7.0%) under higher nitrogen fertilizer application (120 kg/hm2) whereas grain Fe/Zn contents showed non-significant effect of nitrogen application level, thus suggesting that the rate of uptake and translocation of macro-elements does not influence the uptake and translocation of micro-elements. The pH, organic matter content and inherent Fe/Zn levels of native soil showed significant effects on grain Fe and Zn contents of all the rice genotypes. Grain Zn content of almost all the tested rice genotypes was found to increase at Location III having loamy soil texture, neutral pH value (pH 6.83) and higher organic matter content than the other two locations (Locations I and II), indicating significant influence of native soil properties on brown rice grain Zn content while grain Fe content showed significant genotype × environment interaction effect. Genotypic difference was found to be the most significant factor to affect grain Fe/Zn contents in all the tested rice genotypes, indicating that although native soil properties influence phyto-availability of micronutrients and consequently influencing absorption, translocation and grain deposition of Fe/Zn ions, yet genetic makeup of a plant determines its response to varied soil conditions and other external factors. Two indica rice genotypes R-RF-31 (27.62 μg/g grain Zn content and 7.80% GPC) and R1033-968-2-1 (30.05 μg/g grain Zn content and 8.47% GPC) were identified as high grain Zn and moderate GPC rice genotypes. These results indicate that soil property and organic matter content increase the availability of Fe and Zn in rhizosphere, which in turn enhances the uptake, translocation and redistribution of Fe/Zn into rice grains.     

Phosphorus reduces salinity stress in micropropated potato

The present study was conducted to determine whether varying the sodium chloride (NaCl) concentrations in Murashige and Skoog (MS) basal medium could affect radiophosphorus (³²P) uptake, and whether high NaCl stress was moderated by the availability of inorganic phosphorus (Pi) to micropropagated potato (Solanum tuberosum L. cv. Russet Burbank). The kinetics of³²P uptake in micropropagated potato plantlets was studied over a 48-hr interval in MS medium containing 1.25 mM Pi and varying concentrations of NaCl (0 to 120 mM). The³²P activity of the top-most trifoliate leaf increased considerably with time, but decreased significantly as medium NaCl concentrations increased. The³²P activity of the root tips at 48 hr was greater, but translocation of Pi into leaves was less, as medium NaCl concentration increased. As medium Pi concentration was increased from 0 to 2.5 mM, in the presence of 120 mM NaCl,³²P activity decreased in root tips but translocation into the topmost leaves occurred more efficiently.     

水稻吸收、运输锌及其籽粒富集锌的机制

 锌是人体必需而又易缺乏的营养元素。在粮食作物可食部位生物强化锌被认为是解决人体缺锌的最有潜力的途径。水稻根吸收锌可分为分泌麦根酸等根系分泌物将土壤颗粒中的金属离子活化和重金属转运蛋白把锌离子转运进植株根部两个过程,ZIP家族基因在后一过程中发挥重要作用。水稻锌在木质部中运输主要以离子态为主,也可同有机酸、尼克酰胺等配体协同运输。地上部锌通过韧皮部再转运到新生组织或装载进入籽粒,水稻韧皮部再转运能力是影响籽粒富锌的关键因素,而锌大量累积在糊粉层中或与植酸等结合后,大大降低了锌的生物有效性。研究粮食作物籽粒富锌机制,利用现代分子生物技术生物强化籽粒中的锌含量,对满足人类锌营养健康具有重要意义。综述了锌在植物体内的生理功能,水稻对锌的吸收、运输和再转运,锌装载进入籽粒,锌在植物体内的分布与赋存形态,以及锌在粮食作物中的生物强化等最新研究进展。     

Could the Supply of Boron and Zinc Improve Resistance of Potato to Early Blight?

The adequate supply of boron (B) and zinc (Zn) can improve the structural integrity and permeability of cell membranes, which is a defence mechanism against fungi infection. A greenhouse experiment was conducted to investigate the effect of the application of B and Zn on plant growth and the incidence and severity of potato early blight, a destructive foliar disease of potato crop caused by Alternaria grandis E.G. Simmons. Potato plants (Solanum tuberosum L. cv. Ágata) were grown in 11-l pots filled with sandy soil, unfertilized or fertilized with 5 mg kg^?1 B and 5 mg kg^?1 Zn (either alone or in combination). Potato plants were inoculated with isolates of Alternaria grandis at 40 days after planting. Early blight incidence and severity were evaluated visually 7 days after inoculation with A. grandis isolates. Disease incidence ranged from 16 to 41% infected leaves, and was significantly highest in the treatment with the application of B, followed by the control, and lowest with application of Zn and B + Zn. Early blight severity ranged from 2.5 to 25%, and was significantly higher in the unfertilized treatment than in those fertilized with Zn either alone or in combination with B. These findings suggest that Zn plays a critical role in potato tolerance to early blight and should be considered as a preventive measure in the disease management plan, since application of zinc reduced the incidence and severity of potato early blight. However, the physiological basis of this remains unknown.     

