Environmental stressors negatively affect crop growth and yield. Limited information is available about the synergistic use of biochar and plant growth-promoting rhizobacteria (PGPR). A field study was conducted to evaluate the effect of biochar in combination with PGPR (Pseudomonas koreensis and Bacillus coagulans) for alleviating water deficit and saline soil in rice (Oryza sativa L.). Two growing seasons, 2017 and 2018, were examined using twelve combinations of three irrigation intervals every 6 days (I₁), 8 days (I₂), and 10 days (I₃) and four soil treatments (control, PGPR, biochar, and combination of PGPR + biochar) in salt-affected soil. The findings exhibited that synergistic use of biochar and PGPR alleviated the negative effect of these stressors. The integrative use of biochar and PGPR caused an increment in soil moisture content and physicochemical properties. Significant increasing in chlorophyll content, relative water content, stomatal conductance, K⁺ and K⁺/Na⁺ contents occurred with decreasing proline content and Na⁺ content, which confirmed the efficacy of this approach. As a result, the highest yield and its related traits were attained when biochar and PGPR were added together under irrigation interval I₁, which was on par with I₂. We concluded that increased nutrients uptake (N, P, and K) were the cause of the superior rice productivity resulting from co-PGPR biochar. Synergistic use of biochar and PGPR could be an effective strategy for improving plant growth and productivity under stressors.

Water deficit is a pivotal abiotic stress that detrimentally constrains rice growth and production. Thereupon, the development of high-yielding and drought-tolerant rice genotypes is imperative in order to sustain rice production and ensure global food security. The present study aimed to evaluate diverse exotic and local parental rice genotypes and their corresponding cross combinations under water-deficit versus well-watered conditions, determining general and specific combining ability effects, heterosis, and the gene action controlling important traits through half-diallel analysis. In addition, the research aimed to assess parental genetic distance (GD) employing simple sequence repeat (SSR) markers, and to determine its association with hybrid performance, heterosis, and specific combining ability (SCA) effects. Six diverse rice genotypes (exotic and local) and their 15 F₁ hybrids were assessed for two years under water-deficit and well-watered conditions. The results revealed that water-deficit stress substantially declined days to heading, plant height, chlorophyll content, relative water content, grain yield, and yield attributes. Contrarily, leaf rolling and the sterility percentage were considerably increased compared to well-watered conditions. Genotypes differed significantly for all the studied characteristics under water-deficit and well-watered conditions. Both additive and non-additive gene actions were involved in governing the inheritance of all the studied traits; however, additive gene action was predominant for most traits. The parental genotypes P₁ and P₂ were identified as excellent combiners for earliness and the breeding of short stature genotypes. Moreover, P₃, P₄, and P₆ were identified as excellent combiners to increase grain yield and its attributes under water-deficit conditions. The hybrid combinations; P₁ × P₄, P₂ × P₅, P₃ × P₄, and P₄ × P₆ were found to be good specific combiners for grain yield and its contributed traits under water-deficit conditions. The parental genetic distance (GD) ranged from 0.38 to 0.89, with an average of 0.70. It showed lower association with hybrid performance, heterosis, and combining ability effects for all the studied traits. Nevertheless, SCA revealed a significant association with hybrid performance and heterosis, which suggests that SCA is a good predictor for hybrid performance and heterosis under water-deficit conditions. Strong positive relationships were identified between grain yield and each of relative water content, chlorophyll content, number of panicles/plant, number of filled grains/panicle, and 1000-grain weight. This suggests that these traits could be exploited as important indirect selection criteria for improving rice grain yield under water-deficit conditions.

Endophytic microorganisms, including bacterial and fungal species, establish symbiotic relationships within plant tissues, contributing to plant growth, nutrient acquisition, and stress resilience. In this review, multiple roles of endophyte-plant interactions have been discussed. Endophytes aid in nitrogen fixation for plants, enhance nutrient solubilization and uptake, control the attack of phytopathogens on plants, and help the plants to tolerate environmental stresses. The molecular mechanisms of these interactions, uncovered by the advancements in genomics, metabolomics, and microbiome engineering, reveal novel bioactive compounds and metabolic pathways that can improve crop resilience. The integration of multi-omics technologies and functional validation holds great potential for sustainable agriculture, offering new strategies for formulating effective biostimulants, bioinoculants, and biocontrol agents to improve crop health, agricultural productivity, and nutritional quality.

