Modern Wheat Cultivars Research Articles

Canadian Organic Wheat Breeding with On-farm Selection: A Case Study using Landrace and Modern Parents

Participatory plant breeding (PPB) has the potential to be an alternative to a centralized breeding model for niche markets that are historically underserved. Our objectives were to evaluate the performance of two parental cultivars from a Canadian PPB program: a modern spring wheat (Triticum aestivum L.) cultivar (5602HR) and a landrace (Red Fife) - with the progeny of the cross when selected by two farmers located 1800 km apart (denoted Farm1 and Farm2) and evaluate progeny differences from each other under organic conditions. Red Fife was 18 cm taller, matured 5 days later, had greater lodging susceptibility, greater seed mass, and 3.5% lower protein concentration than 5602HR. Farmer genotypes were similar to 5602HR in protein concentration and lodging severity, and similar to Red Fife in plant height (14 cm taller than 5602HR) and seed mass. Farmer genotypes did not yield differently from either parent. Farmer genotypes did not differ from each other in most parameters measured, however, Farm1 had greater lodging resistance under high fertility conditions than Farm2 despite similar plant height. This research provides a proof of concept for the role that farmer selectors can play in selecting for positive traits for organic production and provide insight into organic farmers’ preferences. The research also demonstrated that using an older landrace (ie., Red Fife) allowed positive features such as tall stature to be incorporated into the resulting progeny.

Insights into the influence of intercropping and arbuscular mycorrhizal inoculation on two modern durum wheat cultivars and their associated microbiota

Insights into the influence of intercropping and arbuscular mycorrhizal inoculation on two modern durum wheat cultivars and their associated microbiota

Nitrogen modulates the ozone response of Mediterranean wheat: Considerations for ozone risk assessment

The experiment was conducted in an Open Top Chamber facility located in the Mediterranean basin to investigate how nitrogen (N) fertilization affects the response of wheat to ozone (O3) exposure. The study considered the response of Artur Nick, a modern wheat cultivar commonly used in the area, to three O3 exposure levels (ambient and elevated ambient, +20 and +40 nL L−1 O3), and two N fertilization doses (100 and 200 kg ha−1). Measurements included leaf gas exchange, leaf chlorophyll content, leaf and grain N content, plant growth and yield parameters. Ozone × N interactive effects were studied and quantified based on accumulated O3 concentrations above a 40 nL L−1 threshold (AOT40) and phytotoxic O3 dose (POD) indices, which are used in O3-risk assessments, from which critical levels (CL) for a 5 % effect were derived.Results revealed that O3 impacts on growth and yield parameters were stronger under the highest N fertilization dose. In consequence, O3 Critical Levels (CL) were as much as 3–4 times lower for grain yield in the high-N compared to the low-N treatment. Interestingly, O3 limited the fertilizer stimulus, strongly reducing the N use efficiency for grain yield and the agronomic efficiency of N for protein yield. Another important aspect was that 71 % of the POD was accumulated before anthesis, stressing the potential importance of O3 exposure during the vegetative phase of wheat under Mediterranean conditions, which is usually considered less important than post-anthesis exposure.In conclusion, this study suggests the need to consider crop N management in the derivation of O3 CLs, due to its effect on dose-response relationships used for CL derivation, including the potential O3 effects in N use efficiency. Therefore, N modulation could be considered in the O3-risk assessment methodology to be applied in risk exercises when negotiating air pollution abatement policies.

