Assessment of changes in physiological and biochemical traits in four pistachio rootstocks under drought, salinity and drought + salinity stresses

Integration analysis of miRNA-mRNA pairs between two contrasting genotypes reveals the molecular mechanism of jujube (Ziziphus jujuba Mill.) response to high-temperature stress

With global warming, high temperature (HT) has become one of the most common abiotic stresses resulting in significant crop yield losses, especially for jujube (Ziziphus jujuba Mill.), an important temperate economic crop cultivated worldwide. This study aims to explore the coping mechanism of jujube to HT stress at the transcriptional and post-transcriptional levels, including identifying differentially expressed miRNAs and mRNAs as well as elucidating the critical pathways involved. High-throughput sequencing analyses of miRNA and mRNA were performed on jujube leaves, which were collected from "Fucumi" (heat-tolerant) and "Junzao" (heat-sensitive) cultivars subjected to HT stress (42 °C) for 0, 1, 3, 5, and 7 days, respectively. The results showed that 45 known miRNAs, 482 novel miRNAs, and 13,884 differentially expressed mRNAs (DEMs) were identified. Among them, integrated analysis of miRNA target genes prediction and mRNA-seq obtained 1306 differentially expressed miRNAs-mRNAs pairs, including 484, 769, and 865 DEMIs-DEMs pairs discovered in "Fucuimi", "Junzao" and two genotypes comparative groups, respectively. Furthermore, functional enrichment analysis of 1306 DEMs revealed that plant-pathogen interaction, starch and sucrose metabolism, spliceosome, and plant hormone signal transduction were crucial pathways in jujube leaves response to HT stress. The constructed miRNA-mRNA network, composed of 20 DEMIs and 33 DEMs, displayed significant differently expressions between these two genotypes. This study further proved the regulatory role of miRNAs in the response to HT stress in plants and will provide a theoretical foundation for the innovation and cultivation of heat-tolerant varieties.

Azolla filiculoides extract improved salt tolerance in wheat (Triticum aestivum L.) is associated with prompting osmostasis, antioxidant potential and stress-interrelated genes

The growth and productivity of crop plants are negatively affected by salinity-induced ionic and oxidative stresses. This study aimed to provide insight into the interaction of NaCl-induced salinity with Azolla aqueous extract (AAE) regarding growth, antioxidant balance, and stress-responsive genes expression in wheat seedlings. In a pot experiment, wheat kernels were primed for 21 h with either deionized water or 0.1% AAE. Water-primed seedlings received either tap water, 250 mM NaCl, AAE spray, or AAE spray + NaCl. The AAE-primed seedlings received either tap water or 250 mM NaCl. Salinity lowered growth rate, chlorophyll level, and protein and amino acids pool. However, carotenoids, stress indicators (EL, MDA, and H2O2), osmomodulators (sugars, and proline), antioxidant enzymes (CAT, POD, APX, and PPO), and the expression of some stress-responsive genes (POD, PPO and PAL, PCS, and TLP) were significantly increased. However, administering AAE contributed to increased growth, balanced leaf pigments and assimilation efficacy, diminished stress indicators, rebalanced osmomodulators and antioxidant enzymes, and down-regulation of stress-induced genes in NaCl-stressed plants, with priming surpassing spray in most cases. In conclusion, AAE can be used as a green approach for sustaining regular growth and metabolism and remodelling the physio-chemical status of wheat seedlings thriving in salt-affected soils.

Metabolomics combined with physiology and transcriptomics reveal how Nicotiana tabacum leaves respond to cold stress

Low temperature-induced cold stress is a major threat to plant growth, development and distribution. Unraveling the responses of temperature-sensitive crops to cold stress and the mechanisms of cold acclimation are critical for food demand. In this study, combined physiological, transcriptomic, and metabolomic analyses were conducted on Nicotiana tabacum suffering short-term 4 °C cold stress. Our results showed that cold stress destroyed cellular membrane stability, decreased the chlorophyll (Chl) and carotenoid contents, and closed stomata, resulting in lipid peroxidation and photosynthesis restriction. Chl fluorescence measurements revealed that primary photochemistry, photoelectrochemical quenching and photosynthetic electron transport in Nicotiana tabacum leaves were seriously suppressed upon exposer to cold stress. Enzymatic and nonenzymatic antioxidants, including superoxide dismutase, catalase, peroxidase, reduced glutathione, proline, and soluble sugar, were all profoundly increased to trigger the cold acclimation defense against oxidative damage. A total of 178 metabolites and 16,204 genes were differentially expressed in cold-stressed Nicotiana tabacum leaves. MEturquoise and MEblue modules identified by WGCNA were highly correlated with physiological indices, and the corresponding hub genes were significantly enriched in pathways related to photosynthesis - antenna proteins and flavonoid biosynthesis. Untargeted metabolomic analysis identified specific metabolites, including sucrose, phenylalanine, glutamine, glutamate, and proline, that enhance plant cold acclimation. Combined transcriptomics and metabolomic analysis highlight the vital roles of carbohydrate and amino acid metabolism in enhancing the cold tolerance of Nicotiana tabacum. Our comprehensive investigation provides novel insights for efforts to alleviate low temperature-induced oxidative damage to Nicotiana tabacum plants and proposes a breeding target for cold stress-tolerant cultivars.

