Background: Rice, one of the main foods in Brazil and the world, is sensitive to chilling (0–15 °C), especially in the germination and reproductive stages. Chilling causes delayed germination and affects coleoptile elongation at the S3 stage (needlepoint), causing poor plant establishment, stunted growth, and non-vigorous plants, also impacting weed management. Elucidating the mechanisms responsible for resilience under cold conditions helps the development of tolerant cultivars. Transcription factors (TFs) act in stress response signaling, making them indispensable in the tolerance mechanism. Objective: Thus, this study aimed to identify and characterize the expression profile of transcription factors in the response to chilling stress in rice at the germination stage. Methods: To determine the transcriptional profile of 2408 genes belonging to 56 TF families, RNAseq was performed on the shoot tissue of seedlings of Oro (chilling-tolerant) and Tio Taka (chilling-sensitive) genotypes grown under control conditions (25 °C) and chilling stress (13 °C) until the S3 stage. Results: Of the total genes analyzed, 22% showed significant differential expression in the analyzed cultivars. There were 117 genes that showed significant differential expression in the tolerant cultivar, 60 of which were downregulated and 57 upregulated. In the sensitive cultivar, 248 genes had a significant differential expression, of which 98 genes were downregulated and 150 genes were upregulated. A total of 170 genes encoding TFs were commonly and significantly differentially expressed in the tolerant and sensitive genotypes. Conclusions: Here, we revealed potential new targets involved in the regulation of chilling stress in rice at the S3 stage.

Water deficit affects rice growth, development, and yield. Knowledge of genetic diversity for water deficit tolerance, as well as the genetic architecture that is responsible for this trait, can accelerate rice cultivars’ improvement. In this study, different tools were applied to assess genetic diversity and identify genome regions associated with shoot and root traits in rice germplasm grown under water deficit at an early vegetative stage. A panel of 177 rice genotypes grown under water deficit was evaluated for root length (RL), root dry weight (RDW), shoot length (SL), and shoot dry weight (SDW). Genetic diversity was investigated using means grouping and principal component analysis. For the genome-wide association study, a general linear model was applied, using RL, RDW, SL, and SDW phenotypic data converted into Best Linear Unbiased Prediction (BLUPs); genotypic data (1185 single nucleotide polymorphism—SNPs-loci); and population structure. Overall, little genetic diversity was observed, but genotypes with a higher water deficit tolerance were identified. Several significant SNPs were mapped, 81, 5, 53, and 41 for RL, RDW, SL, and SDW, respectively. Among the identified genes, there are those encoding kinases, proteins involved in phytohormone and cell wall metabolism, and Cytochrome P450. The obtained results provide insight into genetic diversity and the genetic architecture of water deficit tolerance, which will be useful in improving this trait in rice grown in Brazil.

Rice (Oryza sativa) is among the most important crops worldwide; however, rice crops demand high water consumption. Future projections indicate reduced water availability and severe drought events, which may affect rice crops as the cereal is highly sensitive to drought stress. Thus, cultivars with lower water demand for irrigation or drought escape capacities are among the strategies to address this issue. This study aimed to assess five mutant rice genotypes in terms of growth cycle length, other agronomic interest traits, and drought response in the reproductive stage. The mutant genotypes evaluated showed a shortening of the growth cycle compared to the original cultivar, BRS Pampeira, representing a drought escape strategy. In addition, mutations did not negatively affect plant height and crop yield. However, similar to the original cultivar, mutants are not tolerant to water deficit in the reproductive stage. The genotypes evaluated have potential to be released as early cycle cultivars, which can reduce water demand during the harvest season while presenting a drought escape strategy.

For the genetic improvement of species of agricultural importance, it is essential to have a broad genetic base, ensuring sufficient variability to increase opportunities for selecting specific traits of interest in the field. Additionally, the use of techniques complementary to conventional breeding systems is crucial for effectively exploring the available genetic variability. Currently, there are several techniques, such as in vitro culture, genetic transformation, gene editing, marker-assisted selection, and mutation induction, among others. This review aims to synthesize the historical development, current applications, and future potential of mutation induction in crop improvement, with an emphasis on its role in adaptation to climate change and food security. Mutation induction techniques have played a key role in addressing challenges related to food security by promoting the development of new varieties for the agricultural sector in various countries. Through the analysis of the FAO/IAEA Mutant Varieties Database, it was possible to identify how mutation induction has contributed to the development of cultivars adapted to the specific needs of food security and climate. The FAO/IAEA program (https://nucleus.iaea.org), which promotes the use of nuclear techniques in agriculture, has resulted in the release of more than 3404 mutant varieties in 233 cultivated species in 75 countries. In several countries, as indicated in the MVD, the use of mutant germplasm in plant breeding programs has been crucial for adapting crops to new climatic conditions, in addition to meeting the growing demand for food. These advances highlight the potential of mutation induction as an essential tool to address future agricultural challenges, underlining the importance of continuing to invest in nuclear techniques for breeding cultivars adapted to climate change and global food security.

The objective of this work was to characterize chilling tolerance in rice mutant families of the M₄ generation, at the seedling stage. Two experiments were carried out: chilling tolerance was evaluated in 43 mutant families, in the 'BRS Querência' original genotype, and in 19 commercial genotypes. In Experiment II, 8 mutant families from Experiment I, 'BRS Querência', and a mutant of the M₅ generation were tested. In both experiments, seedlings were evaluated under two conditions: 10°C for seven days and 25°C for seven days. In Experiment I, the induced mutations in rice led to varied responses in chilling tolerance traits, with some M₄ mutant families outperforming the original genotype. Experiment II highlighted the impact of mutations on chilling-tolerance, particularly in terms of leaf discoloration and plant recovery. Mutant families of the M₄ generation differ from the original genotype 'BRS Querência' in chilling tolerance at the seedling stage. The mutant families M36, M54, and M56 and 'BRS Querência' show genetic similarity, indicating a lack of chilling tolerance during the seedling stage. The mutant families M17, M21, M22, and M26 are promising for rice breeding programs because they present chilling tolerance. The M30 mutant family exhibits the best performance for all analyzed traits, indicating chilling tolerance at the seedling stage.

Rice (Oryza sativa L.) is a staple food for more than half of the world's population, but its production is threatened by salinity, which affects its development in both early and reproductive stages. Gamma radiation-induced mutation has been used to generate genetic variability and develop cultivars better adapted to saline conditions. However, selecting tolerant mutants is challenging due to the genetic complexity of salinity response and the need for large populations. In this study, 100 rice mutants (M5 and M6) and two control cultivars (sensitive and tolerant) were evaluated under salt stress (NaCl 120 mM) in a greenhouse, assessing shoot and root growth and dry weight. Despite the variability generated, no mutant outperformed the tolerant cultivar in all traits analyzed, highlighting the difficulty of selecting promising individuals from small populations. Furthermore, environmental factors may have contributed to inconsistencies between generations, reinforcing the need for large-scale screening. The most effective strategy involves initial field selection, validation under controlled conditions, and further agronomic reassessment. Technologies such as remote sensing-based phenotyping could improve efficiency, but they remain costly. Future studies should integrate new methodologies and keep the selection of salt-tolerant mutants in early generations (M2 and M3) from large populations, alongside yield evaluation to confirm their agronomic applicability under salinity conditions.