Genetic Variation in Lowland Switchgrass (Panicum virgatum L.)

Switchgrass (Panicum virgatum L.) is identified as one of the main cellulosic biofuel feedstocks in the USA. Understanding genetic variation for biomass yield in switchgrass would be helpful in determining the appropriate breeding approach for cultivar development. In order to estimate the genetic component of variation in lowland switchgrass, 10 half-sib families and 47 full-sib families produced by making crosses between selected genotypes from one of the Noble Foundation's lowland breeding populations were evaluated in a nested design. The seedlings of these 47 families, and two checks, 'Alamo' and 'Blade (TM) EG 1101', were established in the greenhouse and transplanted in late summer of 2007 at two Oklahoma (USA) locations, Ardmore and Burneyville, using a honeycomb planting design with 1.5 m plant-spacing. Each family was represented by 30 genotypes, including 15 reciprocals, at each location. The biomass from individual plants was harvested separately after the killing frost in 2008. Genetic components of variation were estimated following the mixed model in SAS, and heritability was estimated. Significant effects due to half-sib and full-sib families suggested both additive and non-additive gene actions were important in biomass dry matter yields of lowland switchgrass. The heritability estimates based on family analysis (0.33) and parent-progeny regression (0.18) were low, suggesting that the trait was under the control of many genes with minor effects and influenced by significant environmental effects. Developing high yielding switchgrass cultivars will probably need to exploit both additive and non-additive gene effects and selection and testing will need to be done in the target environments.