Heterosis in switchgrass: Biomass yield in swards
Improving the biomass yield of switchgrass (Panicum virgatum L.) will improve its utility as a dedicated energy crop by increasing both its net and total energy yield per hectare. In a previous space-transplanted study, midparent heterosis for biomass yield was reported for population and specific F1 hybrids of the lowland-tetraploid cultivar Kanlow and the upland-tetraploid cultivar Summer. These two cultivars were proposed to be two different heterotic groups. The objective of this study was to determine the extent of heterosis for biomass yield in reciprocal Kanlow (K) and Summer (S) F1 population hybrids grown in simulated swards and to determine the effect of advance in generation on biomass yield. Parent populations and their F1, F2, and F3 population hybrids were grown in transplanted sward plots located near Mead, NE, for a three-year period. Plant density in the simulated swards was equivalent to acceptable stands in seeded plots. Plots were not harvested the establishment year to enable them to become fully established. Biomass yields were determined for the following two years. There was significant high-parent heterosis of 30 to 38% (P 0.01) for biomass yield for both the K x S F1 and S x K F1 hybrid populations. Heterosis for biomass yield declined with advance in generation. Heterosis for biomass yield in switchgrass may need the competitive conditions of swards to be fully expressed. Additional trials of specific hybrids established from seed are needed to further verify these conclusions. These results do provide ample justification for additional research to develop switchgrass population and specific hybrids.