Cell wall composition and biomass digestibility diversity in Mexican maize (Zea mays L) landraces and CIMMYT inbred lines

Maize is one of the most important crops worldwide. Historically, breeding efforts in this crop have been primarily focused on the improvement of grain yield and stability and just recently also on the potential utility of maize stover (above ground biomass excluding the grain) as a source of biomass for the production of feed, fiber and cellulosic ethanol. The International Maize and Wheat Improvement Center (CIMMYT) holds one of the largest maize germplasm collections in the world and therefore is an important source of phenotypic and genetic diversity for many traits. Our objectives were to assess the phenotypic diversity for cell wall composition and biomass digestibility in Mexican tropical, subtropical and highland maize landraces and elite maize lines (CMLs) in the CIMMYT germplasm collection, as well as to evaluate the relationship between place of origin of these materials and phenotypic expression of biomass compositional traits. The range of variation for neutral detergent fiber for three groups of landraces was from 47 to 73%. Slightly larger levels of phenotypic variation were observed for this trait in the set of CMLs evaluated (42 to 78%). Some of the inbred lines, such as CML 507, presented superior characteristics in terms of cell wall composition and digestibility. The Tuxpeño tropical-subtropical race, widely used in CIMMYT breeding programs, formed a cluster characterized by high cell wall content and low biomass digestibility. The CIMMYT germplasm collection appears to be a vast source of untapped genetic and phenotypic variation for the improvement of maize biomass composition

Selection for Silage Yield and Composition Did Not Affect Genomic Diversity Within the Wisconsin Quality Synthetic Maize Population

Maize silage is forage of high quality and yield, and represents the second most important use of maize in the United States. The Wisconsin Quality Synthetic (WQS) maize population has undergone five cycles of recurrent selection for silage yield and composition, resulting in a genetically improved population. The application of high-density molecular markers allows breeders and geneticists to identify important loci through association analysis and selection mapping, as well as to monitor changes in the distribution of genetic diversity across the genome. The objectives of this study were to identify loci controlling variation for maize silage traits through association analysis and the assessment of selection signatures and to describe changes in the genomic distribution of gene diversity through selection and genetic drift in theWQS recurrent selection program. We failed to find any significant marker-trait associations using the historical phenotypic data from WQS breeding trials combined with 17,719 high-quality, informative single nucleotide polymorphisms. Likewise, no strong genomic signatures were left by selection on silage yield and quality in the WQS despite genetic gain for these traits. These results could be due to the genetic complexity underlying these traits, or the role of selection on standing genetic variation. Variation in loss of diversity through drift was observed across the genome. Some large regions experienced much greater loss in diversity than what is expected, suggesting limited recombination combined with small populations in recurrent selection programs could easily lead to fixation of large swaths of the genome

TIPS: a system for automated image-based phenotyping of maize tassels

Abstract Background The maize male inflorescence (tassel) produces pollen necessary for reproduction and commercial grain production of maize. The size of the tassel has been linked to factors affecting grain yield, so understanding the genetic control of tassel architecture is an important goal. Tassels are fragile and deform easily after removal from the plant, necessitating rapid measurement of any shape characteristics that cannot be retained during storage. Some morphological characteristics of tassels such as curvature and compactness are difficult to quantify using traditional methods, but can be quantified by image-based phenotyping tools. These constraints necessitate the development of an efficient method for capturing natural-state tassel morphology and complementary automated analytical methods that can quickly and reproducibly quantify traits of interest such as height, spread, and branch number. Results This paper presents the Tassel Image-based Phenotyping System (TIPS), which provides a platform for imaging tassels in the field immediately following removal from the plant. TIPS consists of custom methods that can quantify morphological traits from profile images of freshly harvested tassels acquired with a standard digital camera in a field-deployable light shelter. Correlations between manually measured traits (tassel weight, tassel length, spike length, and branch number) and image-based measurements ranged from 0.66 to 0.89. Additional tassel characteristics quantified by image analysis included some that cannot be quantified manually, such as curvature, compactness, fractal dimension, skeleton length, and perimeter. TIPS was used to measure tassel phenotypes of 3530 individual tassels from 749 diverse inbred lines that represent the diversity of tassel morphology found in modern breeding and academic research programs. Repeatability ranged from 0.85 to 0.92 for manually measured phenotypes, from 0.77 to 0.83 for the same traits measured by image-based methods, and from 0.49 to 0.81 for traits that can only be measured by image analysis. Conclusions TIPS allows morphological features of maize tassels to be quantified automatically, with minimal disturbance, at a scale that supports population-level studies. TIPS is expected to accelerate the discovery of associations between genetic loci and tassel morphology characteristics, and can be applied to maize breeding programs to increase productivity with lower resource commitment

Forage quality and composition measurements as predictors of ethanol yield from maize (Zea mays L.) stover

