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112 Kochi University Review, No. 97options replace the variety planted, without necessarily increasing the number ofvarieties planted at one time.In terms of the index of whether or not certain specie....

112 Kochi University Review, No. 97options replace the variety planted, without necessarily increasing the number ofvarieties planted at one time.In terms of the index of whether or not certain species dominate others, theBerger-Parker index ranged from as low as 1.02 (the case of Davao Oriental, wherethe IR64 quality is distinct and demanded by consumers so that almost 98% of thetotal area was planted with IR64) to as high as 8.5 (the case of Laguna province, whichis located near IRRI, where as many as 26 different rice varieties were planted in atotal of 64 hectares sampled. This range and the relatively large standard deviationespecially in the 2002 DS indicate wide variability in the extent to which one varietydominates in a given area. The Berger-Parker Index overall mean though is relativelylow considering the total number of commercially released varieties, implying thatselected preferred rice varieties indeed dominate the farmers’ fields. The Berger-Indexshowed a lowering of dominance between the 1992-93 and 1996-97 periods, but noconsistent trend from the 1996-97 to 2001-02 periods. Decreased dominance is alsoevident during the DS which suggests that farmers are probably trying more varietiesduring the less risky DS. Farmers try new varieties during the DS because it is lessvulnerable to pests and diseases and the optimum yield can be better expressed.The wide difference in the diversity index across provinces is also reflected inthe calculated Shannon index--for example, both close to zero (0.13) and a maximumof 2.85 in the 2001 WS. A close to zero Shannon index means that the area sharedistribution of the varieties is not even. The mean Shannon index has not significantlychanged from the 1996-97 to 2001-02 periods although there is an observed slightdecrease implying a less even area share distribution.ConclusionThe main contribution of this paper is to document and describe, using three setsof nationwide farmers’ surveys, the recent adoption of rice varieties in farmers’ fields,especially the later generation varieties. Data showed a progression in the use of MVsfrom the early to the later generations evident from the decreasing trend in the use ofMV2s and the increasing trend in the use of MV4s. This information can be used toencourage policymakers to continually support and strengthen the current efforts ofpublic rice breeding research and extension. One observation is that the proximity