Alleviation of the effects of saline-alkaline stress on maize seedlings by regulation of active oxygen metabolism by Trichoderma asperellum

Alternative Splicing Plays a Crucial Role in the Salt Tolerance of Foxtail Millet

Foxtail millet is an important cereal crop that is relatively sensitive to salt stress, with its yield significantly affected by such stress. Alternative splicing (AS) widely affects plant growth, development, and adaptability to stressful environments. Through RNA-seq analysis of foxtail millet under different salt treatment periods, 2078 AS events were identified, and analyses were conducted on differential gene (DEG), differential alternative splicing gene (DASG), and overlapping gene. To investigate the regulatory mechanism of AS in response to salt stress in foxtail millet, the foxtail millet AS genes SiCYP19, with two AS variants (SiCYP19-a and SiCYP19-b), were identified and cloned. Yeast overexpression experiments indicated that SiCYP19 may be linked to the response to salt stress. Subsequently, we conducted overexpression experiments of both alternative splicing variants in foxtail millet roots to validate them experimentally. The results showed that, under salt stress, both SiCYP19-a and SiCYP19-b jointly regulated the salt tolerance of foxtail millet. Specifically, overexpression of SiCYP19-b significantly increased the proline content and reduced the accumulation of reactive oxygen species (ROS) in foxtail millet, compared to that in SiCYP19-a. This shows that SiCYP19-b plays an important role in increasing the content of proline and promoting the clearance of ROS, thus improving the salt tolerance of foxtail millet.

Inroads into saline-alkaline stress response in plants: unravelling morphological, physiological, biochemical, and molecular mechanisms

MAIN CONCLUSION

This article discusses the complex network of ion transporters, genes, microRNAs, and transcription factors that regulate crop tolerance to saline-alkaline stress. The framework aids scientists produce stress-tolerant crops for smart agriculture. Salinity and alkalinity are frequently coexisting abiotic limitations that have emerged as archetypal mediators of low yield in many semi-arid and arid regions throughout the world. Saline-alkaline stress, which occurs in an environment with high concentrations of salts and a high pH, negatively impacts plant metabolism to a greater extent than either stress alone. Of late, saline stress has been the focus of the majority of investigations, and saline-alkaline mixed studies are largely lacking. Therefore, a thorough understanding and integration of how plants and crops rewire metabolic pathways to repair damage caused by saline-alkaline stress is of particular interest. This review discusses the multitude of resistance mechanisms that plants develop to cope with saline-alkaline stress, including morphological and physiological adaptations as well as molecular regulation. We examine the role of various ion transporters, transcription factors (TFs), differentially expressed genes (DEGs), microRNAs (miRNAs), or quantitative trait loci (QTLs) activated under saline-alkaline stress in achieving opportunistic modes of growth, development, and survival. The review provides a background for understanding the transport of micronutrients, specifically iron (Fe), in conditions of iron deficiency produced by high pH. Additionally, it discusses the role of calcium in enhancing stress tolerance. The review highlights that to encourage biomolecular architects to reconsider molecular responses as auxiliary for developing tolerant crops and raising crop production, it is essential to (a) close the major gaps in our understanding of saline-alkaline resistance genes, (b) identify and take into account crop-specific responses, and (c) target stress-tolerant genes to specific crops.

Wastewater irrigation and Trichoderma colonization in tomato plants: effects on plant traits, antioxidant activity, and performance of the insect pest Macrosiphum euphorbiae

The scarcity of freshwater for agriculture in many regions has led to the application of sewage and saline water for irrigation. Irrigation with non-conventional water sources could become a non-harmful process for plant cultivation, and the effects of their use on crops should be monitored in order to develop optimal management strategies. One possibility to overcome potential barriers is to use biostimulants such as Trichoderma spp. fungi. Tomato is a crop of great economic importance in the world. This study investigated the joint effects of Trichoderma afroharzianum T-22 on tomato plants irrigated with simulated unconventional waters. The experiment consisted of a control and three water treatments. In the control, the plants were watered with distilled water. The three water treatments were obtained by using an irrigation water added with nitrogen, a wastewater effluent, and a mixed groundwater-wastewater effluents. Potted tomato plants (variety Bobcat) were grown in a controlled growth chamber. Antioxidant activity, susceptibility to the aphids Macrosiphum euphorbiae, and tomato plant growth parameters were estimated. Trichoderma afroharzianum T-22 had a positive effect on plant growth and antioxidant defenses when plants were irrigated with distilled water. Instead, no significant morphological effects induced by T. afroharzianum T-22 on plants were observed when unconventional water was used for irrigation. However, inoculation with T. afroharzianum T-22 activated a stress response that made the colonized plants more susceptible to aphid development and increased their fecundity and longevity. Thanks to this study, it may be possible for the first time to open a new discussion on the practical possibility of using reclaimed wastewater for crop irrigation with the addition of a growth-promoting fungal symbiont.

