Abstract
Drought is a major abiotic stress factor affecting the growth and development of plants at all stages. Developing a screening tool for identifying drought stress tolerance during seedling establishment is important in the deployment of rice varieties suited to water-limited growing environments. An experiment was conducted to evaluate 100 rice genotypes, mostly belonging to the tropical japonica subspecies, for drought stress tolerance using low-cost, pre-fabricated mini-hoop structures. The rice seedlings were subjected to two different soil moisture regimes- control pots managed at 100% and drought pots at 50% field capacity, from 12 to 30 days after sowing (DAS). Several morpho-physiological parameters including root traits were measured to assess the response of genotypes to drought stress. Significant moisture stress × genotype interactions were found for most of the parameters measured. A cumulative drought stress response index (CDSRI) was developed by adding the individual response indices of all cultivars. Based on CDSRI and standard deviation values, 5 and 28 genotypes were identified as highly sensitive and sensitive to drought, respectively, and 45 as moderately sensitive. On the other hand, 16 and 6 genotypes were classified as tolerant and highly tolerant to drought, respectively. Cheniere, a released cultivar, and RU1402174, an experimental breeding line, were identified as the least and most tolerant to drought among the 100 genotypes tested. Significant linear correlation coefficients were obtained between CDSRI and root growth parameters (R2 = 0.91, n = 100) and CDSRI with shoot growth parameters (R2 = 0.48, n = 100), revealing the importance of root traits in studying and identifying drought tolerant lines during the seedling establishment stages in rice. The tolerant rice genotypes identified will be valuable for rice scientists in studying the mechanism for early season drought as well as for rice breeders for developing new genotypes best suited under growing environments prone to early-season drought.
Highlights
Rice (Oryza sativa L.) is one of the most widely consumed cereal crops across the globe, providing a staple diet for almost half of the human population [1]
Non-significant interactions were observed in root surface area (RSA), average root diameter (ARD), number of root tips (NRT), Longest root length (LRL), and RN while for physiological traits, the non-significant interaction was observed in SPAD
Significant variation was observed for most traits among lines and even across experimental setups, indicating the presence of genetic variation, which could be exploitable through breeding
Summary
Rice (Oryza sativa L.) is one of the most widely consumed cereal crops across the globe, providing a staple diet for almost half of the human population [1]. Water is undoubtedly one of the most precious inputs that rice requires to grow optimally during its entire life cycle starting from. For its growth and development and to be able to produce higher yields. With the onset of climate change-related challenges, the intensity and frequency of droughts are predicted to increase in most of the rice-growing areas. Drought could extend further into water-limited irrigated areas with greater severity. Water scarcity already affects more than 23 million hectares of rainfed rice production area in South and Southeast Asia alone. In Africa, recurring drought affects about 80% of the potential 20 million hectares of rainfed lowland rice. Drought affects rice production in Australia, China, USA, and many other countries. The world’s irrigated area per capita has decreased from 48 ha/1000 people in late 1970 to about 42 ha/1000 people in 2002 [3]
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