Cell Wall Composition and Underlying QTL in an F1 Pseudo-Testcross Population of Switchgrass

Abstract

Natural genetic variation for reduced recalcitrance can be used to improve switchgrass for biofuel production. A full-sib switchgrass mapping population developed by crossing a lowland genotype, AP13, and upland genotype, VS16, was evaluated at three locations (Ardmore and Burneyville, OK and Watkinsville, GA). Biomass harvested after senescence in 2009 and 2010 was evaluated at the National Renewable Energy Laboratory (NREL) for sugar release using enzymatic hydrolysis and for lignin content and syringyl/guaiacyl lignin monomer (S/G) ratio using pyrolysis molecular beam mass spectrometry (py-MBMS). Glucose and xylose release ranged from 120 to 313 and 123 to 263 mg g −1 , respectively, while lignin content ranged from 19 to 27 % of the dry biomass. Statistically significant differences were observed among the genotypes and the environments for the cell wall composition traits. Regression analysis showed that a unit increase in lignin content reduced total sugar release by an average of 10 mg g −1 . Quantitative trait loci (QTL) analysis detected 9 genomic regions underlying sugar release and 14 for lignin content. The phenotypic variation explained by the individual QTL identified for sugar release ranged from 4.5 to 9.4 and for lignin content from 3.8 to 11.1 %. Mapping of the QTL regions to the switchgrass genome sequence (v1.1) found that some of the QTL colocalized with genes involved in carbohydrate processing and metabolism, plant development, defense systems, and transcription factors. The markers associated with QTL can be implemented in breeding programs to efficiently develop improved switchgrass cultivars for biofuel production.

Transgenic switchgrass (Panicum virgatum L.) targeted for reduced recalcitrance to bioconversion: a 2‐year comparative analysis of field‐grown lines modified for target gene or genetic element expression

“…Our report extends this observation as a general trend affecting all transgenic and control switchgrass lines studied within BESC. This trend towards increased recalcitrance in switchgrass tissue over years was also observed in native population studies (Serba et al, 2016).…”

High‐density linkage map reveals QTL underlying growth traits in AP13×VS16 biparental population of switchgrass

“…QTL with positive additive effects for postharvest regrowth were reported on chromosome 5N (5b) of a switchgrass biparental population, Kanlow-K5×Alamo-A4 (Lowry et al, 2015). Linkage map from the same pseudo-F 1 testcross population was constructed using SSR, STS, and DArT markers, and QTL for biomass yield, plant height, and recalcitrant traits were identified (Serba et al, 2015(Serba et al, , 2016(Serba et al, , 2013.…”

Identification of Quantitative Trait Loci for Plant Height, Crown Diameter, and Plant Biomass in a Pseudo-F2 Population of Switchgrass

“…The current study identified six QTLs for HT, CD, or PB using a pseudo-F 2 population of switchgrass. The number of identified QTLs in this study was smaller than some previous studies [14][15][16][17][18][19]. The variations in QTL numbers in different studies could be due to varied mapping populations (e.g., F 1 or F 2 crosses made by lowland × lowland or lowland × upland genotypes), and a number of traits and environments assessed for the population.…”

“…Such relationships provide insights into the genetic control of a trait of interest, as well as providing a mechanism to improve the efficiency of a breeding program. When multiple QTLs are identified as genetic components explaining variation of a trait, the trait is typically referred to as Bcomplex.^Toward this end, QTLs for tillering, plant height, flowering time, cell wall composition, and biomass yield have been detected across a variety of studies and mapping populations in switchgrass [13][14][15][16][17][18][19][20]. For example, a high number of QTL on chromosome 5a (20 QTLs) and 2a (26 QTLs) for six tillering-related traits assessed in 2 years at two locations have been identified in a lowland full-sib F 1 mapping population and a selfed population, respectively [18].…”

“…Using outbred reciprocal crosses derived from lowland and upland genotypes, 33 QTLs were detected across 11 growth and disease resistance traits collected in the field and in a greenhouse [19]. Most of these studies were performed using populations derived by crosses between two lowland genotypes with a few between lowland and upland ecotypes, but all phenotypic traits were evaluated in southern US regions [14][15][16][17][18][19]. Moreover, large-effect colocalizing QTLs for multiple traits have not always been detected [19].…”