In vitro assessment of physiological traits and ROS detoxification pathways involved in tolerance of Damask rose genotypes under salt stress

Rosa damascena is one of the most important medicinal and ornamental plants in Iran which is tolerant of salinity to some extent. However, the selection of genotypes that are more tolerant to salinity will influence on Damask cultivation in salt stress-affected regions. For this purpose, a factorial experiment in a completely randomized design with three replicates was performed under in vitro conditions on four Damask rose genotypes (Atashi, Bi-Khar, Chahar-Fasl and Kashan) at 5 concentrations of NaCl (0, 25, 50, 75, and 100 mM), and the physico-chemical traits were measured 14 and 28 days after treatment.The results showed that Atashi genotype with high levels of Chl a, Chl b, total Chl content, carotenoids, relative leaf water content, proline, total soluble protein, TPC, TFC, TAA, and the highest increase in the activity of antioxidant enzymes such as GPX, APX, CAT, SOD, and POD as well as the lowest amount of hydrogen peroxide showed a better protection mechanism against oxidative damage than the other three genotypes (Bi-Khar, Chahar-Fasl and Kashan) in the 14th and 28th days by maintaining the constructive and induced activities of antioxidant enzymes, it was shown that Bi-Khar genotype had moderate tolerance and Kashan and Chahar-Fasl genotypes had low tolerance to salinity stress. In vitro selection methods can be used effectively for salt tolerant screening of Damask rose genotypes, although the same experiment should be conducted in open filed cultures to verify the in vitro experimental results.

Alleviation role of exogenous cadaverine on cell cycle, endogenous polyamines amounts and biochemical enzyme changes in barley seedlings under drought stress

Cadaverine (Cad), which has an independent synthesis pathway compared to other polyamine (PA) types, contributes to the health of plants by regulating plant growth and development, abiotic stress tolerance and antioxidant defense mechanisms. In this work, experiments were carried out to understand the effects of exogenous Cad (10 µM) application under drought stress (%22 PEG 6000) and without stress on cell cycle, total protein content, endogenous PA levels, and biochemical enzyme activities in barley (Hordeum vulgare cv. Burakbey) considering the potential of Cad to stimulate the drought-related tolerance system. Cad application in a stress-free environment showed an effect almost like low-impact drought stress, causing changes in all parameters examined compared to samples grown in distilled water environment (Control). The results clearly show that Cad applied against the negative effects of drought stress on all parameters creates a drought resistance mechanism of the plant. Accordingly, Cad applied together with drought stress increased the density of cells in the cell cycle (G1-S and S-G2 phases) and the amount of endogenous (spermidine 10% and spermine 40%) PAs. In addition, while superoxide dismutase (SOD) (5%), (CAT) (55%) and ascorbate peroxidase (APX) (18%) enzyme levels increased, a stress response mechanism occurred due to the decrease in total protein content (20%) and malondialdehyde (MDA) (80%). As a result, exogenous application of 10 µM Cad showed that it reduced the negative effects of drought stress on endogenous PA amounts, cell division and biochemical activities in barley.

Effectiveness of Phosphate and Zinc Solubilizing Paenarthrobacter nitroguajacolicus P1 as Halotolerant Rhizobacterium with Growth-Promoting Activity on Pistacia vera L