Novel Sources of aus Rice for Zinc Deficiency Tolerance Identified Through Association Analysis Using High-Density SNP Array

Zinc (Zn) deficiency is a major soil constraint limiting rice crop growth and yield, yet the genetic control of tolerance mechanisms is still poorly understood. Here, we presented promising loci and candidate genes conferring tolerance to Zn deficiency and identified through association analysis using a 365 K single nucleotide polymorphism (SNP) marker array in a diverse aus (semi-wild type rice) panel. Tolerant accessions exhibited higher growth rate with relatively rare stress symptoms. Two loci on chromosomes 7 and 9 were strongly associated with plant vigor under Zn deficiency at a peak-stress stage. Based on previous microarray data from the same experimental plots, we highlighted four candidate genes whose expressions were accompanied by significant genotype and/or environment effects under Zn deficiency. Network-gene ontology supported known tolerance mechanisms, such as ascorbic acid pathway, and also suggested the importance of photosynthesis genes to overcome Zn deficiency symptoms.     

Phosphorus application affects the nutritional quality of millet grain in the Sahel

The application of phosphorus (P) and crop residues (CR) to acid sandy soils of the Sahel has been shown to increase yields of pearl millet (Pennisetum glaucum L.) several-fold. Information is lacking, however, about possible detrimental effects of such yield-enhancing amendments on grain quality, in particular the bioavailability of zinc (Zn) as defined by the phytate:zinc molar ratio (PZMR) and the concentrations of calcium, micronutrients, and protein. To determine the effects of CR and P on grain quality, millet seeds taken from the grain stores of 14 farmers and from a 2-yr on-station fertilizer experiment were analyzed for macronutrients, Zn, copper, iron, and phytate-P. The on-station experiment comprised four millet lines, P applied at 0 and 13 kg ha⁻¹, and CR applied at 500 and 2000 kg ha⁻¹ as surface mulch or ash. Grain from farmers' unfertilized millet had PZMRs ranging from 15 to 30. Application of P increased the concentrations of phytic acid in the grain between 25 and 29% and decreased Zn concentrations between 6 and 11%. The reasons for this were greater P uptake and a dilution of Zn by the large yield increases after P application. Phosphorus application decreased protein concentrations in both years, and increased the PZMRs from 20 to 28 in 1992 and from 21 to 29 in 1993. Although CR markedly increased millet yield, their application had little effect on PZMRs. While PZMRs above 15 are generally considered critical for Zn nutrition of humans, meat consumption and traditional practices of millet processing may increase Zn bioavailability in local dishes. Further studies of full diets are therefore needed, particularly among rural groups at particularly high risk of Zn deficiency such as nursing women and small children before definitive conclusions can be drawn about the effects of P fertilizer application to millet on the nutritional status of farmers in the Sahel.     

Chlorophyll Meter for the Evaluation of Potato N Status

Here, we propose a new approach to determine the level of plant N nutrition, based on the relationship between chlorophyll meter (CM) readings and total biomass in potato plants. The objectives of this work were i) to determine the critical curve CM (CM_c) readings; ii) to establish the relationship between N nutrition index of CM (NNI_CM), and relative tuber yields (RY), and iii) to establish the crop N required (NR). The experiments were carried out during four growing seasons. The cultivar Innovator was planted in a randomized complete block design with three replications and four N treatments (N0, N1, N2 y N3) to cover the range from deficient through surplus N. The CM reading was assessed with the Minolta SPAD 502 at different times during each growing season. The NNI_CM was determined as the ratio between the actual CM reading (CMa) and the CMc. The NR was determined as the difference between actual N uptake and the critical N uptake, divided the N utilization efficiency. The CMc for cultivar innovator was determined [CMc?=?51.4 W (Mg ha^_1)^?0.13; R²?=?0.83]. The NNI_CM ranged from 0.78 to 1.17. The relation between RY and NNI_CM was expressed as a linear-plateau function. For NNI_CM ≥0.9, the RY was near 98.0 %, whereas for NNI_CM below 0.9, the RY decreased [RY?=?7.73?+?100.0 NNI_CM; R²?=?0.55]. The relationship between the observed N uptake and the estimated N uptake values showed positive significant associations (p?<?0.0001). We conclude that the CM reading can be used as an easy and fast tool to predict NR in potato plants under field conditions during the vegetative growth period.     

