Ahmed Abdelrahim

Water scarcity is a major constraint to wheat production in arid regions, highlighting the need for sustainable approaches to improve crop productivity and irrigation water-use efficiency (IWUE). Although Bacillus-based bioinoculants have been widely investigated, the potential of indigenous strains adapted to arid environments remains underutilized for the developing of site-specific bioinoculants. This study developed an integrated screening strategy combining plant growth-promoting (PGP) traits characterization, greenhouse evaluation, correlation analysis, and multivariate analyses to identify elite indigenous Bacillus strains capable of improving wheat performance under contrasting irrigation regimes. Fifty-one indigenous Bacillus strains representing 19 species, identified by 16S rRNA gene sequencing, were characterized for indole-3-acetic acid (IAA), ammonia (NH₃), siderophore production, and potassium-solubilizing activity and subsequently evaluated in greenhouse conditions under full (FI) and deficit (DI) irrigation. Plant growth was assessed at 85 days after sowing, while yield and yield-related traits were evaluated at physiological maturity (130 DAS). Significant variation was observed among the strains in both PGP traits and their effects on wheat performance. Selected strains increased vegetative growth traits by 22.2–53.7% under FI and 16.4–49.2% under DI, while improving yield-related traits and IWUE by 24.7–52.3% and 14.7–67.2%, respectively, compared with the uninoculated control. Correlation analysis identified IAA production as the PGP trait most strongly associated with wheat growth, grain yield, and IWUE, followed by NH₃ production, whereas siderophore production showed weak associations with most agronomic traits. Hierarchical cluster analysis and principal component analysis consistently identified Bacillus cereus A2, B. pumilus D2 and E3, and B. safensis D5 as the elite strains, while several additional indigenous strains also exhibited considerable potential under both irrigation regimes. This study demonstrates that the integrated screening approach enabled the identification of strain-level differences that could not be adequately captured by individual PGP traits alone, highlighting indigenous Bacillus strains as valuable resources for developing locally adapted bioinoculants to improve wheat productivity, IWUE, and drought resilience in arid and semi-arid agroecosystems.

Soil salinity and the scarcity of freshwater resources are two of the most common environmental constraints that negatively affect plant growth and productivity worldwide. The tomato (Solanum lycopersicum Mill.) plant is moderately sensitive to salinity. The identification of salinity-responsive genes in tomato that control long-term salt tolerance could provide important guidelines for its breeding programs and genetic engineering. In this study, a holistic approach of RNA sequencing combined with measurements of physiological and agronomic traits were applied in two advanced tomato breeding lines (susceptible L46 and tolerant L56) under long-term salinity stress (9.6 dS m⁻¹). Genotype L56 showed the up-regulation of known and novel differentially expressed genes (DEGs) that aid in the salinity tolerance, which was supported by a high salt tolerance index (81%). Genotype L46 showed both similar and different gene families of DEGs. For example, 22 paralogs of CBL-interacting kinase genes were more up-regulated in L56 than in L45. In addition, L56 deployed more SALT OVERLY SENSITIVE paralogs than L45. However, both genotypes showed the up-regulation of ROS-detoxifying enzymes and ROS-scavenging proteins under salinity stress. Therefore, L56 was more effective in conveying the stress message downstream along all available regulatory pathways. The salt-tolerant genotype L56 is genetically robust, as it shows an enhanced expression of a complete network of salt-responsive genes in response to saline conditions. In contrast, the salt-susceptible genotype L46 shows some potential genetic background. Both genotypes have great potential in future breeding programs.

Justification: Water-use efficiency (WUE) is the amount of carbon assimilated as biomass or grain produced per unit of water the crop uses, and it is considered a critical factor in maintaining the balance between carbon gain and water loss during photosynthesis, particularly in the face of global warming and drought challenges. Improving agricultural WUE is essential for sustainable crop production in water-scarce regions. Objective: This article explores the significance of WUE enhancement in agriculture, especially under drought conditions, and discusses various strategies to optimize WUE for improved crop productivity. Methods: We searched the scientific literature for articles on water-use efficiency published between 2010 and 2023 and selected the 42 most relevant studies for a comprehensive overview of strategies, technologies, and approaches to investigate sustainable agricultural practices to improve water-use efficiency in agriculture, particularly focusing on agronomic methods such as mulching, cover crops, canopy management, deficit irrigation, and irrigation modernization. Results: This review highlights several practical techniques for enhancing WUE, including sustainable irrigation practices, crop-specific agronomic strategies, and innovative technological solutions. By adopting these approaches, farmers can improve water management efficiency, reduce crop vulnerability to water stress, and ultimately enhance agricultural sustainability. In conclusion, improving water-use efficiency is an essential factor for ensuring food security in the face of climate change and water scarcity. By implementing innovative strategies and exploiting the power of technology, we can enhance WUE in agriculture, optimize crop production, conserve natural resources, and contribute to a more sustainable future.

