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概要：
108 Kochi University Review, No. 97irrigated (IRR) MV areas were planted with varieties released from 1986 to 1992. In1997, varieties released from 1990 to 1996 covered more than 50% of the rice areap....

108 Kochi University Review, No. 97irrigated (IRR) MV areas were planted with varieties released from 1986 to 1992. In1997, varieties released from 1990 to 1996 covered more than 50% of the rice areaplanted during the DS, in the irrigated areas. PSB Rc10 and PSB Rc14, both releasedin 1992, and PSB Rc18, released in 1994, were widely used varieties in the 1996-97 cropping year. In 2002, new rice varieties occupied 24% to 36% of the rice area.When compared with the 1997 situation, the area is relatively lower because PSBRc18, IR64, PSB Rc10, and Masipag varieties, none of which are ‘new variety’ perdefinition, dominated the farmers’ fields. Province level analysis indicates that in 2002,most of the farmers still used varieties released before the 1997 period, even while newvarieties occupied a significant portion of the rice area.In the few rainfed (RF) DS areas, only 10% of the areas were planted with newvarieties in 1992, but in the 1997 and 2002 surveys, 57% and 32% were plantedwith new varieties. These results imply that rainfed-rice farmers also adopt new ricevarieties almost as much as the irrigated-rice farmers. Some farmers also use irrigatedvarieties in the rainfed areas probably because there are only a few rainfed varietiesand the WS in favorable rainfed areas is almost similar to an irrigated ecosystem.However, the same surveys showed that more farmers in the irrigated areas (21%) usecertified and good seeds compared with rainfed farmers (10%). In 2002, 28% of thefarmer-respondents in irrigated areas adopted certified seeds or better, compared withonly 17% in the rainfed areas. It is possible that farmers in the rainfed rice areas buyTable 2. Trends of rice variety planted by farmers (%), by variety groupVariety Group1992 WS 1993 DS 1996 WS 1997 DS 2001 WS 2002 DSIRR RF IRR RF IRR RF IRR RF IRR RF IRR RFMV1a 3.3 6.8 2.1 0.0 2.3 2.1 2.1 2.0 0.4 0.5 0.1 0.0MV2b 29.2 31.0 27.1 70.0 12.2 20.3 12.0 15.7 4.6 9.0 4.1 3.3MV3c 53.0 56.7 56.1 20.0 73.7 66.7 71.4 68.5 73.2 59.0 60.7 55.5MV4d 0.1 0.2 0.2 0.0 0.8 0.5 1.3 0.7 7.3 10.4 18.8 14.7Hybrid 0.0 0.0 0.0 0.0 0.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0Masipag 0.1 0.7 0.0 0.0 2.7 2.5 3.3 2.7 4.8 7.4 5.1 9.7Traditional 8.6 1.8 8.4 0.0 0.6 1.1 1.2 1.4 5.0 6.6 4.0 8.8Unclassified 5.6 2.9 6.2 10.0 7.6 6.8 8.7 8.9 4.6 7.2 7.2 8.0a MV1 - IR series from IR5 to IR34; C4 series from the mid-1960s to the mid-1970sb MV2 - IR36 to IR62 released from the mid-1970s to the mid-1980sc MV3 - IR64 to IR72; PSB Rc varieties released from mid-1980s to mid-1990sd MV4 - Varieties released after 1995Note: IRR - irrigated; RF - rainfed