Publications by authors named "María E Otegui"

6 Publications

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A practical guide to estimating the light extinction coefficient with nonlinear models-a case study on maize.

Plant Methods 2021 Jun 12;17(1):60. Epub 2021 Jun 12.

Department of Agronomy, Kansas State University, 1712 Claflin Rd, Manhattan, KS, 66506, USA.

Background: The fraction of intercepted photosynthetically active radiation (fPARi) is typically described with a non-linear function of leaf area index (LAI) and k, the light extinction coefficient. The parameter k is used to make statistical inference, as an input into crop models, and for phenotyping. It may be estimated using a variety of statistical techniques that differ in assumptions, which ultimately influences the numerical value k and associated uncertainty estimates. A systematic search of peer-reviewed publications for maize (Zea Mays L.) revealed: (i) incompleteness in reported estimation techniques; and (ii) that most studies relied on dated techniques with unrealistic assumptions, such as log-transformed linear models (LogTLM) or normally distributed data. These findings suggest that knowledge of the variety and trade-offs among statistical estimation techniques is lacking, which hinders the use of modern approaches such as Bayesian estimation (BE) and techniques with appropriate assumptions, e.g. assuming beta-distributed data.

Results: The parameter k was estimated for seven maize genotypes with five different methods: least squares estimation (LSE), LogTLM, maximum likelihood estimation (MLE) assuming normal distribution, MLE assuming beta distribution, and BE assuming beta distribution. Methods were compared according to the appropriateness for statistical inference, point estimates' properties, and predictive performance. LogTLM produced the worst predictions for fPARi, whereas both LSE and MLE with normal distribution yielded unrealistic predictions (i.e. fPARi < 0 or > 1) and the greatest coefficients for k. Models with beta-distributed fPARi (either MLE or Bayesian) were recommended to obtain point estimates.

Conclusion: Each estimation technique has underlying assumptions which may yield different estimates of k and change inference, like the magnitude and rankings among genotypes. Thus, for reproducibility, researchers must fully report the statistical model, assumptions, and estimation technique. LogTLMs are most frequently implemented, but should be avoided to estimate k. Modeling fPARi with a beta distribution was an absent practice in the literature but is recommended, applying either MLE or BE. This workflow and technique comparison can be applied to other plant canopy models, such as the vertical distribution of nitrogen, carbohydrates, photosynthesis, etc. Users should select the method balancing benefits and tradeoffs matching the purpose of the study.
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http://dx.doi.org/10.1186/s13007-021-00753-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8196512PMC
June 2021

Genetically modified maize hybrids and delayed sowing reduced drought effects across a rainfall gradient in temperate Argentina.

J Exp Bot 2021 Jul;72(14):5180-5188

INTA, Agencia de Extensión San Luis, San Luis, Argentina.

Before the introduction of genetically modified insect-tolerant maize (Zea mays L.) in 1997, most of the production of this staple in Argentina was concentrated in humid and sub-humid temperate regions. Early spring sowings minimized the risk of water deficit around flowering and yield reduction due to pests. Use of genetically modified maize allowed optimization of sowing dates to synchronize critical periods for kernel set determination with the times of the year when water deficits are less likely, reducing large interannual variations in grain yield. This change in sowing date did not start until 2009, after the occurrence of two successive dry phases of the El Niño-Southern Oscillation phenomenon. The area of land cropped to maize in Argentina has expanded dramatically since then, particularly beyond the humid areas. Currently, maize is sown in an almost 50%/50% distribution between early and late sowings, including double cropping. Changes in agronomic practices such as sowing date and production area can lead to changes in the timing and intensity of water deficits along the maize growth cycle. This review provides an overview of new patterns of water deficit across humid, sub-humid, and semi-arid mid-latitude environments of Argentina, and their effects on grain yield and yield components.
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http://dx.doi.org/10.1093/jxb/erab139DOI Listing
July 2021

Artificial selection for grain yield has increased net CO2 exchange of the ear leaf in maize crops.

J Exp Bot 2021 05;72(10):3902-3913

Universidad de Buenos Aires, Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET), Instituto de Investigaciones Fisiológicas y Ecológicas Vinculadas a la Agricultura (IFEVA), Facultad de Agronomía, Buenos Aires, Argentina.

Identifying the physiological traits indirectly selected during the search for high-yielding maize hybrids is useful for guiding further improvements. To investigate such traits, in this study we focused on the critical period of kernel formation because kernel number is the main yield component affected by breeding. Our results show that breeding has increased the number of florets per ear and ear growth rate but not the vegetative shoot growth rate, suggesting localised effects around the ear. Consistent with this possibility, breeding has increased the net CO2 exchange of the ear leaf in field-grown crops grown at high population densities. This response is largely accounted for by increased light interception (which increases photosynthesis) and by reduced rates of respiration of the ear leaf in modern hybrids compared to older ones. Modern hybrids show increased ear-leaf area per unit leaf dry matter (specific leaf area), which accounts for the reduced respiratory load per unit leaf area. These observations are consistent with a model where the improved ear leaf CO2 exchange helps the additional florets produced by modern hybrids to survive the critical period of high susceptibility to stress and hence to produce kernels.
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http://dx.doi.org/10.1093/jxb/erab119DOI Listing
May 2021

Successful field performance in warm and dry environments of soybean expressing the sunflower transcription factor HB4.

