Risk Of Lodging Research Articles

Spelt Wheat: An Alternative for Sustainable Plant Production at Low N-Levels

Sustainable agriculture strives for maintaining or even increasing productivity, quality and economic viability while leaving a minimal foot print on the environment. To promote sustainability and biodiversity conservation, there is a growing interest in some old wheat species that can achieve better grain yields than the new varieties in marginal soil and/or management conditions. Generally, common wheat is intensively studied but there is still a lack of knowledge of the competitiveness of alternative species such as spelt wheat. The aim is to provide detailed analysis of vegetative, generative and spectral properties of spelt and common wheat grown under different nitrogen fertiliser levels. Our results complement the previous findings and highlight the fact that despite the lodging risk increasing together with the N fertiliser level, spelt wheat is a real alternative to common wheat for low N input production both for low quality and fertile soils. Vitality indices such as flag leaf chlorophyll content and normalized difference vegetation index were found to be good precursors of the final yield and the proposed estimation equations may improve the yield forecasting applications. The reliability of the predictions can be enhanced by including crop-specific parameters which are already available around flowering, beside soil and/or weather parameters.

Experiments and FE-analysis of 2-D root-soil contact problems based on node-to-segment approach

Accurate predictions of the mechanical response of root-soil systems are required for assessing and reducing the risk of landslides, surface erosions, and lodging. The present paper proposes the use of the node-to-segment (NTS) approach with the finite element method for predicting contact phenomena between roots and soils, such as collision, sliding, and separation. To obtain reliable predictions for the deformation of such geometrically complex problems, a stabilizing algorithm within the NTS approach is proposed and implemented here. The proposed algorithm prevents the well-known non-uniqueness problem of the pairing algorithm in the NTS approach, which has been an obstacle to applying the approach to root-soil systems. The current method is employed for two numerical examples. The first is an example of validation, in which pullout experiments are re-analyzed to examine the applicability of the method to a geometrically simple root-soil contact problem. It is shown that the current method provides a reasonable prediction of the pullout response, and that both the friction and the cohesion can also be accurately estimated with it. The second is an example of a realistic problem, in which a 2-D lodging experiment, analogous to pile-loading problems, is conducted and simulated to demonstrate the accuracy and applicability of the NTS approach in plant-scale problems with complex root geometries. The relationship between the displacement and the reaction force of the simulation is consistent with that of the experiment, and it enables the visualization of the stress contour and deformation of the rhizosphere.

Impact of Nitrogen Regimes and Planting Densities on Stem Physiology, Lignin Biosynthesis and Grain Yield in Relation to Lodging Resistance in Winter Wheat (Triticum aestivum L.)

Higher plant population and nitrogen management is an adopted approach for improving crop productivity from limited land resources. Moreover, higher plant density and nitrogen regimes may increase the risk of stalk lodging, which is a consequence of complex interplant competition of individual organs. Here, we aimed to investigate the dynamic change in morphology, chemical compositions and lignin promoting enzymes of the second basal inter-nodes altering lodging risk controlled by planting density and nitrogen levels. A field trial was conducted at the Mengcheng research station (33°9′44″N, 116°32′56″E), Huaibei plain, Anhui province, China. A randomized complete block design was adopted, in which four plant densities, i.e., 180, 240, 300, and 360 × 104 ha−1 and four N levels, i.e., 0, 180, 240, and 300 kg ha−1 were studied. The two popular wheat varieties AnNong0711 and YanNong19 were cultivated. Results revealed that the culm lodging resistance (CLRI) index of the second basal internodes was positively and significantly correlated with light interception, lignin and cellulose content. The lignin and cellulose contents were significantly and positive correlated to light interception. The increased planting density and nitrogen levels declined the lignin and its related enzymes activities. The variety AnNong0711 showed more resistive response to lodging compared to YanNong19. Overall our study found that increased planting densities and nitrogen regimes resulted in poor physical strength and enzymatic activity which enhanced lodging risk in wheat varieties. The current study demonstrated that stem bending strength of the basal internode was significantly positive correlated to grains per spike. The thousand grain weight and grain yield had a positive and significant relationship with stem bending strength of the basal internode. The results suggested that the variety YanNong19 produces higher grain yield (9298 kg ha−1) at density 240 × 104 plants ha−1, and 180 kg ha−1 nitrogen, while AnNong0711 produced higher grain yield (10178.86 kg ha−1) at density 240 × 104 plants ha−1 and with 240 kg ha−1 nitrogen. Moreover, this combination of nitrogen and planting density enhanced the grain yield with better lodging resistance.