Plant growth-promoting rhizobacteria (PGPR) are beneficial microorganisms to develop microbial fertilizers. Biofertilizers can accelerate plant growth and enhance crop yields. The current research aimed to isolate and identify rhizobacterium with plant growth-promoting activity in the rhizospheric region of pistachio trees in arid and salty region of Iran. In the present study, 26 bacterial isolates were isolated from the rhizospheric region of the pistachio trees. Plant growth-promoting characteristics of isolated bacteria, including the ability to solubilize phosphate and zinc, produce hydrolyzing enzymes, and hydrogen cyanide (HCN), as well as synthesize indole-3-acetic acid (IAA) were evaluated through in vitro assays. Based on these activities, five multifunctional bacterial strains designated P1, P10, P11, P17, and P19 were then applied and their effect was studied on the growth and physiological properties of Pistacia vera L. seedlings by pot experiments under normal conditions. Finally, the most efficient strain has been identified by analysis of the 16S rRNA gene sequence. According to the results, all the isolated bacteria exhibited considerable plant growth-promoting properties. They could produce amylase (n = 26, 2 ± 0.00-13 ± 0.42 mm), lipase (n = 24, 2 ± 0.00-9 ± 0.23 mm), protease (n = 20, 1 ± 0.00-17 ± 0.0 mm), indole-3-acetic acid (n = 26, ranging from 5.05 ± 0.08 to 11.5 ± 0.11 μg/mL) and HCN (n = 24). Six isolates showed significant growth at 20% w/v NaCl. Inoculation of P1, P17, and P19 increased chlorophyll, carotenoid, and phenolic content in treated Pistacia vera L. seedlings. P1 and P11 inoculated plants showed an enhanced level of anthocyanin and proline. These most effective strains were catalase and Gram-positive bacterium and showed antibiotic sensitivity. They can consider as halotolerant PGPR, due to the growth in the presence of NaCl (20% w/v). Finally, P1 inoculated plants exhibited higher levels of sugar content. This strain showed the most similarity (99.92%-1322 bp) to Paenarthrobacter nitroguajacolicus based on 16S rRNA gene sequence. Based on the results, Paenarthrobacter nitroguajacolicus P1 with multiple PGPR can be applied as a promising candidate in the soil-Pistacia vera L. system to improve their productivity and health by increasing available nutrient content, improving photosynthetic parameters, and producing phytohormones and HCN.

Response of Soil Microenvironment and Crop Growth to Cyclic Irrigation Using Reclaimed Water and Brackish Water

The scarcity of freshwater resources has increased the use of nonconventional water resources such as brackish water, reclaimed water, etc., especially in water-scarce areas. Whether an irrigation cycle using reclaimed water and brackish water (RBCI) poses a risk of secondary soil salinization to crop yields needs to be studied. Aiming to find an appropriate use for different nonconventional water resources, pot experiments were conducted to study the effects of RBCI on soil microenvironments, growth, physiological characteristics and antioxidation properties of crops. The results showed the following: (1) compared to FBCI, the soil moisture content was slightly higher, without a significant difference, while the soil EC, sodium and chloride ions contents increased significantly under the RBCI treatment. With an increase in the reclaimed water irrigation frequency (Tri), the contents of EC, Na⁺ and Cl^- in the soil decreased gradually, and the difference was significant; the soil moisture content also decreased gradually. (2) There were different effects of the RBCI regime on the soil's enzyme activities. With an increase in the Tri, the soil urease activity indicated a significant upward trend as a whole. (3) RBCI can alleviate the risk of soil salinization to some extent. The soil pH values were all below 8.5, and were without a risk of secondary soil alkalization. The ESP did not exceed 15 percent, and there was no possible risk of soil alkalization except that the ESP in soil irrigated by brackish water irrigation went beyond the limit of 15 percent. (4) Compared with FBCI, no obvious changes appeared to the aboveground and underground biomasses under the RBCI treatment. The RBCI treatment was conducive to increasing the aboveground biomass compared with pure brackish water irrigation. Therefore, short-term RBCI helps to reduce the risk of soil salinization without significantly affecting crop yield, and the irrigation cycle using reclaimed-reclaimed-brackish water at 3 g·L^-1 was recommended, according to the experimental results.

Comparative Analysis of Antioxidant System and Salt-Stress Tolerance in Two Hibiscus Cultivars Exposed to NaCl Toxicity

Hibiscus (Hibiscus syriacus L.) is known as a horticultural plant of great ornamental and medicinal value. However, the effect of NaCl stress on hibiscus seedlings is unclear. Little is known about H. syriacus 'Duede Brabaul' (DB) and H. syriacus 'Blueberry Smoothie' (BS). Here, the effects of solutions with different concentrations of NaCl on the organic osmolytes, ion accumulation, and antioxidant enzyme activity of hibiscus seedling leaves were determined. The results showed that the Na⁺/K⁺ ratio was imbalanced with increasing NaCl concentration, especially in BS (range 34% to 121%), which was more sensitive than DB (range 32% to 187%) under NaCl concentrations of 50 to 200 mM. To cope with the osmotic stress, the content of organic osmolytes increased significantly. Additionally, NaCl stress caused a large increase in O₂·^- and H₂O₂, and other reactive oxygen species (ROS), and antioxidant enzyme activity was significantly increased to remove excess ROS. The expression level of genes related to salt tolerance was significantly higher in DB than that in BS under different NaCl concentrations. Taken together, DB possessed a stronger tolerance to salt stress and the results suggest membrane stability, Na⁺/K⁺, H₂O₂, catalase and ascorbate peroxidase as salt tolerance biomarkers that can be used for gene transformation and breeding in future hibiscus research.

