Boro rice cultivation is a special system of rice cultivation in low productive, waterlogged, low-lying deepwater land during November-May in eastern India. In such land, neither kharif (Jul-Oct) rice nor rabi (Nov-Apr) wheat is successful because of excess water. The boro crop is usually sown in November and transplanted when the temperature starts rising from January onward. The average minimum temperature during this period varies from 8 to 12°C. Crop productivity is very high (Thakur and Mishra 1990); consequently, boro rice has become popular in Bihar and eastern Uttar Pradesh. The suitability of rice varieties for boro cultivation mainly depends on their germination, tolerance for low temperature at the seedling stage, and seedling vigor.