Ways to Increase Camelina (Camelina Sativa (L.) Crantz) Productivity in Russia’s Nonchernozem Zone

Abstract—In the nonchernozem zone of Russia, including the Ryazan oblast, spring camelina is a minor crop like other oilseeds, such as flax, rape, and mustard species. Expansion of this crop is constrained by lack of exhaustive recommendations on its cultivation technology. The aims were to study the productivity characteristics of the Yubilar spring camelina variety and to optimize the main elements of the variety-specific technology (seeding rate and sowing time) for obtaining high and stable yields of oilseeds in this region. The research was conducted at the Kostychev Ryazan State Agrotechnological University on the experimental fields of the Agrotechnopark Education and Scientific Innovation Center in Ryazan raion of Ryazan oblast on gray forest soils. To obtain stable sustainable yields of spring camelina, the crop density at harvesting time should be at least 420 plants/m2, while the optimal density is 400–450 plants m–2. Increasing the seeding rate above 8 million units of viable seeds per 1 ha led to a very dense crop stand, which led to a decrease in both yield and quality of seeds. The seeding rate of 7.0 million viable seeds per 1 ha should be considered optimal for spring camelina. Increasing the rate up to 8.0 million units per 1 ha did not significantly enhance crop productivity but caused an excessive seed discharge, while deteriorating the sprouting quality and increasing the risk of lodging and diseases. The best sowing period in our experiments was the first decade of May.

Management of nitrogen fertilization to balance reducing lodging risk and increasing yield and protein content in spring wheat

Crop lodging (stem and root lodging) is one of the main constraints limiting grain yield and quality in spring wheat production, especially under high–yielding conditions. Few studies have been conducted to clarify the trade–off between grain yield and lodging resistance, and assess whether it is possible to manage lodging risk without a yield reduction penalty. Developing appropriate nitrogen (N) fertilizer management strategies for driving grain yield/quality while reducing (or at least not increasing) the risk of lodging is needed to achieve this. The risks of stem and root lodging were quantified by “safety factor” (SF) indicator, which represents the number of times a support organ can bear the self–weight moment of the organ that it is supporting. Two varieties with contrasting stature (tall vs. semi–dwarf), were tested under different timing and rates of N application strategies. The advantage of split–N (preplant plus top–dress application at the jointing stage) over equivalent preplant–only N application was not evidenced on yield, but grain protein (%) was improved by up to 7.5% without a yield penalty. The risk of lodging was increased with increasing N rates from zero to the highest N treatment, as indicated by decreasing stem safety factor SFs (–23.7%) and root safety factor SFr (–32.2%) across both years, and increasing visual lodging score (by 7–fold) in 2017. The split–N treatment N50 + 50 (50 kg N ha–1 at preplant plus 50 kg N ha–1 at jointing stage) showed a promising lodging resistance with SFs, SFr and visual lodging scores similar to the zero N treatment. Taken together, the moderate split–N application (N50 + 50) is recommended due to the relative high grain protein (%) and strong lodging resistance while sustaining a promising yield. Spring wheat was more susceptible to root lodging than to stem lodging in the specific conditions of these experiments. Additionally, breeding for and cultivation with cultivars with improved stem strength is likely to be required to counter the escalating lodging risk arising from continued yield increases.