Proteomics approach to investigating osmotic stress effects on pistachio

Osmotic stress can occur due to some stresses such as salinity and drought, threatening plant survival. To investigate the mechanism governing the pistachio response to this stress, the biochemical alterations and protein profile of PEG-treated plants was monitored. Also, we selected two differentially abundant proteins to validate via Real-Time PCR. Biochemical results displayed that in treated plants, proline and phenolic content was elevated, photosynthetic pigments except carotenoid decreased and MDA concentration were not altered. Our findings identified a number of proteins using 2DE-MS, involved in mitigating osmotic stress in pistachio. A total of 180 protein spots were identified, of which 25 spots were altered in response to osmotic stress. Four spots that had photosynthetic activities were down-regulated, and the remaining spots were up-regulated. The biological functional analysis of protein spots exhibited that most of them are associated with the photosynthesis and metabolism (36%) followed by stress response (24%). Results of Real-Time PCR indicated that two of the representative genes illustrated a positive correlation among transcript level and protein expression and had a similar trend in regulation of gene and protein. Osmotic stress set changes in the proteins associated with photosynthesis and stress tolerance, proteins associated with the cell wall, changes in the expression of proteins involved in DNA and RNA processing occur. Findings of this research will introduce possible proteins and pathways that contribute to osmotic stress and can be considered for improving osmotic tolerance in pistachio.

Physiological and Biochemical Responses of Commercial Strawberry Cultivars under Optimal and Drought Stress Conditions

Improving the extent of adaptation and the choice of the most tolerant cultivar is the first step to mitigating the adverse effects of limited water, especially in susceptible plants such as strawberries. To address this issue, two commercial strawberry cultivars (Camarosa and Gaviota) were compared when irrigated to match 100, 75, 50, and 25% field capacity (FC) to simulate the control, slight, moderate, and severe drought stress conditions, respectively. Drought stress induced the reduction of total chlorophyll, carotenoid, relative water content, and phenolic content significantly, whereas the activity of antioxidant enzymes, electrolyte leakage, osmolyte accumulation, and oxidative markers upsurged progressively in drought severity-dependent behavior. Gaviota produced more proline, hydrogen peroxide as a marker of membrane lipid peroxidation and disposed of by higher electrolyte leakage, significantly. On the other hand, Camarosa having higher soluble carbohydrates as well as enzymatic and non-enzymatic antioxidants could be considered a drought-tolerant cultivar. Genotypic variation between these cultivars could be used in breeding projects to promote drought-tolerant strawberries in the future.

Transcriptomic and metabolic regulatory network characterization of drought responses in tobacco

Drought stress usually causes huge economic losses for tobacco industries. Drought stress exhibits multifaceted impacts on tobacco systems through inducing changes at different levels, such as physiological and chemical changes, changes of gene transcription and metabolic changes. Understanding how plants respond and adapt to drought stress helps generate engineered plants with enhanced drought resistance. In this study, we conducted multiple time point-related physiological, biochemical,transcriptomic and metabolic assays using K326 and its derived mutant 28 (M28) with contrasting drought tolerance. Through integrative analyses of transcriptome and metabolome,we observed dramatic changes of gene expression and metabolic profiles between M28 and K326 before and after drought treatment. we found that some of DEGs function as key enzymes responsible for ABA biosynthesis and metabolic pathway, thereby mitigating impairment of drought stress through ABA signaling dependent pathways. Four DEGs were involved in nitrogen metabolism, leading to synthesis of glutamate (Glu) starting from NO-3 /NO-2 that serves as an indicator for stress responses. Importantly, through regulatory network analyses, we detected several drought induced TFs that regulate expression of genes responsible for ABA biosynthesis through network, indicating direct and indirect involvement of TFs in drought responses in tobacco. Thus, our study sheds some mechanistic insights into how plant responding to drought stress through transcriptomic and metabolic changes in tobacco. It also provides some key TF or non-TF gene candidates for engineering manipulation for breeding new tobacco varieties with enhanced drought tolerance.

