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The GRAS transcription factors play an indispensable role in plant growth and responses to environmental stresses. The GRAS gene family has extensively been explored in various plant species; however, the comprehensive investigation of GRAS genes in white lupin remains insufficient. In this study, bioinformatics analysis of white lupin genome revealed 51 LaGRAS genes distributed into 10 distinct phylogenetic clades. Gene structure analyses revealed that LaGRAS proteins were considerably conserved among the same subfamilies. Notably, 25 segmental duplications and a single tandem duplication showed that segmental duplication was the major driving force for the expansion of GRAS genes in white lupin. Moreover, LaGRAS genes exhibited preferential expression in young cluster root and mature cluster roots and may play key roles in nutrient acquisition, particularly phosphorus (P). To validate this, RT‐qPCR analysis of white lupin plants grown under +P (normal P) and −P (P deficiency) conditions elucidated significant differences in the transcript level of GRAS genes. Among them, LaGRAS38 and LaGRAS39 were identified as potential candidates with induced expression in MCR under −P. Additionally, white lupin transgenic hairy root overexpressing OE‐LaGRAS38 and OE‐LaGRAS39 showed increased root growth, and P concentration in root and leaf compared to those with empty vector control, suggesting their role in P acquisition. We believe this comprehensive analysis of GRAS members in white lupin is a first step in exploring their role in the regulation of root growth, tissue development, and ultimately improving P use efficiency in legume crops under natural environments. [ABSTRACT FROM AUTHOR]

Global warming, climate change, and environmental pollution present plants with unique combinations of different abiotic and biotic stresses. Although much is known about how plants acclimate to each of these individual stresses, little is known about how they respond to a combination of many of these stress factors occurring together, namely a multifactorial stress combination. Recent studies revealed that increasing the number of different co-occurring multifactorial stress factors causes a severe decline in plant growth and survival, as well as in the microbiome biodiversity that plants depend upon. This effect should serve as a dire warning to our society and prompt us to decisively act to reduce pollutants, fight global warming, and augment the tolerance of crops to multifactorial stress combinations. A multifactorial stress combination occurs when more than two to three abiotic and/or biotic stress factors simultaneously impact a plant. Global warming, climate change, and industrial pollution could result in an increase in the frequency, complexity, and intensity of multifactorial stress combinations impacting plants, soils, and microbial communities. With the increase in the number of factors simultaneously impacting plants, the survival and growth of plants declines, even if the levels of each of these individual stresses is very low. The response of plants to a multifactorial stress combination is unique and involves many transcripts and genes that are not altered in response to each of the different stresses applied individually. The harmful effects of a multifactorial stress combination on the survival and growth of plants, different soil properties, and diversity of microbial communities should serve as a dire warning to our society and prompt us to act drastically to reduce the different sources of multifactorial stresses in our environment. [ABSTRACT FROM AUTHOR]

Manganese is an essential nutrient and plays key roles in photosynthetic processes, including in NAD‐malic enzyme (NAD‐ME)‐type C4 plants as an activator of NAD‐ME. However, little is known about the Mn requirements of switchgrass (Panicum virgatum L.). To study Mn requirements for optimum growth and biomass production, a lowland ('Alamo') and an upland ('Cave‐in‐Rock') switchgrass ecotype were grown with either washed sand, vermiculite, or perlite and fertilized with nutrient solutions ranging in [Mn] from 0 to 200 μM. In the perlite experiment, pearl millet [Pennisetum glaucum (L.) R. Br. 'KGraze'] was also grown. Shoot [Mn] was highly responsive to increasing Mn in the nutrient solution. When grown in washed sand and vermiculite, tissue [Mn] remained above those normally considered deficient, even in the 0 μM Mn treatment, and no Mn treatment effects on biomass production were found. In perlite, end‐of‐season shoot [Mn] were <5 mg kg−1 in all entries when no Mn was supplied, and a decrease in biomass production compared with 10–25 μM Mn treatments was observed for Alamo and KGraze, but not for Cave‐in‐Rock. Relative chlorophyll contents of switchgrass were lower in the 0 μM Mn treatment than in other treatments late in the season, but in KGraze, they were low early in the season and increased throughout the season, resulting in less pronounced (but still significant) differences at late stages. Overall, results indicated that switchgrass and pearl millet respond differently to low Mn availability and that even low levels of shoot tissue [Mn] allow switchgrass to maintain biomass production. [ABSTRACT FROM AUTHOR]

Episodes of heat waves combined with drought can have a devastating impact on agricultural production worldwide. These conditions, as well as many other types of stress combinations, impose unique physiological and developmental demands on plants and require the activation of dedicated pathways. Here, we review recent RNA sequencing studies of stress combination in plants, and conduct a meta-analysis of the transcriptome response of plants to different types of stress combination. Our analysis reveals that each different stress combination is accompanied by its own set of stress combination-specific transcripts, and that the response of different transcription factor families is unique to each stress combination. The alarming rate of increase in global temperatures, coupled with the predicted increase in future episodes of extreme weather, highlight an urgent need to develop crop plants with enhanced tolerance to stress combination. The uniqueness and complexity of the physiological and molecular response of plants to each different stress combination, highlighted here, demonstrate the daunting challenge we face in accomplishing this goal. Dedicated efforts combining field experimentation, omics, and network analyses, coupled with advanced phenotyping and breeding methods, will be needed to address specific crops and particular stress combinations relevant to maintaining our future food chain secured. [ABSTRACT FROM AUTHOR]

Post-silking nitrogen (N) fluxes from vegetative tissues to developing kernels affect both N use efficiency (NUE) and grain yield in maize, while the impacts of various N applications at and especially after silking on temporal dynamics of post-silking N uptake and remobilization are poorly understood. Field experiments were conducted with N regimes ranging from low to high N levels. Nitrogen applications above optimal rates at and after silking neither increased late-season N uptake and leaf photosynthesis, nor reduced leaf N export during grain filling compared to the optimal N input, and thus significantly reduced the NUE. In most experiments, reductions in leaf N concentrations were observed around 15 days after silking (DAS). A 15 N labeling study revealed that remobilization of N taken up prior to silking from vegetative tissues during the entire grain-filling phase was 58%–60%, which contributed 53%–61% of the total grain N at maturity, and more than 60% of it was remobilized during the 0–30 DAS. N remobilization initially occurred preferentially from stems relative to leaves, while significant amounts of N were remobilized from leaves during late grain filling and deposited in the stem, particularly in high N treatments. No matter whether 15 N was applied before or at silking, a greater proportion of 15 N taken up was allocated to leaves under N deficient than under N sufficient conditions. At maturity, 70%–76% of the N taken up after silking was allocated to grain. Under N deficiency, direct N allocation to grains originating from post-silking uptake was 45%, 56%, 70% and 96% at 0–15, 15–30, 30–46 and 46–60 DAS, respectively, while these values were relatively lower and constant in N-sufficient plants (43%–50%). Overall, results indicated a strong developmental control over post-silking N fluxes with limited differences observed between N deficient and N sufficient maize, but no impact of high N applications to N-sufficient plants at or after silking. [ABSTRACT FROM AUTHOR]

As a measure of a plants ability to convert solar energy into biomass, radiation use efficiency (RUE) can be used to compare species and genotypes within species. Despite considerable research on RUE of biofuel species, few reports on sweet sorghum ( Sorghum bicolor (L.) Moench.) RUE are available. Radiation use efficiency and biomass yield of four sweet sorghum genotypes (‘Dale’, ‘M 81E’, ‘Topper 76-6’, and ‘Sugar Drip’) was assessed in response to two late planting dates in a two-year study. The late planting dates would coincide with abandoning double-crop plantings of soybean following wheat. Aboveground biomass yield and RUE (g biomass MJ −1 intercepted photosynthetically active radiation (IPAR)) was measured every two weeks beginning four weeks after planting. Two estimates of RUE were calculated differing only in growth periods used (emergence to anthesis [EA] and during rapid linear growth [Max]). Biomass yields, EA, and Max RUE were similar between years and sorghum cultivars, but differed between planting dates. Early-July plantings resulted in greater RUE than mid-July plantings. Averaged across cultivars at the first planting date both years EA and Max RUE were 3.11 and 3.96 g MJ −1 IPAR, respectively, compared to 2.40 (EA RUE) and 2.79 g MJ −1 IPAR (Max RUE) at the second planting date. Mean biomass yield across years and cultivars was 10.67 and 8.63 Mg ha −1 at the first and second planting dates, respectively. These results confirm expected decreases in RUE and biomass production of late-planted sweet sorghum, but also illustrate that, even when planted late, sweet sorghum efficiently converts intercepted PAR to biomass. [ABSTRACT FROM AUTHOR]