Ethephon Improved Stalk Strength of Maize (Zea Mays L.) Mainly through Altering Internode Morphological Traits to Modulate Mechanical Properties under Field Conditions

Stalk strength is critical for reducing maize stalk lodging and maintaining grain yield. Ethephon has been widely applied to molding compact plant-type to reduce the lodging risk in maize production. However, there is little information on how ethephon regulates internode mechanical properties to improve maize stalk strength. Multiyear field experiments (2013–2017) were conducted to determine the effects of foliar-applied ethephon on summer maize internode morphological, chemical and mechanical characteristics. The hypothetical structural equation model was used to analyze the contribution of ethephon-induced changes of internode morphological and chemical traits to stalk mechanical strength. Ethephon significantly reduced the basal internode length, while increasing internode diameters and breaking resistance. Meanwhile, ethephon significantly increased the ratio of structural dry matter to total dry matter and the amount of structural dry matter per unit length and volume. Mechanical assays suggested that ethephon significantly altered geometric properties and increased the maximum bending moment, maximum failure force, while depressing the material properties. Furthermore, correlation and path analyses revealed strong correlations and significant contribution of internode morphological properties to stalk mechanical strength, respectively. These results support the conclusion that ethephon-induced morphology alteration played a major role in improving maize internode strength.

Remote sensing-based crop lodging assessment: Current status and perspectives

Rapid and quantitative assessment of crop lodging is important for understanding the causes of the phenomena, improving crop management, making better production and supporting loss estimates in general. Accurate information on the location and timing of crop lodging is valuable for farmers, agronomists, insurance loss adjusters, and policymakers. Lodging studies can be performed to assess the impact of lodging events or to model the risk of occurrence, both of which rely on information that can be acquired by field observations, from meteorological data and from remote sensing (RS). While studies applying RS data to assess crop lodging dates back three decades, there has been no comprehensive review of the status, potential, current approaches, and challenges in this domain. In this position paper, we review the trends in field/lab-based and RS-based studies for crop lodging assessment and discuss the strengths and weaknesses of current approaches. Theoretical background on crop lodging is presented, and the scope of RS in assessing plant characteristics associated with lodging is reviewed and discussed. The review focuses on RS-based studies, grouping them according to the platform deployed (i.e., ground-based, airborne and spaceborne), with an emphasis on analyzing the pros and cons of the technology. Finally, the challenges, research gaps, perspectives for future research, and an outlook on new sensors and platforms are presented to provide state-of-the-art and future scenarios of RS in lodging assessment. Our review reveals that the use of RS techniques in crop lodging assessment is still in an experimental stage. However, there is increasing interest within the RS scientific community (based on the increased rate of publications over time) to investigate its use for crop lodging detection and risk mapping. The existing satellite-based lodging assessment studies are very few, and the operational application of the current approaches over large spatial extents seems to be the biggest challenge. We identify opportunities for future studies that can develop quantitative models for estimating lodging severity and mapping lodging risk using RS data.

Use of EDAH Improves Maize Morphological and Mechanical Traits Related to Lodging

Core Ideas Use of EDAH decreased maize lodging across plant densities. EDAH increased strength, thickness and lignin content of internodes. The use of EDAH lowered ear position and leaf area above the ear. Use of EDAH lowered leaf angle so more leaves were erect. Lodging in maize (Zea mays L.) is a major constraint to crop yield and quality, especially at high plant densities. A novel growth regulator EDAH, which contains ethephon and diethyl aminoethyl hexanoate (DA‐6), has been recently introduced in maize cultivation in China to alleviate lodging and yield loss. In this study, we aimed to identify how lodging‐relevant morphological and mechanical traits of two maize genotypes respond to EDAH at different plant densities. Two maize hybrids (Zhengdan 958 and Pioneer 335) were compared in treatments with or without EDAH at plant densities of 4.5, 6.0, 7.5 and 9.0 plants m−2. Lodging percentage was increased at higher plant density in both varieties due to weaker stems and taller plants. The use of EDAH significantly decreased lodging by increasing stem breaking strength, associated with larger stem diameter and higher stem cellulose and lignin contents compared with untreated check. The moment of the wind force on the plant was reduced by the use of EDAH as a result of lower ear positions, more erect leaves, smaller top leaf areas, and shorter internodes. At low plant density, the reduction of lodging by EDAH was mainly due to morphological changes, while at high plant density, the reduction in lodging was mainly due to improved stem breaking strength. We conclude that EDAH reduces lodging risk through the improvement of both morphological and mechanical plant traits and that these effects are expressed across a range of plant densities. The results help to better understand the mechanism of lodging‐yield relationships.

Effect of change from a determinate to a semi-determinate growth habit on the yield and lodging resistance of soybeans in the northeast region of Japan.

