Abstract:

Rice landraces harbor extensive genetic diversity, and those sustained on-farm are intrinsically embedded within their surrounding ecological and cultural contexts. However, this diversity manifests in multiple ways and is often obscured by a morphologically uniform exterior. This review explores multiple dimensions of diversity in rice landraces, aiming to establish a hierarchy of genetic variations both within and among landrace populations, as well as their patterns of genetic differentiation. The review describes the natural, cultural, and agroecological niches, in which rice landraces have evolved across Asia. It then proceeds to review the structure of genetic diversity, as established through both varietal nomenclature and molecular analyses. Functional diversity within and among landrace populations, particularly that underlying key adaptation traits and grain quality characteristics, is described. The principal finding is that rice landraces are not merely reservoirs of genetic diversity, but rather well-structured genetic systems. These dynamic populations arise from the interplay of natural selection, cultural practices, and farmers’ preferences, carrying both practical and evolutionary significance. Growing evidence from farmers’ fields confirms that genetic diversity in rice landraces underpins their capacity for sustained, dynamic adaptation to environmental change, while also enabling the capture of new economic and other opportunities, a feature that distinctly sets them apart from genetically uniform modern varieties and pure-line cultivars. Molecular analyses and functional trait identification have revealed significant and well-structured genetic variation, often concealed beneath morphological uniformity. The hierarchical structure of this diversity, within fields, among seed lots, and across landscapes, is critical not only for local adaptation and resilience to changing conditions, but also for the design of effective conservation and utilization strategies. Thus, rice landraces represent not merely the legacy of past selection, but a vital resource for securing future economic prospects and navigating an uncertain world.

Key words: farmer’s selection, functional trait, local variety, molecular diversity, population structure