Zinc deficiency as a practical problem in plant and human nutrition in Turkey: A NATO-science for stability project

Zinc (Zn) deficiency is a critical nutritional problem for plants and humans in Turkey. About 14 Mha of cropped land in Turkey are known to be Zn deficient, particularly cereal growing areas of Anatolia. In 1993, a joint research project was started in Turkey with the financial support of the NATO-Science for Stability Programme to select and characterize cereal genotypes with high yield and/or high Zn accumulation in grain under deficient supply of Zn.Field, greenhouse and growth chamber experiments were carried to study morphological, physiological and genetic factors determining the bases of genotypical differences in Zn efficiency among cereal species and within cultivars of wheat. Among the cereals, rye had particularly high Zn efficiency (high yield under Zn deficiency). There were large genotypical differences among wheat lines. High Zn efficiency was closely associated with enhanced capacity of some lines to take up Zn from soils, but not with increased Zn accumulation per unit dry weight of shoot or grain. Measurement of Zn-containing superoxide dismutase activity in leaves revealed that an efficient utilization of Zn at the tissue or cellular level is an additional major factor involved in Zn efficiency of cereals.Zinc present in grains from Anatolia seems to be not bioavailable. Phytate : Zn molar ratios in grains, a widely accepted predictor of Zn bioavailability, were extremely high and ranged between 95 and 216 for crops grown severely on Zn-deficient soils of Central Anatolia. In the studies concerning determination of Zn nutritional status of school children in Southeastern Anatolia, most children were found to be of shorter stature and had very low levels of Zn (<100 mg kg⁻¹) in hair.     

Iron Uptake and Loading into Rice Grains

Iron (Fe) is an important micronutrient for living organisms. Fe deficiency severely impairs plant growth and is a widespread human dietary problem, with particularly high numbers of affected children and females. Rice (Oryza sativa) is a source of energy for more than half of the world’s population. Thus, understanding the mechanisms of Fe uptake and translocation in rice is of utmost importance in the development of rice varieties that are tolerant to low Fe availability and with high seed levels of Fe. In recent years, the mechanisms underlying Fe transport and homeostasis have been revealed, providing opportunities to increase the Fe content of rice grain. As excess Fe is toxic to cells, plants have developed sophisticated mechanisms to control Fe flow, making it difficult to alter Fe transport. Thus, choosing appropriate chelators and Fe transporters driven by appropriate promoters seems to be the key in developing rice that is tolerant to low Fe availability and which accumulates high grain levels of Fe. Many recent studies have been aimed at increasing the Fe content of rice. Here, we summarize these efforts and review recent progress in understanding the mechanisms of Fe transport.     

Recovery of starter nitrogen-15 fertilizer with supplementarily applied ammonium nitrate on irrigated potato

Nitrogen contamination in ground water of potato (Solanum tuberosum L.) producing areas has indicated a need for improved management of N and water, particularly on sandy soil. Therefore, a field experiment was conducted with the objective of following the recovery and partitioning of starter¹⁵NH₄ and¹⁵NO₃ into potato plant tops and tubers in conjunction with additional supplementarily applied NH₄NO₄. Potato plants treated with starter¹⁵NH₄ or¹⁵NO₃ tended to increase the percent recovery of starter¹⁵N in tubers sampled from one growth time to the next to reach nearly 40% recovery toward the end of the season. Whole plants reached peak recovery of around 50% of the starter¹⁵N near mid-season. From then on, there was a trend for loss of starter¹⁵N by senescence, defoliation or translocation to the roots. The percent recovery of starter¹⁵N was significantly higher at final tuber harvest (not whole plants) for the treatment with starter¹⁵NH₄ at 112 kg ha^?1 combined with 112 kg ha^?1 of supplemental N as compared to the treatment with 112 kg ha^?1 of starter¹⁵NH₄ plus 224 kg ha^?1 of supplemental N. This difference may have been a result of isotope dilution. Early in June the accumulation of starter¹⁵NO₃ in whole plants was about five times as high as that from starter¹⁵NH₄. Later there was no difference in percent recovery of these two forms of N. The temporary delay in starter¹⁵NH₄ uptake was probably related to slow nitrification early in the season instead of preferential uptake of starter¹⁵NO₃.     

