Improving Sweet Sorghum for the Southeast.

The sugary juice of sweet sorghum (Sorghum bicolor (L.) Moench) can be used to produce ethanol or other chemicals. The bagasse can be burned for energy or used for cellulosic ethanol, and the grain and leaf portions for livestock feed.  Most current cultivars are pure lines that produce little seed on very tall plants, which is a major limitation.  Hybrid seed can be produced using short-statured seed parents.  A test was conducted at Tifton, GA to assess heterosis and combining ability for various yield components in sweet sorghum, using a Design II mating design with 57 hybrids.  At harvest, a sample of three stalks was taken from each plot and separated into leaves, stems, and panicles, and the juice was extracted from the stems.  All components were weighed both fresh and dried.  The yield of each component was estimated based on its proportion of the total biomass yield.  Plant height, lodging percentage, and days to anthesis were also recorded.  A similar test was later conducted using a subset of hybrids to investigate the effects of planting date.  Total biomass yields of hybrids were generally similar to those of their male parents, but hybrids also tended to mature earlier.  Early planting produced higher yields and resulted in less lodging than later planting.  Incorporating genes for insect and disease resistance is also a major goal of our breeding program.  A major recessive gene for resistance to white sugarcane aphid (Melanaphis sacchari) is being mapped, as well as a major dominant gene for root-knot nematode (Meloidogyne incognita) resistance in sweet sorghum.