Trehalose alleviates the inhibition of adventitious root formation caused by drought stress in cucumber through regulating ROS metabolism and activating trehalose and plant hormone biosynthesis

Trehalose (Tre) plays a vital role in response to drought stress in plants but its regulatory mechanism remains unclear. Here, this study explores the mechanism of re-regulated drought tolerance during cucumber adventitious root formation. Our results indicate that 2 mM Tre displays remarkable drought alleviation in the aspect of root number, root length, fresh weight, and dry weight. Under drought stress, Tre could inhibit greatly the MDA, H2O2, and O2- accumulation, enhance obviously the activities of SOD, POD, and CAT enzymes and up-regulate significantly the transcript levels of SOD, POD, and CAT genes. Furthermore, Tre treatment also promotes Tre metabolism during drought stress: significantly increases starch and Tre contents and decreases glucose content, the biosynthesis enzymatic activity of the Tre metabolic pathway including TPS and TPP are enhanced and the activity of degradation enzyme THL is decreased, and corresponding genes TPS1, TPS2, TPPA, and TPPB are up-regulated. Tre significantly reversed the decrease caused by PEG in IAA, ethylene, ABA, and BR contents and the increase caused by PEG in GA3 and KT contents. Collectively, Tre appears to be the effective treatment in counteracting the negative effects of drought stress during adventitious root formation by regulating ROS, Tre metabolisms and plant hormones.

The effect of Trichoderma harzianum agents on physiological-biochemical characteristics of cucumber and the control effect against Fusarium wilt

At the seedling and adult plant phases, pot experiments were carried out to enhance the physiological-biochemical characteristics of cucumber, guarantee its high yield, and ensure its cultivation of quality. Trichoderma harzianum conidia agents at 104, 105, 106, and 107 cfu g-1 were applied in accordance with the application of Fusarium oxysporum powder at concentrations of 104 cfu/g on the protective enzyme activity, physiological and biochemical indices, seedling quality, resilience to Fusarium wilt, quality, and yield traits. Fusarium oxysporum powder at 104 cfu g-1 was used to treat CK1, while Fusarium oxysporum powder and T. harzianum conidia agents were not used to treat CK2. The results show that different T. harzianum agents improved the activities of superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), and peroxidase (POD) in cucumber seedlings, improved chlorophyll content, root activity, root-shoot ratio, and seedling strength index, and decreased malondialdehyde (MAD) content (P < 0.05). T3, a combination of 104 cfu g-1 Fusarium oxysporum powder and 106 cfu g-1 T. harzianum conidia agents, had the greatest promoting effect. The effects of different T. harzianum conidia agents and their application amounts on the control of cucumber Fusarium wilt were explored. T3 had the best promotion impact, and the control effect of cucumber Fusarium wilt at seedling stage and adult stage reached 83.98% and 70.08%, respectively. The quality index and yield formation of cucumber were also increased by several T. harzianum agents, with T3 having the strongest promotion effects. In comparison to CK1, the soluble sugar, Vc, soluble protein, and soluble solid contents of T3 cucumber fruit were 120.75%, 39.14%, 42.26%, and 11.64% higher (P < 0.05), respectively. In comparison to CK2, the soluble sugar, Vc, soluble protein, and soluble solid contents of T3 cucumber fruit were 66.06%, 24.28%, 36.15%, and 7.95% higher (P < 0.05), respectively. In comparison to CK1 and CK2, the yields of T3 cucumber were 50.19% and 35.86% higher, respectively. As a result, T. harzianum agents can enhance the physiological and biochemical traits of cucumber seedlings, raise the quality of cucumber seedlings, have a controlling impact on Fusarium wilt, and increase the yield and quality of cucumber fruit. The greatest effectiveness of T3 comes from its use. In this study, Trichoderma harzianum conidia agents demonstrated good impacts on cucumber yield formation and plant disease prevention, demonstrating their high potential as biocontrol agents.

Overexpression of the aldehyde dehydrogenase AhALDH3H1 from Arachis hypogaea in soybean increases saline-alkali stress tolerance

