30 Years of Progress toward Increased Biomass Yield of Switchgrass and Big Bluestem

Abstract

Breeding to improve biomass production of switchgrass (Panicum virgatum L.) and big bluestem (Andropogon gerardii Vitman) for conversion to bioenergy began in 1992. The purpose of this study was (i) to develop a platform for uniform regional testing of cultivars and experimental populations for these species, and (ii) to estimate the gains made by breeding during 1992 to 2012. A total of 25 switchgrass populations and 16 big bluestem populations were planted in uniform regional trials at 13 locations in 2012 and 2014. The reference region was USDA Hardiness Zones 3 through 6 in the humid temperate United States. Significant progress toward increased biomass yield was made in big bluestem and within upland‐ecotype populations, lowland‐ecotype populations, and hybrid‐derived populations of switchgrass. Four mechanisms of increasing biomass yield were documented: (i) increased biomass yield per se, (ii) later flowering to extend the growing season, (iii) combined later flowering from the lowland ecotype with survivorship of the upland ecotype in hybrid‐derived populations, and (iv) increased survivorship of late‐flowering lowland populations in hardiness zones that represent an expansion of their natural adaption zone. Switchgrass exhibited all four mechanisms in one or more improved populations, whereas improved populations of big bluestem were likely influenced by two of the four mechanisms. The uniform testing program was successful at documenting increases in biomass yield, identifying the mechanisms for increased yield, and determining adaptation characteristics and limitations of improved populations.

Breeding progress and preparedness for mass‐scale deployment of perennial lignocellulosic biomass crops switchgrass, miscanthus, willow and poplar

“…Many more biomass‐type cultivars are expected within the next few years as these and other breeding programmes mature. The average rate of gain for biomass yield in long‐term switchgrass breeding programmes has been 1%–4% per year, depending on ecotype, population and location of the breeding programme (Casler & Vogel, ; Casler et al, ). The hybrid derivative Liberty has a biomass yield 43% higher than the better of its two parents (Casler & Vogel, ; Vogel et al, ).…”

“…The hybrid derivative Liberty has a biomass yield 43% higher than the better of its two parents (Casler & Vogel, ; Vogel et al, ). The development of cold‐tolerant and late‐flowering lowland‐ecotype populations for the northern United States has increased biomass yields by 27% (Casler et al, ).…”

Soil Quality and Region Influence Performance and Ranking of Switchgrass Genotypes

“…Photoperiod and temperature are the most important factors driving GE interactions in switchgrass (Casler et al, 2004(Casler et al, , 2007. Recent breeding efforts have shown that genetic variation for cold tolerance exists within late-flowering southern populations and the frequency of cold-tolerant plants can be increased by selection within random-mating, late-flowering populations (Casler et al, 2018). Southern populations of switchgrass are later in flowering, more heat tolerant, and less cold tolerant than northern populations (Casler, 2012;Casler et al, 2012).…”

“…Gains have been made by selection within Hardiness Zone 5, specifically near Madison, WI, and Lincoln, NE, but these gains have not led to increased persistence or biomass yield in Hardiness Zones 3 or 4, due to insufficient selection pressure under these more extreme conditions (Casler et al, 2018). Breeding late-flowering lowland switchgrass for adaptation to northern environments (e.g., Hardiness Zones 3-5) provides a relevant example.…”

“…Indeed, Brummer and Casler (2014) indicated that a wide range of indirect selection efforts to improve forage or biomass yield of perennial crops have failed to produce gains equivalent to those achieved by direct selection. Uniform testing collaborations are an effective mechanism to accomplish this for switchgrass (e.g., Casler et al, 2017Casler et al, , 2018. The choice of TPE for breeding should be defined according to hardiness zone, soil moisture availability, and, to the extent possible, soil quality.…”