Assessment of water stress on rice landraces from different agro-climatic zones in farwest Nepal

Abstract

Rice holds a significant position globally as the second most essential staple food, and in Nepal, it stands as the primary food source. Its cultivation demands considerable water. However, the growing prevalence of drought due to climate change poses a severe threat to rice production, particularly affecting Nepal's food security. Indigenous landraces, adapted to local microclimates, could potentially possess drought-tolerant qualities. Hence, this study focuses on assessing the response of selected rice landraces from the Far-west region of Nepal to drought conditions. The research covers three distinct agroclimatic zones of the region: Tarai, inner Tarai, and midhills. From each zone, four varieties were chosen, amounting to a total of 12 varieties. Each variety underwent three treatments: control, intermittent drought, and complete drought, with five replications for each treatment. The experiments were done under the plastic tunnel in farmers field. A range of morpho-agronomic variables such as tiller count, root length, hill height, shoot and root weight, panicle length, grain count per panicle, total filled and unfilled grain count per panicle, and yield were measured. Additionally, chlorophyll content and catalase activity were measured as biochemical parameters. Drought tolerance indices were calculated based on these measurements. Under water stress, most rice landraces decrease in tiller number, root length, and hill height. However, these landraces were able to maintain stable root and shoot weights despite the stressful conditions. While panicle length was reduced due to water stress, the number of grains per panicle remained consistent. This resulted in compromised yield under such stress condition. At the biochemical level, these rice landraces showed resilience by retaining their chlorophyll content and sustaining photosynthesis even during water stress. The range of the total chlorophyll was found to be 0.72 - 4.78 μg/g FW. The range of the catalase activity 0.14 – 0.51units/min/gram FW. Interestingly, landraces responded to water stress by increasing catalase activity, a sign of adaptation to cope with the stress. Based on drought indices, the Jhumke variety from Baitadi, Batebudo variety from Dadeldhura, and Sauthyari variety from Kanchanpur exhibited higher drought tolerance. It is recommended to extend the screening of drought tolerance to other rice landraces that are yet to be characterized and assessed for drought tolerance. The findings hold practical implications for local farmers and stakeholders. Key words: Rice-landraces, Water-stress, Agro-morphonomic traits, Drought tolerance, Crop resilience