Evaluation of released and pre-released upland rice (Oryza sativa L.) for drought tolerance at germination and early seedling stage
No Thumbnail Available
Date
2025-05-19
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Uganda Christian University
Abstract
In this study, evaluation of the effect of drought on germination and early seedling traits, targeting both released and pre-released upland rice varieties for genotype identification suitable to rainfed conditions in Uganda. Considering the susceptibility of upland rice to water stress at early growing stages, particularly in regions with low and erratic rainfall, this study was also designed to provide more information for breeding programs, as well as policies aimed at promoting robust rice cultivation in these regions. The study which was carried out at Uganda’s National Crops Resources Research Institute (NaCRRI) applied a Split Plot arrangement under a Completely Randomized Design evaluating fifteen rice genotypes at 5 levels of simulated drought stress using Polyethylene Glycol 6000 (PEG-6000) concentrations of: 0%, 5%, 10%, 15%, and 20%. Germination metrics (percentage, velocity index, mean germination time, and synchrony) as well as early seedling parameters (shoot length, root length, fresh weight, dry weight, and drought injury scores) were evaluated. All germination and seedling performance indices were significantly reduced by increasing PEG concentrations, with PEG 20 having the most adverse effect on plants. Under extreme stress, the released varieties such as NamChe-5 had higher germination percentages (33.33%), the fastest mean germination time (4.88 days), the highest germination velocity index (3.28), and retained superior seedling dry weight (0.87 mg) and root length (2.47 cm), confirming its strong drought tolerance. However, some of these lines like UP-25(45) which were pre-released compared with released top cultivars demonstrated better performance, indicating their potential for varietal release in near future. While the drought-sensitive control IR64 demonstrated significantly lower responses in all parameters. The results demonstrate that early-generation screening can identify lines that outperform in drought environments, and pre-released genotypes offer potential for reducing yield losses in Uganda's rainfed upland rice production systems. It is, therefore, critical to incorporate early-stage drought tolerance in breeding programs for sustainable rice production under climate variability.