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概要：
Recent Adoption and Spatial Diversity of Modern Rice Varieties in the Philippines 113of the rice area to the source of original seeds has an effect on the current state ofmorphological diversity and t....

Recent Adoption and Spatial Diversity of Modern Rice Varieties in the Philippines 113of the rice area to the source of original seeds has an effect on the current state ofmorphological diversity and that farmer to farmer learning is a strong factor for this.Thus, it is important that the current provincial variety adoption rates and diversity betaken into account when planning for variety testing and promotion. Variety monitoringis important and should be considered as part of the mandate of the Bureau ofAgricultural Statistics (BAS) which conducts quarterly surveys of rice-based farmers.Regarding variety diversification, the three cross-section data showed that around70% to 80% of the rice areas in the country are planted with only 10 different varietiesin a given period, the majority of which are varieties released more than five yearsbefore the survey period. The spatial diversity indices implied that there are relativelywide differences in diversity across provinces but not so clear trends across periods.There is an indication of a relative increase in richness and lower variety dominancein the DS, but there is no sufficient evidence of significant changes in spatial diversity.This suggests that the continued development of varieties may be maintainingthe current morphological diversity in farmers’ fields. The data, however, is onlyquinquennial which limits more trend analysis of diversity and variety replacement.Further studies on the exact genetic diversity of varieties in farmers’ fields consideringparentage, and on the determinants of the spatial diversity will be necessary forbiodiversity conservation purposes. Further analysis of the relationship between spatialdiversity and vulnerability to pests and diseases is also recommended.Remarks: This is an abridged version of a paper published in Agronomy Journal 100:1380-1389,American Society of Agronomy, 2008 (USA).ReferencesBenin, S. et al., 2004. The economic determinants of cereal crop diversity on farms in theEthiopian highlands. Agricultural Economics 31, 197-208.Brennan, J.P., 1984. Measuring the contribution of new varieties to increasing wheat yields.Review of Marketing and Agricultural Economics 52(3), 175-95.Brennan, J.P., and D. Byerlee, 1991. The rate of crop varietal replacement on farms: Measures andempirical results for wheat. Plant Varieties and Seeds 4, 99-106.Casiwan C.B. and Y. Morooka, 2007. Can the use of hybrid rice improve farmers’ yield andincome in the Philippines? Japanese Journal of Farm Management 45 (1), 94-98.David, C. and K. Otsuka, 1994. “Technological Change, Land Reform, and Income Distribution