Natural variation in photosynthetic electron transport of wheat flag leaves in response to dark-induced senescence

Early leaf senescence affects photosynthetic efficiency and limits growth during the late production stage of winter wheat (Triticum aestivum). Natural variation in photosystem response to senescence represents a valuable resource for improving the aging traits of flag leaves. To explore the natural variation of different phases of photosynthetic electron transport in modern wheat cultivars during senescence, we exposed the flag leaves of 32 wheat cultivars to dark conditions to induce senescence process, and simultaneously measured prompt fluorescence and modulated 820 nm reflection. The results showed that the chlorophyll content, activity of PSII donor side, PSI and electron transfer between PSII and PSI were all decreased during dark-induced senescence, but they showed different sensitivity to dark-induced senescence. Furthermore, natural variation in photosynthetic parameters among the 32 wheat cultivars were also observed and showed by variation coefficient of the different parameters. We observed that PSII and PSI activity showed less sensitivity to dark-induced senescence than electron transfer between them, while PSII and PSI activity exhibit greater natural variation than electron transport between PSII and PSI. It suggests that Cytb6f might degrade faster and have less variation than PSII and PSI during dark-induced senescence.

Changes in phosphorus-related performance attributes of dryland winter wheat cultivars released between the 1940s and 2010s in Shaanxi Province, China.

Water and nutrients are two main determinants of wheat yield, which are vital for maintaining high crop yields. In the present study, the effects of water and phosphate fertilization on wheat yield, photosynthetic parameters, water productivity and phosphate use efficiency were investigated. Five dryland wheat cultivars from the 1940s to the 2010s that are widely cultivated in Shaanxi Province, China, were used. Experiments were conducted from 2019 to 2022 using two irrigation levels (normal rainfall and no precipitation after the reviving stage) and two phosphorus application levels (0 and 100 kg ha-1). Compared with old cultivars ('Mazha'), the grain yield of modern cultivars ('Changhan 58') was 89.24% higher and was closely correlated with chlorophyll index, leaf area index, photosynthetic rate and tillers. With the replacement of cultivars, the phosphorus content, water potential and phosphatase activity of wheat leaves increased. Considering water-phosphorus interactions, the water use efficiency and phosphorus use efficiency of wheat showed a significant positive correlation. Our findings indicate that modern wheat cultivars are more responsive to phosphorus. Further analysis revealed that modern varieties have evolved two phosphorus absorption strategies in response to phosphorus deficiency - namely, the formation of a phosphorus supply source, which may result in larger numbers of green organs; and an increase in phosphorus sinks, which tended to activation and transport of plant phosphorus. Our results may thus contribute to water conservation, increased yields and the development of strategies for efficient phosphorus fertilization. © 2024 Society of Chemical Industry.

Wheat yield and grain-filling characteristics due to cultivar replacement in the Haihe Plain in China.

The Haihe Plain plays an important role in wheat production and food security in China and has experienced continuous cultivar replacement since the 1950s.This study assessed the evolution of the yield and grain-filling characteristics of the main winter wheat cultivars in the Haihe Plain over the last seven decades (1950s to date). Cultivar characterization indicated that the increase in yield was negatively affected by spike number and positively affected by the number of kernels per spike before the 2000s and kernel weight after the 2000s. Field trials were conducted across two ecological zones over two consecutive wheatgrowing seasons. The results showed that genetic gains in grain yield, spike number, and kernel weight during 1955 to 2021 were 0.629%, 0.574%, and 0.332% year-1 on a relative basis or 39.12 kg ha-1, 24,350 hm-2, and 0.15 g year-1 on an absolute basis, respectively. However, the increase in the kernel number per spike was not significant. Moreover, cultivar replacement explained 25.6%, 12.8%, and 37.5% of the total variance in grain yield, spike number, and kernel weight, respectively. In summary, during the initial grain-filling stage, wheat cultivar replacement led to the shortening of grain-filling duration and rapid grain-filling rate. However, a longer active grain-filling duration was produced by prolonged durations of rapid and late grain-filling. Additionally, the experimental year had a greater effect on the kernel number, which explained 53.2% of the total variance. Ultimately, modern wheat cultivars had a greater kernel weight. Although the increase in kernel weight has affected grain yield during cultivar replacements in the Haihe Plain, the potential for further yield increase through kernel weight enhancement alone is limited. Consequently, future breeding efforts and cultivation practices should focus on improving spike traits and canopy architecture to enhance productivity.

