Divergent metabolic changes in rhizomes of lowland and upland switchgrass (panicum virgatum) from early season through dormancy onset

Authors: Palmer, Nathan - Nate; Sarath, Gautam; Bowman, Michael; Saathoff, Aaron; Edme, Serge; Mitchell, Robert - Rob; Tobias, Christian; MADHAVAN, SOUNDARARAJAN - University Of Nebraska; Scully, Erin; Sattler, Scott

Submitted to: Plants
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2023
Publication Date: 4/21/2023
Citation: Palmer, N.A., Sarath, G., Bowman, M.J., Saathoff, A.J., Edme, S.J., Mitchell, R., Tobias, C.M., Madhavan, S., Scully, E.D., Sattler, S.E. 2023. Divergent metabolic changes in rhizomes of lowland and upland switchgrass (panicum virgatum) from early season through dormancy onset. Plants. 12(8). Article 1732. https://doi.org/10.3390/plants12081732.
DOI: https://doi.org/10.3390/plants12081732

Interpretive Summary: Switchgrass is a perennial warm-season grass. Perenniality resides in its ability to grow new shoot every year from below ground rhizomes. Death of rhizomes due to winter kill can strongly impact future yields and sustainability of biomass production for end uses such as biofuels and forage. There are northerly and southerly adapted cultivars with divergent response to winter survival. In this study rhizome metabolism was investigated in two cultivars, namely Kanlow (southerly adapted), and Summer (northerly adapted) to detect similarities and differences differences in rhizome metabolism that influence winter dormancy. In both cultivars there was an increase in levels of the plant hormone, abscisic acid (ABA) during the transition to dormancy. ABA regulated metabolic pathways were similarly changed indicating that increased ABA levels are a common determinant driving switchgrass dormancy. Gene expression analyses indicated cultivar specific metabolism, but this difference was not apparently linked to rhizome dormancy. However, cultivar-specific changes in cellular metabolites and regulatory genes could impact dormancy related processes in differential ways. A delayed transition to rhizome dormancy in the southerly adpated Kanlow could be a factor that increases winter kill in this cultivar relative to the northerly adapted Summer.

Technical Abstract: High biomass yielding southerly adapted switchgrass (Panicum virgatum L.) frequently suffer from unpredictable winter hardiness in more northerly sites arising from damage to rhizomes that prevent effective spring regrowth. Previously, changes occurring over the growing season in rhizomes sampled from a cold-adapted tetraploid upland cultivar Summer, demonstrated a role for ABA, starch accumulation and transcriptional reprogramming as drivers of dormancy onset and potential keys to rhizome health during winter dormancy. Here, rhizome metabolism of a high-yielding southerly adapted tetraploid switchgrass cultivar Kanlow, that is a significant source of genetics for yield improvement, was studied over a growing season at a northern site. Metabolite levels and transcript abundances were combined to develop physiological profiles accompanying greening through the onset of dormancy in Kanlow rhizomes. Next, comparisons of these data to rhizome metabolism occurring in the adapted upland cultivar Summer were performed. These data revealed both similarities as well as significant differences in rhizome metabolism, indicative of physiological adaptations unique to each cultivar. Similarities included elevated ABA levels and accumulation of starch in rhizomes during dormancy onset. Notable differences were observed in the accumulation of specific metabolites, expression of genes encoding transcription factors and several enzymes linked to primary metabolism.