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概要：
Recent Adoption and Spatial Diversity of Modern Rice Varieties in the Philippines 105Several studies have documented the rapid adoption of MVs over the period from1968 to the 1980s (David et al., 1994....

Recent Adoption and Spatial Diversity of Modern Rice Varieties in the Philippines 105Several studies have documented the rapid adoption of MVs over the period from1968 to the 1980s (David et al., 1994; Herdt et al., 1983). Not much data, however,have been publicly available on more recent time periods, especially about thedevelopment or diffusion of new rice varieties from the 1990s. A recent study assessedthe changing contributions of successive generations of modern varieties (MVs) ofrice to yield increase and stability and changes in total factor productivity (TFP) in thePhilippines (Estudillo et al., 2006), but this study used adoption data only from CentralLuzon, Philippines, and secondary data in which the use of specific MVs can not bedistinguished.In addition, plant breeders justify the continuous breeding and release of varietiesas a means to promote genetic diversification which can contribute to the sustainabilityof rice production growth in the future. Genetic diversity is known to substantiallyreduce a crop’s vulnerability to diseases especially in tropical countries where thereis staggered planting. Understanding the variety dispersal in the major rice producingregions of the country would indicate to some extent the genetic diversity of the ricecrops being planted in the country.This paper thus aims to (1) measure variety adoption rates of officially releasedrice varieties, particularly the later generation varieties, using three rounds of nationalrice-based farm household surveys (RBFHS); (2) present the spatial diversificationof varieties planted in farmers’ fields, and (3) draw policy recommendations from theresults of the study.1. Data and methods1) Data usedThe study used data from the RBFHS being conducted by the SocioeconomicsDivision (SED) of PhilRice every five years covering the 1992-93, 1996-97 and 2001-02 crop years. The RBFHS in 1992-93 covered 15 major rice-producing provinceswith 977 respondents. The total rice area in these major rice-producing provincescomprise around 50% of the country’s total rice area harvested. On the other hand,the 1996-97 and 2001-02 surveys covered 30 and 33 provinces with 2239 and 2474valid respondents, respectively. The sum of the rice areas represented by the provincescovered in the 1996-97 and 2001-02 rounds is around 70% of the country’s total rice