The Role of Stalk Traits in Influencing Sorghum Juice Yield
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Sweet sorghum is an outstanding feedstock choice for bioethanol production, but the gap between theoretical and commercial ethanol yields must be reduced to improve economic viability. Extractable juice yield is a primary limiting factor for higher ethanol yield. Juice yield is genetically complex and laborious to measure with current phenotyping techniques. Therefore, dissecting the genetic basis underlying juice yield and alternative approaches to measure the trait during selection are needed. Because stem properties directly influence sorghum juice yield, the major objectives of this study were to assess the ability to predict juice yield using stem traits and to map quantitative trait loci controlling such characters by conducting two independent and complimentary studies. Coefficient path analysis showed that stalk weight and stalk volume had the greatest total effect on juice yield, followed by stalk diameter, stalk length and plant height. The direct effects for stalk diameter on stalk volume and juice yield were positive and approximately two-fold greater than the direct effect for plant height on the same traits. Equation modeling demonstrated that juice yield was satisfactorily predicted by jointly assessing stalk weight and stalk moisture or stalk diameter, plant height, and stalk juiciness. More importantly, these traits were moderately to highly repeatable within and across environments. One constitutive QTL for stem pithiness was mapped on chromosome 6 that co-localized with a stem moisture QTL recently mapped in sorghum. Moreover, two other adaptive QTLs were found on chromosomes 7 and 9 for the same trait, the presence of which appeared to be influenced by water availability. A consistent pleiotropic QTL affecting stem moisture, bagasse moisture, and stem diameter was detected on chromosome 1. Results from this research suggest that the genetic control of juice yield component stem-traits is mostly governed by adaptive QTLs, whose presence and magnitude vary greatly between experiments. Overall, the results indicated that phenotypic prediction models and marker-assisted selection can be used to accelerate the selection process of juice yield.
De Carvalho Junior, Geraldo Afonso (2016). The Role of Stalk Traits in Influencing Sorghum Juice Yield. Doctoral dissertation, Texas A&M University. Available electronically from