TMT-based quantitative proteomic analysis of indica rice cultivars reveals that novel components of the signaling pathways might play a role in grain length regulation

Grain length is one of the most important rice grain appearance components. To better understand the protein regulated by grain length in indica rice, the tandem mass tag (TMT) labeling combined with LC-MS/MS analysis was used for quantitative identification of differentially regulated proteins by comparing six long-grain cultivars (MeiB, LongfengB, YexiangB, FengtianB, WantaiB, and DingxiangB) to the short-grain cultivar BoB, respectively. A total of 6622 proteins were detected for quantitative analysis by comparing protein content of six long-grain cultivars to the short-grain cultivar, and 715 proteins were significantly regulated, consisting of 336 uniquely over-accumulated proteins and 355 uniquely down-accumulated proteins. KEGG pathway analysis revealed that most of accumulated proteins are involved in metabolic pathways, biosynthesis of secondary metabolites and phenylpropanoid biosynthesis. Four down-accumulated proteins maybe involved in the signaling pathways for grain length regulation. LC-PRM/MS quantitative analysis was used to analyze 10 differentially expressed proteins. The results were almost consistent with the TMT quantitative analysis. qRT-PCR analysis results showed that the transcription level was not always parallel to the protein content. This study identified many novel grain length accumulated proteins through the quantitative proteomics approach, providing candidate genes for further study of grain size regulatory mechanisms. SIGNIFICANCE: Rice grain length is one of the most important characteristics influencing appearance and yield. Six long-grain cultivars (MeiB, LongfengB, YexiangB, FengtianB, WantaiB, and DingxiangB obtained in Guangxi province of China from the 2000s to 2020s) and one short-grain cultivar (BoB obtained in Guangxi province of China in 1980s) were used for comparative analyses. Totally, 715 differentially expressed proteins (DEPs) were identified using TMT-base proteomic analysis. The numbers of DEPs increased as the grain length increased. 4 DEPs may be related to rice's signaling pathways for grain size regulation. A total of 85 DEPs regulated in at least four long-grain cultivars compared with the short-grain cultivar BoB, and 7 proteins were over-accumulated, and 3 proteins were down-accumulated in six long-grain cultivars. These findings provide valuable information to better understand the mechanisms of protein regulation by grain length in rice.

ThASR3 confers salt and osmotic stress tolerances in transgenic Tamarix and Arabidopsis

BACKGROUND

ASR (abscisic acid-, stress-, and ripening-induced) gene family plays a crucial role in responding to abiotic stresses in plants. However, the roles of ASR genes protecting plants against high salt and drought stresses remain unknown in Tamarix hispida.

RESULTS

In this study, a salt and drought-induced ASR gene, ThASR3, was isolated from Tamarix hispida. Transgenic Arabidopsis overexpressing ThASR3 exhibited stimulating root growth and increasing fresh weight compared with wild-type (WT) plants under both salt and water deficit stresses. To further analyze the gain- and loss-of-function of ThASR3, the transgenic T. hispida plants overexpressing or RNA interference (RNAi)-silencing ThASR3 were generated using transient transformation. The overexpression of ThASR3 in Tamarix and Arabidopsis plants displayed enhanced reactive oxygen species (ROS) scavenging capability under high salt and osmotic stress conditions, including increasing the activities of antioxidant enzymes and the contents of proline and betaine, and reducing malondialdehyde (MDA) content and electrolyte leakage rates.

CONCLUSION

Our results indicate that ThASR3 functions as a positive regulator in Tamarix responses to salt and osmotic stresses and confers multiple abiotic stress tolerances in transgenic plants, which may have an important application value in the genetic improvement of forest tree resistance.

Effects of Kiwifruit Rootstocks with Opposite Tolerance on Physiological Responses of Grafting Combinations under Waterlogging Stress

Kiwifruit is commonly sensitive to waterlogging stress, and grafting onto a waterlogging-tolerant rootstock is an efficient strategy for enhancing the waterlogging tolerance of kiwifruit plants. KR5 (Actinidia valvata) is more tolerant to waterlogging than ‘Hayward’ (A. deliciosa) and is a potential resistant rootstock for kiwifruit production. Here, we focused on evaluating the performance of the waterlogging-sensitive kiwifruit scion cultivar ‘Zhongmi 2′ when grafted onto KR5 (referred to as ZM2/KR5) and Hayward (referred to as ZM2/HWD) rootstocks, respectively, under waterlogging stress. The results showed ‘Zhongmi 2′ performed much better when grafted onto KR5 than when grafted onto ‘Hayward’, exhibiting higher photosynthetic efficiency and reduced reactive oxygen species (ROS) damage. Furthermore, the roots of ZM2/KR5 plants showed greater root activity and energy supply, lower ROS damage, and more stable osmotic adjustment ability than the roots of ZM2/HWD plants under waterlogging stress. In addition, we detected the expression of six key genes involved in the kiwifruit waterlogging response mechanism, and these genes were remarkably induced in the ZM2/KR5 roots but not in the ZM2/HWD roots under waterlogging stress. Moreover, principal component analysis (PCA) further demonstrated the differences in the physiological responses of the ZM2/KR5 and ZM2/HWD plants under waterlogging stress. These results demonstrated that the KR5 rootstock can improve the waterlogging tolerance of grafted kiwi plants by regulating physiological and biochemical metabolism and molecular responses.