Integrating information on nitrogen (N) mineralization potentials into a fertilization plan could lead to improved N use efficiency. A controlled incubation mineralization study examined microbial biomass dynamics and N mineralization rates for two soils receiving 56 and 168 kg N ha−1in a Panoche clay loam (Typic Haplocambid) and a Wasco sandy loam (Typic Torriorthent), incubated with and without cotton(Gossypium hirsutumL.)residues at 10 and 25°C for 203 days. Microbial biomass activity determined from mineralized carbon dioxide (CO2) was higher in the sandy loam than in clay loam independent of incubation temperature, cotton residue addition and N treatment. In the absence of added cotton residue, N mineralization rates were higher in the sandy loam. Residue additions increased N immobilization in both soils, but were greater in clay loam. Microbial biomass and mineralization were significantly affected by soil type, residue addition and temperature but not by N level. [ABSTRACT FROM AUTHOR]

• The co-occurrence of heat and water-deficit stress during flowering negatively impacts crop productivity. • Heat, water-deficit, and their combination alter developmental processes associated with plant reproduction. • Stress-induced changes in sugar metabolism, reactive oxygen species and hormone levels are thought to play a role in yield reduction during stress combination. • Understanding the molecular processes associated with yield reduction during stress combination would allow the development of climate-resilient crops. Historically, extended droughts combined with heat waves caused severe reductions in crop yields estimated at billions of dollars annually. Because global warming and climate change are driving an increase in the frequency and intensity of combined water-deficit and heat stress episodes, understanding how these episodes impact yield is critical for our efforts to develop climate change-resilient crops. Recent studies demonstrated that a combination of water-deficit and heat stress exacerbates the impacts of water-deficit or heat stress on reproductive processes of different cereals and legumes, directly impacting grain production. These studies identified several different mechanisms potentially underlying the effects of stress combination on anthers, pollen, and stigma development and function, as well as fertilization. Here we review some of these findings focusing on unbalanced reactive oxygen accumulation, altered sugar concentrations, and conflicting functions of different hormones, as contributing to the reduction in yield during a combination of water-deficit and heat stress. Future studies focused on the effects of water-deficit and heat stress combination on reproduction of different crops are likely to unravel additional mechanisms, as well as reveal novel ways to develop stress combination-resilient crops. These could mitigate some of the potentially devastating impacts of this stress combination on agriculture. [ABSTRACT FROM AUTHOR]

The xylem-limited bacterium Xylella fastidiosa causes Pierce's disease (PD), whose disease symptoms are primarily the result of xylem vessel blockage in susceptible grapevines. Stem internode and petiole tissues from infected and uninfected control plants of four grape genotypes (Vitis vinifera, V. rufotomentosa, V. smalliana, and V. arizonica/candicans) differing in PD susceptibility were examined using scanning electron microscopy (SEM). Tyloses, fibrillar networks, and gum plugs were observed in lumens of tracheary elements in petioles and internodes of both water-inoculated control plants and X. fasfidiosa-inoculated plants of all genotypes. Bacteria were not observed in control plants. In both petiole and internode tissues, the greatest number of occluded xylem vessels were observed in V. vinifera and the smallest number in V. arizonica/candicans. The number of xylem vessels infested with X. fastidiosa was greatest in V. vinifera and did not differ among the other three genotypes. Systemic infection was found in all genotypes. The frequency with which X. fastidiosa infested vessels were observed using SEM corresponded well with bacterial levels estimated by enzyme-linked immunosorbent assay. Among infected plants, tylose formation in internodes was lowest in V. arizonica/candicans and did not differ among the other three genotypes. Infection with X. fastidiosa strongly induced tylose formation in V vinifera and V. smalliana but not in V. arizonica/candicans. Analysis across tissues and genotypes indicated an induction of fibrillar networks and gum occlusions in response to X. fastidiosa infection, whereas treatment comparisons within genotypes were not significant except for V vinifera petioles. Limiting the spread of X. fastidiosa infection by xylem conduit occlusions does not appear to be the mechanism conferring PD resistance or tolerance to V. arizonica/candicans, V. smalliana, or V. rufotomentosa. In contrast, the strong induction of tyloses may be detrimental rather than beneficial for V. vinifera survival after X. fastidiosa infection. [ABSTRACT FROM AUTHOR]

Abstract: An inverse relationship between soybean [Glycine max (L.) Merr.] seed protein and oil concentration is well documented in the literature. A negative correlation between protein and yield is also often reported. The objective of this study was to determine the effect of high rates of N applied at planting on seed protein and oil. Nitrogen was surface-applied at soybean emergence at rates of 290kgha−1 in 2002, 310kgha−1 in 2003, and 360kgha−1 in 2004. Eight cultivars ranging from Maturity Group II–IV were evaluated under the Early Soybean Production System (ESPS). However, not all cultivars were evaluated in all 3 years. Glyphosate herbicide was used in all 3 years and a non-glyphosate herbicide treatment was applied in 2002. Cultivars grown in 2003 were also evaluated under an application of 21.3kgha−1 of Mn. All cultivar, herbicide, and Mn treatments were evaluated in irrigated and non-irrigated environments with fertilizer N (PlusN treatment) or without fertilizer N (ZeroN treatment). When analyzed over all management practices (years, cultivars, herbicide, and Mn treatments), the PlusN treatment resulted in a significant decrease in protein concentration (2.7 and 1.9%), an increase in oil concentration (2.2 and 2.7%), and a decrease in the protein/oil ratio (4.7 and 4.6%) for the irrigated and non-irrigated environments, respectively. However, the overall protein and oil yield increased with the application of fertilizer N at planting (protein: 5.0% irrigated, 12.7% non-irrigated and oil: 9.9% irrigated and 18.9% non-irrigated). These increases were due to the increase in seed yield with the application of large amounts of fertilizer at planting. Additionally, a significant correlation (r =0.45, P =0.0001) was found between seed protein concentration and seed yield. No significant correlation was found between seed oil concentration and seed yield. The data demonstrate the inverse relationship between protein and oil and indicate that large amounts of N applied at planting do not change this relationship. [Copyright &y& Elsevier]

Little is known about the availability of residual fertilizer-N and cotton (Gossypium spp.) residue-N to subsequent crops. This study determined the effects of two soil types and N fertilization rates on the recovery of residual 15N-fertilizer and 15N from labeled cotton residue in the soil and plants of subsequent cotton crops. Microplots in the San Joaquin Valley, California, on a Panoche day loam [fine-loamy, mixed (calcareous), thermic Typic Terriorthents] and a Waseo sandy loam (coarse-loamy, mixed, nonacid, thermic Typic Torriorthents) were used to trace the fate of 15N from labeled aboveground cotton residue separately from the 15N in roots and soil. Total 15N-fertilizer recovery in the second year after application averaged 5.8% for Acala (G. hirsutum L.) and 2.9% for Pima (G. barbadense L.) cotton. In the third year after application, total 15N-fertilizer recovered by Acala averaged 2.0% on the clay loam soil and 3.3% on the sandy loam. Most of this recovered 15N-fertilizer was cycled through soil pools and roots and only small amounts originated from labeled aboveground residue. Virtually all of the 15N applied in the form of labeled aboveground residue and recovered in the soil was found in the top 0.3 m. The 15N-fertilizer which cycled through belowground pools was found mainly in the top 0.6 m of the soil. Recovery of residual 15N-fertilizer appears to contribute little to total cotton N uptake in the second and third crop after application. [ABSTRACT FROM AUTHOR]

