Calcium-Dependent Protein Kinase 5 (OsCPK5) Overexpression in Upland Rice (Oryza sativa L.) under Water Deficit.

Water deficit significantly affects global crop growth and productivity, particularly in water-limited environments, such as upland rice cultivation, reducing grain yield. Plants activate various defense mechanisms during water deficit, involving numerous genes and complex metabolic pathways. Exploring homologous genes that are linked to enhanced drought tolerance through the use of genomic data from model organisms can aid in the functional validation of target species. We evaluated the upland rice OsCPK5 gene, an A. thaliana AtCPK6 homolog, by overexpressing it in the BRSMG Curinga cultivar. Transformants were assessed using a semi-automated phenotyping platform under two irrigation conditions: regular watering, and water deficit applied 79 days after seeding, lasting 14 days, followed by irrigation at 80% field capacity. The physiological data and leaf samples were collected at reproductive stages R3, R6, and R8. The genetically modified (GM) plants consistently exhibited higher OsCPK5 gene expression levels across stages, peaking during grain filling, and displayed reduced stomatal conductance and photosynthetic rate and increased water-use efficiency compared to non-GM (NGM) plants under drought. The GM plants also exhibited a higher filled grain percentage under both irrigation conditions. Their drought susceptibility index was 0.9 times lower than that of NGM plants, and they maintained a higher chlorophyll a/b index, indicating sustained photosynthesis. The NGM plants under water deficit exhibited more leaf senescence, while the OsCPK5-overexpressing plants retained their green leaves. Overall, OsCPK5 overexpression induced diverse drought tolerance mechanisms, indicating the potential for future development of more drought-tolerant rice cultivars.

Physiological and yield responses of contrasting upland rice genotypes towards induced drought.

Drought alters rice morphophysiology and reduces grain yield. This study hypothesized that the combined analysis of morphophysiological and agronomic traits enables a systemic approach to responses to water deficit, allowing the selection of resistance markers to upland rice. The objectives were to evaluate the effects of water deficit applied at the reproductive stage in plant water status, leaf gas exchanges, leaf non-structural carbohydrate contents, and agronomic traits in upland rice genotypes; and to verify if the analyzed variables may be applied to group the genotypes according to their tolerance level. Water deficit was induced by irrigation suppression in eight genotypes at R2-R3. Physiological and biochemical traits were evaluated at the end of the water deficit period, thenceforth irrigation was restored until grain maturation for the analysis of the agronomic traits. Water deficit reduced: Ψw (63.64%, average); gs (28-90%); transpiration rate (40.63-65.45%); RWC from Serra Dourada to Esmeralda (43.36-61.48%); net CO2 assimilation from Serra Dourada to Primavera (70.04-99.91%); iWUE from Esmeralda to Primavera (83.98-99.85%); iCE in Esmeralda (99.92%); 100-grain weight in CIRAD and Soberana (13.65-20.63%); and grain yield from Primavera to IAC 164 (34.60-78.85%). Water deficit increased Ci from Cambará to Early mutant (79.64-215.23%), and did not affect the tiller number, shoot dry biomass, fructose, and sucrose contents. The alterations in the variables distinguished groups according to the water regime. RWC, Ψw, leaf gas exchanges, and iCE were valuable traits to distinguish the water regime treatments, but not to group the genotypes according to the drought tolerance level. Supplementary Information: The online version contains supplementary material available at 10.1007/s12298-023-01287-8.

Phenotyping Root Systems in a Set of Japonica Rice Accessions: Can Structural Traits Predict the Response to Drought?