Changes and Correlation Between Physiological Characteristics of Rhododendron simsii and Soil Microbial Communities Under Heat Stress

The relationship between Rhododendron simsii and its soil microbial community under heat stress was not clear. In this study, the effects of heat stress on the physiological characteristics, soil physicochemical properties and soil microbial community structure of R. simsii were investigated. The experimental control (CK) was set as day/night (14/10 h) 25/20°C and experimental treatments were set as light heat stress (LHS) 35/30°C and high heat stress (HHS) 40/35°C. Our results showed that, compared with CK, LHS treatment significantly increased malondialdehyde, hydrogen peroxide, proline and soluble sugar contents, as well as catalase and peroxidase activities, while HHS treatment significantly increased ascorbate peroxidase activity and decreased chlorophyll content. Compared with CK, LHS treatment significantly reduced soil ammonium-nitrogen and nitrate-nitrogen content, while HHS significantly increased soil ammonium-nitrogen content. Compared with CK, both treatments changed the soil microbial community structure. For bacterial community, LHS and HHS treatment resulting in the significant enrichment of Burkholderia-Caballeronia-Paraburkholderia and Occallatibacte, respectively. For fungal community, LHS treatment resulting in the significant enrichment of Candida, Mortierella and Boothiomyces. The redundancy analysis showed that plant physiological characteristics, soil ammonium-nitrogen content were significantly correlated with the soil microbial community. Therefore, heat stress altered the soil microbial community structure, and affected the availability of soil available nitrogen, which in turn affected the physiological characteristics of R. simsii. We suggest that soil microbial community may play an important role in plant resistance to heat stress, and its mechanism deserves further study.

Dehydrin responsive HVA1 driven inducible gene expression enhanced salt and drought tolerance in wheat

Heterologous expression of plant genes is becoming an important strategy for the improvement of specific traits in existing cultivars. This study presents the response of a salt-sensitive high-yielding wheat variety under stress-inducible expression of barley HVA1 gene belonging to the Late embryogenesis abundance (LEA) gene family. Six homozygous transgenic wheat plants were developed and advanced for testing under various water regimes and salt stress conditions. Putative transgenic plants showed better germination and root shoot development at the early developmental stages under drought stress conditions. Moreover, transgenic plants illustrated higher values of physiological features as compared to non-transgenic plants under both drought and salinity stresses that indicate improved physiological processes in transgenic plants. Higher membrane stability index (MSI) and lower electrolyte leakage (EL) after exposure to abiotic stresses reveal improved cellular membrane stability (CMS) and reduced injury to chloroplast membrane. Interestingly, under salinity stress, transgenic wheat plants showed preference towards higher K⁺ accumulation in the shoot, which is not a well-understood HVA1 mediated Na ⁺ avoidance mechanism under excessive subsurface salts. The predisposition of K⁺/Na ⁺ under salt stress conditions on heterologous expression of the HVA1 gene in wheat needs to be studied in detail in further studies.

Triacontanol regulates morphological traits and enzymatic activities of salinity affected hot pepper plants

Potential role of triacontanol applied as a foliar treatment to ameliorate the adverse effects of salinity on hot pepper plants was evaluated. In this pot experiment, hot pepper plants under 75 mM NaCl stress environment were subjected to foliar application of 25, 50, and 75 µM triacontanol treatments; whereas, untreated plants were taken as control. Salt stress had a significant impact on morphological characteristics, photosynthetic pigments, gas exchange attributes, MDA content, antioxidants activities, electrolytes leakage, vitamin C, soluble protein, and proline contents. All triacontanol treatments significantly mitigated the adversative effects of salinity on hot pepper plants; however, foliar application triacontanol at 75 µM had considerably improved the growth of hot pepper plants in terms of plant height, shoot length, leaf area, plant fresh/dry biomasses by modulating above mentioned physio-biochemical traits. While, improvement in gas exchange properties, chlorophyll, carotenoid contents, increased proline contents coupled with higher SOD and CAT activities were observed in response to 75 µM triacontanol followed by 50 µM triacontanol treatment. MDA and H₂O₂ contents were decreased significantly in hot pepper plants sprayed with 75 µM triacontanol followed by 50 µM triacontanol foliar treatment. Meanwhile, root and shoot lengths were maximum in 50 µM triacontanol sprayed hot pepper plants along with enhanced APX activity on exposure to salt stress. In crux, exogenous application triacontanol treatments improved hot pepper performance under salinity, however,75 µM triacontanol treatment evidently was more effective in mitigating the lethal impact of saline stress via controlling the ROS generation and increment in antioxidant enzyme activities.