J Exp Bot 2020 05;71(10):3142-3156

Instituto de Agrobiotecnología del Litoral, Universidad Nacional del Litoral - CONICET, Facultad de Bioquímica y Ciencias Biológicas, Santa Fe, Argentina.

Soybean yield is limited primarily by abiotic constraints. No transgenic soybean with improved abiotic stress tolerance is commercially available. We transformed soybean plants with genetic constructs able to express the sunflower transcription factor HaHB4, which confers drought tolerance to Arabidopsis and wheat. One line (b10H) carrying the sunflower promoter was chosen among three independent lines because it exhibited the best performance in seed yield, and was evaluated in the greenhouse and in 27 field trials in different environments in Argentina. In greenhouse experiments, transgenic plants showed increased seed yield under stress conditions together with greater epicotyl diameter, larger xylem area, and increased water use efficiency compared with controls. They also exhibited enhanced seed yield in warm and dry field conditions. This response was accompanied by an increase in seed number that was not compensated by a decrease in individual seed weight. Transcriptome analysis of plants from a field trial with maximum difference in seed yield between genotypes indicated the induction of genes encoding redox and heat shock proteins in b10H. Collectively, our results indicate that soybeans transformed with HaHB4 are expected to have a reduced seed yield penalty when cultivated in warm and dry conditions, which constitute the best target environments for this technology.
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http://dx.doi.org/10.1093/jxb/eraa064DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7260725PMC
May 2020

Maize expressing the sunflower transcription factor HaHB11 has improved productivity in controlled and field conditions.

Plant Sci 2019 Oct 9;287:110185. Epub 2019 Jul 9.

CONICET- INTA-FAUBA, Estación Experimental Pergamino, Facultad de Agronomía Universidad de Buenos Aires, Buenos Aires, Argentina. Electronic address:

HaHB11 is a sunflower transcription factor from the homeodomain-leucine zipper I family. Transgenic Arabidopsis plants expressing HaHB11 had larger rosettes and improved seed yield. In this work maize plants from hybrid HiII were transformed with 35S:HaHB11, ZmUBI:HaHB11 and ProHaHB11:HaHB11 and then backcrossed to B73 to obtain a more homozygous inbred phenotype. Transgene expression levels were stable at least during three generations. Greenhouse-grown HaHB11 transgenic lines had larger leaf area and delayed senescence than controls, together with increased total biomass (up to 25%) and seed yield (up to 28%). Field trials conducted with T2 and T4 generations indicated that enhanced leaf area (up to 18%), stem diameter (up to 28%) and total biomass (up to 40%) as well as delayed leaf senescence were maintained among transgenic individuals when upscaling from pots in the greenhouse to communal plants in the field. The T4 field-grown transgenic generation had increased light interception and radiation use efficiency as well as seed yield (43-47% for events driven by the 35S promoter). Results suggest that HaHB11 is a promising tool for crop improvement because differential traits observed in the Arabidopsis model plant were preserved in a crop like maize independently of growth conditions and backcross level.
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http://dx.doi.org/10.1016/j.plantsci.2019.110185DOI Listing
October 2019

A role for LAX2 in regulating xylem development and lateral-vein symmetry in the leaf.

Ann Bot 2017 10;120(4):577-590

Instituto de Agrobiotecnología del Litoral, Universidad Nacional del Litoral - CONICET, Facultad de Bioquímica y Ciencias Biológicas, Colectora Ruta Nacional 168 km 0, Santa Fe, Argentina.

Background And Aims: The symmetry of venation patterning in leaves is highly conserved within a plant species. Auxins are involved in this process and also in xylem vasculature development. Studying transgenic Arabidopsis plants ectopically expressing the sunflower transcription factor HaHB4, it was observed that there was a significant lateral-vein asymmetry in leaves and in xylem formation compared to wild type plants. To unravel the molecular mechanisms behind this phenotype, genes differentially expressed in these plants and related to auxin influx were investigated.

Methods: Candidate genes responsible for the observed phenotypes were selected using a co-expression analysis. Single and multiple mutants in auxin influx carriers were characterized by morphological, physiological and molecular techniques. The analysis was further complemented by restoring the wild type (WT) phenotype by mutant complementation studies and using transgenic soybean plants ectopically expressing HaHB4 .

Key Results: LAX2 , down-regulated in HaHB4 transgenic plants, was bioinformatically chosen as a candidate gene. The quadruple mutant aux1 lax1 lax2 lax3 and the single mutants, except lax1, presented an enhanced asymmetry in venation patterning. Additionally, the xylem vasculature of the lax2 mutant and the HaHB4 -expressing plants differed from the WT vasculature, including increased xylem length and number of xylem cell rows. Complementation of the lax2 mutant with the LAX2 gene restored both lateral-vein symmetry and xylem/stem area ratio in the stem, showing that auxin homeostasis is required to achieve normal vascular development. Interestingly, soybean plants ectopically expressing HaHB4 also showed an increased asymmetry in the venation patterning, accompanied by the repression of several GmLAX genes.

Conclusions: Auxin influx carriers have a significant role in leaf venation pattering in leaves and, in particular, LAX2 is required for normal xylem development, probablt controlling auxin homeostasis.
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http://dx.doi.org/10.1093/aob/mcx091DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5737667PMC
October 2017