shortened to 100 days by producing varieties whose light sensitivity is reduced, harvesting is possible within the dry season and it will be possible to have two or three harvests a year in the same paddy field.
As a result of research by IRRI into the development of new varieties to match these target specifications, it was found that Dee-Geowoo-Gen, which is a dwarf variety from Taiwan, was the most promising starting material as it is responsive to fertilizers, and this led to the successful development of a revolutionary new variety called 1R8 by cross-breeding it with the Peta variety from Indonesia in 1966.
1R8 is an Indica rice which was only 60% of the height of the ordinary varieties earning them the name semi-dwarf, and many more grains were produced without it falling down when it was well fertilized, as the stalk was thick and much sunlight could be harnessed as the leaves stood upright. 1R8 was a really revolutionary variety which gave a high yield of eight tons per hectare under the right conditions, by reducing the negative characteristics of the traditional varieties.
The cultivated area rapidly expanded from 2 millions hectares in the rice growing season of 1967/8, to 4 million in 1968/69, after the distribution of the 1R8 seeds to farmers, and there was an increase in rice production also.
However, although 1R8 had the above qualities, its resistance to disease was weak, and virus diseases which were not common before suddenly increased, and damage by harmful insects such as the leafhopper and fly also increased. Also, it didn't taste as good as the traditional varieties.
The IRRI tried to modify development of the new varieties by using low input technology instead of high input technology to rectify those failings in 1R8, and 1R5 in 1968, and 1R20 in 1969, were developed to be more resistant to disease and insects, and to be taller than 1R8. However, insects quickly adapted to the challenge, and the damage caused to 1R20 became greater, so in 1973, 1R26 was recommended as the strongest variety against the leafhopper, fly, grass moth, and virus and white dry disease.
Additionally, significant damage was done by a previously unknown type
