Estimation of genetic variability and heritability for biofuel feedstock yield in several populations of switchgrass

Information on heritability and predicted gains from selection for increased biomass yield for ethanol production in switchgrass is limited and may vary among breeding populations. The purpose of this study was to estimate heritability and predicted gains from selection for higher biomass yield within a lowland ecotype switchgrass population, Southern Lowland 93 (SL-93), and two upland ecotype switchgrass populations, Southern Upland Northern Upland Early Maturing (SNU-EM) and Southern Upland Northern Upland Late Maturing (SNU-LM). Narrow-sense heritabilities (h(n)(2)) for biomass yield in each of the three populations were estimated via progeny-parent regression analysis. Half-sib (HS) progeny families from 130 randomly selected plants from the SL-93 population were evaluated for biomass yield in replicated trials in 2002 and 2003. Clonal parent plants were evaluated for biomass yield in separate environments to provide unbiased h(n)(2) estimates from progeny-parent regression. Yield differences were highly significant among SL-93 HS progenies within and over years. For the SL-93 population, h(n)(2) estimates were 0.13 and 0.12 based on individual plant and phenotypic family mean (PFM) selection, respectively. Predicted genetic gains (Delta G) per selection cycle were 0.15 kg dry matter (dm) plant(-1) and 0.10 kg dm plant(-1) for PFM and individual plant selection methods, respectively. For the SNU-EM and SNU-LM populations, year and year x HS family effects were highly significant (P < 0.01) and the HS family effect over years was nonsignificant (P < 0.05). However, HS family effects were highly significant within respective years (P < 0.01). Estimates of h(n)(2) for the SNU-EM and SNU-LM populations based on PFM and individual plant selection were similar, ranging from 0.44 to 0.47; Delta G per selection cycle ranged from 0.22 to 0.33 kg dm plant(-1). The magnitudes of the estimates of additive genetic variation suggest that selection for higher biomass yield should be possible. The substantial effect of environment on biomass yields in the upland populations and the failure of families to respond similarly over years stress the importance of adequately testing biomass yield over years to assess yield.