Integrating molecular insights on stress responses and agronomic traits for breeding in forage grasses

Abstract

In Latin America, pasture-based systems form the backbone of cattle production, with tropical forage grasses providing the primary and most economical feed source for ruminants. These grasses are cultivated across millions of hectares because of their high biomass yield, adaptability to poor soils, and suitability for extensive grazing. However, shifting land-use patterns and climate change are pushing forage systems into more marginal environments, where water scarcity and declining soil fertility compromise productivity and nutritional quality. Despite their critical role in regional and global livestock supply chains, tropical forage grasses have historically received limited breeding attention, largely owing to biological constraints such as apomixis, polyploidy, and self-incompatibility. This review explores the current understanding of the molecular mechanisms regulating key morphophysiological traits in tropical forage species, focusing on plant responses to abiotic (e.g. drought, heat) and biotic (e.g. pests, pathogens) stress. We highlight progress in building genomic resources, with emphasis on quantitative trait locus (QTL) mapping, transcriptomics, and genome-wide association studies (GWAS), which are uncovering trait-linked markers that can inform selection strategies. Additionally, we examine how transgenic technologies and gene editing tools such as CRISPR-Cas can be employed to circumvent reproductive barriers and accelerate the development of improved cultivars. By integrating conventional breeding with cutting-edge molecular tools, we propose a roadmap for developing climate-resilient, nutritionally enhanced tropical forages to support the long-term sustainability of grass-based livestock systems.