The genetic architecture of shoot and root trait divergence between upland and lowland ecotypes of a perennial grass.

Recent climate trends are driving rapid shifts in global precipitation patterns, leading to changes in soil water availability that can impact plant performance and distribution. Soil water availability is an especially important driver of contemporary evolution and ecotypeformation in plant populations. In the process of ecotypeformation, populations can diverge across many traits and exhibit different niche characteristics, which requires coordination between plant organ systems. For instance, although plant water loss is largely governed by shoot systems, root systems determine water access and constrain shoot water status. Understanding the genetic architectureof root traits and their relationship with shoot traits helps to develops a more complete picture of the adaptive differences that arise between ecotypesin response to changes in water availability. Panicum halliiis an emerging model system for C4 perennial grasses, including the important biofuel crop switchgrass ( Panicum virgatum). Here, we produced an intercross between individuals of the xeric and mesic ecotypesof P. hallii , utilized a single seed decent method to generate a population of recombinant inbred lines (RIL) at the F7 generation and subsequently constructed a new genetic map based on whole genome re-sequencing. Utilizing extensive phenotyping of root and shoot traits and a quantitative geneticapproach, we identified several genomic 9hotspots9 which control suites of correlated root and shoot traits, thus indicating genetic coordination between plant organ systems in the process of ecotypicdivergence. In addition, we found that genomic regions of colocalizedQTL for the majority of shoot and root growth related traits were independent of colocalizedQTL for shoot and root resource acquisition traits. Finally, we confirmed major finding from the greenhouse in a field setting.