A better understanding of plant nitrogen (N) dynamics in modern varieties of Acala (Gossypium hirsutum L.) and Pima (G. barbadense L.) cotton grown with prevailing management practices may help in the design of N management strategies that optimize N utilization and lint yields. The response of Acala cotton to different N fertility levels was evaluated on a Panoche clay loam (fine-loamy, mixed (calcareous), thermic Typic Torriorthents) and on a Wasco sandy loam (coarse-loamy, mixed, nonacid, thermic Typic Torriorthents). Nitrogen treatments of 56, 112, 168, and 224 kg N ha-1 and check plots were established in 1998, 1999, and 2000. Plant shoots were collected and fractionated into different components at several growth stages for determination of N concentration. Both Acala and Pima tissue N concentrations were strongly affected by developmental stage and N treatment. Acala tissue N concentrations differed significantly between soil types. Maximum N uptake rates of both Pima and Acala occurred between early square and early bloom. Physiological N use efficiency averaged 11.4 kg lint kg-1 plant N for Acala grown on the Panoche clay loam and 9.4 kg kg-1 on the Wasco sandy loam, and 13.2 kg kg-1 for Pima grown on Panoche clay loam. Leaf N concentration as an in-season indicator of N status and estimates of seasonal soil N mineralization potential may be useful in optimizing cotton N management. [ABSTRACT FROM AUTHOR]

Key message: The genetic architecture of symbiotic N fixation and related traits was investigated in the field. QTLs were identified for percent N derived from the atmosphere, shoot [N] and C to N ratio. Soybean [Glycine max (L.) Merr.] is cultivated worldwide and is the most abundant source of plant-based protein. Symbiotic N2 fixation (SNF) in legumes such as soybean is of great importance; however, yields may still be limited by N in both high yielding and stressful environments. To better understand the genetic architecture of SNF and facilitate the development of high yielding cultivars and sustainable soybean production in stressful environments, a recombinant inbred line population consisting of 190 lines, developed from a cross between PI 442012A and PI 404199, was evaluated for N derived from the atmosphere (Ndfa), N concentration ([N]), and C to N ratio (C/N) in three environments. Significant genotype, environment and genotype × environment effects were observed for all three traits. A linkage map was constructed containing 3309 single nucleotide polymorphism (SNP) markers. QTL analysis was performed for additive effects of QTLs, QTL × environment interactions, and QTL × QTL interactions. Ten unique additive QTLs were identified across all traits and environments. Of these, two QTLs were detected for Ndfa and eight for C/N. Of the eight QTLs for C/N, four were also detected for [N]. Using QTL × environment analysis, six QTLs were detected, of which five were also identified in the additive QTL analysis. The QTL × QTL analysis identified four unique epistatic interactions. The results of this study may be used for genomic selection and introgression of favorable alleles for increased SNF, [N], and C/N via marker-assisted selection. [ABSTRACT FROM AUTHOR]

SummaryAtmospheric CO2 concentration ([CO2]) and temperature are likely to increase in the future and may change plant growth and composition characteristics. Rhizoma peanut (Arachis glabrata Benth.) and bahiagrass (Paspalum notatum Flügge) were grown on a natural field soil in temperature-gradient greenhouses to evaluate the effects of elevated [CO2] and temperature on tissue composition and digestibility during the establishment year. Carbon dioxide levels were maintained at 365 (ambient) and 640 μL CO2 L–1 air. The temperature-gradient greenhouses were regulated to obtain air temperature sectors of 0.2, 1.5, 2.9, and 4.5 °C above ambient. Samples were taken of previously undefoliated herbage at 57, 86, 121, 148, and 217 days after planting and entire plots were harvested at 218 days after planting. Elevated [CO2] increased total nonstructural carbohydrate concentration in rhizoma peanut leaves by almost 50%. Rhizoma peanut leaf N concentration was 6% lower at elevated than at ambient [CO2]. The N concentration in new rhizomes of rhizoma peanut was increased by high [CO2], while the N concentration in bahiagrass was not affected by temperature or [CO2]. No effects of [CO2] and temperature were found on neutral detergent fibre in rhizoma peanut leaves or stems; however, elevated [CO2] increased neutral detergent fibre in bahiagrass leaves. Only at season end was in vitro organic matter digestion of rhizoma peanut higher at ambient (623 g kg–1) than at elevated [CO2] (609 g kg–1). Elevated [CO2] had a greater effect on tissue composition of rhizoma peanut than of bahiagrass. These data suggest that elevated temperature and CO2-induced changes in chemical composition of forage species adapted to humid subtropics will be relatively small, particularly for C4 species. [ABSTRACT FROM AUTHOR]

AbstractConcerns about climatic change have stimulated interest in the response of plants to increasing CO2 concentration ([CO2]), temperature, and their possible interactions. The purpose of this study was to determine the effects of elevated [CO2] and air temperature on photosynthesis, development, and biomass production of rhizoma peanut (Arachis glabrata Benth.) and bahiagrass (Paspalum notatum Flügge) during the establishment year. Forages were grown in four temperature-gradient greenhouses on a natural Grossarenic Paleudult soil profile at temperatures of 0.2, 1.5, 2.9, and 4.5 °C above ambient, and at [CO2] of 365 and 640 μL CO2 L–1 air. Elevated [CO2] accelerated establishment and ground cover of both species. Leaf and canopy photosynthesis of both species increased at elevated [CO2], with greater increases in rhizoma peanut than bahiagrass. Averaged across five sampling dates, total biomass production of rhizoma peanut and bahiagrass responded to elevated [CO2] with a 52 and 9% increase, respectively. Increasing temperature enhanced biomass production of bahiagrass but not rhizoma peanut. Forage yield at the end of the growing season in CO2-enriched treatments was increased over that in ambient [CO2] treatments (385 vs. 318 g m–2 for rhizoma peanut and 376 vs. 321 g m–2 for bahiagrass). Overall, the enhancement of rhizoma peanut under elevated [CO2] was greater than that of bahiagrass; however, bahiagrass responded more positively to increasing temperature. [ABSTRACT FROM AUTHOR]

Construction economics of plant roots exhibit predictable relationships with root growth, death, and nutrient uptake strategies. Plant taxa with inexpensively constructed roots tend to more precisely explore nutrient hotspots than do those with costly constructed roots but at the price of more frequent tissue turnover. This trade-off underlies an acquisitive to conservative continuum in resource investment, described as the "root economics spectrum (RES)." Yet the adaptive role and genetic basis of RES remain largely unclear. Different ecotypes of switchgrass (Panicum virgatum) display root features exemplifying the RES, with costly constructed roots in southern lowland and inexpensively constructed roots in northern upland ecotypes. We used an outbred genetic mapping population derived from lowland and upland switchgrass ecotypes to examine the genetic architecture of the RES. We found that absorptive roots (distal first and second orders) were often "deciduous" in winter. The percentage of overwintering absorptive roots was decreased by northern upland alleles compared with southern lowland alleles, suggesting a locally-adapted conservative strategy in warmer and acquisitive strategy in colder regions. Relative turnover of absorptive roots was genetically negatively correlated with their biomass investment per unit root length, suggesting that the key trade-off in framing RES is genetically facilitated. We also detected strong genetic correlations among root morphology, root productivity, and shoot size. Overall, our results reveal the genetic architecture of multiple traits that likely impacts the evolution of RES and plant aboveground-belowground organization. In practice, we provide genetic evidence that increasing switchgrass yield for bioenergy does not directly conflict with enhancing its root-derived carbon sequestration. [ABSTRACT FROM AUTHOR]

SUMMARY: Global warming, climate change, and industrial pollution are altering our environment subjecting plants, microbiomes, and ecosystems to an increasing number and complexity of abiotic stress conditions, concurrently or sequentially. These conditions, termed, "multifactorial stress combination" (MFSC), can cause a significant decline in plant growth and survival. However, the impacts of MFSC on reproductive tissues and yield of major crop plants are largely unknown. We subjected soybean (Glycine max) plants to a MFSC of up to five different stresses (water deficit, salinity, low phosphate, acidity, and cadmium), in an increasing level of complexity, and conducted integrative transcriptomic‐phenotypic analysis of their reproductive and vegetative tissues. We reveal that MFSC has a negative cumulative effect on soybean yield, that each set of MFSC condition elicits a unique transcriptomic response (that is different between flowers and leaves), and that selected genes expressed in leaves or flowers of soybean are linked to the effects of MFSC on different vegetative, physiological, and/or reproductive parameters. Our study identified networks and pathways associated with reactive oxygen species, ascorbic acid and aldarate, and iron/copper signaling/metabolism as promising targets for future biotechnological efforts to augment the resilience of reproductive tissues of major crop plants to MFSC. In addition, we provide unique phenotypic and transcriptomic datasets for dissecting the mechanistic effects of MFSC on the vegetative, physiological, and reproductive processes of a crop plant. [ABSTRACT FROM AUTHOR]