Assessing the impact of early and terminal droughts on root growth, grain yield and yield stability in old and modern wheat cultivars on the Loess Plateau

Understanding changes in root traits of high-yielding genotypes that consistently perform during different drought periods is crucial for improving wheat production and yield stability. A 2-year field trial and a pot experiment were conducted to determine the response of root growth and grain yield to early and terminal droughts in old and modern cultivars (FC3: 1960s and CH1: 2010s) under rainfed and irrigated conditions in the field. Rainfed wheat faced terminal drought in 2015–2016 and early drought in 2016–2017. Plants in the pot experiment were exposed to terminal drought, early drought, and well-watered. Both field and pot experiments showed higher grain yield in modern cultivar CH1 compared to FC3. Early and terminal droughts reduced grain yield in both cultivars, with a greater reduction in FC3. CH1 exhibited higher yield stability under drought conditions and experienced less reduction in early drought. Compared to FC3, CH1 produced more root biomass in the early growth stage. At anthesis, CH1 had significantly lower root biomass and root length density in the topsoil layer (00.2 m) and higher in the subsoil layer (0.21.0 m) than FC3, respectively. At maturity, the retention rate of subsoil root biomass in CH1 was higher, especially under early drought (80.2 % in field and 93.9 % in pot experiments). Both cultivars consumed similar seasonal water use, but CH1 reduced pre-anthesis water use and consumed more water after anthesis. This study indicates that modern cultivar had vigorous root growth at early stage. A higher proportion of root biomass preserved in deep soil after anthesis enhanced post-anthesis water use and photosynthetic rate, improved post-anthesis dry matter accumulation, and thus resulted in higher thousand kernel weight. These factors ensure higher yield and yield stability under both early and terminal drought stress.

Molecular characterization of QTL for grain zinc and iron concentrations in wheat landrace Chinese Spring.

Three stable QTL for grain zinc concentration were identified in wheat landrace Chinese Spring. Favorable alleles were more frequent in landraces than in modern wheat cultivars. Wheat is a major source of dietary energy for the growing world population. Developing cultivars with enriched zinc and iron can potentially alleviate human micronutrient deficiency. In this study, a recombinant inbred line (RIL) population with 245 lines derived from cross Zhou 8425B/Chinese Spring was used to detect quantitative trait loci (QTL) for grain zinc concentration (GZnC) and grain iron concentration (GFeC) across four environments. Three stable QTL for GZnC with all favorable alleles from Chinese Spring were identified on chromosomes 3BL, 5AL, and 5BL. These QTL explaining maxima of 8.7%, 5.8%, and 7.1% of phenotypic variances were validated in 125 resequenced wheat accessions encompassing both landraces and modern cultivars using six kompetitive allele specific PCR (KASP) assays. The frequencies of favorable alleles for QGZnCzc.caas-3BL, QGZnCzc.caas-5AL and QGZnCzc.caas-5BL were higher in landraces (90.4%, 68.0%, and 100.0%, respectively) compared to modern cultivars (45.9%, 35.4%, and 40.9%), suggesting they were not selected in breeding programs. Candidate gene association studies on GZnC in the cultivar panel further delimited the QTL into 8.5Mb, 4.1Mb, and 47.8Mb regions containing 46, 4, and 199 candidate genes, respectively. The 5BL QTL located in a region where recombination was suppressed. Two stable and three less stable QTL for GFeC with favorable alleles also from Chinese Spring were identified on chromosomes 4BS (Rht-B1a), 4DS (Rht-D1a), 1DS, 3AS, and 6DS. This study sheds light on the genetic basis of GZnC and GFeC in Chinese Spring and provides useful molecular markers for wheat biofortification.

Does Exogenous Application of salicylic acid induce salt stress tolerance in potentially high-yielding modern wheat cultivars?

Does Exogenous Application of salicylic acid induce salt stress tolerance in potentially high-yielding modern wheat cultivars?