Water scarcity, particularly in arid and semi-arid regions, poses a significant challenge to crop production, with drought being a prevalent factor limiting grain production globally. Enhancing agricultural water use efficiency is crucial for managing water resources effectively in these areas. Water resource management involves planning, developing, distributing, and optimizing the use of water resources. Water use efficiency management is also essential for crop growth in arid regions. Various agronomic and irrigation strategies can improve crop water use efficiency and drought tolerance. The primary goal of these strategies is to maximize irrigation efficiencies by applying the precise amount of water needed to restore soil moisture to the desired level. These sustainable practices not only reduce the cost of water and labor for farmers through reduced irrigation but also optimize the use of soil moisture storage. This review paper explores practical techniques to improve water use efficiency, highlighting the role of nutrients in enhancing water use efficiency in crop plants.

Salinity affects the morphological, physiological, and biochemical characteristics of several plant species. The current study was conducted to investigate differential salt tolerance potentials among ten duckweed clones under different salt-stress conditions. Morphological and physiological parameters, including fronds length, fronds number, root length, root number, Na⁺/K⁺, chlorophyll, proline contents, and fresh harvest weight, were recorded for each of the ten duckweed clones collected from different Saudi Arabia regions. Additionally, the expression patterns of seven salt-related genes were monitored in a salt-tolerant duckweed genotype. The results show that the Madinah-2 (Spirodela polyryiza) and Al-Qassim (Landoltia punctata) clones presented higher performances for all the tested morphological and physiological parameters compared to other genotypes under salt-stress conditions. At concentrations greater than 150 mM NaCl, these aforementioned traits were affected for all the genotypes tested, except Madinah-2 (S. polyryiza) and Al-Qassim (L. punctata) clones, both of which exhibited high tolerance behavior under high salt conditions (200 mM and 250 mM NaCl). The principal component analysis (PCA) showed that the first five principal components accounted for 94.8% of the total variance among the studied traits. Morphological and physiological traits are the major portions of PC1. Moreover, the expression pattern analysis of NHX, BZIP, ST, and KTrans transcript revealed their upregulation in the Al-Qassim clone under salt-stress conditions, suggesting that these genes play a role in this clone’s tolerance to salt-induced stress. Overall, this study indicates that the Al-Qassim clone could be used in a brackish-water duckweed-based treatment program with a simultaneous provision of valuable plant biomass.

Duckweeds, or Lemnaceae, are widespread aquatic plants. Morphology-based identification of duckweed species is difficult because of their structural complexity. Hence, molecular tools provide significant advantages for characterizing and selecting species or clones for sustainable commercial use. In this study, we collected and characterized ten duckweed isolates from nine different regions in Saudi Arabia (SA). Based on the morphological characterization and phylogenetic analysis of intergenic spacer sequences of chloroplast DNA using six barcoding markers, the clones were classified into three genera, represented by seven species: Lemna gibba L., Lemna minor L., Lemna japonica Landolt, Lemna aequinoctialis Welw., Lemna perpusilla Torr., Spirodela polyryiza (L.) Schleid., and Landoltia punctate G. Mey. Lemna gibba was revealed to be a distinct dominant duckweed species in many regions of SA. Five barcoding markers showed that L. gibba, L. minor, and L. punctata were the most widely distributed species in the country. However, L. punctata, L. perpusilla, and S. polyryiza were the dominant species in the Al-Qassim, Madinah-1, and Madinah-2 regions, respectively. Moreover, the morphological traits revealed variations for these clones, relative to other studied duckweed clones. According to the results obtained in this study, three out of six plastid markers (trnH-psbA, matK, and atpF-atpH) helped to identify the dominant duckweed species in Saudi Arabia. Further evaluation based on adaptability, molecular genetic studies, and functional genomics is needed for these species to be used at the commercial level in Saudi Arabia.