The complexity of environmental factors affecting crops in the field is gradually increasing due to climate change-associated weather events, such as droughts or floods combined with heat waves, coupled with the accumulation of different environmental and agricultural pollutants. The impact of multiple stress conditions on plants was recently termed "multifactorial stress combination" (MFSC) and defined as the occurrence of 3 or more stressors that impact plants simultaneously or sequentially. We recently reported that with the increased number and complexity of different MFSC stressors, the growth and survival of Arabidopsis (Arabidopsis thaliana) seedlings declines, even if the level of each individual stress is low enough to have no significant effect on plants. However, whether MFSC would impact commercial crop cultivars is largely unknown. Here, we reveal that a MFSC of 5 different low-level abiotic stresses (salinity, heat, the herbicide paraquat, phosphorus deficiency, and the heavy metal cadmium), applied in an increasing level of complexity, has a significant negative impact on the growth and biomass of a commercial rice (Oryza sativa) cultivar and a maize (Zea mays) hybrid. Proteomics, element content, and mixOmics analyses of MFSC in rice identified proteins that correlate with the impact of MFSC on rice seedlings, and analysis of 42 different rice genotypes subjected to MFSC revealed substantial genetic variability in responses to this unique state of stress combination. Taken together, our findings reveal that the impacts of MFSC on 2 different crop species are severe and that MFSC may substantially affect agricultural productivity. [ABSTRACT FROM AUTHOR]

Summary: Climate change‐driven extreme weather events, combined with increasing temperatures, harsh soil conditions, low water availability and quality, and the introduction of many man‐made pollutants, pose a unique challenge to plants. Although our knowledge of the response of plants to each of these individual conditions is vast, we know very little about how a combination of many of these factors, occurring simultaneously, that is multifactorial stress combination, impacts plants.Seedlings of wild‐type and different mutants of Arabidopsis thaliana plants were subjected to a multifactorial stress combination of six different stresses, each applied at a low level, and their survival, physiological and molecular responses determined.Our findings reveal that, while each of the different stresses, applied individually, had a negligible effect on plant growth and survival, the accumulated impact of multifactorial stress combination on plants was detrimental. We further show that the response of plants to multifactorial stress combination is unique and that specific pathways and processes play a critical role in the acclimation of plants to multifactorial stress combination.Taken together our findings reveal that further polluting our environment could result in higher complexities of multifactorial stress combinations that in turn could drive a critical decline in plant growth and survival. [ABSTRACT FROM AUTHOR]

A combination of drought and heat stress, occurring at the vegetative or reproductive growth phase of many different crops can have a devastating impact on yield. In soybean (Glycine max), a considerable effort has been made to develop genotypes with enhanced yield production under conditions of drought or heat stress. However, how these genotypes perform in terms of growth, physiological responses, and most importantly seed production, under conditions of drought and heat combination is mostly unknown. Here, we studied the impact of water deficit and heat stress combination on the physiology, seed production, and yield per plant of two soybean genotypes, Magellan and Plant Introduction (PI) 548313, that differ in their reproductive responses to heat stress. Our findings reveal that although PI 548313 produced more seeds than Magellan under conditions of heat stress, under conditions of water deficit, and heat stress combination its seed production decreased. Because the number of flowers and pollen germination of PI 548313 remained high under heat or water deficit and heat combination, the reduced seed production exhibited by PI 548313 under the stress combination could be a result of processes that occur at the stigma, ovaries and/or other parts of the flower following pollen germination. [ABSTRACT FROM AUTHOR]

SUMMARY: Global warming and climate change are driving an alarming increase in the frequency and intensity of extreme climate events, such as droughts, heat waves, and their combination, inflicting heavy losses to agricultural production. Recent studies revealed that the transcriptomic responses of different crops to water deficit (WD) or heat stress (HS) are very different from that to a combination of WD + HS. In addition, it was found that the effects of WD, HS, and WD + HS are significantly more devastating when these stresses occur during the reproductive growth phase of crops, compared to vegetative growth. As the molecular responses of different reproductive and vegetative tissues of plants to WD, HS, or WD + HS could be different from each other and these differences could impact many current and future attempts to enhance the resilience of crops to climate change through breeding and/or engineering, we conducted a transcriptomic analysis of different soybean (Glycine max) tissues to WD, HS, and WD + HS. Here we present a reference transcriptomic dataset that includes the response of soybean leaf, pod, anther, stigma, ovary, and sepal to WD, HS, and WD + HS conditions. Mining this dataset for the expression pattern of different stress response transcripts revealed that each tissue had a unique transcriptomic response to each of the different stress conditions. This finding is important as it suggests that enhancing the overall resilience of crops to climate change could require a coordinated approach that simultaneously alters the expression of different groups of transcripts in different tissues in a stress‐specific manner. [ABSTRACT FROM AUTHOR]

[Display omitted] Soybean is a pivotal agricultural commodity around the world, primarily because of its high seed protein and oil concentration. Therefore, farmers, breeders and end-users are highly interested in understanding and predicting the soybean seed composition traits from the individual field level or agroecosystem. Seed composition traits are the proportions of different chemical and physical makeup of soybean seeds. Frequent daily coverage of PlanetScope (PS) satellite provides a unique opportunity of estimating seed composition due to its ability to track crop growth and development with its unique combination of high spatial and temporal resolution. We aim to predict six different soybean seed composition traits (i.e., protein, oil, sucrose, fiber, ash, starch) using PS imagery of standing soybean crops and machine learning algorithms. We developed multi-stream deep neural network which is based on two types of recurrent neural networks, i.e., long short-term memory (LSTM) and gated recurrent unit (GRU) that utilize temporal phenology observed from PS. Four statistical machine learning algorithms, i.e., partial least squares (PLSR), random forest (RFR), gradient boosting machine (GBM), support vector machine (SVR) were used for comparison. Our results show that GRU worked well for protein (R2 0.36, NRMSE 3.62%) and oil (R2 0.53, NRMSE 4.78%), SVR showed the best results for sucrose (R2 0.74, NRMSE 8.34%), fiber (R2 0.21, NRMSE 4.20%), and starch (R2 0.15, NRMSE 16.84%), and PLSR provided the best result for ash (R2 0.60, NRMSE 1.70%). Among the features, vegetation indices at later reproductive stages were found as the most important variables compared to texture features. Overall, the study reveals the feasibility and efficiency of PS images and machine learning for plot-level seed composition estimation. [ABSTRACT FROM AUTHOR]

Nitrogen (N) plays a key role in plants because it is a major component of RuBisCO and chlorophyll. Hence, N is central to both the dark and light reactions of photosynthesis. Genotypic variation in canopy greenness provides insights into the variation of N and chlorophyll concentration, photosynthesis rates, and N2 fixation in legumes. The objective of this study was to identify significant loci associated with the intensity of greenness of the soybean Glycine max (L.) Merr.] canopy as determined by the Dark Green Color Index (DGCI). A panel of 200 maturity group IV accessions was phenotyped for canopy greenness using DGCI in three environments. Association mapping identified 45 SNPs that were significantly (P ≤ 0.0003) associated with DGCI in three environments, and 16 significant SNPs associated with DGCI averaged across all environments. These SNPs likely tagged 43 putative loci. Out of these 45 SNPs, eight were present in more than one environment. Among the identified loci, 21 were located in regions previously reported for N traits and ureide concentration. Putative loci that were coincident with previously reported genomic regions may be important resources for pyramiding favorable alleles for improved N and chlorophyll concentrations, photosynthesis rates, and N2 fixation in soybean. [ABSTRACT FROM AUTHOR]