The benefits of experimental breeding research genotypes for the genetic resources of spring durum wheat

AbstractOur study aimed to incorporate 60 newly acquired spring durum wheat genotypes into the Prague Gene Bank collection, focusing on 54 experimental breeding research genotypes and their technological quality contributions for conservation and future use. We analyzed a total of 11 field and 6 technological parameters of grain quality. Additionally, we identified the composition of high molecular weight glutenin subunits (HMW-GSs) in 13 accessions with contrasting technological characteristics. Two different extraction procedures were employed to detect HMW-GSs: one based on total protein extraction and the other on gliadin pre-extraction. The tested parameters exhibited a significant range of variability, with the relative standard deviation ranging from 2.1% for starch content to 96.7% for the gluten index. Additionally, six breeding research genotypes exhibited high technological grain quality comparable to the two modern durum wheat cultivars. Two accessions: M90-99–2 and IG 142076 showed above-average Zeleny sedimentation values, probably positively influenced by the presence of HMW-GSs A1: (2*). Genotypes PI 675012 and IG 142039 displayed the highest grain stability in technological parameters. Both extraction methods also detected the specific subunit B1: (6 + 8*) in the genotype IG 142039. Preserving these genotypes thus represents a substantial expansion of genetic resources in the genebank.

A tale of two eras: assessing the impact of breeding programs on historical and modern German wheat cultivars under distinct management

Breeding advancements have significantly improved grain yield over recent decades, yet further progress is needed to meet global food demands amid a growing population. In this study, we systematically examine the responses of both historical and modern winter wheat cultivars, released between 1895 and 2007 in Germany, to varying management intensities. We quantified the independent contributions of nitrogen (N) levels, growth regulators, and plant protection measures to crop productivity and growth variables over two growing seasons. Historical cultivars (pre-1960) exhibited a lower yield (4.6 t ha−1) and harvest index (0.30) compared to modern cultivars (post-1960), which demonstrated a higher yield (6.8 t ha−1) and harvest index (0.40) across all treatments, even those excluding both nitrogen and agrochemicals. We found positive trends in the yield and yield components for both historical (1895–1960) and modern (1961–2007) cultivars; however, significance was only noted for modern cultivars. Crop growth in historical cultivars was aided more by growth regulators, while modern cultivars gained more benefits from plant protection. However, both categories of cultivars produced a synergistic response when combining agronomic practices. Based on a comparison of N application rates and agronomic practices, N had a distinctly greater impact on yield and yield components than other treatments. In both historical and modern cultivars, grain number per ear was the most influential contributing factor to yield. Nevertheless, the effect of the thousand grain weight on yield was notably less for modern cultivars compared to their historical ones. Grain nitrogen yield increased up to mid-supply nitrogen application but remained constant at high rates. Results underscored that cultivar-specific responses for yield and yield components need to consider the interactions between fertilization and other agronomic practices.

Genomic insights into the origin and evolution of spelt (Triticum spelta L.) as a valuable gene pool for modern wheat breeding

Spelt (Triticum aestivum ssp. spelta) is an important wheat subspecies mainly cultivated in Europe before the 20th century that has contributed to modern wheat breeding as a valuable genetic resource. However, relatively little is known about the origins and maintenance of spelt populations. Here, using resequencing data from 416 worldwide wheat accessions, including representative spelt wheat, we demonstrate that European spelt emerged when primitive hexaploid wheat spread to the west and hybridized with pre-settled domesticated emmer, the putative maternal donor. Genomic introgression regions from domesticated emmer confer spelt’s primitive morphological characters used for species taxonomy, such as tenacious glumes and later flowering. We propose a haplotype-based “spelt index” to identify spelt-type wheat varieties and to quantify utilization of the spelt gene pool in modern wheat cultivars. This study reveals the genetic basis for the establishment of the spelt wheat subspecies in a specific ecological niche and the vital role of the spelt gene pool as a unique germplasm resource in modern wheat breeding.

