SUBMERGENCE TOLERANCE IN SELECTED RICE VARIETIES OF SRI LANKA: AN EVALUATION OF Oryza sativa L. ACROSS DIVERSE WATER SOURCES

Abstract

Submergence poses a major challenge to rice cultivation, significantly reducing harvest outcomes. Therefore, the adoption of rice varieties with enhanced tolerance to submergence is crucial. This study examines how water quality and environmental conditions influence the submergence tolerance of selected improved rice varieties (Oryza sativa L.) in Sri Lanka. After 24 hours pretreatment procedure, LD 376, LD 253, LD 368, and LD 408 selected rice varieties were submerged for 12 days with Well water, Canal water and Chlorinated tap water from 6 different locations. During the pretreatment, each sample was submerged in corresponding water of each location for 24 hours followed by the weight treatment for 24 hours. Then, cultivation was carried out using Well water obtained from Walasmulla (L1) and Udugama (L2) locations, Canal water from Embilipitiya (L3) and Hambantota (L4) locations and chlorinated tap water from Tangalle (L5) and Galle (L6) locations. SPAD readings were obtained from randomly selected rice plants after 12 days, while bud length was measured daily with respective water samples. According to analyzed data, LD 408 variety showed the highest bud growth rate in Canal water which has high conductivity values and also LD 408 rice sample which was submerged in Canal water in Location 3 & 4 has relatively high SPAD values. Thus, LD 408 rice variety exhibited resilience to Canal water with high conductivity, resulting from dissolved soil minerals such as NaCl and CaSO₄ as well as sewage, maintaining rapid bud growth and elevated SPAD values, which indicates strong tolerance to submergence and ionic stress. It implies its suitability for cultivation in flash-flood-prone areas and other marginal environments with saline or nutrient-rich water in Sri Lanka.