Although an indeterminate growth habit is attractive to develop high-yield soybean varieties with higher number of pods (Glycine max (L). Merr.), lodging in indeterminate varieties remains a problem in Japan. As the semi-determinate varieties have shorter main stem length than the indeterminate varieties, this trait can be useful to improve varieties with high yield and low lodging risk. We introduced the genes Dt1 and Dt2, which regulate stem growth habit, into three determinate varieties by backcrossing and evaluated the resulting effects on yield and lodging tendency under four different growing environments. The yield and lodging degree of the semi-determinate and indeterminate lines were higher and more severe than those of the determinate lines. Despite the lower overall lodging score, the semi-determinate lines had marginally lower overall yield than that of the indeterminate lines. However, the effect of introduction of semi-determinate traits on yield and lodging degree was different in the three backgrounds, with the yield of semi-determinate lines being the highest and the difference in lodging degree between the semi-determinate and determinate lines being under 1.0 in one background. Therefore, semi-determinate growth habit has potential to develop high yielding varieties with low lodging risk.

Asset-light strategy and real estate risk of lodging C−corps and REITs

The asset-light strategy has been gaining popularity among practitioners for its virtues in lowering capital investment burden and allowing efficient expansion. Meanwhile, arguably the greatest advantage of the strategy—a mitigating effect on the real estate risk exposure—has yet to be validated. To empirically test this effect, this study adopts a comparative approach, utilizing data on both lodging C-corporations and real estate investment trusts (REITs). Yearly firm-level real estate betas are estimated through an augmented Fama-French asset-pricing model for all lodging firms and REITs between the years 2002–2016, and further used for a second-stage analysis on their relationship with real estate ownership and liquidity. Findings reveal that 1) lodging firms are significantly less exposed to real estate risk than REITs, 2) lodging firms may still be conditionally exposed to real estate risk under liquidity constraints, and 3) certain unique characteristics of REITs render differences in the effects of liquidity.

Characterization of the Effect of Increased Plant Density on Canopy Morphology and Stalk Lodging Risk.

Plants react to the environment and to management interventions by undergoing architectural and structural modifications. A field trial was conducted in China in 2016 to study the effects of the plant population on morphological development of the maize canopy. The main objectives of the current study were (i) to characterize the effects of increased plant density on canopy morphology and stalk lodging and (ii) to explore the relationships between organ morphology and stalk lodging. The field experiment was composed of five plant densities (4.5, 6, 7.5, 9, and 15 plants m−2) of three cultivars: Zhengdan 958 (lodging-resistant cultivar), Longping 206 and Jinqiu 119 (lodging-susceptible cultivars). In response to plant densities of all the three cultivars, the lamina and sheath lengths increased in lower phytomers but decreased in upper phytomers. The lamina width and internode diameter decreased for all phytomers in response to plant densities for all the cultivars. The correlation between organ morphology, plant density and stalk lodging was linear. Data obtained from characterization used in this study (that is, canopy morphology, correlation of organ morphology with stalk lodging traits in response to various plant densities for different cultivars, etc.) will be useful in future modeling studies to predict the morphology characteristics of the canopy affected by interplant competition and stalk lodging.

Application of paclobutrazol: a strategy for inducing lodging resistance of wheat through mediation of plant height, stem physical strength, and lignin biosynthesis.

Lodging is a major constraint contributing to poor grain yield and quality of wheat (Triticum aestivum L.) worldwide. The use of plant growth regulators is becoming a foremost agro-chemical approach for minimizing the risk of lodging in cereal crops. The present study was conducted to examine the effects of the paclobutrazol application on culm physical strength, lignin content, and lodging resistance of wheat. Wheat seeds were soaked in paclobutrazol at the concentrations of 0 (CK, as control), 200 (PB1), 300 (PB2), and 400 (PB3) mgL-1. Our results showed that paclobutrazol resulted in a dose-dependent decrease of plant height, internode length, and center of gravity height. Paclobutrazol treatments evidently increased the culm diameter, culm filling degree, and wall thickness of basal internodes, resulting in greater stalk-breaking strength and lodging resistance index (CLRI), where their maximum values were obtained with PB1 treatment. In addition, the activities of lignin-related enzymes were improved by paclobutrazol, particularly at low concentration, which increased the lignin accumulation of the basal internodes of wheat, subsequently improving the capability of stalk lodging resistance. Moreover, the correlation analysis revealed significant correlations between stem diameter, culm filling degree, and lignin with stalk bending strength and CLRI. The paclobutrazol concentration ≥ 300mgL-1 (PB2 and PB3 treatments) showed inhibitive effects on various culm morphological traits. These results suggest that not only the plant height, but also the lignin contents and physical strength of internodes are closely related with the lodging resistance of wheat, and reduction in plant height along with improved culm morphological characteristics and higher lignin accumulation in basal internodes could effectively relieve the risk of lodging.

