Heterosis in sweet sorghum and selection of a new sweet sorghum hybrid for use in syrup production in appalachia

Although heterosis is well established in grain and forage sorghum [Sorghum bicolor (L.) Moench], reports of heterosis in sweet sorghum are limited to results from grain sorghum × sweet sorghum hybrids. Recent development of cytoplasmic male-sterile sweet sorghum lines allows creation of sweet sorghum hybrids for research and industry. Male sterility may also affect allocation of photosynthate to plant parts, creating the potential to increase sugar content in stems by eliminating seed as a sink. The objectives of this study were to compare performance of A₃ cytoplasmic male-sterile lines and A₃ cytoplasmic male-sterile hybrids to fertile B₃ counterparts and to each other. A₃ cytoplasmic male-sterile 'Dale', 'Wray', 'Sugar Drip', and N100 were crossed in all combinations to their male-fertile counterparts, resulting in 20 genotypes including the male-fertile lines. The 20 genotypes were grown in a randomized complete block in 2004 and 2005 at Lexington, KY. Male-sterile hybrids and lines had higher brix than male-fertile lines. Hybrids produced greater stalk yield due to taller plants with greater stem diameter. Juice fraction and juice composition remained relatively unchanged. Only six hybrids showed positive heterosis for brix. The greater juice yield and higher sugar content of selected hybrids such as A₃ N100 × Dale could produce more total syrup or ethanol than current pureline sweet sorghum varieties.