In Nepal, rice, with an annual production of 4.45 million t from 1.56 million ha, ranks first among the crops grown in the country (MOAC 2004). Early-maturing genotypes are grown mainly during chaite (spring) and bhadaiya (summer) seasons under irrigated conditions. Nearly 21% of total cultivated land is under irrigation.
Cultivation of chaite-season rice is limited because of poor quality and low yield. However, a single variety, Ch 45, has been planted since the late 1950s in most parts of the country. In 1998, brown planthopper damaged the monocrop, causing heavy losses in Chitwan District. In 2002, neck blast affected Ch 45 in 40% of the rice area in Chitwan. To improve production and productivity, suitable, early-maturing, and high-yielding genotypes with better grain quality were required in these areas.