Stand establishment and early growth are important for successful cotton (Gossypium hirstum L.) production, but in comparison with other crops, cotton seedlings develop slowly after emergence. The objectives of this study were to compare and contrast early vigor of diverse cotton genotypes under greenhouse and field conditions. A total of 144 genotypes were grown in a greenhouse and destructively sampled 34 d after planting (DAP). A range of seedling characteristics including areas and weights of the cotyledons and first, second, and third leaves were determined, and leaf weight ratio, specific leaf area, and leaf area ratio were calculated. Of the 144 genotypes that were grown in the greenhouse, a subset of 40 were selected and planted in the field where plant characteristics were assessed at 17, 27, 35, and 48 DAP. Genotypes differed in shoot and stem dry weights, as well as cotyledon, first, second, and third leaf, and total leaf area, as well as dry weight. A positive correlation of seed weight and rapid early growth as indicated by shoot biomass was observed at 34 DAP in the greenhouse through 48 DAP in the field. Shoot biomass of field‐grown plants sampled at 17, 27, 35, and 48 DAP was positively correlated with the size of the cotyledons and the first leaf measured at 17 DAP, as well as with the seed weight. Further characterization of high‐ and low‐seedling‐vigor genotypes identified in this study may provide insights into the physiological and genetic mechanisms associated with early vigor of cotton. [ABSTRACT FROM AUTHOR]

Low productivity and nutritive value of cool-season perennial forages, such as tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] during summer necessitates the identification of warm-season forages that improve nutritive value and yield of cool-season-based forage systems. A fast-growing, warm-season tropical legume sunn hemp (Crotalaria juncea L.) has the potential to accomplish this. Our objectives were to evaluate herbage accumulation and nutritive value (crude protein [CP], in vitro true digestibility [IVTD], neutral detergent fiber [NDF], acid detergent fiber [ADF], and NDF digestibility [NDFD, 48 h]) of sunn hemp harvested 35, 45, and 55 d after planting (DAP) at 10- and 15-cm heights and to determine regrowth potential when harvested 20 d after each initial harvest over two consecutive years. Sunn hemp herbage accumulation averaged 1.9 and 3.1 Mg ha-1 at 45 and 55 DAP, respectively. Herbage accumulation of initial harvest increased linearly from 35 to 45 to 55 DAP by 119 and 57%, respectively. Herbage accumulation of regrowth after the 35 DAP initial harvest was 262 and 303% greater than the 45 and 55 DAP initial harvests, respectively. Cutting height did not affect (P > 0.05) any variables. The greatest CP (154 g kg-1 dry matter) was observed at 35 DAP and decreased linearly with DAP. Both NDF (P < 0.01) and ADF (P = 0.01) concentrations increased linearly with DAP for both initial and regrowth harvests. The IVTD of initial and regrowth harvests averaged 794 and 624 g kg-1 dry matter, respectively. Forage NDFD for initial and regrowth harvests averaged 487 and 392 g kg-1 NDF, respectively. Nutritive value and herbage accumulation of sunn hemp can be optimized by initially harvesting between 35 and 45 DAP, and leaving at least 10 cm of residue to allow for regrowth. [ABSTRACT FROM AUTHOR]

Climate change is causing an increase in the frequency and intensity of droughts, heat waves, and their combinations, diminishing agricultural productivity and destabilizing societies worldwide. We recently reported that during a combination of water deficit (WD) and heat stress (HS), stomata on leaves of soybean (Glycine max) plants are closed, while stomata on flowers are open. This unique stomatal response was accompanied by differential transpiration (higher in flowers, while lower in leaves) that cooled flowers during a combination of WD + HS. Here, we reveal that developing pods of soybean plants subjected to a combination of WD + HS use a similar acclimation strategy of differential transpiration to reduce internal pod temperature by approximately 4 °C. We further show that enhanced expression of transcripts involved in abscisic acid degradation accompanies this response and that preventing pod transpiration by sealing stomata causes a significant increase in internal pod temperature. Using an RNA-Seq analysis of pods developing on plants subjected to WD + HS, we also show that the response of pods to WD, HS, or WD + HS is distinct from that of leaves or flowers. Interestingly, we report that although the number of flowers, pods, and seeds per plant decreases under conditions of WD + HS, the seed mass of plants subjected to WD + HS increases compared to plants subjected to HS, and the number of seeds with suppressed/aborted development is lower in WD + HS compared to HS. Taken together, our findings reveal that differential transpiration occurs in pods of soybean plants subjected to WD + HS and that this process limits heat-induced damage to seed production. [ABSTRACT FROM AUTHOR]

Switchgrass, a potential biofuel crop, is a genetically diverse species with phenotypic plasticity enabling it to grow in a range of environments. Two primary divergent ecotypes, uplands and lowlands, exhibit trait combinations representative of acquisitive and conservative growth allocation strategies, respectively. Whether these ecotypes respond differently to various types of environmental drivers remains unclear but is crucial to understanding how switchgrass varieties will respond to climate change. We grew two upland, two lowland, and two intermediate/hybrid cultivars of switchgrass at three sites along a latitudinal gradient in the central United States. Over a 4‐year period, we measured plant functional traits and biomass yields and evaluated genotype‐by‐environment (G × E) interaction effects by analyzing switchgrass responses to soil and climate variables. We found substantial evidence of G × E interactions on biomass yield, primarily due to deviations in the response of the southern lowland cultivar Alamo, which produced more biomass in hotter and drier environments relative to other cultivars. While lowland cultivars had the highest potential for yield, their yields were more variable year‐to‐year compared to other cultivars, suggesting greater sensitivity to environmental perturbations. Models comparing soil and climate principal components as explanatory variables revealed soil properties, especially nutrients, to be most effective at predicting switchgrass biomass yield. Also, positive correlations between biomass yield and conservative plant traits, such as high stem mass and tiller height, became stronger at lower latitudes where the climate is hotter and drier, regardless of ecotype. Lowland cultivars, however, showed a greater predisposition to exhibit these conservative traits. These results suggest switchgrass trait allocation trade‐offs that prioritize aboveground biomass production are more tightly associated in hot, dry environments and that lowland cultivars may exhibit a more specialized strategy relative to other cultivars. Altogether, this research provides essential knowledge for improving the viability of switchgrass as a biofuel crop. [ABSTRACT FROM AUTHOR]

Emerging biofuel feedstock systems are well suited for use on less productive marginal soils in the Midwestern USA. The systems could replace commodity crop agriculture that may not be economically feasible on these soils with current input and output prices, and meet a growing renewable energy demand. Three annual bioenergy crops, maize ( Zea mays L.), sweet sorghum ( Sorghum bicolor (L.) Moench), and high biomass sorghum (HBS) were grown in rotation with soybean ( Glycine max L.) for five years on marginal soils at two locations. Maize aboveground dry matter (DM) yield and grain yield, sweet sorghum aboveground DM yield, and juice yield and Brix, and HBS DM yield were evaluated and used to calculate theoretical ethanol yields. Intermittent drought occurred at both sites during three of the five years notably reducing yield; a terminal drought in 2011 reduced sorghum yields and inhibited maize grain development at both sites. Theoretical ethanol yields averaged across years from sweet sorghum and HBS were greater than from maize at both locations, and indicate that sweet sorghum has the greatest yield potential, but HBS yield was the most stable. The central Missouri site maintained greater dry matter yield, and theoretical ethanol yield than the southwestern Missouri site. Due to the occurrence of drought during the study, the findings have relevance for evaluating marginal land management for annual bioenergy crops in differing rainfall patterns with climate change. [ABSTRACT FROM AUTHOR]

Certain cultivars of maize show increased tolerance to water deficit conditions by maintenance of root growth. To better understand the molecular mechanisms related to this adaptation, nodal root growth zone samples were collected from the reference inbred line B73 and inbred line FR697, which exhibits a relatively greater ability to maintain root elongation under water deficits. Plants were grown under various water stress levels in both field and controlled environment settings. FR697-specific RNA-Seq datasets were generated and used for a de novo transcriptome assembly to characterize any genotype-specific genetic features. The assembly was aided by an Iso-Seq library of transcripts generated from various FR697 plant tissue samples. The Necklace pipeline was used to combine a Trinity de novo assembly along with a reference guided assembly and the Viridiplantae proteome to generate an annotated consensus "SuperTranscriptome" assembly of 47,915 transcripts with a N50 of 3152 bp in length. The results were compared by Blastn to maize reference genes, a Benchmarking Universal Single-Copy Orthologs (BUSCO) genome completeness report and compared with three maize reference genomes. The resultant 'SuperTranscriptome' was demonstrated to be of high-quality and will serve as an important reference for analysis of the maize nodal root transcriptomic response to environmental perturbations. [ABSTRACT FROM AUTHOR]