The Influence of Climatic Variations on the Stability of Wheat Plant Height

Abstract The decrease of variability sources and the genotypes instability as a result of climate changes from the last years were issues addressed in the breeding programs. For breeders the stability of some parameters like plant height is very important in selection process, therefore the influence of climatic variations it is aimed to be reduced by genetic response of the genotypes. Semi-dwarf genotypes are preferred by breeders because in this way is avoided the lodging risk. A set of 307 mutant and mutant/recombinant wheat DH lines, along with parental genotypes, was analyzed in three different years for plant height and the semi-dwarf selected lines were evaluated for stability of this parameter. The material was also analyzed for the presence of Lr34, or genes and 1A/1R translocation. In our study the reduced plant height and its stability was not associated with any of the genetic background

An Integration of Genome-Wide Association Study and Gene Co-expression Network Analysis Identifies Candidate Genes of Stem Lodging-Related Traits in Brassica napus.

Lodging is a persistent problem which severely reduce yield and impair seed quality in rapeseed (Brassica napus L.). Enhancing stem strength (SS) has proven to be an effective approach to decrease lodging risk. In the present study, four interrelated stem lodging-related traits, including stem breaking resistance (SBR), stem diameter (SD), SS, and lodging coefficient (LC), were investigated among 472 rapeseed accessions. A genome-wide association study (GWAS) using Brassica 60K SNP array for stem lodging-related traits identified 67 significantly associated quantitative trait loci (QTLs) and 71 candidate genes. In parallel, a gene co-expression network based on transcriptome sequencing was constructed. The module associated with cellulose biosynthesis was highlighted. By integrating GWAS and gene co-expression network analysis, some promising candidate genes, such as ESKIMO1 (ESK1, BnaC08g26920D), CELLULOSE SYNTHASE 6 (CESA6, BnaA09g06990D), and FRAGILE FIBER 8 (FRA8, BnaC04g39510D), were prioritized for further research. These findings revealed the genetic basis underlying stem lodging and provided worthwhile QTLs and genes information for genetic improvement of stem lodging resistance in B. napus.

Responses of Intermediate Wheatgrass to Plant Growth Regulators and Nitrogen Fertilizer

Core Ideas Trinexapac‐ethyl reduces height and lodging in wheatgrass.Trinexapac‐ethyl increased grain yield when lodging risk was high.Prohexanedione calcium had no effect on wheatgrass.Trinexapac‐ethyl can reduce risk of yield losses due to lodging. Intermediate wheatgrass (Thinopyrum intermedium; IWG), a new perennial grain crop, has the potential to provide ecosystem services while producing food‐grade grain; however, productivity is currently limited by high rates of lodging. Trinexapac‐ethyl (TE) and prohexadione‐calcium (PC) are widely used plant growth regulators (PGRs) for mitigating lodging and improving seed yield in other grass crops. Our objectives were to determine the effects of the PGRs PC and TE, PGR application rate, and nitrogen (N) fertilizer rate (0, 40, 80 kg N ha−1) on IWG lodging, height, and grain and biomass yields. Experiments were initiated in first‐ and third‐year stands at St. Paul and Rosemount, MN. Few effects of PC on IWG height, lodging, or yields were observed, while TE consistently reduced plant height by 10 to 20% and lodging by up to 20% in a year with high lodging risk. Application of TE to IWG at the recommended rate (437 g a.i. ha−1) or higher rates increased grain yields by 65 to 100% when lodging incidence was high, but did not affect grain yields in years with lower lodging risk. While a negative correlation between lodging and grain yields was observed, nitrogen fertilizer affected IWG grain and biomass yields in only one of five site‐years, and there was no interaction between N fertilizer and PGR effects on IWG. Nonetheless, the PGR TE demonstrated the potential to reduce plant height and lodging, thereby increasing IWG yield potential.

