To screen rice germplasm with different genetic backgrounds for cadmium (Cd) accumulation in brown rice from common cultivated rice, we monitored grain Cd concentrations and characterized their patterns of 54 main varieties planted at two sites [Fuyang (FY) and Changshan (CS) in Zhejiang Province, China] with both low and high Cd-polluted levels. We found most varieties got higher Cd levels than 0.2 mg/kg in the Cd-polluted soil with the normal agronomic management, which suggested high risk of Cd exposure from the two sites. High Cd accumulation pattern was found in hybrid rice, but it differed between subspecies. Moreover, varieties with the same female or male parent may have different Cd accumulation capacities, meaning that the environment factors should be considered to screen low-Cd-accumulation varieties.

Uncovering the mechanism of hydrogen sulfide (H₂S) in improving rice seed germination under aluminum (Al) toxicity conditions is important for rice production in acidic soil. In the present study, an Al sensitive rice variety Kasalath was used. Pretreatment with 0.1 mmol/L sodium hydrosulfide (NaHS, H₂S donor) under 70 mmol/L AlCl₃ (indicated as Al + NaHS treatment) increased rice seed germination by 27.95%, germination potential by 474.16%, and the germination index by 43.44%, compared with Al treatment. The treatment of Al + NaHS reduced the Al content in rice seeds by 16.31% and 32.11% and increased the internal H₂S content by 3.82% and 8.90% at 3 and 5 d of treatment, respectively, compared with Al treatment. Al + NaHS treatment significantly increased the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), peroxidase (POD) and ascorbic acid- glutathione (AsA-GSH) synthesis, and significantly reduced H₂O₂, O₂·̄ and malonaldehyde (MDA) contents in rice seeds at 3 and 5 d of treatment, compared with Al treatment. Al + NaHS treatment significantly decreased the pectin content, inhibited pectin methyl esterase (PME) activity, upregulated the expression of OsSTAR1/2 to reduce or mask Al-binding sites in the cell wall, and inhibited the expression of Al transporter gene ONRAT1 to reduce Al uptake, compared with Al treatment. The expression of the vacuolar Al transporter gene OsALS1 was significantly increased under Al + NaHS treatment to promote the transport of cytoplasmic Al into the vacuoles under Al toxicity conditions. In addition, compared with Al treatment, the phytohormones zeatin, dihydrozeatin, gibberellin and auxin, which are related to cell division and seed germination, were significantly increased under Al + NaHS treatment.

Assessing the impact of climate change (CC) on agricultural production systems is mainly done using crop models associated with climate model outputs. This review is one of the few, with the main objective of providing a recent compendium of CC impact studies on irrigation needs and rice yields for a better understanding and use of climate and crop models. We discuss the strengths and weaknesses of climate impact studies on agricultural production systems, with a particular focus on uncertainty and sensitivity analyses of crop models. Although the new generation global climate models (GCMs) are more robust than previous ones, there is still a need to consider the effect of climate uncertainty on estimates when using them. Current GCMs cannot directly simulate the agro-climatic variables of interest for future irrigation assessment, hence the use of intelligent climate tools. Therefore, sensitivity and uncertainty analyses must be applied to crop models, especially for their calibration under different conditions. The impacts of CC on irrigation needs and rice yields vary across regions, seasons, varieties and crop models. Finally, integrated assessments, the use of remote sensing data, climate smart tools, CO₂ enrichment experiments, consideration of changing crop management practices and multi-scale crop modeling, seem to be the approaches to be pursued for future climate impact assessments for agricultural systems.

Aromatic rice is considered an important commodity in the global market because of its strong aroma and eating and cooking quality. Asian countries, such as India and Pakistan, are the leading traders of Basmati rice, whereas Thailand is the major supplier of Jasmine rice in the international market. The strong aroma of rice is associated with more than 300 volatile compounds, among which 2-acetyl-1-pyrroline (2-AP) is the principal component. 2-AP is a phenotypic expression of spontaneous mutations in the recessive gene OsBadh2 or Badh2. The present review focuses on the origin, evolution and diversity of genetic resources of aromatic rice available worldwide. A brief discussion is presented on the genes responsible for quality traits along with details of their molecular genetics. This compilation and discussion will be useful for future breeding programs and the biofortification of quality traits of aromatic rice to ensure food security and nutritional need.

Rice is sensitive to salinity stress at both the seedling and reproductive stages. The present study used 145 rice genotypes comprising of 100 landraces and 45 advanced breeding lines collected from different regions of India. These genotypes were evaluated in hydroponics under control [electrical conductivity (EC_e) ~1.2 dS/m] and saline (EC_e ~10.0 dS/m) environments along with susceptible (IR29) and tolerant (FL478) checks. The stress susceptibility index for eight morphophysiological traits was estimated. Analysis of variance showed significant differences among the genotypes for all the parameters studied in control, stress and relative stress conditions. We identified 3 landraces (Kuttimanja, Tulasimog and IET-13713I) as tolerant and 14 lines as moderately tolerant to salt stress. Strong correlations in the morphological (root and shoot lengths) and physiological traits (shoot Na⁺, Ca²⁺ and Mg²⁺ contents, and Na⁺/K⁺ ratio) were observed under all the conditions. The hierarchical cluster analysis grouped the genotypes into five clusters, among which cluster II comprised salt-tolerant lines. Haplotyping of Saltol region using 11 simple sequence repeat markers on 17 saline tolerant and moderately tolerant lines was conducted. Markers AP3206F, RM10793 and RM3412b, located close to SKC1 gene (11.23‒12.55 Mb), displayed diverse allelic variations and they were not related to the FL478 type. In this region, tolerant lines like Kuttimanja, IET-13713I and Tulasimog have new alleles. As a result, these lines may be suitable candidates for novel genomic regions governing rice salinity tolerance. Salt-tolerance ability of Kuttimanja, Tulasimog and IET-13713I was validated in two years in three salinity stress environments. These promising lines can be used in breeding programs to broaden the genetic base of salinity tolerance in rice, and it may help to dissect key genomic regions responsible for salinity tolerance.