In this paper, a new robotic architecture for plant phenotyping is being introduced. The architecture consists of two robotic platforms: an autonomous ground vehicle (Vinobot) and a mobile observation tower (Vinoculer). The ground vehicle collects data from individual plants, while the observation tower oversees an entire field, identifying specific plants for further inspection by the Vinobot. The advantage of this architecture is threefold: first, it allows the system to inspect large areas of a field at any time, during the day and night, while identifying specific regions affected by biotic and/or abiotic stresses; second, it provides high-throughput plant phenotyping in the field by either comprehensive or selective acquisition of accurate and detailed data from groups or individual plants; and third, it eliminates the need for expensive and cumbersome aerial vehicles or similarly expensive and confined field platforms. As the preliminary results from our algorithms for data collection and 3D image processing, as well as the data analysis and comparison with phenotype data collected by hand demonstrate, the proposed architecture is cost effective, reliable, versatile, and extendable. [ABSTRACT FROM AUTHOR]

The pre-harvest estimation of seed composition from standing crops is imperative for field management practices and plant phenotyping. This paper presents for the first time the potential of Unmanned Aerial Vehicles (UAV)-based high-resolution hyperspectral and LiDAR data acquired from in-season stand crops for estimating seed protein and oil compositions of soybean and corn using multisensory data fusion and automated machine learning. UAV-based hyperspectral and LiDAR data was collected during the growing season (reproductive stage five (R5)) of 2020 over a soybean test site near Columbia, Missouri and a cornfield at Urbana, Illinois, USA. Canopy spectral and texture features were extracted from hyperspectral imagery, and canopy structure features were derived from LiDAR point clouds. The extracted features were then used as input variables for automated machine-learning methods available with the H2O Automated Machine-Learning framework (H2O-AutoML). The results presented that: (1) UAV hyperspectral imagery can successfully predict both the protein and oil of soybean and corn with moderate accuracies; (2) canopy structure features derived from LiDAR point clouds yielded slightly poorer estimates of crop-seed composition compared to the hyperspectral data; (3) regardless of machine-learning methods, the combination of hyperspectral and LiDAR data outperformed the predictions using a single sensor alone, with an R2 of 0.79 and 0.67 for corn protein and oil and R2 of 0.64 and 0.56 for soybean protein and oil; and (4) the H2O-AutoML framework was found to be an efficient strategy for machine-learning-based data-driven model building. Among the specific regression methods evaluated in this study, the Gradient Boosting Machine (GBM) and Deep Neural Network (NN) exhibited superior performance to other methods. This study reveals opportunities and limitations for multisensory UAV data fusion and automated machine learning in estimating crop-seed composition. [ABSTRACT FROM AUTHOR]

Plant function arises from a complex network of structural and physiological traits. Explicit representation of these traits, as well as their connections with other biophysical processes, is required to advance our understanding of plant‐soil‐climate interactions. We used the Terrestrial Regional Ecosystem Exchange Simulator (TREES) to evaluate physiological trait networks in maize. Net primary productivity (NPP) and grain yield were simulated across five contrasting climate scenarios. Simulations achieving high NPP and grain yield in high precipitation environments featured trait networks conferring high water use strategies: deep roots, high stomatal conductance at low water potential ("risky" stomatal regulation), high xylem hydraulic conductivity and high maximal leaf area index. In contrast, high NPP and grain yield was achieved in dry environments with low late‐season precipitation via water conserving trait networks: deep roots, high embolism resistance and low stomatal conductance at low leaf water potential ("conservative" stomatal regulation). We suggest that our approach, which allows for the simultaneous evaluation of physiological traits, soil characteristics and their interactions (i.e., networks), has potential to improve our understanding of crop performance in different environments. In contrast, evaluating single traits in isolation of other coordinated traits does not appear to be an effective strategy for predicting plant performance. Our process‐based model uncovered two beneficial but contrasting trait networks for maize which can be understood by their integrated effect on water use/conservation. Modification of multiple, physiologically aligned, traits were required to bring about meaningful improvements in NPP and yield. [ABSTRACT FROM AUTHOR]

Key message: We investigate the genetic basis of panicle architecture in switchgrass in two mapping populations across a latitudinal gradient, and find many stable, repeatable genetic effects and limited genetic interactions with the environment. Grass species exhibit large diversity in panicle architecture influenced by genes, the environment, and their interaction. The genetic study of panicle architecture in perennial grasses is limited. In this study, we evaluate the genetic basis of panicle architecture including panicle length, primary branching number, and secondary branching number in an outcrossed switchgrass QTL population grown across ten field sites in the central USA through multi-environment mixed QTL analysis. We also evaluate genetic effects in a diversity panel of switchgrass grown at three of the ten field sites using genome-wide association (GWAS) and multivariate adaptive shrinkage. Furthermore, we search for candidate genes underlying panicle traits in both of these independent mapping populations. Overall, 18 QTL were detected in the QTL mapping population for the three panicle traits, and 146 unlinked genomic regions in the diversity panel affected one or more panicle trait. Twelve of the QTL exhibited consistent effects (i.e., no QTL by environment interactions or no QTL × E), and most (four of six) of the effects with QTL × E exhibited site-specific effects. Most (59.3%) significant partially linked diversity panel SNPs had significant effects in all panicle traits and all field sites and showed pervasive pleiotropy and limited environment interactions. Panicle QTL co-localized with significant SNPs found using GWAS, providing additional power to distinguish between true and false associations in the diversity panel. [ABSTRACT FROM AUTHOR]

Summary: Heat waves occurring during droughts can have a devastating impact on yield, especially if they happen during the flowering and seed set stages of the crop cycle. Global warming and climate change are driving an alarming increase in the frequency and intensity of combined drought and heat stress episodes, critically threatening global food security.Because high temperature is detrimental to reproductive processes, essential for plant yield, we measured the inner temperature, transpiration, sepal stomatal aperture, hormone concentrations and transcriptomic response of closed soybean flowers developing on plants subjected to a combination of drought and heat stress.Here, we report that, during a combination of drought and heat stress, soybean plants prioritize transpiration through flowers over transpiration through leaves by opening their flower stomata, while keeping their leaf stomata closed. This acclimation strategy, termed 'differential transpiration', lowers flower inner temperature by about 2–3°C, protecting reproductive processes at the expense of vegetative tissues.Manipulating stomatal regulation, stomatal size and/or stomatal density of flowers could serve as a viable strategy to enhance the yield of different crops and mitigate some of the current and future impacts of global warming and climate change on agriculture. [ABSTRACT FROM AUTHOR]

Increasing demand for high-yielding, alternative biofuel feedstocks elicits the need to fully understand sweet sorghum ( Sorghum bicolor (L.) Moench) yield response to varying nitrogen (N) fertilization rates in the U.S. Midwest. The objective of this three-year study was to determine the optimum N fertilization rates for the production of two common sweet sorghum cultivars (Dale and Top 76-6) in central Missouri. Five N rates (0, 56, 112, 168, 224 kg N ha −1 ) were imposed and tested for their effects on dry matter yield, stem juice yield, Brix, fermentable sugar yield, theoretical juice ethanol yield, theoretical lignocellulosic ethanol yield, and total theoretical ethanol yield. Except for Brix, N treatment significantly influenced all yield parameters in all three years. The two varieties yielded similarly across most measured parameters. Total dry matter yields averaged 16.8 Mg ha −1 , juice yields averaged 9113 L ha −1 , and fermentable sugar yields averaged 1055 kg ha −1 across years and varieties. Total ethanol yields averaged 7488 L ha −1 and were highest at 168 kg N ha −1 across the three years, indicating that sweet sorghum in Missouri may reach maximum yields near that fertilization rate. Annual precipitation and temperature differences greatly influenced dry matter, stem juice, and sugar yields, thereby affecting theoretical ethanol yields, such that yields were lower in years with less rainfall and lower temperatures, which also limited the N response in these years. [ABSTRACT FROM AUTHOR]