Effects of different antifreeze chemicals on late spring frost in pistachio

Frost injury is one of the major limiting factors to horticultural crops production and distribution. Despite numerous efforts and researches concerning freezing injury reduction, it still accounts for more than 50% of the fruit losses in the horticulture sector. In the present investigation, we aimed to investigate the effects of different antifreeze compounds (Tiofer®, Cropaid®, Bio-Bloom®, amino acid (mixture), salicylic acid, and water (control)) on pistachio trees behavior under low-temperature regimes (2 °C, 0 °C, -2 °C, -4 °C, -6 °C, and spring natural temperature). The applied chemicals improved the osmolyte content during the cold stress. Tiofer® and Cropaid® could increase the proline content better than other compounds. Salicylic acid and Cropaid® application increased the guaiacol peroxidase (GPX) content better than other compounds. For ascorbate peroxidase (APX), Tiofer® and Bio-Bloom®, and for catalase (CAT), Tiofer®, Cropaid®, and salicylic acid performed better. Applying chemicals also improved the photosynthetic pigments under cold stress. Among all treatments, Tiofer® and Bio-Bloom® improved the chlorophyll a (Chla), while chlorophyll b (Chlb) better improved by Tiofer® and Cropaid®; moreover, carotenoids had better increase in Cropaid®, amino acid, and salicylic acid treatments. All applied chemicals except Tiofer® had a good effect on the anthocyanin content increase under cold stress. In conclusion, based on the findings presented here, applying antifreeze compounds, such as Tiofer®, Cropaid® Bio-Bloom®, salicylic acid, and amino acid, could effectively ameliorate the adverse effects of cold stress. Osmolytes and antioxidant (GPX, APX, CAT) contents, photosynthetic pigments (chlorophyll a and b and carotenoid), and anthocyanins were improved. Among all applied antifreezes, Tiofer® and Cropaid® were the most effective ones.

Auxin drives tomato spotted wilt virus (TSWV) resistance through epigenetic regulation of auxin response factor ARF8 expression in tomato

Tomato spotted wilt virus (TSWV) causes severe losses of tomato crops worldwide. To cope dynamically with such a threat, plants deploy strategies acting at the molecular and the epigenetic levels. We found that tomato symptoms progress in a specific-genotype-manner upon TSWV infection. Susceptible genotypes showed within the Auxin Response Factor (ARF8) promoter coupled to enhanced expression of miRNA167a, reduced ARF8 gene and decreased levels of the hormone auxin. This constitutes a deliberate attempt of TSWV to disrupt plant growth to promote spread in sensitive cultivars. Epigenetic regulation through the level of cytosine methylation and the miR167a-ARF8 module are part of a complex network modulating auxin-triggered synthesis and shaping tomato responses to TSWV. Furthermore, modulation of miR167a-ARF8 regulatory module could be applied in tomato-resistance breeding programs.

Negative effects of long-term exposure to salinity, drought, and combined stresses on halophyte Halogeton glomeratus

Plants are subjected to salt and drought stresses concurrently but our knowledge about the effects of combined stress on plants is limited, especially on halophytes. We aim to study if some diverse drought and salt tolerance traits in halophyte may explain their tolerance to salinity and drought stresses, individual and in combination, and identify key traits that influence growth under such stress conditions. Here, the halophyte Halogeton glomeratus was grown under control, single or combinations of 60 days drought and salt treatments, and morphophysiological responses were tested. Our results showed that drought, salinity, and combination of these two stressors decreased plant growth (shoot height, root length, and biomass), leaf photosynthetic pigments content (chlorophyll a, b, a + b and carotenoids), gas exchange parameters (Net photosynthesis rate [P_N ], transpiration rate [E], stomatal conductance [g_s ]), and water potential (ψ_w ), and the decreases were more prominent under combined drought and salinity treatment compared with these two stressors individually performed. Similarly, combined drought and salinity treatment induced more severe oxidative stress as indicated by more hydrogen peroxide (H₂ O₂ ) and malondialdehyde (MDA) accumulated. Nevertheless, H. glomeratus is equipped with specific mechanisms to protect itself against drought and salt stresses, including upregulation of superoxide dismutases (SOD; EC 1.15.1.1) and catalase (CAT; EC 1.11.1.6) activities and accumulation of osmoprotectants (Na⁺ , Cl^- , and soluble sugar). Our results indicated that photosynthetic pigments content, gas exchange parameters, water potential, APX activity, CAT activity, soluble sugar, H₂ O₂ , and MDA are valuable screening criteria for drought and salt, alone or combined, and provide the tolerant assessment of H. glomeratus.

