Exploring Environmental and Genetic Impacts on Lignin Content in Sorghum Bicolor.

Lignin is a polymer in plant cell walls that is important for maintenance of the structural integrity of the plant. Lignin provides defense against pests, most pathogens, and lodging caused by high winds. Lignin content has been classically important in agronomics due to its negative impacts on animal digestibility of plant biomass and cellulosic ethanol production. In the experiment presented here, we analyzed 279 Sorghum bicolor genotypes for acid-insoluble ("Klason") lignin content using high-throughput techniques. Included in these analyses were both photoperiod-sensitive (PS) and -insensitive lines. PS lines do not initiate flowering in the Midwest due to a lack of appropriate day-length signals. Instead, these genotypes continue to accumulate biomass until frost sets in. The photoperiod-insensitive lines are further broken down into "tall" and "short" growth types. All genotypes were replicated across two separate fields. Our results indicate that PS lines may accumulate more lignin than both tall and short photoperiod-insensitive lines, regardless of field location. This may, in part, be due to the increased biomass of the PS lines, which may require the plants to synthesize more lignin to adequately support their own weight. Conversely, differences in lignin content between tall and short photoperiod-insensitive genotypes were only significant for replicates in one field location. These results support prior observations that lignin content is highly influenced by environmental factors. Future studies will focus on dissecting the genetic controls of sorghum lignin content using the data collected in this study. Unraveling the genetic controls of lignin content in sorghum will aid breeders in developing new varieties for food and biofuel production. Additionally, these findings may also prove useful for understanding the genetic controls of lignin in other related crop species.