Corn ( Zea mays L.) grain composition is important for human and livestock nutrition, when used as seed, and for ethanol production. However, few studies have evaluated the effects of common cultural practices on corn grain composition. This study was conducted to determine whether corn grain elemental composition is affected by tillage practices (tillage or no-tillage), and whether tillage affects grain, protein, and oil yield, and removal of elements from the field in grain. The concentration of protein, oil, P, K, Ca, Mg, Mn, Fe, Zn, Cu, and B, and grain yield were determined in years 20 and 22 of long-term tillage and no-tillage treatments. Tillage treatment did not affect any grain component across both years of sampling, but Cu concentrations were greater under no-tillage in one year. Grain, oil, and protein yield was not affected by tillage treatments across years, but was greater one year under tillage and one year under no-till. The removal of P and Fe was greater under tillage in 2010, and that of Ca and Mn was greater under no-till in 2012. Removal of Cu was greater one year under tillage and one year under no-tillage. Correlation and principle components analysis suggests that there are some differences in the relationships among the grain components between tillage treatments. However, results indicate that tillage is not a dominant factor affecting corn grain composition and removals of nutrients are dominated by grain yield and not the concentration in the grain. [ABSTRACT FROM AUTHOR]

Aims: Urea is the most commonly used N fertilizer worldwide, but can easily volatilize as ammonia and be lost from the soil. Enhanced Efficiency Fertilizers (EEFs) have been developed to increase nutrient use efficiency, reduce N losses, and increase crop yield. Methods: The efficacy of different EEF urea technologies was compared to untreated urea when surface applied to no-till maize (Zea mays L.) in three field seasons. Treatments included untreated urea, urea-ammonium nitrate (UAN), polymer-coated urea (ESN and Duration), urea treated with urease inhibitors (Agrotain) and urea treated with both urease and nitrification inhibitors (Nutrisphere and SuperU). Ammonia volatilization, soil nitrogen content and maize yield were determined in order to evaluate EEFs. Results: Volatilization losses, measured for 25 days after fertilization (DAF) in the first year, and 25 and 82 DAF in the second and third year, differed among products and years. Polymer-coated urea and urea treated with urease inhibitor effectively reduced ammonia volatilization peaks and resulted in a consequent decrease of ammonia losses at 25 DAF and 82 DAF in most years. The double inhibitor-treated urea (Nutrisphere and SuperU) showed similar ammonia losses as untreated urea. Overall, EEFs maintained maize grain yield produced with untreated urea, except for one polymer-coated urea product which increased yields. Conclusions: The efficacy of EEF in mitigating NH3 losses varied with precipitation and other environmental conditions. We found that the polymer-coated urea presented the best performance reducing ammonia losses and maintaining or even increasing maize grain yields in this study. [ABSTRACT FROM AUTHOR]

Polyploidy results from whole-genome duplication and is a unique form of heritable variation with pronounced evolutionary implications. Different ploidy levels, or cytotypes, can exist within a single species, and such systems provide an opportunity to assess how ploidy variation alters phenotypic novelty, adaptability, and fitness, which can, in turn, drive the development of unique ecological niches that promote the coexistence of multiple cytotypes. Switchgrass, Panicum virgatum, is a widespread, perennial C4 grass in North America with multiple naturally occurring cytotypes, primarily tetraploids (4×) and octoploids (8×). Using a combination of genomic, quantitative genetic, landscape, and niche modeling approaches, we detect divergent levels of genetic admixture, evidence of niche differentiation, and differential environmental sensitivity between switchgrass cytotypes. Taken together, these findings support a generalist (8×)-specialist (4×) trade-off. Our results indicate that the 8× represent a unique combination of genetic variation that has allowed the expansion of switchgrass' ecological niche and thus putatively represents a valuable breeding resource. [ABSTRACT FROM AUTHOR]

Soybean (Glycine max [L.] Merr.) grain composition determines its uses, nutritional quality, value, and the amount of nutrients removed from agricultural ecosystems. Yet few studies have evaluated the effects of annual farming practices on composition. This study was conducted to determine whether soybean grain composition is altered by farming practices and how these practices impact yield and nutrient removal. The effects of long-term cropping systems (continuous soybean or soybean in rotation with corn (Zea mays L.), both tilled and no-till) on yield and concentrations of grain protein, oil, and nine mineral components, after 20 and 22 years of continuous management, were determined. Grain yield, protein, K, Zn, B, and Cu concentrations differed among cropping systems in both years while Mn concentration differed in one of two years. Oil, P, Ca, Mg, and Fe concentrations did not differ among cropping systems in either year, but across both years mean Fe concentration was affected. Differences in K, Fe, and Zn concentrations were mostly attributed to tillage each year, while those in protein and Cu concentrations were mostly attributed to rotation each year. Distinct B concentrations were attributed to tillage while distinct Mn concentrations were attributed to rotation. Grain yield differences were attributable to both rotation and tillage each year. In most instances, oil and protein yield, and mineral removal were dominated by grain yield differences and not concentration. Nonetheless, long-term tillage and rotation greatly affected soybean grain composition. Thus, rotation and tillage should be accounted for when assessing seed quality and seed composition. [ABSTRACT FROM AUTHOR]

Highlights: [•] Diurnal response of maize photosynthesis, nonstructural carbohydrates and ear dry matter were examined in response to N. [•] Nitrogen application increased plant N uptake, yield, leaf area, chlorophyll content, and soluble protein concentration. [•] Nitrogen application increased photosynthetic rates only during periods of high light intensities in the diurnal cycle. [•] Clear diurnal pattern of leaf sucrose and starch concentrations were found. [Copyright &y& Elsevier]

Nitrogen (N) limitation reduces leaf growth and photosynthetic rates of maize ( Zea mays), and constrains photosynthate translocation to developing ears. Additionally, the period from about 1 week before to 2 weeks after silking is critical for establishing the reproductive sink capacity necessary to attain maximum yield. To investigate the influence of carbohydrate availability in plants of differing N status, a greenhouse study was performed in which exogenous sucrose (Suc) was infused around the time of silking into maize stems grown under different N regimes. N deficiency significantly reduced leaf area, leaf longevity, leaf chlorophyll content and photosynthetic rate. High N-delayed leaf senescence, particularly of the six uppermost leaves, compared to the other two N treatments. While N application increased ear leaf soluble protein concentration, it did not influence glucose and suc concentrations. Interestingly, ear leaf starch concentration decreased with increasing N application. Infusion of exogenous suc tended to increase non-structural carbohydrate concentrations in the developing ears of all N treatments at silking and 6 days after silking. However, leaf photosynthetic rates were not affected by suc infusion, and suc infusion failed to increase grain yield in any N treatment. The lack of an effect of suc infusion on ear growth and the high ear leaf starch concentration of N-deficient maize, suggest that yield reduction under N deficiency may not be due to insufficient photosynthate availability to the developing ear during silking, and that yield reduction under N deficiency may be determined at an earlier growth stage. [ABSTRACT FROM AUTHOR]

Recently, sweet sorghum [Sorghum bicolor (L) Moench] has garnered renewed attention as a promising feedstock for ethanol production. A byproduct of this is bagasse, which is sweet sorghum stalks remaining after juice extraction. It is possible that sweet sorghum bagasse could provide a source of livestock feed and that its nutritive value could be increased by ammoniation. Ammoniation refers to the treatment of lowquality forages with NH3 to improve crude protein concentration, digestibility, and animal intake. The main objective of this study was to evaluate sweet sorghum bagasse as a livestock feed and determine the effect of ammoniation on in vitro true digestibility (IVTD) and crude protein (CP) of sweet sorghum bagasse. In vitro true digestibility and CP were determined on bagasse of 12 sweet sorghum cultivars grown in three environments and treated with and without anhydrous NH3 (39.0 g kg-1). Across environments, ammoniation increased bagasse IVTD from a mean of 731 g kg-1 dry matter (DM) to a mean of 750 g kg-1 DM, but IVTD of bagasse from only two of three environments was increased. Crude protein averaged 117 g kg-1 DM for ammoniated samples compared to 26 g kg-1 DM for nontreated samples. Ammoniation increased CP in every cultivar and in every environment. Sweet sorghum bagasse IVTD and CP characteristics combined with large yields indicate that this byproduct could serve as livestock feed and merits further investigation. [ABSTRACT FROM AUTHOR]

The article discusses a study which investigated the effects of different light intensities on biomass production and nitrogen concentration and nodule number and nodule biomass of Desmodium canescens, Desmodium canadense, and Desmodium illinoense. The species were grown in N-free media while supplying N-free nutrient solution as required by the study. Among the findings were the variations in legume species in dry weight and number of nodules produced.