Knowledge of combining ability and genetic diversity are important prerequisites for the development of outstanding hybrids that are tolerant to high plant density. This work was carried out to assess general combining ability (GCA) and specific combining ability (SCA), identify promising hybrids, estimate genetic diversity among the inbred lines and correlate genetic distance to hybrid performance and SCA across different plant densities. A total of 28 F₁ hybrids obtained by crossing eight adverse inbred lines (four local and four exotic) were evaluated under three plant densities 59,500 (D1), 71,400 (D2) and 83,300 (D3) plants ha⁻¹ using spilt plot design with three replications at two locations during 2018 season. Increasing plant density from D1 to D3 significantly decreased leaf angle (LANG), chlorophyll content (CHLC), all ear characteristics and grain yield per plant (GYPP). Contrarily, days to silking (DTS), anthesis–silking interval (ASI), plant height (PLHT), ear height (EHT), and grain yield per hectare (GYPH) were significantly increased. Both additive and non-additive gene actions were involved in the inheritance of all the evaluated traits, but additive gene action was predominant for most traits. Inbred lines L₁, L₂, and L₅ were the best general combiners for increasing grain yield and other desirable traits across research environments. Two hybrids L₂ × L₅ and L₂ × L₈ were found to be good specific combiners for ASI, LANG, GYPP and GYPH. Furthermore, these hybrids are ideal for further testing and promotion for commercialization under high plant density. Genetic distance (GD) among pairs of inbred lines ranged from 0.31 to 0.78, with an average of 0.61. Clustering based on molecular GD has effectively grouped the inbred lines according to their origin. No significant correlation was found between GD and both hybrid performance and SCA for grain yield and other traits and proved to be of no predictive value. Nevertheless, SCA could be used to predict the hybrid performance across all plant densities. Overall, this work presents useful information regarding the inheritance of maize grain yield and other important traits under high plant density.

The aim of the study was to estimate the impact of soil amendments (i.e., phosphogypsum and plant growth-promoting rhizobacteria (PGPR)) separately or their combination on exchangeable sodium percentage (ESP), soil enzymes’ activity (urease and dehydrogenase), pigment content, relative water content (RWC), antioxidant enzymatic activity, oxidative stress, productivity, and quality of quinoa under deficient irrigation conditions in two field experiments during the 2019–2020 and 2020–2021 seasons under salt-affected soil. Results revealed that ESP, soil urease activity, soil dehydrogenase activity, leaf chlorophyll a, b, and carotenoids, leaf K content, RWC, SOD (superoxide dismutase), CAT (catalase), and POD (peroxidase) activities were declined, resulting in overproduction of leaf Na content, proline content, and oxidative stress indicators (H₂O₂, malondialdehyde (MDA) and electrolyte leakage) under water stress and soil salinity, which negatively influence yield-related traits, productivity, and seed quality of quinoa. However, amendment of salt-affected soil with combined phosphogypsum and seed inoculation with PGPR under deficient irrigation conditions was more effective than singular application and control plots in ameliorating the harmful effects of water stress and soil salinity. Additionally, combined application limited Na uptake in leaves and increased K uptake and leaf chlorophyll a, b, and carotenoids as well as improved SOD, CAT, and POD activities to ameliorate oxidative stress indicators (H₂O₂, MDA, and electrolyte leakage), which eventually positively reflected on productivity and quality in quinoa. We conclude that the potential utilization of phosphogypsum and PGPR are very promising as sustainable eco-friendly strategies to improve quinoa tolerance to water stress under soil salinity.

Siderophores are iron-chelating low-molecular-weight compounds that bind iron (Fe³⁺) with a high affinity for transport into the cell. The newly isolated strain Streptomyces tricolor HM10 secretes a pattern of secondary metabolites. Siderophore molecules are the representatives of such secondary metabolites. S. tricolor HM10 produces catechol, hydroxamate, and carboxylate types of siderophores. Under 20 μM FeCl₃ conditions, S. tricolor HM10 produced up to 6.00 µg/mL of catechol siderophore equivalent of 2,3-DHBA (2,3-dihydroxybenzoic acid) after 4 days from incubation. In silico analysis of the S. tricolor HM10 genome revealed three proposed pathways for siderophore biosynthesis. The first pathway, consisting of five genes, predicted the production of catechol-type siderophore similar to petrobactin from Bacillus anthracis str. Ames. The second proposed pathway, consisting of eight genes, is expected to produce a hydroxamate-type siderophore similar to desferrioxamine B/E from Streptomyces sp. ID38640, S. griseus NBRC 13350, and/or S. coelicolor A3(2). The third pathway exhibited a pattern identical to the carboxylate xanthoferrin siderophore from Xanthomonas oryzae. Thus, Streptomyces strain HM10 could produce three different types of siderophore, which could be an incentive to use it as a new source for siderophore production in plant growth-promoting, environmental bioremediation, and drug delivery strategy.