Response of Sunflower to Nitrogen and Phosphorus in North Dakota

Core Ideas Nitrogen availability and fertilization can increase sunflower see yield.Nitrogen fertilization may decrease oil concentration of oilseed sunflower.Nitrogen fertilization increases sunflower lodging risk in windy regions. The N and P recommendations for sunflowers growers in North Dakota have not been changed in 30 yr. Twenty‐two N and P rate experiments were conducted during 2014 and 2015. The objective was to determine the response of seed yield, oil concentration, and lodging to available N and P. In 2014 studies were a randomized complete block split plot with N rate as main plots and P rate as subplots. Nitrogen was applied at rates of 0, 45, 90, 134, 179, and 224 kg N ha−1. Phosphorus was applied to establish P rates of 0, 13, 26, and 39 kg P ha−1. In 2015, the field design included only 0 and 26 kg P ha−1. Experiments were taken to yield and lodging was recorded at harvest. Oil seed sunflower (17 experimental locations) was also analyzed for oil concentration. The N response of sunflower seed yield was quadratic. Increased N rate resulted in lower oil concentration in half of the oilseed experiments. Increased N rate was linearly related to increasing lodging at several sites. Phosphate fertilization had little effect on seed yield, oil concentration, and lodging, despite many of the sites having soil P levels considered ‘low’. Future N rate recommendations should be based on seed yield response with increasing N and oil concentration reduction with increasing N for oilseed sunflower. A limit to maximum N rate should also be considered because of the lodging risk in this wind‐plagued region.

Dissecting the complex regulation of lodging resistance in Brassica napus

Lodging continues to be a major cause of yield loss in important crop species such as Brassica napus. Understanding the genetic regulation of lodging resistance is therefore of key interest to breeders worldwide. Current strategies aimed at minimising lodging risk involve the incorporation of dwarfing genes or the application of plant growth regulators. However, despite these efforts, lodging continues to be a persistent problem and it is therefore of high interest that novel, complimentary strategies for lodging control are implemented. One approach would be to focus on understanding the genetic properties underlying stem mechanical strength. With this in mind, we screened a training genetic diversity panel of B. napus accession for variation in stem mechanical strength and related traits. Using Associative Transcriptomics, we identified molecular markers for a suite of valuable traits. Using an independent test genetic diversity panel, we show that the methods employed are robust for identification of predictive markers. Furthermore, based on conserved synteny with Arabidopsis thaliana, we are able to provide a biological context to the marker associations detected and provide evidence for a role in pectin methylesterification in contributing to stem mechanical strength in Brassicaceae.

Effect of nitrogen levels and nitrogen ratios on lodging resistance and yield potential of winter wheat (Triticum aestivum L.).

Lodging is one of the constraints that limit wheat yields and quality due to the unexpected bending or breaking stems on wheat (Triticum aestivum L.) production worldwide. In addition to choosing lodging resistance varieties, husbandry practices also have a significant effect on lodging. Nitrogen management is one of the most common and efficient methods. A field experiment with Yangmai 20 as research material (a widely-used variety) was conducted to study the effects of different nitrogen levels and ratios on culm morphological, anatomical characters and chemical components and to explore the nitrogen application techniques for lodging tolerance and high yield. Results showed that some index of basal internodes, such as stem wall thickness, filling degree, lignin content, cellulose content, water-soluble carbohydrate (WSC) and WSC/N ratio, were positively and significantly correlated with culm lodging-resistant index (CLRI). As the increase of nitrogen level and basal nitrogen ratio, the basal internodes became slender and fragile with the thick stem wall, while filling degree, chemical components and the strength of the stem decreased gradually, which significantly increased the lodging risk. The response of grain yield to nitrogen doses was quadratic and grain yield reached the highest at the nitrogen ratio of 50%:10%:20%:20% (the ratio of nitrogen amount applied before sowing, at tillering stage, jointing stage and booting stage respectively, abbreviated as 5:1:2:2). These results suggested that for Yangmai 20, the planting density of 180×104ha-1, nitrogen level of 225 kg ha-1, and the ratio of 5: 1: 2: 2 effectively increased lodging resistance and grain yield. This combination of planting density and nitrogen level and ratio could effectively relieve the contradiction between high-yielding and anti-lodging.

