A landrace preserved by hunters
In the rugged, mountainous Tōhoku region of northern Japan, the Matagi are traditional winter hunters. For centuries, these communities have lived a life deeply connected to the land, hunting bear and deer while practicing a sustainable existence in places like the Ani area of Akita Prefecture. This relative isolation allowed for the preservation of unique cultural practices and agricultural traditions, including the cultivation of distinct rice landraces. A landrace is a domesticated plant variety that has adapted over time to its specific natural and cultural environment. Unlike modern commercial cultivars, which are bred for uniform traits, landraces maintain a greater degree of genetic diversity.
The Matagi cultivated rice that could withstand the colder climate and shorter growing seasons of northern Honshu. Generations of seed saving and small-scale farming created a crop perfectly suited to the local ecology. This process, free from the pressures of modern agricultural standardization, inadvertently protected genetic traits that have become highly valuable today. The rice associated with the Matagi is a source of sustenance; it comes from a specific, long-standing relationship between a people and their environment.
The genetics of slow digestion
The reason for this heritage rice's unique property lies in its starch composition. All rice starch is made of two types of molecules: amylopectin and amylose. Amylopectin has a branched structure and is easily broken down by digestive enzymes, causing a rapid increase in blood sugar. Amylose has a linear structure that forms tight, crystalline bundles, making it harder to digest and resulting in a slower, more gradual release of glucose. Rice with a higher proportion of amylose generally has a lower glycemic index (GI), a measure of how quickly a food raises blood sugar levels.
The synthesis of amylose in the rice grain is controlled primarily by a single gene known as Waxy (Wx). This gene codes for an enzyme called granule-bound starch synthase (GBSS I), which is essential for building the long, straight chains of amylose. Different versions, or alleles, of the Waxy gene lead to different levels of enzyme activity and, consequently, different amounts of amylose in the rice. High-amylose rice varieties can have an amylose content of 25-33%, compared to low-amylose varieties (10-20%) like many popular Japanese table rices, which are prized for their sticky texture. The Matagari landrace possesses a genetic profile that results in this high amylose content, a trait preserved through traditional farming that is now of great interest for managing blood sugar.