Meta-QTL analysis and candidate genes for quality traits, mineral content, and abiotic-related traits in wild emmer.

Wild emmer (Triticum turgidum ssp. dicoccoides) genotypes were studied for their high-nutritional value and good tolerance to various types of stress; for this reason, several QTL (quantitative trait loci) studies have been conducted to find favorable alleles to be introgressed into modern wheat cultivars. Given the complexity of the QTL nature, their interaction with the environment, and other QTLs, a small number of genotypes have been used in wheat breeding programs. Meta-QTL (MQTL) analysis helps to simplify the existing QTL information, identifying stable genomic regions and possible candidate genes for further allele introgression. The study aimed to identify stable QTL regions across different environmental conditions and genetic backgrounds using the QTL information of the past 14 years for different traits in wild emmer based upon 17 independent studies. A total of 41 traits were classified as quality traits (16), mineral composition traits (11), abiotic-related traits (13), and disease-related traits (1). The analysis revealed 852 QTLs distributed across all 14 chromosomes of wild emmer, with an average of 61 QTLs per chromosome. Quality traits had the highest number of QTLs (35%), followed by mineral content (33%), abiotic-related traits (28%), and disease-related traits (4%). Grain protein content (GPC) and thousand kernel weight (TKW) were associated with most of the QTLs detected. A total of 43 MQTLs were identified, simplifying the information, and reducing the average confidence interval (CI) from 22.6 to 4.78 cM. These MQTLs were associated with multiple traits across different categories. Nine candidate genes were identified for several stable MQTLs, potentially contributing to traits such as quality, mineral content, and abiotic stress resistance. These genes play essential roles in various plant processes, such as carbohydrate metabolism, nitrogen assimilation, cell wall biogenesis, and cell wall extensibility. Overall, this study underscores the importance of considering MQTL analysis in wheat breeding programs, as it identifies stable genomic regions associated with multiple traits, offering potential solutions for improving wheat varieties under diverse environmental conditions.

Natural variation of STKc_GSK3 kinase TaSG-D1 contributes to heat stress tolerance in Indian dwarf wheat

Heat stress threatens global wheat (Triticum aestivum) production, causing dramatic yield losses worldwide. Identifying heat tolerance genes and comprehending molecular mechanisms are essential. Here, we identify a heat tolerance gene, TaSG-D1E286K, in Indian dwarf wheat (Triticum sphaerococcum), which encodes an STKc_GSK3 kinase. TaSG-D1E286K improves heat tolerance compared to TaSG-D1 by enhancing phosphorylation and stability of downstream target TaPIF4 under heat stress condition. Additionally, we reveal evolutionary footprints of TaPIF4 during wheat selective breeding in China, that is, InDels predominantly occur in the TaPIF4 promoter of Chinese modern wheat cultivars and result in decreased expression level of TaPIF4 in response to heat stress. These sequence variations with negative effect on heat tolerance are mainly introduced from European germplasm. Our study provides insight into heat stress response mechanisms and proposes a potential strategy to improve wheat heat tolerance in future.

A new winter wheat genetic resource harbors untapped diversity from synthetic hexaploid wheat

