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The biomechanical role of the clasping leaf sheath in stalk lodging events has been historically understudied. Results from this study indicate that in some instances the leaf sheath plays an even larger role in reinforcing wheat against stalk lodging than the stem itself. Interestingly, it appears the leaf sheath does not resist bending loads by merely adding more material to the stalk (i.e., increasing the effective diameter). The radial preload of the leaf sheath on the stem, the friction between the sheath and the stem and several other complex biomechanical factors may contribute to increasing the stalk bending strength and stalk flexural rigidity of wheat. Results demonstrated that removal of the leaf sheath induces alternate failure patterns in wheat stalks. In summary the biomechanical role of the leaf sheath is complex and has yet to be fully elucidated. Many future studies are needed to develop high throughput phenotyping methodologies and to determine the genetic underpinnings of the clasping leaf sheath and its relation to stalk lodging resistance. Research in this area is expected to improve the lodging resistance of wheat. [ABSTRACT FROM AUTHOR]

Plant mechanical failure, also known as lodging, is the cause of significant and unpredictable yield losses in cereal crops. Lodging occurs in two distinct failure modes—stalk lodging and root lodging. Despite the prevalence and detrimental impact of lodging on crop yields, there is little consensus on how to phenotype plants in the field for lodging resistance and thus breed for mechanically resilient plants. This review provides an overview of field‐based mechanical testing approaches to assess stalk and root lodging resistance. These approaches are placed in the context of future perspectives. Best practices and recommendations for acquiring field‐based mechanical phenotypes of plants are also presented. [ABSTRACT FROM AUTHOR]

Stalk lodging in the monocot Zea mays is an important agricultural issue that requires the development of a genome-to-phenome framework, mechanistically linking intermediate and high-level phenotypes. As part of that effort, tools are needed to enable better mechanistic understanding of the microstructure in herbaceous plants. A method was therefore developed to create finite element models using CT scan data for Zea mays. This method represents a pipeline for processing the image stacks and developing the finite element models. 2-dimensional finite element models, 3-dimensional watertight models, and 3-dimensional voxel-based finite element models were developed. The finite element models contain both the cell and cell wall structures that can be tested in silico for phenotypes such as structural stiffness and predicted tissue strength. This approach was shown to be successful, and a number of example analyses were presented to demonstrate its usefulness and versatility. This pipeline is important for two reasons: (1) it helps inform which microstructure phenotypes should be investigated to breed for more lodging-resistant stalks, and (2) represents an essential step in the development of a mechanistic hierarchical framework for the genome-to-phenome modeling of herbaceous plant stalk lodging. • A pipeline was developed for processing the image stacks and developing the finite element models. • 2-dimensional and 3-dimensional finite element models were created. • The finite element models contain both the cell and cell wall structures that can be tested in silico. [ABSTRACT FROM AUTHOR]

Stalk lodging (mechanical failure of stalks or stems before harvest) is a major problem in grain production that significantly reduces yield. Efforts to improve stalk lodging are hampered by a limited understanding of the determinants of stalk failure. This study examined the structural bending properties and material bending properties of maize (Zea mays L.) stalks. First, an in-field phenotyping device known as DARLING (Device for Assessing Resistance to Lodging In Grains) was used to determine structural properties of maize stalks. Stalks were then subjected to a rind penetration protocol and morphological measurements were acquired. Finally, small strips of rind tissue were excised from the stalks and micro three-point bending tests were conducted to determine the material properties of the rind tissue. Results showed that the material bending strength of the rind tissue was approximately twice as large as the bending stresses present in the rind tissue when failure occurred during field testing. This indicates that stalks ultimately fail due to some form of buckling (i.e., structural failure) as opposed to material failure. This result is relevant to genetic and breeding studies seeking to address the problem of stalk lodging. In particular, these results suggest that improvements in stalk lodging resistance should focus on the stalk's geometric features, such as the ratio of rind thickness to diameter, rather than solely on enhancing material strength. For the samples in this study, material strength ranged between 64 and 197 MPa whereas material stiffness ranged between 4 and 12 GPa. Rind penetration resistance was found to be a good predictor of material properties but a poor predictor of structural properties. • Structural and material bending properties measured for each maize stalk. • Material strength of the rind was twice as large as the structural stress at failure. • Maize stalks lodged due to local buckling (structural failure) not material failure. • Geometrical properties primarily influenced stalk bending strength. • Rind penetration resistance was a poor predictor of structural bending properties. [ABSTRACT FROM AUTHOR]