Reducing shade avoidance responses in a cereal crop.

Several researchers have hypothesized that shade avoidance behaviour is favoured by natural selection because it increases the fitness of individuals. Shade avoidance can be disadvantageous for crops, however, because it reduces allocation of resources to reproductive yield, increases the risk of lodging and reduces weed suppression. One approach to develop varieties with reduced shade avoidance and enhanced agronomic performance is by inducing mutations followed by phenotypic screening. We treated spring wheat seeds with ethyl methanesulfonate and screened the seedlings repeatedly under green filters for plants showing reduced elongation of the first leaf sheath and second leaf lamina. The shade avoidance responses of five promising mutant lines were further compared to non-mutated plants in a climate chamber experiment with added far-red light. Two of the selected lines displayed significantly reduced elongation under all light treatments while two lines showed reduced elongation only in added far-red light. The most promising mutant line did not differ in height from the non-mutated cultivar in neutral light, but elongated 20.6% less in strong far-red light. This traditional forward approach of screening mutagenized spring wheat produced plants with reduced shade avoidance responses. These mutants may generate new molecular handles to modify the reaction of plants to changes in light spectral distribution in traditional and novel cultivation systems.

Shading Contributes to the Reduction of Stem Mechanical Strength by Decreasing Cell Wall Synthesis in Japonica Rice (Oryza sativa L.).

Low solar radiation caused by industrial development and solar dimming has become a limitation in crop production in China. It is widely accepted that low solar radiation influences many aspects of plant development, including slender, weak stems and susceptibility to lodging. However, the underlying mechanisms are not well understood. To clarify how low solar radiation affects stem mechanical strength formation and lodging resistance, the japonica rice cultivars Wuyunjing23 (lodging-resistant) and W3668 (lodging-susceptible) were grown under field conditions with normal light (Control) and shading (the incident light was reduced by 60%) with a black nylon net. The yield and yield components, plant morphological characteristics, the stem mechanical strength, cell wall components, culm microstructure, gene expression correlated with cellulose and lignin biosynthesis were measured. The results showed that shading significantly reduced grain yield attributed to reduction of spikelets per panicles and grain weight. The stem-breaking strength decreased significantly under shading treatment; consequently, resulting in higher lodging index in rice plant in both varieties, as revealed by decreased by culm diameter, culm wall thickness and increased plant height, gravity center height. Compared with control, cell wall components including non-structural carbohydrate, sucrose, cellulose, and lignin reduced quite higher. With histochemical straining, shading largely reduced lignin deposition in the sclerenchyma cells and vascular bundle cells compared with control, and decreased cellulose deposition in the parenchyma cells of culm tissue in both Wuyunjing23 and W3668. And under shading condition, gene expression involved in secondary cell wall synthesis, OsPAL, OsCOMT, OsCCoAOMT, OsCCR, and OsCAD2, and primary cell wall synthesis, OsCesA1, OsCesA3, and OsCesA8 were decreased significantly. These results suggest that gene expression involved in the reduction of lignin and cellulose in both sclerenchyma and parenchyma cells, which attribute to lignin and cellulose in culm tissue and weak mechanical tissue, consequently, result in poor stem strength and higher lodging risks.Highlights:(1) Shading decreases the stem mechanical strength of japonica rice by decreasing non-structural carbohydrate, sucrose, lignin, and cellulose accumulation in culms.(2) The decrease of carbon source under shading condition is the cause for the lower lignin and cellulose accumulation in culm.(3) The expression of genes involved in lignin and primarily cell wall cellulose biosynthesis (OsCesA1, OsCesA3, and OsCesA8) at the stem formation stage are down-regulated under shading condition, inducing defective cell wall development and poor lodging resistance.