<p>Abstract</p> <p>Background</p> <p>Improvement of biofeedstock quality for cellulosic ethanol production will be facilitated by inexpensive and rapid methods of evaluation, such as those already employed in the field of ruminant nutrition. Our objective was to evaluate whether forage quality and compositional measurements could be used to estimate ethanol yield of maize stover as measured by a simplified pretreatment and simultaneous saccharification and fermentation assay. Twelve maize varieties selected to be diverse for stover digestibility and composition were evaluated.</p> <p>Results</p> <p>Variation in ethanol yield was driven by glucan convertibility rather than by glucan content. Convertibility was highly correlated with ruminal digestibility and lignin content. There was no relationship between structural carbohydrate content (glucan and neutral detergent fiber) and ethanol yield. However, when these variables were included in multiple regression equations including convertibility or neutral detergent fiber digestibility, their partial regression coefficients were significant and positive. A regression model including both neutral detergent fiber and its ruminal digestibility explained 95% of the variation in ethanol yield.</p> <p>Conclusion</p> <p>Forage quality and composition measurements may be used to predict cellulosic ethanol yield to guide biofeedstock improvement through agronomic research and plant breeding.</p

Harnessing Phenotypic Plasticity to Improve Maize Yields

Plants can produce different phenotypes when exposed to different environments. Understanding the genetic basis of these plastic responses is crucial for crop breeding efforts. We discuss two recent studies that suggest that yield plasticity in maize has been under selection but is controlled by different genes than yield

La relación de la innovación tecnológica y el desempeño exportador de las empresas agroexportadoras peruanas del sector frutas frescas durante el periodo 2012-2020

En los últimos años las exportaciones agrícolas peruanas han presentado un incremento constante, lo cual ha tenido como resultado que este sector se convierta en el segundo sector económico con mayor participación en las exportaciones peruanas al 2020, después de la minería tradicional. El objetivo de la presente investigación es determinar si la innovación tecnológica está relacionada con el desempeño exportador de las empresas agroexportadoras peruanas de frutas frescas durante el periodo 2012-2020. Considerando como dimensiones la “Innovación tecnológica” (innovación de producto e innovación de procesos) y “Desempeño exportador” (ventas de exportación y objetivos estratégicos). Para desarrollar la investigación se utilizó una técnica de estudio mixto con diseño descriptivo correlacional. De igual forma, para recolectar información cualitativa, se realizaron entrevistas semiestructuradas a 9 expertos del sector agroexportador, dichos entrevistados son representantes de entidades privadas y públicas, representantes de AGAP, representantes de PROMPERU, representantes de la INIA, representantes de PROHASS, representantes de empresas agroexportadoras y representantes de Organiko Latam. Para la codificación y el análisis de estas entrevistas, se utilizó el programa Atlas Ti. En cuanto al desarrollo cuantitativo, se diseñó una encuesta de tipo cerrada en escala de Likert, la cual fue realizada a 20 empresas del sector agroexportación de frutas frescas, tomando en cuenta las principales frutas exportadoras (uva, arándano, palta, mango y plátano) las cuales representan un 20% del total de las empresas agroexportadoras de frutas en general, estas fueron desarrolladas por presidentes, gerentes, gerentes de innovación, jefes de producción y socios, dichas encuestas se analizaron a través del software SPSS. En cuanto a los resultados obtenidos a través de la técnica Rho Spearman, se validó que la innovación tecnológica se relaciona positivamente con el desempeño exportador de las empresas agroexportadoras peruanas de frutas frescas durante el periodo 2012-2020. Sin embargo, Al analizar de forma independiente cada dimensión, se obtuvo como resultado, que la innovación de procesos tiene una mayor relación con el desempeño exportador que la innovación de productos, ya que esta última, aún es un tipo de innovación que no está tan desarrollado por las empresas agroexportadoras peruanas de frutas frescas, debido a que se requiere altos niveles de inversión.In recent years, Peruvian agricultural exports have shown a constant increase, which has resulted in this sector becoming the second economic sector with the highest participation in Peruvian exports by 2020, after traditional mining. The main objective of this research is to determine whether technological innovation is related to the export performance of Peruvian agro-export companies of fresh fruits during the period 2012-2020. Considering “Technological innovation” (product innovation and process innovation) and “Export performance” (export sales and strategic objectives) as dimensions. For the development, the mixed research technique was applied with a descriptive-correlational design. Likewise, for the collection of qualitative information, semi-structured interviews were conducted with 9 experts in the agro-export sector, said interviewees are representatives of private and public entities, representatives of AGAP, representatives of PROMPERU, representatives of INIA, representatives of PROHASS, representatives of agro-export companies and representatives of Organiko Latam. These interviews were transcribed, coded, and analyzed on the Atlas Ti program. Regarding the quantitative development, a closed Likert scale survey was designed, which was validated with 20 companies in the fresh fruit agro-export sector, considering the main exporting fruits (grape, blueberry, avocado, mango, and banana) which They represent 20% of the total of fruit agro-export companies in general, these were developed by presidents, managers, innovation managers, production managers and partners, these surveys were analyzed through the SPSS software. Regarding the results obtained through the Rho Spearman technique, it was validated that technological innovation is positively related to the export performance of Peruvian fresh fruit agro-export companies during the 2012-2020 period. However, when independently analyzing each dimension, it was obtained as a result that process innovation has a greater relationship with export performance than product innovation, since the latter is still a type of innovation that is not so developed by Peruvian agro-export companies of fresh fruits, due to the high levels of investment required.Tesi

