The development of improved rice varieties in most countries of Asia has generally resulted in their widespread adoption by farmers, with the replacement of traditional varieties leading to the erosion of the rice germplasm base in these countries. In most Asian countries, this change took place during the 1970s and 1980s. However, in Lao PDR there had been little impact on the way rice was cultivated and as late as the early 1990s, more than 90% of lowland rice cultivation in the country was still based on the use of traditional varieties, and almost 100% of upland rice cultivation being based on traditional varieties (Schiller et al 2001). Changes in rice production practices in Lao PDR started about 1995, following the release of the first of a series of improved varieties that were developed within the country. Anticipating that Lao farmers would quickly adopt the improved varieties in combination with technologies capable of significantly improving rice yields, a program to collect a representative sample of the traditional rice germplasm for long-term conservation commenced in mid-1995. In a collaborative project between the Lao Ministry of Agriculture and Forestry and the International Rice Research Institute (IRRI), between 1995 and early 2000 a total of 13,192 samples of cultivated rices were collected, together with 237 samples of six wild rice species in the genus Oryza. Subsequent to 2000, a further 510 samples of traditional cultivated rices were collected from remote areas of special interest by the Lao National Agriculture and Forestry Research Institute. This paper describes the classification of the traditional rice germplasm which was collected and which is now preserved in the Genetic Resources Center (GRC) of IRRI. More detailed information on the collections is available in records maintained by the GRC, as well as in Appa Rao et al (2006a,b,c,d,e). The Lao collection now preserved at the GRC is second largest for any single country after India, and the largest collection of glutinous rice for any country (Laos being recognised as a center of origin of glutinous rices). The remarkable genetic diversity of the traditional rice cultivars in the Lao PDR jointly reflects 92 The Lao Journal of Agriculture and Forestry, No. 28 (Special Issue) January - June 2013 the country’s rich cultural and geographic diversity, together with the country’s relative isolation until recent times. The collecting that was undertaken between 1995 and 2000 
was timely, in that many of the traditional varieties collected in that period are no longer available in the farming areas where they were developed and grown, often for many generations. As with many other countries in the Asian region, farmers have been receptive to the adoption of improved higher-yielding varieties that have quickly replaced traditional varieties, particularly in lowland rice growing areas.

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