BACKGROUND: The root system plays a major role in plant growth and development and root system architecture is reported to be the main trait related to plant adaptation to drought. However, phenotyping root systems in situ is not suited to high-throughput methods, leading to the development of non-destructive methods for evaluations in more or less controlled root environments. This study used a root phenotyping platform with a panel of 20 japonica rice accessions in order to: (i) assess their genetic diversity for a set of structural and morphological root traits and classify the different types; (ii) analyze the plastic response of their root system to a water deficit at reproductive phase and (iii) explore the ability of the platform for high-throughput phenotyping of root structure and morphology. RESULTS: High variability for the studied root traits was found in the reduced set of accessions. Using eight selected traits under irrigated conditions, five root clusters were found that differed in root thickness, branching index and the pattern of fine and thick root distribution along the profile. When water deficit occurred at reproductive phase, some accessions significantly reduced root growth compared to the irrigated treatment, while others stimulated it. It was found that root cluster, as defined under irrigated conditions, could not predict the plastic response of roots under drought. CONCLUSIONS: This study revealed the possibility of reconstructing the structure of root systems from scanned images. It was thus possible to significantly class root systems according to simple structural traits, opening up the way for using such a platform for medium to high-throughput phenotyping. The study also highlighted the uncoupling between root structures under non-limiting water conditions and their response to drought.

Aging indicators for stored carioca beans.

High temperature, moisture content and radiation conditions, common in the tropics, accelerate the physiological post-harvest disorders in beans, affect integument color and bean hardness. This study explored the darkening and hardening mechanisms in carioca type beans during storage. The contrasting genotypes for bean darkening and hardening (BRS Estilo and BRS Pontal: rapid darkening and hardening; BRSMG Madrepérola and CNFC 10467: slow darkening and partially resistant to hardening; and a Canadian genotype of the Pinto Bean type resistant to darkening (negative control)) were evaluated right after harvest and after six months storage at 20.3 ±â€¯0.2 °C and 78.9 ±â€¯6.0% RH, with respect to their physicochemical, biochemical and morphological attributes. All the samples hardened with time, but the velocity of darkening did not always parallel the degree of hardening of the beans (that increase linearly with time), which indicates that the color of the bean integument was not a safe indicator to predict the culinary quality of carioca beans. During storage, the SOD (superoxide dismutase) activity and LP (lipid peroxidation) in the cotyledon increased, and the increase was more significant in the integument of the rapid-darkening genotypes. The oxidative stress detected in the beans apparently started in the green bean formation phase, continuing during post-harvest, especially for the rapid-darkening beans. Quantification of the bivalent ions in the bean fractions, together with the degree of membrane damage was positively associated with bean darkening, independent of the group. Thus, aging of the carioca beans could be triggered by a complex mechanism involving diverse intrinsic factors in different degrees according to the genotype and the post-harvest period, but some parameters could serve as indicators, as cooking time, hardness and color, to differentiate between rapid and slow darkening beans.

Genome-wide analysis of the transcriptional response to drought stress in root and leaf of common bean.

Genes related to the response to drought stress in leaf and root tissue of drought-susceptible (DS) and tolerant (DT) genotypes were characterized by RNA-Seq. In total, 54,750 transcripts, representative of 28,590 genes, were identified; of these, 1,648 were of high-fidelity (merge of 12 libraries) and described for the first time in the Andean germplasm. From the 1,239 differentially expressed genes (DEGs), 458 were identified in DT, with a predominance of genes in categories of oxidative stress, response to stimulus and kinase activity. Most genes related to oxidation-reduction terms in roots were early triggered in DT (T75) compared to DS (T150) suggestive of a mechanism of tolerance by reducing the damage from ROS. Among the KEGG enriched by DEGs up-regulated in DT leaves, two related to the formation of Sulfur-containing compounds, which are known for their involvement in tolerance to abiotic stresses, were common to all treatments. Through qPCR, 88.64% of the DEGs were validated. A total of 151,283 variants were identified and functional effects estimated for 85,780. The raw data files were submitted to the NCBI database. A transcriptome map revealed new genes and isoforms under drought. These results supports a better understanding of the drought tolerance mechanisms in beans.

