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ARS Home » Plains Area » Temple, Texas » Grassland Soil and Water Research Laboratory » Research » Publications at this Location » Publication #328133
Title: QTL and drought effects on leaf physiology in lowland Panicum virgatum

Author
item TAYLOR, SAMUEL - University Of Texas
item LOWRY, DAVID - Michigan State University
item ASPINWALL, MICHAEL - Western Sydney University
item BONNETTE, JASON - University Of Texas
item Fay, Philip
item JUENGER, THOMAS - University Of Texas

Submitted to: BioEnergy Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/11/2016
Publication Date: 6/27/2016
Publication URL: http://handle.nal.usda.gov/10113/5608192
Citation: Taylor, S.H., Lowry, D.B., Aspinwall, M.J., Bonnette, J.E., Fay, P.A., Juenger, T.E. 2016. QTL and drought effects on leaf physiology in lowland Panicum virgatum. BioEnergy Research. 9:1241-1259.

Interpretive Summary: Switchgrass breeding for bioenergy purposes is being facilitated by the development of genetic maps. One approach, called QTL mapping is an important component of switchgrass improvement programs because it identifies the native genetic variability, and when linked to measurement of traits important to plant growth, can contribute to selection of improved varieties. This study examined the ‘Albany’ population of switchgrass, which are the offspring of two highly productive switchgrass cultivars, ‘Alamo’ and ‘Kanlow’, and specifically sought to identify portions of the Albany genetic map that was related to traits conferring drought tolerance. The approach was to grow plants from the Albany population under well-watered and water-stressed conditions, measure parameters related to photosynthetic carbon gain and plant water stress, and use genetic mapping techniques to associate portions of the plant genome with the traits. Using this approach we were able to map the genome regions associated with leaf size and density, leaf stomatal conductance, a trait closely tied to photosynthesis and plant water loss (gs) and intrinsic water use efficiency, a parameter describing the balance between the conflicting processes of carbon uptake and water loss. These results provide the foundation for selection for leaf traits that could enhance breeding for enhanced biomass production in switchgrass.

Technical Abstract: Switchgrass is a key component of plans to develop sustainable cellulosic ethanol production for bioenergy in the U.S. We sought quantitative trait loci (QTL) for leaf structure and function, and tested for genotype × environment interactions in response to drought using the Albany full-sib mapping population, an F1 derived from lowland tetraploid parents. We also tested for G×E using check clones drawn from the parent cultivars. We determined phenotypes for leaf structure and physiological performance under well watered conditions in two consecutive years, and applied drought to one of two replicates to test for GxE. Phenotypes for the two check clones varied with location in our plot and drought impacted their photosynthetic performance, but there was limited evidence of GxE except in quantum yield (QPSII). Phenotypes of Albany were also influenced by plant location within our plot, but after correcting for experimental design factors and spatial effects we detected QTL for leaf size, tissue density, and stomatal conductance (gs). In addition, a QTL for intrinsic water use efficiency (iWUE) that was expressed only under drought provided clear evidence of GxE. Loci influencing physiological traits had small additive effects, showed complex patterns of heritability, and did not co-localize with QTL for morphological traits. These insights into the genetic architecture of leaf structure and function set the stage for consideration of leaf phenotypes as a component of switchgrass improvement for bioenergy purposes.