Rice yield and its relation to root growth and nutrient-use efficiency under SRI and conventional cultivation: an evaluation in Madagascar

While plant growth and productivity are known to derive from the interaction between genetic potential (G) and environmental factors (E), efforts to improve rice production have usually proceeded assuming a standard E that is created by conventional rice-growing practices. Genotypes have been assessed for their performance in continuously flooded paddy soils, with optimally dense plant populations, with reliance on inorganic fertilization to raise yields. The System of Rice Intensification (SRI) developed in Madagascar and now becoming accepted in much of Asia proposes that GxE interactions can be made more productive with different management practices: optimally sparse populations, established with very young seedlings carefully transplanted, intermittent flooding of paddies, with active soil aeration and with soil organic matter enhanced as much as possible. This article evaluates the effects of alternative SRI cultural practices on grain yield with particular attention to their impact on the growth and functioning of rice plant roots and on associated nutrient-use efficiencies that could be contributing to the observed higher grain yields. On-station experiments and on-farm surveys were conducted in Madagascar to evaluate SRI practices in comparison with standard cultural methods, considering how rice plants’ expression of their genetic potential was affected by different crop management practices. Controlling for both soil and farmer effects, rice plants cultivated with SRI methods produced average yields more than double those from standard practice (6.26 vs. 2.63 t ha⁻¹). The most evident phenotypic difference was in plant root growth, assessed by root-pulling resistance (RPR), a summary measure of root system development. On average, uprooting single SRI plants required 55.2 kg of force plant⁻¹, while pulling up clumps of three conventionally grown plants required 20.7 kg hill⁻¹, or 6.9 kg plant⁻¹. SRI plants thus offered 8 times more resistance per plant to uprooting. Direct measurements confirmed that SRI methods induced both greater and deeper root growth, which could be contributing to increased nutrient uptake throughout the crop cycle, compared with the shallower rooting and shorter duration of root functioning under continuous flooding. Rice plants grown with SRI methods took up more macronutrients than did the roots of conventionally managed plants, which was reflected in the higher SRI yields. When grain yield was regressed on nutrient uptake to assess nutrient-use efficiency, SRI plants achieved higher grain yield per unit of N taken up, compared to plants grown with conventional methods. The internal efficiency (IE) of SRI plants in utilizing macronutrients was 69.2 for N, 347.2 for P, and 69.7 for K, while the IE in plants conventionally grown was 74.9, 291.1, and 70.4 for these three macronutrients, respectively. Although no significant differences in IE were observed for N and K, the uptake of P was significantly greater, indicating more efficient use of P by SRI plants for grain production. More research needs to be done on such relationships, but this study indicates that productive changes in the structure and functioning of rice plants, particularly their roots, can be induced by alternative management methods.     

Genotypic variations in zinc accumulation and bioaccessibility among wheat (Triticum aestivum L.) genotypes under two different field conditions

Zinc (Zn) is an essential micronutrient for human health. Breeding zinc-rich crop genotypes is considered as potential solution to Zn deficiency. In this study, variation of Zn uptake, accumulation, distribution and the estimated bioaccessibility among 30 wheat genotypes across two locations were investigated with field experiments. A significant difference in grain Zn concentrations occurred across the two locations, with the corresponding values of 55.24 and 57.14 mg kg⁻¹. Grain Zn concentration was significantly and positively correlated with grain Mn concentration (0.698**, 0.617** for two locations). The estimated grain Zn bioaccessibility also showed a significant difference, a trend similar to grain Zn concentrations but with lower values (13.87 and 13.49 mg Zn d⁻¹ for two locations). These results indicate that the interaction of locations * genotypes may play an important role in grain Zn concentrations and Zn bioaccessibility.     