Iron (Fe) toxicity, generated from excess reduced ferrous Fe (Fe²⁺) ion formation within the soil under submerged condition, is a potent environmental stress that limits lowland rice production. Total 11 diverse Thai rice genotypes, including a recognized tolerant genotype Azucena and a susceptible genotype IR64, were evaluated against 5 Fe²⁺ levels [0 (control), 150, 300, 600 and 900 mg/L] to screen the tested genotypes for their Fe-toxicity tolerance and to classify them as a sensitive/tolerant category. The evaluation was conducted by a germination study, followed by a polyhouse study on growth, yield and physiochemical performances. Results showed significant variations in Fe²⁺-tolerance across genotypes. Increasing Fe²⁺ level beyond 300 mg/L was detrimental for germination and growth of all the tested genotypes, although germination responses were negatively affected at Fe²⁺ ³ 300 mg/L. Physiochemical responses in the form of leaf greenness, net photosynthetic rate, membrane stability index and Fe contents in leaf and root were the most representative of Fe²⁺-toxicity-mediated impairments on overall growth and yield. Difference in physiochemical responses was effectively correlated with the contrasting ability of the genotypes on lowering excess Fe²⁺ in tissues. Analysis of average tolerance and stress tolerance index unveiled that the genotypes RD85 and RD31 were the closest to the tolerant check Azucena and the sensitive check IR64, respectively. The unweighted pair group method with arithmetic means clustering revealed three major clusters, with cluster II (four genotypes) being Fe²⁺ tolerant and cluster I (four genotypes) being Fe²⁺ sensitive. Principal component (PC) analysis and genotype by trait-biplot analysis showed that the first two components explained 90.5% of the total variation, with PC1 accounting for 56.6% and PC2 for 33.9% of the total variation. The identified tolerant rice genotypes show potentials for cultivation in Fe²⁺-toxic lowlands for increased productivity. The findings contribute to the present understanding on Fe²⁺-toxicity response and provide a basis for future genotype selection or rice crop improvement programs against Fe²⁺-toxicity.

As an abiotic stress, adverse germination temperatures cause serious disruptions in physiological and biochemical processes involved in seed germination. Using a factorial experiment, we examined the effects of different seed priming treatments on enzymatic and biochemical performances of rice seed germination under different temperatures. Each of the rice genotypes (Hashemi, Sadry-domsefid, IRON-70-7053-7 and NORIN-22) was primed with hydro-hardening, KCl, CaCl₂ and ascorbic acid (AsA) and without a priming agent as a control at low (15 ºC), optimum (25 ºC) and high (35 ºC) germination temperatures. The results showed that the enzymatic and biochemical performances of all the rice genotypes were affected by the seed priming agents, especially under the low germination temperature. At 15 ºC, seed priming with AsA was found to be the best agent for the activities of amylase, α-amylase, catalase (CAT), peroxidase (POX), ascorbate peroxidase (APOX) and superoxide dismutase (SOD) as well as the content of soluble sugars in the NORIN-22 genotype, and for protease activity and soluble protein content in the IRON-70-7053-7 genotype. SOD at the low germination temperature and CAT, POX and protease at the optimum and high germination temperatures were the most important enzymes in occurrence of germination potential in terms of seedling length, vigor index, normal seedling rate and germination rate. Under the priming agents, the highest changes in normal seedling rate were observed at the low and optimum germination temperatures by AsA priming in the Hashemi and NORIN-22 genotypes, and at the high germination temperature under KCl priming in the Hashemi genotype.

Alternate wetting and drying (AWD) system, in which water has been reduced by approximately 35% with an increased occurrence of beneficial arbuscular mycorrhizal (AM) symbiosis and no negative impact on rice yield, was proposed to utilize water and nutrients more sustainable. In this study, we selected six rice cultivars (Centauro, Loto, Selenio, Vialone nano, JSendra and Puntal) grown under AWD conditions, and investigated their responsiveness to AM colonization and how they select diverse AM taxa. In order to investigate root-associated AM fungus communities, molecular cloning-Sanger sequencing on small subunit rDNA data were obtained from five out of the six rice cultivars and compared with Next Generation Sequencing (NGS) data, which were previously obtained in Vialone nano. The results showed that all the cultivars were responsive to AM colonization with the development of AM symbiotic structures, even if with differences in the colonization and arbuscule abundance in the root systems. We identified 16 virtual taxa (VT) in the soil compartment and 7 VT in the root apparatus. We emphasized that the NGS analysis gives additional value to the results thanks to a more in-depth reading of the less represented AM fungus taxa.