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104 Kochi University Review, No. 97continue to ensure stable and sustainable rice production through the development ofhigh yielding, pest and abiotic stress resistant and good grain quality rice vari....

104 Kochi University Review, No. 97continue to ensure stable and sustainable rice production through the development ofhigh yielding, pest and abiotic stress resistant and good grain quality rice varieties.To date, since 1968, 138 MVs have been released -- 92 for irrigated, 19 for rainfed,13 for upland, 6 for cool-elevated, and 8 for saline-prone rice areas in the Philippines.These varieties are grouped into four generations based on the dates of release andtheir distinct characteristics (Estudillo et al., 2006). The MV first-generation (MV1)consisting of the IR series from IR5 to IR34 developed by IRRI and the C4 seriesdeveloped by UPLB were released from the mid-1960s to the mid-1970s. MV1 waspotentially higher yielding than traditional varieties (TVs) under ideal conditions butmore fertilizer responsive than TVs because it was short in stature with stiff strawsthat enabled it to bear more grains. The MV second-generation (MV2) consisting ofIR36 to IR62 was released from the mid-1970s to the mid-1980s. MV2 was designedto ensure yield stability by incorporating resistance to multiple pests and diseases. TheMV third-generation (MV3) consisting of IR64 to IR72 and PSBRc2 to PSBRc74 wasreleased from the mid-1980s to the mid-1990s. MV3 incorporated better grain qualityand stronger host plant resistance. The MV fourth-generation (MV4) were releasedafter 1995 and especially developed for production in adverse environments. Hybridrice varieties are also being developed under the national program for hybrid ricecommercialization and are now being adopted (Casiwan et al., 2007).-1020304050607080901001965 1967 1969 1971 1973 1975 1977 1979 1981 1983 1985 1987 1989 1991 1993 1995 1997 1999 2001 2003Year% MV0.00.51.01.52.02.53.03.54.04.55.05.56.0Area harvested (M ha)Irrigated (%MV)Rainfed (%MV)Upland (%MV)All ecosystems (%MV)Total area harvestedFig. 1. Trends in MV area harvested, 1965 to 2002, The Philippines