|DES MARAIS, D - Harvard University
|RAZZAQUE, S - University Of Texas
|HERNANDEZ, K - University Of Chicago
|JUENGER, T - University Of Texas
Submitted to: Plant Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/23/2016
Publication Date: 10/1/2016
Citation: Des Marais, D.L., Razzaque, S., Hernandez, K.M., Garvin, D.F., Juenger, T.E. 2016. Quantitative trait loci associated with natural diversity in water-use efficiency and response to soil drying in Brachypodium distachyon. Plant Science. 251:2-11.
Interpretive Summary: Water is a limiting resource for agricultural production, and access to adequate water expected to become more limited in the future. Faced with an impending large increase in the human population on earth, it is imperative to identify strategies to maintain or even improve crop productivity under water-limiting conditions. In this study, the model grass Brachypodium distachyon, a close relative of vital human staple crops including wheat, was employed to genetically dissect different aspects water use efficiency by crops, which is a measure of productivity and how much it is reduced as water becomes more restricted. Water use efficiency is complex and has multiple facets. Two different genotypes of Brachypodium were compared for differences in a number of traits related to water use efficiency. Differences were found in some, but not all of the traits that were examined. Subsequently a population of plants from a cross between the two Brachypodium genotypes was examined for the same traits. Using genetic analysis, it was possible to identify the chromosome locations of several genes controlling some of the variation in several traits associated with water use efficiency between the two Brachypodium genotypes. Our results suggest that Brachypodium can serve as a surrogate for dissecting the genetic and molecular basis of improved water use efficiency, including isolating the specific genes involved. Knowledge gained from such experimentation in Brachypodium, when transferred to grass crops such as wheat, will result in crops better able to maintain their productivity under water-limited conditions. This will enhance global food security as the human population grows at the same time that access to water for agricultural purposes decreases.
Technical Abstract: All plants must optimize their growth with finite resources. Water use efficiency (WUE) measures the relationship between biomass acquisition and transpired water. In the present study, we performed two experiments to understand the genetic basis of WUE and other parameters of plant-water interaction under constitutive and water-limited conditions. Our study used two natural accessions of Brachypodium distachyon, a model grass species with close phylogenetic affinity to temperate forage and cereal crops. First, we identify the soil water content which causes a reduction in leaf relative water content and an increase in WUE. Second, we present results from a large phenotyping experiment utilizing a recombinant inbred line mapping population derived from these same two genotypes. We identify QTLs associated with environmentally-insensitive genetic variation in WUE, including a pair of epistatically interacting loci. We identify QTLs associated with constitutive differences in biomass and a QTL describing an environmentally-sensitive difference in leaf Carbon content. Finally, we present a new linkage map for this mapping population based on new SNP markers as well as updated genomic positions for previously described markers. Our studies provide an initial characterization of plant-water relations in B. distachyon and identify candidate genomic regions involved in WUE.