Advances in Rootstock Breeding of Nut Trees: Objectives and Strategies

The production and consumption of nuts are increasing in the world due to strong economic returns and the nutritional value of their products. With the increasing role and importance given to nuts (i.e., walnuts, hazelnut, pistachio, pecan, almond) in a balanced and healthy diet and their benefits to human health, breeding of the nuts species has also been stepped up. Most recent fruit breeding programs have focused on scion genetic improvement. However, the use of locally adapted grafted rootstocks also enhanced the productivity and quality of tree fruit crops. Grafting is an ancient horticultural practice used in nut crops to manipulate scion phenotype and productivity and overcome biotic and abiotic stresses. There are complex rootstock breeding objectives and physiological and molecular aspects of rootstock-scion interactions in nut crops. In this review, we provide an overview of these, considering the mechanisms involved in nutrient and water uptake, regulation of phytohormones, and rootstock influences on the scion molecular processes, including long-distance gene silencing and trans-grafting. Understanding the mechanisms resulting from rootstock × scion × environmental interactions will contribute to developing new rootstocks with resilience in the face of climate change, but also of the multitude of diseases and pests.

Impact of granite irradiation on aflatoxin reduction in pistachio

In this research with the effect of radioactive granite gamma radiation, the reduction of aflatoxin B1 in pistachios was examined in three steps. In the first step, the aflatoxin reduction in small packets by granite bed was tested. In this step, the aflatoxin level of 300 g pistachios packets was reduced up to 81.3 ± 1.5 percent by 4 kg granite bed after 4 days. After observation of aflatoxin reduction by granite bed, the second step was done with increasing the granite and pistachio mass and irradiation time. In this step, the aflatoxin level of 1 kg pistachios was reduced up to 4949 ± 2.6 percent by 6 kg granite after 9 days. According to the results, the aflatoxin reduction of 1 kg pistachios by 1 kg granite after 1 days (as aflatoxin Reduction Coefficient (ARC)) was calculated as ARC = 0.0090 ± 0.0025 (kg. day)^-1. The aflatoxin types of detected in this research were B1 and B2 types that AFB2 level was much less than one. Therefore the effect of granite irradiation on AFB2 reduction wasn't considered. The final step was designed for testing the aflatoxin Reduction Coefficient (ARC). This step was shown that the confidence level between practical result and aflatoxin Reduction Coefficient (ARC) result is about 97 percent. The results indicated that the level of fat and protein of pistachios by granite gamma radiation did not change after 9 days. Therefore the granite irradiation can be used for aflatoxin reduction of pistachios.

Root vacuolar sequestration and suberization are prominent responses of Pistacia spp. rootstocks during salinity stress

Understanding the mechanisms of stress tolerance in diverse species is needed to enhance crop performance under conditions such as high salinity. Plant roots, in particular in grafted agricultural crops, can function as a boundary against external stresses in order to maintain plant fitness. However, limited information exists for salinity stress responses of woody species and their rootstocks. Pistachio (Pistacia spp.) is a tree nut crop with relatively high salinity tolerance as well as high genetic heterogeneity. In this study, we used a microscopy-based approach to investigate the cellular and structural responses to salinity stress in the roots of two pistachio rootstocks, Pistacia integerrima (PGI) and a hybrid, P. atlantica x P. integerrima (UCB1). We analyzed root sections via fluorescence microscopy across a developmental gradient, defined by xylem development, for sodium localization and for cellular barrier differentiation via suberin deposition. Our cumulative data suggest that the salinity response in pistachio rootstock species is associated with both vacuolar sodium ion (Na+) sequestration in the root cortex and increased suberin deposition at apoplastic barriers. Furthermore, both vacuolar sequestration and suberin deposition correlate with the root developmental gradient. We observed a higher rate of Na+ vacuolar sequestration and reduced salt-induced leaf damage in UCB1 when compared to P. integerrima. In addition, UCB1 displayed higher basal levels of suberization, in both the exodermis and endodermis, compared to P. integerrima. This difference was enhanced after salinity stress. These cellular characteristics are phenotypes that can be taken into account during screening for sodium-mediated salinity tolerance in woody plant species.