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Title: Trait components of whole plant water use efficiency are defined by unique, environmentally responsive genetic signatures in the model C4 grass Setaria

Author
item FELDMAN, MAX - Donald Danforth Plant Science Center
item ELLSWORTH, PATRICK - Washington State University
item FAHLGREN, NOAH - Donald Danforth Plant Science Center
item GEHAN, MALIA - Donald Danforth Plant Science Center
item COUSINS, ASAPH - Washington State University
item Baxter, Ivan

Submitted to: bioRxiv
Publication Type: Pre-print Publication
Publication Acceptance Date: 12/15/2017
Publication Date: 12/15/2017
Citation: Feldman, M.J., Ellsworth, P.Z., Fahlgren, N., Gehan, M., Cousins, A., Baxter, I.R. 2017. Trait components of whole plant water use efficiency are defined by unique, environmentally responsive genetic signatures in the model C4 grass Setaria. bioRxiv. Article 234708. https://doi.org/10.1101/234708.
DOI: https://doi.org/10.1101/234708

Interpretive Summary: Water is a major limitation to crop growth, and making agriculture more water efficient is a key improvement goal. However, biomass and water use are difficult to evaluate using traditional methods. Destructive harvesting methods are required to estimate the weight of biomass a specific portion of a field is capable of producing and measurement of water used by the plant is difficult, even in greenhouse settings. High-throughput phenotyping (the visual appearance of a plant or group of plants) aims to use highthroughput digital image analysis and robotic weighing systems to rapidly assess traits on large plant populations so that recent advances in crop improvement strategies (e.g., whole genome sequencing) can be leveraged to reveal links between traits and the genes that define them. Here we leverage these systems to dissect the genetic architecture of a model grass and demonstrate that there are two genetic programs contributing to components of water use efficiency. Future research can apply this knowledge to crop improvement.

Technical Abstract: Plant growth and water use are interrelated processes influenced by the genetic control of both plant morphological and biochemical characteristics. Improving plant water use efficiency (WUE) to sustain growth in different environments is an important breeding objective that can improve crop yields and enhance agricultural sustainability. However, genetic improvements of WUE using traditional methods have proven difficult due to low throughput and environmental heterogeneity encountered in field settings. To overcome these limitations the study presented here utilizes a high-throughput phenotyping platform to quantify plant size and water use of an interspecific Setaria italica x Setaria viridis recombinant inbred line population at daily intervals in both well-watered and water-limited conditions. Our findings indicate that measurements of plant size and water use in this system are strongly correlated; therefore, a linear modeling approach was used to partition this relationship into predicted values of plant size given water use and deviations from this relationship at the genotype level. The resulting traits describing plant size, water use and WUE were all heritable and responsive to soil water availability, allowing for a genetic dissection of the components of plant WUE under different watering treatments. Linkage mapping identified major loci underlying two different pleiotropic components of WUE. This study indicates that alleles controlling WUE derived from both wild and domesticated accessions of the model C4 species Setaria can be utilized to predictably modulate trait values given a specified precipitation regime.