Key messageThe NIAB_WW_SHW_NAM population, a large nested association mapping panel, is a useful resource for mapping QTL from synthetic hexaploid wheat that can improve modern elite wheat cultivars.The allelic richness harbored in progenitors of hexaploid bread wheat (Triticum aestivum L.) is a useful resource for addressing the genetic diversity bottleneck in modern cultivars. Synthetic hexaploid wheat (SHW) is created through resynthesis of the hybridisation events between the tetraploid (Triticum turgidum subsp. durum Desf.) and diploid (Aegilops tauschii Coss.) bread wheat progenitors. We developed a large and diverse winter wheat nested association mapping (NAM) population (termed the NIAB_WW_SHW_NAM) consisting of 3241 genotypes derived from 54 nested back-cross 1 (BC1) populations, each formed via back-crossing a different primary SHW into the UK winter wheat cultivar ‘Robigus’. The primary SHW lines were created using 15 T. durum donors and 47 Ae. tauschii accessions that spanned the lineages and geographical range of the species. Primary SHW parents were typically earlier flowering, taller and showed better resistance to yellow rust infection (Yr) than ‘Robigus’. The NIAB_WW_SHW_NAM population was genotyped using a single nucleotide polymorphism (SNP) array and 27 quantitative trait loci (QTLs) were detected for flowering time, plant height and Yr resistance. Across multiple field trials, a QTL for Yr resistance was found on chromosome 4D that corresponded to the Yr28 resistance gene previously reported in other SHW lines. These results demonstrate the value of the NIAB_WW_SHW_NAM population for genetic mapping and provide the first evidence of Yr28 working in current UK environments and genetic backgrounds. These examples, coupled with the evidence of commercial wheat breeders selecting promising genotypes, highlight the potential value of the NIAB_WW_SHW_NAM to variety improvement.

Nitrogen use efficiency in modern wheat cultivars affected by sowing dates

Nitrogen use efficiency in modern wheat cultivars affected by sowing dates

Field phenotyping of ten wheat cultivars under elevated CO2 shows seasonal differences in chlorophyll fluorescence, plant height and vegetation indices.

In the context of climate change and global sustainable development goals, future wheat cultivation has to master various challenges at a time, including the rising atmospheric carbon dioxide concentration ([CO2]). To investigate growth and photosynthesis dynamics under the effects of ambient (~434 ppm) and elevated [CO2] (~622 ppm), a Free-Air CO2 Enrichment (FACE) facility was combined with an automated phenotyping platform and an array of sensors. Ten modern winter wheat cultivars (Triticum aestivum L.) were monitored over a vegetation period using a Light-induced Fluorescence Transient (LIFT) sensor, ground-based RGB cameras and a UAV equipped with an RGB and multispectral camera. The LIFT sensor enabled a fast quantification of the photosynthetic performance by measuring the operating efficiency of Photosystem II (Fq'/Fm') and the kinetics of electron transport, i.e. the reoxidation rates Fr1' and Fr2'. Our results suggest that elevated [CO2] significantly increased Fq'/Fm' and plant height during the vegetative growth phase. As the plants transitioned to the senescence phase, a pronounced decline in Fq'/Fm' was observed under elevated [CO2]. This was also reflected in the reoxidation rates Fr1' and Fr2'. A large majority of the cultivars showed a decrease in the harvest index, suggesting a different resource allocation and indicating a potential plateau in yield progression under e[CO2]. Our results indicate that the rise in atmospheric [CO2] has significant effects on the cultivation of winter wheat with strong manifestation during early and late growth.

Antioxidant and Secondary Metabolite Responses in Wheat under Cereal Leaf Beetle (Oulema melanopus L.) Infestation

AbstractWheat is one of the most important cereal crops grown in the Western Himalayas of India but its production is challenged by the insect “cereal leaf beetle (CLB)”. This study explores the impact of domestication and modern crop improvement on wheat's defense mechanisms against the CLB, a global threat to wheat cultivation. Sixteen diverse wheat genotypes having different ploidy levels were investigated, including wild wheat, landraces, mutants, advanced breeding lines, commercial varieties, and a Rye grass genotype. Genotypes with resistance genes, landraces, and wild wheat exhibited the lowest CLB infestation and oxidative damage. These genotypes displayed enhanced antioxidant enzyme activity, such as peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), superoxide dismutase (SOD), and polyphenol oxidase (PPO), reduced reactive oxygen species (ROS) production, and increased plant secondary metabolite (phenol and tannin) production upon CLB infestation. Resistant durum wheat demonstrated moderate responses and exhibited higher levels of flavonoid production. On the other hand, susceptible durum wheat genotypes, commercial variety Shalimar Wheat‐02 (SW‐2), showed high CLB infestation, ROS production, reduced antioxidant enzyme and secondary metabolite production. This may be because modern varieties like SW‐2 were not selected for insect resistance. These findings emphasize the significance of preserving genetic diversity from wild wheat and landraces to bolster wheat breeding programs against pests such as CLB. This study underscores the need to harness ancestral wheat lines to enhance insect pest resistance in modern wheat cultivars.