The article investigates the effects of three different light intensities, namely 100%, 45% and 20% on biomass production and nitrogen concentration, and nodule number and nodule biomass of three native legume species, including Desmodium canescens, Desmodium canadense and Desmodium illinoense. It relates the features of the greenhouse experiment. It has revealed that these native legumes grow as well at 45% light as they do at 100% light.

Nitrogen supplied by N2 fixation to soybean [Glycine max (L.) Merr.] may not be sufficient to maximize yield. Field studies were conducted in 2002, 2003, and 2004 on Sharkey clay soil (very-fine, smectitic, thermic Chromic Epiaquert) at Stoneville, MS (33°26′ N lat). The objective was to determine the effect of high rates of N applied as a replacement for N2 fixation in nonirrigated and irrigated environments. Eight cultivars ranging from Maturity Group II to IV were planted on 17 Apr. 2002, 2 Apr. 2003, and 25 Mar. 2004. Not all cultivars were evaluated in all 3 yr. Glyphosate herbicide was used in all 3 yr and a non-glyphosate herbicide treatment was applied in 2002. Cultivars grown in 2003 were also evaluated under an application of 21.3 kg ha-1 of Mn. All cultivar, herbicide, and Mn treatments were evaluated in irrigated and nonirrigated environments with fertilizer N (PlusN treatment) or without fertilizer N (ZeroN treatment). In the PlusN treatment, granular NH4NO3 was surface applied at soybean emergence at rates of 290 kg ha-1 in 2002, 310 kg ha-1 in 2003, and 360 kg ha-1 in 2004. When analyzed over all management practices (years, cultivars, herbicide, and Mn treatments), the PlusN treatment resulted in significantly decreased ureide concentration (57.2 and 53.5% reduction) and significantly increased biomass accumulation (14.1 and 16.7%), N accumulation (12.8 and 28.1%), and seed yield (7.7 and 15.5%) for the irrigated and nonirrigated environments, respectively. The majority of the yield increase in each environment resulted from increased number of seed (9.5% irrigated and 16.2% nonirrigated). These results confirm the sensitivity of N2 fixation to drought and indicate that N2 fixation may limit yield of soybean grown in both irrigated and nonirrigated environments of the midsouthern USA, and that N2 fixation deficiencies occur before the beginning of processes that determine number of seed. [ABSTRACT FROM AUTHOR]

Ionomics measures elemental concentrations in biological organisms and provides a snapshot of physiology under different conditions. In this study, we evaluate genetic variation of the ionome in outbred, perennial switchgrass in three environments across the species' native range, and explore patterns of genotype-by-environment interactions. We grew 725 clonally replicated genotypes of a large full sib family from a four-way linkage mapping population, created from deeply diverged upland and lowland switchgrass ecotypes, at three common gardens. Concentrations of 18 mineral elements were determined in whole post-anthesis tillers using ion coupled plasma mass spectrometry (ICP-MS). These measurements were used to identify quantitative trait loci (QTL) with and without QTL-by-environment interactions (QTLxE) using a multi-environment QTL mapping approach. We found that element concentrations varied significantly both within and between switchgrass ecotypes, and GxE was present at both the trait and QTL level. Concentrations of 14 of the 18 elements were under some genetic control, and 77 QTL were detected for these elements. Seventy-four percent of QTL colocalized multiple elements, half of QTL exhibited significant QTLxE, and roughly equal numbers of QTL had significant differences in magnitude and sign of their effects across environments. The switchgrass ionome is under moderate genetic control and by loci with highly variable effects across environments. [ABSTRACT FROM AUTHOR]

Background: Carbon (C) and nitrogen (N) assimilate availability and their ratios are crucial for maize grain production and N‐use efficiency. Aim: Our aim was to give a mechanistic understanding of yield formation regulated by assimilate C:N balance during both early ear development and rapid grain filling. Methods: Maize was grown under field conditions with 0, 200, and 300 kg N ha−1 (referred to as N0, N200, and N300, respectively). Ear growth, grain yield, and dynamics of total C and N accumulation in ear leaves, cobs, and developing kernels (apical and basal proportions separated from the longitudinally middle of ear) were investigated, as well as the non‐structural carbohydrates and free amino acids. Results: Compared to N‐sufficient plants, low‐N plants contained 16% to 70% less N and 8% to 50% less C in the developing kernels, causing 43% to 52% yield losses, which indicated that low‐N kernels received less amino acid per unit sugar from the maternal plants. This was supported by lower concentrations of the main N transport molecules (glutamine and asparagine) in ear leaves at silking and 21 days after silking (DAS) coupled with the larger amounts of C accumulated as starch under N deficient compared to adequate N supply. Nitrogen treatment did not influence the concentrations of total free amino acids and soluble protein in the cob, neither at silking nor 21 DAS, but it did influence cob free amino acid composition. Compared to the adequate N supply, low‐N plants contained 75% and 57% less glutamine and asparagine in apical kernels at silking, as well as 36% and 31% less in basal kernels. Free amino acid concentrations in both cob and kernels were less responsive to N treatments at 21 DAS than at silking, especially in the basal ear halves. Conclusion: Maize grain production under low‐N environment can be more attributed to the balance in assimilate composition, particularly the amino acid profile, than the C‐assimilate availability for ear growth and development. [ABSTRACT FROM AUTHOR]

Agricultural management at field-scale is critical for improving yield to address global food security, as providing enough food for the world's growing population has become a wicked problem for both scientists and policymakers. County- or regional-scale data do not provide meaningful information to farmers who are interested in field-scale yield forecasting for effective and timely field management. No studies directly utilized raw satellite imagery for field-scale yield prediction using deep learning. The objectives of this paper were twofold: (1) to develop a raw imagery-based deep learning approach for field-scale yield prediction, (2) investigate the contribution of in-season multitemporal imagery for grain yield prediction with hand-crafted features and WorldView-3 (WV) and PlanetScope (PS) imagery as the direct input, respectively. Four WV-3 and 25 PS imagery collected during the growing season of soybean were utilized. Both 2-dimensional (2D) and 3-dimensional (3D) convolution neural network (CNN) architectures were developed that integrated spectral, spatial, temporal information contained in the satellite data. For comparison, hundreds of carefully selected spectral, spatial, textural, and temporal features that are optimal for crop growth monitoring were extracted and fed into the same deep learning model. Our results demonstrated that (1) deep learning was able to predict yield directly using raw satellite imagery to the extent that was comparable to feature-fed deep learning approaches; (2) both 2D and 3D CNN models were able to explain nearly 90% variance in field-scale yield; (3) limited number of WV-3 outperformed multi-temporal PS data collected during entire growing season mainly attributed to RedEdge and SWIR bands available with WV-3; and (4) 3D CNN increased the prediction power of PS data compared to 2D CNN due to its ability to digest temporal features extracted from PS data. [ABSTRACT FROM AUTHOR]

Nutrient uptake is critical for crop growth and is determined by root foraging in soil. Growth and branching of roots lead to effective root placement to acquire nutrients, but relatively little is known about absorption of nutrients at the root surface from the soil solution. This knowledge gap could be alleviated by understanding sources of genetic variation for short-term nutrient uptake on a root length basis. A modular platform called RhizoFlux was developed for high-throughput phenotyping of multiple ion-uptake rates in maize (Zea mays L.). Using this system, uptake rates were characterized for the crop macronutrients nitrate, ammonium, potassium, phosphate, and sulfate among the Nested Association Mapping (NAM) population founder lines. The data revealed substantial genetic variation for multiple ion-uptake rates in maize. Interestingly, specific nutrient uptake rates (nutrient uptake rate per length of root) were found to be both heritable and distinct from total uptake and plant size. The specific uptake rates of each nutrient were positively correlated with one another and with specific root respiration (root respiration rate per length of root), indicating that uptake is governed by shared mechanisms. We selected maize lines with high and low specific uptake rates and performed an RNA-seq analysis, which identified key regulatory components involved in nutrient uptake. The high-throughput multiple ion-uptake kinetics pipeline will help further our understanding of nutrient uptake, parameterize holistic plant models, and identify breeding targets for crops with more efficient nutrient acquisition. [ABSTRACT FROM AUTHOR]