Reduced Translocation Is Associated with Tolerance of Common Lambsquarters (\u3ci\u3eChenopodium album\u3c/i\u3e) to Glyphosate

Common lambsquarters tolerance to glyphosate is problematic because of the species’ widespread distribution, competitive ability with many crop species, the widespread use of glyphosate in agriculture, and the weed’s potential to develop decreased sensitivity to multiple herbicide sites of action. The mechanism that confers common lambsquarters tolerance to glyphosate is not known. Therefore, we conducted experiments to determine the mechanism of tolerance to glyphosate in an accession of common lambsquarters from Indiana relative to a sensitive accession from Wisconsin. The ED50 (the effective dose that reduced shoot mass 50% relative to nontreated plants) value for the tolerant accession (1.6 kg ae ha-1 ± 0.4 standard error of the mean [SEM]) was eightfold greater than the ED50 for the sensitive accession (0.2 kg ae ha-1 ± 0.2 SEM) 28 d after treatment. The glyphosate target-site (EPSPS) DNA sequence at proline 106, shikimate accumulation as an estimate of EPSPS sensitivity, and EPSPS protein abundance did not differ between accessions. Absorption of 14Cglyphosate was slightly greater in the tolerant accession than it was in the sensitive accession at 48 and 72 h after treatment (HAT). However, the tolerant accession translocated a smaller percentage of absorbed 14C-glyphosate to the tissue above the treated leaf, which included the shoot apical meristem, at 24, 48, and 72 HAT (P ≤ 0.05, 0.01, and 0.10, respectively). These results suggest an important role of reduced translocation in conferring tolerance of common lambsquarters to glyphosate

Stover Composition in Maize and Sorghum Reveals Remarkable Genetic Variation and Plasticity for Carbohydrate Accumulation

Carbohydrates stored in vegetative organs, particularly stems, of grasses are a very important source of energy. We examined carbohydrate accumulation in adult sorghum and maize hybrids with distinct phenology and different end uses (grain, silage, sucrose or sweetness in stalk juice, and biomass). Remarkable variation was observed for non-structural carbohydrates and structural polysaccharides during three key developmental stages both between and within hybrids developed for distinct end use in both species. At the onset of the reproductive phase (average 65 days after planting, DAP), a wide range for accumulation of non-structural carbohydrates (free glucose and sucrose combined), was observed in internodes of maize (11–24%) and sorghum (7–36%) indicating substantial variation for transient storage of excess photosynthate during periods of low grain or vegetative sink strength. Remobilization of these reserves for supporting grain fill or vegetative growth was evident from lower amounts in maize (8–19%) and sorghum (9–27%) near the end of the reproductive period (average 95 DAP). At physiological maturity of grain hybrids (average 120 DAP), amounts of these carbohydrates were generally unchanged in maize (9–21%) and sorghum (16–27%) suggesting a loss of photosynthetic assimilation due to weakening sink demand. Nonetheless, high amounts of non-structural carbohydrates at maturity even in grain maize and sorghum (15–18%) highlight the potential for developing dual-purpose (grain/stover) crops. For both species, the amounts of structural polysaccharides in the cell wall, measured as monomeric components (glucose and pentose), decreased during grain fill but remained unchanged thereafter with maize biomass possessing slightly higher amounts than sorghum. Availability of carbohydrates in maize and sorghum highlights the potential for developing energy-rich dedicated biofuel or dual-purpose (grain/stover) crops

Genome-wide association analysis of stalk biomass and anatomical traits in maize.

BackgroundMaize stover is an important source of crop residues and a promising sustainable energy source in the United States. Stalk is the main component of stover, representing about half of stover dry weight. Characterization of genetic determinants of stalk traits provide a foundation to optimize maize stover as a biofuel feedstock. We investigated maize natural genetic variation in genome-wide association studies (GWAS) to detect candidate genes associated with traits related to stalk biomass (stalk diameter and plant height) and stalk anatomy (rind thickness, vascular bundle density and area).ResultsUsing a panel of 942 diverse inbred lines, 899,784 RNA-Seq derived single nucleotide polymorphism (SNP) markers were identified. Stalk traits were measured on 800 members of the panel in replicated field trials across years. GWAS revealed 16 candidate genes associated with four stalk traits. Most of the detected candidate genes were involved in fundamental cellular functions, such as regulation of gene expression and cell cycle progression. Two of the regulatory genes (Zmm22 and an ortholog of Fpa) that were associated with plant height were previously shown to be involved in regulating the vegetative to floral transition. The association of Zmm22 with plant height was confirmed using a transgenic approach. Transgenic lines with increased expression of Zmm22 showed a significant decrease in plant height as well as tassel branch number, indicating a pleiotropic effect of Zmm22.ConclusionSubstantial heritable variation was observed in the association panel for stalk traits, indicating a large potential for improving useful stalk traits in breeding programs. Genome-wide association analyses detected several candidate genes associated with multiple traits, suggesting common regulatory elements underlie various stalk traits. Results of this study provide insights into the genetic control of maize stalk anatomy and biomass