Estimation of the Production Function of some (Modern) Wheat Cultivars in Salah Al-Din Governorate for the Agricultural Season (2020-2021)

The study aims to measure the effect of using modern varieties on increasing the productivity of a dunum of wheat crop, and to study the economic impact of cultivar change on the transmission of the supply function of the wheat crop, and to determine the amount of increase in production by replacing high-producing varieties with low-yielding varieties, and the study used Harry’s model Ir_Edward Shaw in estimating the transfer coefficients in the resulting supply of the different varieties of the wheat crop for the districts and sub-districts of Salah al-Din Governorate (Tikrit, Samarra, Al-Alam, Al-Dur), according to a questionnaire form, where the sample size included (160) farmers for the wheat crop, as it was found that the use of modern technologies led to shift the supply function to the right by (1.192 ‘1.510 ’ 1.351) % respectively, which means an increase in the quantity supplied of wheat and the trend towards self-sufficiency of this crop, and from the estimation of the joint production function for farms applied to modern technologies, the results of the imaginary variable parameter (X8) became clear. Its value was (0.811) and its sign was positive and it is significant at the level of (1%), and this means that the use of modern technologies has a positive effect by raising the productivity of farms applying modern technologies.

Genetic improvement of photosynthetic nitrogen use efficiency of winter wheat in the Yangtze River Basin of China

ContextImproving the photosynthetic capacity of crops is key to achieving synergism between high crop yield and nitrogen (N) efficiency, and it is also an important target for future cultivar breeding and cultivation management. Although photosynthetic N use efficiency (PNUE) is commonly used to determine the N economy of leaves, it is unclear whether the PNUE of wheat has improved through genetic engineering of wheat cultivars. ObjectivesThe objectives of this study were to investigate the development of net photosynthetic rate (Pn) and PNUE, and to identify the key factors that limited Pn and PNUE in the tested cultivars. MethodsA 2-year field experiment with three different N fertilizer application rates using five wheat cultivars developed between 1950 s and 2010 s was conducted to examine the evolution and physiological processes of wheat Pn and PNUE. ResultsGrain yield, N recovery efficiency (NRE), leaf Pn, leaf area, the content of N in leaves (LNC), and the content of N per unit area in leaves (NA) increased through genetic engineering of wheat cultivars. However, the increase in Pn was lower than that in NA, resulting in a decrease in PNUE. Modern cultivars had a higher Pn, which was attributed to the improvement of NA, which likely enhanced the maximum ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) carboxylation rate (Vcmax), maximum electron transport rate (Jmax), electron transport rate from photosystem II (JF), and electron transport rate from the cytochrome b6f complex (Jc). The Rubisco content and activity of modern cultivars were higher than those of early cultivars, but the activation state decreased, which was related to the downregulation expression of TaRca1α and TaRca2β-A and the decrease of the adenosine diphosphate/adenosine triphosphate (ADP/ATP) ratio in modern cultivars, resulting in decreased Rubisco activase (Rca) content and activity. Increasing N application increased NA and Pn but decreased the PNUE. N fertilizer had a greater effect on Rubisco content and PNUE than genetic engineering, while it had a smaller effect on NA, leaf mass per area (LMA), Rubisco activity, and Rca content and activity than genetic engineering. ConclusionsOur results suggest that lower Rubisco activation is a major reason for the lower PNUE of modern wheat cultivars, and improving Rca content and activity in the future could enhance Pn and PNUE while improving the N utilization of leaves to enhance crop yield and N efficiency of wheat under current or lower leaf N conditions.