Restoration of the traditional high-altitude rice variety Dumbja in Bhutan

Farmers and consumers in Bhutan perceive that the quality traits of the popular, local, high-altitude rice variety Dumbja, which has been cultivated since ancient times, has deteriorated in terms of its phenotypic characteristics, particularly its taste and aroma. This four-year study therefore aimed to agronomically evaluate and compare accessions of the traditional Bhutanese rice variety Dumbja and a commonly grown improved cultivar with what is considered to be the official Dumbja variety. Fifteen accessions of the Dumbja variety—nine conserved in-situ by farmers and six conserved ex-situ by the National Gene Bank—were evaluated agronomically in a partially replicated design over four cropping seasons. The trials were conducted in Tshento, Paro district, a high-altitude rice-growing area, 2400 m.a.s.l., where the variety has been grown since ancient times. Trials identified significant differences for 1000 kernel weight, plant height, and tiller number, but not for grain yield. Compared with the improved cultivar used as a control, all 15 accessions were taller, with smaller kernels and, in some cases, with more tillers. As a group, the in-situ accessions were significantly shorter, with more tillers than the ex-situ accessions. Only one of the ex-situ accessions held by the National Gene Bank was recognized by farmers as the original Dumbja variety. The results are discussed in relation to in-situ vs ex-situ agrobiodiversity conservation strategies and also highlight the key role of farmers’ knowledge in restoring a traditional variety.