Screening of Beneficial Microorganisms to Improve Soybean Growth and Yield

Abstract The objective of this research was to identify the best microorganisms, alone or in mixture for total biomass gain (root + shoot), positive change in gas exchange, nutrient uptake (root, shoot and grain) and yield and yield components in the soybean crop. Trial under greenhouse conditions had the experimental design in a completely randomized scheme with 26 treatments and four replicates. The treatments consisted of the rhizobacteria BRM 32109, BRM 32110 and 1301 (Bacillus sp.), BRM 32111 and BRM 32112 (Pseudomonas sp.), BRM 32113 (Burkholderia sp.), BRM 32114 (Serratia sp.), Ab-V5 (Azospirillum brasilense) and 1381 (Azospirillum sp.), and the fungus Trichoderma asperellum (a mix of the isolates UFRA.T06, UFRA.T09, UFRA.T12 and UFRA.T52). Besides, the same isolates were combined in pairs, completing 16 combinations. Control treatments received no microorganism. Microorganisms applied isolated or in combination, provided biomass gain, positive gas exchange, increases in nutrients uptake at the shoot and grain, and improved grain yield and its components than control plants. Stood out the combination Ab-V5 + T. asperellum pool, which provided a 25% improvement in grain yield.

Physiological characterization of common bean (Phaseolus vulgaris L.) under abiotic stresses for breeding purposes.

In the Brazilian wet and dry seasons, common beans (Phaseolus vulgaris L.) are grown under rainfed conditions with unexpected episodes of drought and high temperatures. The objective of this study was to evaluate the physiological mechanisms associated with drought adaptation traits in landraces and line/cultivars of beans from the Andean and Mesoamerican gene pools. Twenty-five genotypes, contrasting in terms of drought tolerance, were evaluated in a phenotyping platform under irrigated and rainfed conditions. Agronomic and physiological parameters such as grain yield, shoot structures, gas exchange, water potential, and osmotic adjustment were evaluated. The stress intensity was estimated to be 0.57, and the grain yield reduction ranged from 22 to 89%. Seven accessions, representative of the Andean and Mesoamerican germplasm (CF 200012, CF 240056, CF 250002, CF 900004, CNF 4497, CNF 7382, and SEA 5), presented superior performance in grain yield with and without stresses. The physiological responses under abiotic stresses were highly variable among the genotypes, and two Mesoamerican accessions (CF 200012 and SEA 5) showed more favorable adaptive responses. As the main secondary physiological traits, gas exchange and osmotic adjustment should be evaluated together with the grain yield to increase the selection efficiency of abiotic stresses-tolerant common bean lines.

Overexpression of a phospholipase (OsPLDα1) for drought tolerance in upland rice (Oryza sativa L.).

This work aimed to evaluate the drought tolerance of transformed plants of the cultivar BRSMG Curinga that overexpress the rice phospholipase D α1 (OsPLDα1) gene. The productivity of independent transformation event plants of the OsPLDα1 gene was evaluated in an experiment where 19 days of water deficit were applied at the reproductive stage, a very strict growing condition for upland rice. The non-genetically modified cultivar (NGM) under drought treatment reduced productivity by 89% compared with that under irrigated treatment, whereas transformed plants (PLDα1_E2) reduced productivity by only 41%. After the drought treatment, the PLDα1_E2 plants productivity was five times greater than that of the NGM plant. Moreover, no adverse effects on growth and development of the transgenic plants were observed. Seven days after the resumption of irrigation, PLDα1_E2 plants had higher stomatal conductance, greater photosynthetic rate, and transpiration rate than did NGM plants, as well as a higher expression level of the OsPLDα1 gene. A delay in the senescence process was observed in these PLDα1_E2 plants, and this was determined for the recovery of photosynthesis, with greater expression of the Rubisco and lower expression of the SOD. This finding was suggestive of decreased oxidative stress, probably due to gas exchange by the partial closure of the stomata of these transformed plants, which prevented the formation of reactive oxygen species. OsPLDα1 gene overexpression resulted in a reduction in production loss under severe water deficit and revealed a possibility for the development of upland rice cultivars that are more tolerant to extreme drought conditions.

Bioagents and silicon promoting fast early upland rice growth.

