Foxtail millet (Setaria italica) has great potential as food, feed, and feedstock in the biofuel industries. Currently, its applications are still few, but research on foxtail millet as a feedstock is growing. Feedstock with high-cellulose and low-lignin content is desirable for feed digestion and biofuel production. The following study aimed at characterizing phenotypic variations related to feedstock utilization in eight Indonesian foxtail millet genotypes and identifying superior genotypes for feed or biofuel feedstock development. The experiment was in a randomized complete block design arrangement with genotypes as a single factor and three replications. Acid detergent fiber (ADF) percentage, cellulose content, lignin content, leaf number, and plant height emerged as key traits for selecting superior foxtail millet for feedstock. These traits showed high broad-sense heritability and moderate to high genotypic and phenotypic variation, indicating strong genetic control. Cellulose content displayed a significant correlation (p < 0.001) with lignin content, plant height, leaf number, tiller number, and heading time. These associations support their use in multi-trait selection. Heatmap clustering and PCA revealed substantial genotypic variability, enabling effective selection based on feedstock quality traits. Hambapraing, Mauliru2, and ICERI7 appeared as promising genotypes for further hybridization programs, contributing desirable traits for feedstock development.

Keywords: Biofuel, cellulose, genotypes, genotypic variability, feed, lignin, selection criteria

Key findings: Among eight Indonesian foxtail millet (S. italica L.) genotypes, Hambapraing, Mauliru2, and ICERI7 emerged as promising parental genotypes, offering favorable attributes for incorporating into breeding programs to improve the feedstock quality.