Abstract

Sweet sorghum is considered one of the best sources of bioethanol due to its higher total reducing sugar content, which ferments completely to produce ethanol coupled with its adaptation to the changing climate. A study was carried out in Ethiopia, during the 2015/16 crop season, to determine the extent of phenotypic and genotypic relationships among 13 agronomic traits and six quality components of 28 sweet sorghum genotypes. Panicle weight and width, dry matter yield, thousand kernel weight and harvest index had significant positive correlation with grain yield and exerted favourable direct effects both at phenotypic and genotypic levels. Ethanol yield was also correlated with juice yield, sugar yield and fresh stalk yield. Therefore, these yield and quality components are suggested to receive due attention during sweet sorghum varietal selection. Moreover, days to maturity had negative correlation and imposed negative direct effect on grain yield, which may indicate the possibility to select high yielding, early maturing dual purpose varieties for dry environments where terminal drought is rampant. The studied genotypes were grouped into three clusters according to their D² values, worthy of future breeding work considering the special merits in each cluster depending on the objectives of the breeding program. Some of the genotypes excelled as one of the two commercial sugarcane varieties used as controls for some quality traits. Therefore, considering their less water requirement, faster production cycle, and additional advantage of grain production over sugarcane, sweet sorghum stalks can serve as alternatives to sugarcane for use as feedstock in drier areas of the world under the changing climate.

Key words: Bioethanol, correlation, juice, path-coefficient, sweet sorghum.