Upland rice can overcome major challenges through the insertion of silicate fertilization and the presence of plant growth-promoting microorganisms (PGPMs) during its cultivation, as these factors promote an increase in vigor and plant disease resistance. Two consecutive experiments were conducted to evaluate the beneficial effects of silicon fertilization combined with the PGPM, Pseudomonas fluorensces, Burkholderia pyrrocinia, and a pool of Trichoderma asperellum, in upland rice seedlings, cultivar BRS Primavera CL: (a) E1, selecting PGPM type and Si doses for rice growth promotion and leaf blast supression, and (b) E2, evaluating physiological characteristics correlated with mechanisms involved in the higher vegetative growth in highlighted treatments from E1. In E1, 2 Si t ha-1 combined with the application of T. asperellum pool or PGPM mixture increased 54% in root dry matter biomass and 35 and 65% in shoot and root lengths, respectively; it also suppressed 99% of rice blast severity. In E2, shoot and root dry matter biomass and length, photosynthetic rate, water use efficiency, total soluble sugar, and chloroplastidic pigments were superior in BRS Primavera CL seedlings treated with 2 Si t ha-1 and T. asperellum pool or PGPM mixture. Higher salicilic and jasmonic acid levels were found in seedlings treated with Si and T. asperellum pool, individually. These physiological characteristics may explain, in part, the higher vigor of upland rice seedlings promoted by the synergistic effect between silicate fertilization and beneficial microorganisms.

Effects of beneficial microorganisms on lowland rice development.

Microorganisms can promote plant growth by increasing phytomass production, nutrient uptake, photosynthesis rates, and grain yield, which can result in higher profits for farmers. However, there is limited information available about the physiological characteristics of lowland rice after treatment with beneficial microorganisms in the tropical region. This study aimed to determine the effects of different beneficial microorganisms and various application forms on phytomass production, gas exchange, and nutrient contents in the lowland rice cultivar 'BRS Catiana' in a tropical region. The experiment was performed under greenhouse conditions utilizing a completely randomized design and a 7 × 3 + 1 factorial scheme with four replications. The treatments consisted of seven microorganisms, including the rhizobacterial isolates BRM 32113, BRM 32111, BRM 32114, BRM 32112, BRM 32109, and BRM 32110 and Trichoderma asperellum pooled isolates UFRA-06, UFRA-09, UFRA-12, and UFRA-52, which were applied using three different methods (microbiolized seed, microbiolized seed + soil drenched with a microorganism suspension at 7 and 15 days after sowing (DAS), and microbiolized seed + plant spraying with a microorganism suspension at 7 and 15 DAS) with a control (water). The use of microorganisms can provide numerous benefits for rice in terms of crop growth and development. The microorganism types and methods of application positively and differentially affected the physiological characteristics evaluated in the experimental lowland rice plants. Notably, the plants treated with the bioagent BRM 32109 on the seeds and on seeds + soil produced plants with the highest dry matter biomass, gas exchange rate, and N, P, Fe, and Mg uptake. Therefore, our findings indicate strong potential for the use of microorganisms in lowland rice cultivation systems in tropical regions. Currently, an additional field experiment is in its second year to validate the beneficial result reported here and the novel input sustainability.

Biomass, gas exchange, and nutrient contents in upland rice plants affected by application forms of microorganism growth promoters.

Microorganisms are considered a genetic resource with great potential for achieving sustainable development of agricultural areas. The objective of this research was to determine the effect of microorganism application forms on the production of biomass, gas exchange, and nutrient content in upland rice. The experiment was conducted under greenhouse conditions in a completely randomized design in a factorial 7 × 3 + 1, with four replications. The treatments consisted of combining seven microorganisms with three application forms (microbiolized seed; microbiolized seed + soil drenched with a microorganism suspension at 7 and 15 days after sowing (DAS); and microbiolized seed + plant sprayed with a microorganism suspension at 7 and 15 DAS) and a control (water). Treatments with Serratia sp. (BRM32114), Bacillus sp. (BRM32110 and BRM32109), and Trichoderma asperellum pool provided, on average, the highest photosynthetic rate values and dry matter biomass of rice shoots. Plants treated with Burkolderia sp. (BRM32113), Serratia sp. (BRM32114), and Pseudomonas sp. (BRM32111 and BRM32112) led to the greatest nutrient uptake by rice shoots. Serratia sp. (BRM 32114) was the most effective for promoting an increase in the photosynthetic rate, and for the greatest accumulation of nutrients and dry matter at 84 DAS, in rice shoots, which differed from the control treatment. The use of microorganisms can bring numerous benefits of rice, such as improving physiological characteristics, nutrient uptake, biomass production, and grain yield.