Insights into fodder quality enhancement in sorghum through genetic and molecular approaches

Abstract

Forage sorghum (Sorghum bicolor L. Moench), a climate-resilient, drought-tolerant fodder crop with high adaptability and biomass potential, plays a significant role in addressing global livestock feed and fodder demands. However, its complex quantitative quality traits, such as crude protein, fibre fractions, crude fat, lignin and antinutritional factors like hydrogen cyanide (HCN) content, show considerable variation across genotypes and are strongly influenced by developmental stage, management practices and environmental conditions. This review comprehensively summarises the genetic and molecular strategies for improving forage quality traits in sorghum, highlighting key trait relationships, yield-quality trade-offs, harvesting effects and emerging genomic tools to accelerate the development of nutritionally superior and safer forage sorghum cultivars. Conventional breeding programs have contributed to the development of improved forage sorghum cultivars. Brown midrib lines have emerged as a successful breeding strategy, with average neutral detergent fibre (NDF) and acid detergent fibre (ADF) contents of 57.5 % and 33.67 % dry matter (DM), compared to 59.45 % and 36.51 % DM in conventional varieties. However, this is often accompanied by biomass yield penalties of approximately 14.33 %. Recent advances in molecular breeding, such as functional genomics, genome-wide association studies (GWAS), quantitative trait loci (QTL) mapping, marker-assisted selection and antisense-mediated downregulation, have enabled the precise identification of the genetic architecture of forage quality traits. In particular, QTL mapping uncovered 43 overlapping QTLs controlling various forage quality traits and biomass traits, demonstrating their interconnections and possibilities for their simultaneous improvement. The identified candidate genes and pleiotropic loci controlling forage quality traits offer new opportunities for genomic-assisted improvement, where gene-editing tools such as CRISPR/Cas9 can simultaneously enhance feed safety, biomass yields and nutritional quality.