Evaluting the Impact of Drought Stress on Growth Responses in Rice

Abstract

Sri Lanka possesses over 2,000 traditional rice (Oryza sativa L.) varieties, many of which exhibit natural resilience to environmental stresses. The study aimed to identify drought-resistant accessions for future breeding and molecular analysis. A total of fourteen rice varieties, including improved high-yielding varieties (Ld376,8g377, At 378, Bg 38i Bg 251,89314,89252), and Sri Lankan traditional varieties (Niyan wee [Ac 1370], Dahanala lAc 6271, Swwandal [Ac 579], Kirimurunga lAc 3401, Masuran lAc 7761, Kahata samba lAc 3271, and Suduru samba lAc 9031), were evaluated under moderate drought stress conditions. The experiment used a completely randomized design (CRD) with five replicates per variety. Drought stress was applied at three growth stages by reducing water to 50o/o of held capacity. Morphological traits, leaf rolling, and leaf drying were assessed using a drought tolerance scoring system. Data analysis in Minitab 17 measured the relative increase (%) of all parameters before and after stress. At the reproductive stage, plant height (p : 0.020), leaf length (p : 0.001), and the number of leaves (p:0.033) showed significant variation, while the number of tillers (p:0.622) was not significantly different. The tallest plant was Kirimurunga (101.4 + 3.09 cm), and the shortest was Ld 376 (65.6 + 2.85 cm). Kirimurunga had the longest leaf length (60.8 + 4.32 cm), while accession 89251 had the shortest (22.6 + 1.88 cm). The highest number of leaves was observed in Bg 252 (16.4 + 2.06), whereas Suduru samba had the lowest (7 .2 + 1.35). The Bg 252 also had the highest number of tillers (5.6 t 0.81), while Suduru samba recorded the lowest (2.3 +0.61). According to the drought tolerance scoring system, the highly drought-tolerant varieties identified at the reproductive stage were Bg 381, Suwadel, Kirimurunga, and Masuran. Additionally, we identified Bg 252 and Bg 381 as drought-tolerant at the seedling stage, andBg257, Ld 316, At 378, and Dahanala at the reproductive stage. At grain filling stage Kirimurunga, Masuran, Bg 252, and At 378 showed increased leaf number, panicle traits, and spikelet count, indicating drought tolerance. These results aid droughttolerant rice breeding and suggest key accessions for molecular studies to reveal genetic traits, supporting marker-assisted selection and genetic engineering. Key words: Breeding selection, Drought stress, Ftrce (Oryza sativa L.), Traditional