Adaptations between Ecotypes and along Environmental Gradients inPanicum virgatum

Abstract

Determining the patterns and mechanisms of natural selection in the wild is of fundamental importance to understanding the differentiation of populations and the evolution of new species. However, it is often unknown the extent to which adaptive genetic variation is distributed among ecotypes between distinct habitats versus along large-scale geographic environmental gradients, such as those that track latitude. Classic studies of selection in the wild in switchgrass, Panicum virgatum, tested for adaptation at both of these levels of natural variation. Here we review what these field experiments and modern agronomic field trials have taught us about natural variation and selection at both the ecotype and environmental gradient levels in P. virgatum. With recent genome sequencing efforts in P. virgatum, it is poised to become an excellent system for understanding the adaptation of grassland species across the eastern half of North America. The identification of genetic loci involved in different types of adaptations will help to understand the evolutionary mechanisms of diversification within P. virgatum and provide useful information for the breeding of high-yielding cultivars for different ecoregions.

Phenotyping Winter Dormancy in Switchgrass to Extend the Growing Season and Improve Biomass Yield

“…Switchgrass production depends on environmental cues to synchronize growth with favorable environmental conditions, and dormancy is triggered when conditions are unfavorable in winter [17]. Photoperiod and temperature are important factors determining plant metabolism in warm season grasses.…”

“…However, despite being low biomass yielders, the upland ecotypes possess the advantage of being more winter hardy and more resistant to cold temperature [15]. Lowry et al [17] reported that the upland ecotypes can grow in hardiness zones 2 -7, while lowland ecotypes are limited to the southern zones of 6 -10, but both ecotypes can be found in the transition zone [18]. Eight regional gene pools or cultivar deployment zones were described based on adaptation to different photoperiod and temperatures.…”

QTL and Drought Effects on Leaf Physiology in Lowland Panicum virgatum

“…Classic physiological studies addressed differences in leaf performance between ecologically differentiated upland and lowland switchgrass populations with distinct vegetative phenotypes and ploidy levels [32,34]. Evidence for local adaptation [35,36] has also led to more recent experiments focused on inter-population variation in productivity and physiological performance [6,33,[37][38][39][40]. Results from these experiments support differences in seasonal patterns of photosynthetic performance that complement adaptive variation in phenology [33,39,40].…”

Variability of nuclear DNA content and agromorphological characteristics of switchgrass (Panicum virgatum L.) germplasm in Lithuania

“…Casler (2005) has pointed out that analysis of morphological characteristics is an effective tool for discriminating between tetraploid and octoploid populations, whereas Lowry et al (2014) have stated that many researchers have not discerned the correlation between plant characteristics and ploidy level.…”

“…Cortese et al (2010) have reported tetraploid populations to be of a later maturity compared with octoploid. Lowry et al (2014) suggest that the phenotypic characteristics (heading, full anthesis, seed maturity dates) of switchgrass populations are largely dependent on the latitude of their origin rather than on ploidy level. We agree with the opinion that that these characteristics are determined by the interaction of various factors (origin, environment).…”