Nitrogen Fixation and Resorption Efficiency Differences Among Twelve Upland and Lowland Switchgrass Cultivars

Abstract

In nitrogen (N)-limited terrestrial ecosystems, plants employ various strategies to acquire and conserve N, including translocation of N in perennial tissues and stimulation of N fixation in roots and soils. Switchgrass (Panicum virgatum) is a genotypically and phenotypically diverse perennial grass with two distinct ecotypes (lowland and upland) and numerous genotypes. It grows well in low-N soils, likely because of its ability to translocate N and to associate with N-fixing microbes, but little is known about variation in these traits among cultivars or even ecotypes. We measured N translocation, N fixation potential in roots and soils, soil net N mineralization, soil net nitrification, and biomass yields in 12 switchgrass cultivars grown in a replicated block experiment in southwestern Michigan, United States. Lowland cultivars had higher yields, rates of N translocation, soil net N mineralization, and N fixation potentials on washed, nonsterile roots, while upland cultivars exhibited higher N fixation potentials in root-free soil. N resorption efficiencies averaged 53 ± 5% (± standard error) for lowland versus 29 ± 3% for upland cultivars. Additionally, there were significant among-cultivar differences for all response variables except mineralization and nitrification, with differences likely explained by cultivar-specific physiologies and microbial communities. The ideal cultivar for biofuels is one that can maintain high yields with minimal fertilizer addition, and there appear to be several cultivars that meet these criteria. In addition, results suggest substantial N cycle differences among cultivars that might be exploited by breeders to create new or improved high-yielding, N-conserving switchgrass lines.

Yükseklik Gradiyenti Boyunca Diospyros kaki L.’de Yaprak Azot, Fosfor, Karbon Değişimi ve N ve P Rezorbsiyonu

“…Roley et. al [26] determined that N resorption efficiencies averaged 53% for lowland versus 29 % for upland switchgrass cultivars. Aerts [22] indicated that the N-RE and P-RE differed among evergreen shrubs and trees, deciduous shrubs and trees, graminoids and forbs, and also varied by sites.…”

Utilizing mycorrhizal responses to guide selective breeding for agricultural sustainability

“…Future research and breeding efforts will likely discover multiple selection criteria within holobiont consortia, as diverse microbiota have both complementary and competitive influences on the hologenome (Theis et al., 2016). By considering the influence of AM fungi, among the most widespread symbiotic partners in both natural and agroecosystems, our work sets a baseline for further study involving additional mutualistic microbes such as nitrogen‐fixing bacteria (Roley et al., 2020).…”

“…Mycorrhizal symbioses are widespread and typically beneficial, suggesting that evaluation of mycorrhizal relationships is critical groundwork for disentangling additional plant-associated microbial dynamics of the total holobiont. For example, switchgrass breeders are also assessing the influence of nitrogen-fixing bacteria on switchgrass growth in low-N soils (Rodrigues et al, 2017;Roley et al, 2020).…”

“…Mycorrhizal symbioses are widespread and typically beneficial, suggesting that evaluation of mycorrhizal relationships is critical groundwork for disentangling additional plant‐associated microbial dynamics of the total holobiont. For example, switchgrass breeders are also assessing the influence of nitrogen‐fixing bacteria on switchgrass growth in low‐N soils (Rodrigues et al., 2017; Roley et al., 2020). As mycorrhizas enhance nutrient uptake, water‐use efficiency, and soil quality in native ecosystems, plant breeding programs that select for increased reliance on mycorrhizas in agroecosystems can potentially deliver synthetic (agronomic) populations that reduce fertilizer requirements (Galván et al., 2011; Porter & Sachs, 2020).…”

Switchgrass sward establishment selection is consistent across multiple environments and fertilization levels

“…Nitrogen is one of the most common limiting nutrients for crops and switchgrass response to nitrogen fertilizer has been variable (Casler, 2021; Casler et al, 2019; Fike et al, 2017). These variable results could be due to the naturally high nutrient efficiency of the crop, residual soil nutrients, or associative nitrogen fixation (Lemus et al, 2008; Roley et al, 2021; Yang et al, 2016; Yost et al, 2017). This uncertainty is challenging for a breeding program.…”