Ecotypes and Morphotypes of Switchgrass Differ In Feedstock Composition.

Switchgrass (Panicum virgatum L.) has two distinct morphotypes, leafy and stemy, observed in both lowland and upland ecotypes. These morphotypes and ecotypes may have divergent feedstock quality. Two leafy and two stemy genotypes each of four varieties, Alamo and Kanlow representing lowland, and Cave-in Rock (CIR) and Blackwell representing upland were investigated for feedstock composition. The fully matured plants from 2009 and 2010 growing season were collected after killing frost. The cellulose and hemicelluloses contents were estimated using the grass hay prediction equation (NIRS Forage and Feed Testing Consortium, Hillsboro, WI).  Acid detergent lignin (ADL) was determined following the ANKOM ADL procedure. There was a significant difference between ecotypes in whole-plant lignin and hemicelluloses contents. As compared with upland genotypes, lowland genotypes had low lignin and high hemicellulose. Further investigation revealed that differences in lignin and hemicelluloses between the two ecotypes were of greater magnitudes in the leaves than in the stems. The effects of morphotypes on lignin and hemicellulose contents were evidenced only at p<0.1, however the results depended on cultivar background.  The cellulose content did not differ between ecotypes, however, lowland Kanlow and upland CIR demonstrated higher cellulose content compared to Alamo and Blackwell genotypes. Two morphotypes were similar in cellulose content. If high lignin content is warrant for the bioenergy process such as pyrolysis and co-firing, the lignin content in the lowland can be potentially improved through introgression. In the other hand, the low lignin traits can be introgressed to upland cultivar from lowland in order to improve forage digestibility.