Stalk lodging causes up to 43 % of yield losses in maize (Zea mays L.) worldwide, significantly worsening food and feed shortages. Stalk lodging resistance is a complex trait specified by several structural, material, and geometric phenotypes. However, the identity, relative contribution, and genetic tractability of these intermediate phenotypes remain unknown. The study is designed to identify and evaluate plant-, organ-, and tissue-level intermediate phenotypes associated with stalk lodging resistance following standardized phenotyping protocols and to understand the variation and genetic tractability of these intermediate phenotypes. We examined 16 diverse maize hybrids in two environments to identify and evaluate intermediate phenotypes associated with stalk flexural stiffness, a reliable indicator of stalk lodging resistance, at physiological maturity. Engineering-informed and machine learning models were employed to understand relationships among intermediate phenotypes and stalk flexural stiffness. Stalk flexural stiffness showed significant genetic variation and high heritability (0.64) in the evaluated hybrids. Significant genetic variation and comparable heritability for the cross-sectional moment of inertia and Young's modulus indicated that geometric and material properties are under tight genetic control and play a combinatorial role in determining stalk lodging resistance. Among the twelve internode-level traits measured on the bottom and the ear internode, most traits exhibited significant genetic variation among hybrids, moderate to high heritability, and considerable effect of genotype × environment interaction. The marginal statistical model based on structural engineering beam theory revealed that 74–80 % of the phenotypic variation for flexural stiffness was explained by accounting for the major diameter, minor diameter, and rind thickness of the stalks. The machine learning model explained a relatively modest proportion (58–62 %) of the variation for flexural stiffness. Characterization of stalk and internode properties using standard phenotyping methods revealed tremendous variation for intermediate phenotypes underlying stalk lodging resistance. The intermediate phenotypes showed moderate to high heritability, indicating their genetic tractability for improving stalk lodging resistance. Stalk geometric and material properties showed complementarity in determining stalk flexural stiffness. Engineering-informed models outperformed machine learning approaches in explaining variation for flexural stiffness. Identification of genetically tractable intermediate phenotypes will boost efforts toward genetic improvement of stalk lodging resistance in maize. Discovering the genetic architecture of the intermediate traits will enhance our understanding of the biological underpinning of stalk lodging resistance. • Stalk lodging is a complex trait that severely undermines yield and quality in maize. • Stalk and internode properties underlying lodging resistance remain poorly defined. • High heritability for flexural stiffness supports using this trait for artificial selection. • Young's modulus and cross-sectional moment of inertia complement each other in determining flexural stiffness. • Stalk diameter and rind thickness explain 74–80 % variation in flexural stiffness. [ABSTRACT FROM AUTHOR]

Stalk lodging is the structural failure of crops due to external loading such as wind. Short-stature (i.e., dwarf) varieties of wheat and rice have shown promise in reducing lodging rates. However, similar dwarfing in large gains like maize and sorghum has typically been accompanied by undesirable commercial characteristics, including significantly decreased grain yields. The purpose of this paper is to quantify the relationship between lodging resistance and plant height in maize to better understand the potential impact of short-stature varieties of maize on lodging resistance. Results from both the engineering analysis and the experimental field study indicate a nearly 1:1 relationship between plant height and plant lodging resistance. These data support the validity of the engineering analysis and suggest that there exists a nearly linear relationship between crop lodging incidence and plant height. Plant height has a direct and quantifiable impact on crop lodging resistance as it influences the bending stresses experienced in the plant stem. This study presents the engineering analysis, supported by field experiments, that explains the cause of this nearly linear 1:1 relationship. • Crop lodging has been a persistent problem for more than 100 years. • Plant height has a direct, measurable impact on crop lodging resistance. • Genetic, environment and GxE interactions have direct measurable impacts on lodging. • lodging resistance index = strength ∙ height − 1.14 . • Newly developed short stature maize varieties can mitigate the problem of crop lodging. [ABSTRACT FROM AUTHOR]

• Stalk bending strength gathered in a fairly small set of locations and years is predictive of lodging incidence in a large number of distinct locations and years. • Stalk bending strength is more predictive of stalk lodging incidence than other predictive phenotypes. • Lignin content was negatively associated with stalk lodging incidence. Stalk lodging in maize results in substantial yield losses worldwide. These losses could be prevented through genetic improvement. However, breeding efforts and genetics studies are hindered by lack of a robust and economical phenotyping method for assessing stalk lodging resistance. A field-based phenotyping platform that induces failure patterns consistent with natural stalk lodging events and measures stalk bending strength in field-grown plants was recently developed. Here we examine the association between data gathered from this new phenotyping platform with counts of stalk lodging incidence on 47 maize hybrids representing a subset of genetic diversity. For comparative purposes, we examine four additional predictive phenotypes commonly assumed to be related to stalk lodging resistance; namely, rind penetrometer resistance (a.k.a. rind puncture resistance), cellulose, hemicellulose, and lignin. Lodging incidence data were gathered on 47 hybrids, grown in 98 distinct environments, spanning four years and 41 unique geographical locations in North America. Using Bayesian generalized linear mixed effects models, we show that stalk lodging incidence is associated with each of the five predictive phenotypes. Further, based on a joint analysis we demonstrate that, among the phenotypes considered, stalk bending strength measured by the new phenotyping platform is the strongest predictive phenotype of naturally occurring stalk lodging incidence in maize, followed by rind penetrometer resistance and cellulose content. This study demonstrates that field-based measurements of stalk bending strength provide a reliable estimate of stalk lodging incidence. The stalk bending strength data acquired from the new phenotyping platform will be valuable for phenotypic selection in breeding programs and for generating mechanistic insights into the genetic regulation of stalk lodging resistance. [ABSTRACT FROM AUTHOR]