Grain yield,zinc efficiency and zinc concentration of wheat cultivars grown in a zinc-deficient calcareous soil in field and greenhouse

Field experiments were carried out to study grain yield, zinc (Zn) efficiency and concentrations of Zn in shoot and grain of 37 bread wheat (Triticum aestivum) and three durum wheat (Triticum durum) cultivars grown in a Zn-deficient calcareous soil with (23 kg Zn ha⁻¹), and without, Zn fertilization in 1993–1994 and 1994–1995. The same Zn-deficient soil was used in greenhouse experiments to study shoot dry weight, Zn efficiency and shoot Zn concentrations of 21 bread and three durum wheat cultivars (same cultivars used in the field experiments). Zinc fertilization of cultivars in the field enhanced grain yield on average by 30% in both years. Increases in grain yield to Zn fertilization varied substantially between cultivars from 8% to 76%. Accordingly, there was large variability in Zn efficiency of cultivars, expressed as the ratio of grain yield or shoot dry-matter yield produced under Zn deficiency compared to that under Zn fertilization. On average, Zn efficiency values ranged from 57% to 92% for grain yield in field experiments and from 47% to 83% for shoot dry weight in greenhouse experiments. Most of the cultivars behaved similarly in their response to Zn deficiency in the field and greenhouse. The cultivars selected from local landraces had both, a high Zn efficiency and high yield under Zn-deficient conditions. The bread wheat cultivars, improved for irrigated conditions, had generally low Zn efficiency and low yield, both in the field and greenhouse. All durum wheat cultivars in this study also showed low levels of Zn efficiency, grain yield and shoot dry weight under Zn deficiency. Overall, there was no relation between Zn efficiency values and Zn concentrations in grain or shoot dry matter. The results presented here demonstrate the existence of substantial variation in Zn efficiency among wheat cultivars, particularly bread wheat cultivars, and suggest that wheat landrace populations are a valuable source of genes to improve high Zn efficiency of wheat for Zn-deficient soils.     

铜与锌对茶树生育特性及生理代谢的影响Ⅳ．锌对茶树体内矿质元素含量及分布的影响

采用叶面喷施和土施相结合的方法,研究了不同锌浓度处理对茶树体内主要矿质元素含量及分布的影响、土壤有效锌含量与茶树吸锌量的关系。结果表明,茶树对锌有很强的吸收能力,叶部（喷施）和根部（土施）吸收的锌能很快转移到茶树的其它部位,除成熟叶外,新梢、生产枝、主根和吸收根的含锌量与土壤有效锌含量均达极显著正相关。新梢可作为茶树缺锌诊断的取样部位。叶面喷锌对茶树体内Ｐ含量影响不大,对Ｋ的吸收有促进作用。土施则降低Ｐ和Ｋ的吸收。Ｐ—Ｚｎ间存在明显的拮抗作用,但这种作用并非发生在茶树体内,而是表现在茶树根系的吸收上。对Ｆｅ、Ｍｎ、Ｃａ和Ｍｇ含量的影响,则无论是叶面喷锌还是土施锌,均表现为茶树多数部位降低,其中土施对这此元素的影响比叶面喷施明显。施锌对Ｃｕ和Ｎａ含量的影响不大。从施锌对茶叶产量、品质和对矿质养分吸收进行综合评价来看,茶树施锌以叶面喷施为宜。     

Estimating N status of winter wheat using a handheld spectrometer in the North China Plain

Excessive nitrogen (N) fertilizer application is very common in the North China Plain. Diagnosis of in-season N status in crops is critical for precision N management in this area. Remote sensing, as a timely and nondestructive tool, could be an alternative to traditional plant testing for diagnosing crop N status. The objectives of this study were to determine which vegetation indices could be used to estimate N status in winter wheat (Triticum aestivum L.) under high N input conditions, develop models to predict winter wheat N uptake using spectral vegetation indices and validate the models with data from farmers’ fields. An N rate experiment and a variety-N experiment were conducted in Huimin, Shandong Province from 2005/2006 to 2006/2007 to develop the models. Positive linear relationships between simple ratio vegetation indices (red vegetation index, RVI and green vegetation index, GVI) and N uptake were observed independent of growth stages and varieties (R², 0.48–0.74). In contrast, the relationships between normalized difference vegetation indices (NDVI and GNDVI), red and green normalized difference vegetation index (RGNDI), and red and green ratio vegetation index (RGVI) were exponentially related to N uptake (R², 0.43–0.79). Subsequently, 69 farmers’ fields in four different villages were selected as datasets to validate the developed models. The results indicated that the prediction using RVI had the highest coefficient of determination (R², 0.60), the lowest root mean square error (RMSE, 39.7 kg N ha⁻¹) and relative error (RE, 30.5%) across different years, varieties and growth stages. We conclude that RVI can be used to estimate nitrogen status for winter wheat in over-fertilized farmers’ fields before heading.