Development of Nutrient-Enriched Silage Sorghum through Strategic Crossbreeding and Marker-Assisted Selection

Commodities

Practices

This project aligns with the Alternative Crops/Animals program's focus by enhancing the nutritional value of sorghum (Sorghum bicolor (L.) Moench) silage, a vital feed resource in semi-arid regions. Sorghum's drought tolerance and high biomass make it a promising alternative to corn silage, but its lower protein and starch digestibility limit its utility. With increasing water constraints, demand for water-efficient silage sorghum has surged. Our recently identified high-protein digestibility (HPD) and waxy (high-starch) sorghum alleles offer a unique opportunity to address these limitations. We propose to breed novel silage sorghum varieties by incorporating these alleles into elite silage sorghum. Additionally, the new germplasm will enable studies on the combined effects of these grain quality traits on seed development and forage quality. This effort will yield silage sorghum with improved nutritional content, digestibility, and resilience, positioning them as competitive alternatives to conventional silage crops. By enhancing forage quality and reducing water dependency, these improved varieties will support the economic viability of livestock production in water-scarce regions. The project leverages advanced breeding techniques and molecular tools to deliver sustainable, high-quality silage sorghum, contributing to food security and agricultural resilience in challenging environments.

Figures_SARE2025This project aims to revolutionize silage sorghum by developing elite germplasm that combines superior nutritional value with the agronomic resilience of silage backgrounds, leveraging proprietary mutant resources, a genomics-driven breeding pipeline, and the extensive sorghum breeding collaborative network established by the PI's lab. From the sorghum mutant population Dr. Jiao created (Jiao et al., 2016; Jiao et al., 2024), we have identified the trait donors for nutrition enhanced silage sorghum: high protein digestibility (HPD) (Application Number: PCT/US25/21601) and waxy endosperm with low amylose content for high starch digestibility (waxy endosperm sorghum) (Pallavi et al., under review) in the grain (Figure-1). The HPD line offers increased protein content and digestibility, valuable for high-quality silage sorghum suitable for livestock. Waxy endosperms provide a strategic advantage in silage production due to their high amylopectin and low amylose content, which significantly enhances starch and protein digestibility (Sattler et al., 2009). Additionally, waxy sorghum's lower viscosity during processing improves nutrient availability, making it a high-value, performance-enhancing forage for sustainable livestock systems.

We aim to improve forage sorghum's nutritional quality by introgressing HPD and high starch digestibility (waxy) alleles into elite silage lines using molecular marker-assisted selection. Notably, the HPD allele is the first sorghum genetic variant with an identified causal gene and available marker for breeding. This novel combination enhances both protein and starch content, offering material to study its impact on seed development and grain quality, addressing a key knowledge gap. The goal will be pursued through two defined objectives.

Objective 1:

Pre-breeding High-Nutrition Silage Sorghum by Introgression Backcrossing

To develop high-nutrition silage sorghum, we will introgress two key traits: high protein digestibility (HPD) and high starch digestibility (waxy) into elite silage sorghum backgrounds. Preliminary F1 material generated from HPD × waxy crosses will serve as the donor source. In Year 1, two successive backcross generations will be conducted in the greenhouse. In Year 2, the remaining two backcross generations will be completed under field conditions to ensure agronomic adaptability (Figure 2). Trait introgression will be guided by Kompetitive Allele-Specific PCR (KASP) genotyping, targeting causal mutations for each trait. Progeny will be screened at each generation to identify individuals carrying the desired recessive alleles. Final selections will focus on silage-type lines homozygous for both traits, combining improved nutritional quality with optimal biomass and agronomic performance.

Objective 2: Evaluate the combined impact of high protein and starch digestibility for sorghum seed development.

This project will generate novel sorghum germplasm featuring both HPD and waxy traits. We will evaluate the combined impact of these traits on grain quality and seed development. Homozygous lines with both alleles will be selected to assess nutritional benefits and any agronomic trade-offs. The Jiao lab, in collaboration with established partners, will employ sorghum seed evaluation protocols such as the Single Kernel Characterization System (SKCS) to measure hardness index, kernel weight, and diameter. Nutritional profiling will include total protein, kafirin, starch content, and amylose concentration via colorimetric analysis, offering a comprehensive view of trait influence on grain composition and digestibility.