Heterosis for Biomass Yield in Photoperiod-Sensitive Hybrid Sorghum.

Photoperiod-sensitive (PS) sorghums (Sorghum bicolor) that accumulate high biomass yields have been identified as a potential feedstock for lignocellulosic biofuel production.  When grown in temperate latitudes, these sorghums remain vegetative until day-lengths shorten to a point that triggers the induction of the reproductive phase.  Many PS sorghums begin flowering in the early to late fall while others never flower before the end of the growing season.  Because of their delayed anthesis and tall height, large-scale production of PS sorghum seed requires a hybrid seed production system using photoperiod-insensitive parents that when crossed, yield photoperiod-sensitive F1 progeny.  The female parent in this system is a short, grain-type sorghum that is amenable to machine harvest and the male is typically a taller, high-biomass photoperiod insensitive sorghum.  This is routinely done to produce PS sorghum seed for forage use.  The objective of this study was to determine the heterosis for biomass yield of hybrid PS sorghums developed specifically for lignocellulosic biofuel production.  This was done in 2007 and 2008 across two locations in Texas.  In 2007 experimental trials, the PS sorghum hybrids averaged 18.4 dry tons/ac in College Station, TX.  In 2008 the PS hybrids averaged 9.34 dry tons/ac in College Station, TX and 10.51 dry tons/ac in Halfway, TX.  High-parent heterosis values for biomass yield ranged from -65% to 154% and averaged 27% across all tests.  The presence of high-parent heterosis for biomass yield indicates that besides facilitating PS sorghum seed production, using hybrid PS sorghums can improve biomass yields.