Soybean production is severely hampered by saline-alkaline stress caused by saline-alkalization. Plants have aldehydrogenase (ALDH) family members that convert reactive aldehydes to carboxylic acids to remove active aldehyde molecules. However, little is known about the increased saline-alkali tolerance caused by the ALDH function in soybean. Here, we introduced a previously identified ALDH coding gene AhALDH3H1 from Arachis hypogaea into the soybean genome to investigate its critical role in response to saline-alkali stress. Transgenic soybean with increased aldehyde dehydrogenase activity showed significant tolerance to saline-alkali stress. It reduced malondialdehyde (MDA) content compared to its receptor, suggesting that over-expression of AhALDH3H1 accelerated soybean tolerance to saline-alkali stress by increasing aldehyde dehydrogenase activity, which is responsible for scavenging toxic MDA. To further analyze the inner mechanisms that allow transgenic plants to tolerate saline-alkali stress, we sequenced the transcriptome and metabolome of P3 (wild type, WT) and transgenic lines which were separately treated with water and a saline-alkali solution. When subjected to saline-alkali stress, the integrated analysis of the transcriptome and metabolome suggested that several genes related to cell wall structure crucial for preserving cell wall extensibility and plasticity were largely responsible for restoring homeostasis within the transgenic cells compared to WT. Metabolites, including both necessary ingredients for cell wall genesis and harmful production produced during the saline-alkali stress response, could be transported efficiently with the help of the ABC transporter, reducing the negative effects of saline-alkali stress. These findings suggest that introducing AhALDH3H1 increases transgenic soybean tolerance to saline-alkali stress may through cell wall structure maintenance and metabolites transport.

Integrated Transcriptome and Metabolome Analysis of Rice Leaves Response to High Saline-Alkali Stress

Rice (Oryza sativa) is one of the most important crops grown worldwide, and saline-alkali stress seriously affects the yield and quality of rice. It is imperative to elucidate the molecular mechanisms underlying rice response to saline-alkali stress. In this study, we conducted an integrated analysis of the transcriptome and metabolome to elucidate the effects of long-term saline-alkali stress on rice. High saline-alkali stress (pH > 9.5) induced significant changes in gene expression and metabolites, including 9347 differentially expressed genes (DEGs) and 693 differentially accumulated metabolites (DAMs). Among the DAMs, lipids and amino acids accumulation were greatly enhanced. The pathways of the ABC transporter, amino acid biosynthesis and metabolism, glyoxylate and dicarboxylate metabolism, glutathione metabolism, TCA cycle, and linoleic acid metabolism, etc., were significantly enriched with DEGs and DAMs. These results suggest that the metabolites and pathways play important roles in rice's response to high saline-alkali stress. Our study deepens the understanding of mechanisms response to saline-alkali stress and provides references for molecular design breeding of saline-alkali resistant rice.

Advances and future research in ecological stoichiometry under saline-alkali stress

Saline-alkali stress is a serious abiotic factor which negatively impacts agricultural production and the ecological environment. Thus, improving the development of saline-alkali soil and reducing the effects of saline-alkali stress is a key issue for sustainable agricultural development and environmental protection. As such, it is unsurprising that researchers have lately focused on how to improve saline-alkali soil, increase the agricultural yield of saline-alkali land, and promote the adaptive growth of plants in saline-alkali soil. This paper reviews the latest research concerning nutrient content changes in saline-alkali soil, along with the associated changes in key nutrients in plants, to summarize which methods are most effective for improving the plant growth under saline-alkali stress. Finally, the prospects for alleviating saline-alkali stress and improving saline-alkali soil are put forward as a theoretical foundation for the stabilization of plant growth in saline-alkali soil, expansion of arable land area, crop yield improvement, and effective environmental protection.

Trichoderma longibrachiatum TG1 increases endogenous salicylic acid content and antioxidants activity in wheat seedlings under salinity stress

Several studies have reported the deleterious effects of excessive salt stress on Triticum aestivum L. seedlings. Seed pretreatment with exogenous salicylic acid (SA) enhances plants to tolerate salt stress. Herein, the present study aims to investigate the potential of plant-growth-promoting fungus Trichoderma longibrachiatum (TG1) to increase the plant growth and enhance the salicylic acid (SA) contents and antioxidants activity in wheat seedlings under different concentrations of salt stress. Wheat seeds were pretreated in TG1 spore suspension before exposure to different salt stresses. Compared with 0, 50, 100, 150 salt stresses, the TG1 and NaCl increased the wheat seeds germination rate, germination potential and germination index significantly; the shoot height and root length were increased by an average of 39.45% and 29.73%, respectively. Compared to NaCl stress across the four concentrations (0, 50, 100, and 150 mM), the TG1 treated wheat seedlings increased SA concentration and phenylalanine ammonia-lyase activity (PAL) by an average of 55.87% and 24.10% respectively. In addition, the TG1+NaCl-treated seedlings increased superoxide dismutase (SOD), peroxidases (POD), and catalase (CAT) activities in the shoot by an average of 47.68%, 23.68%, and 38.65% respectively compared to NaCl-stressed seedlings. Significantly, the genes, SOD, CAT, and POD were relatively up-regulated in the salt-tolerant TG1-treated seedlings at all NaCl concentrations in comparison to the control. Wheat seedlings treated with TG1+NaCl increased the transcript levels of SOD, POD and CAT by 1.35, 1.85 and 1.04-fold at 50 mM NaCl concentration, respectively, compared with 0 mM NaCl concentration. Our results indicated that seeds pretreatment with TG1 could increase endogenous SA of plants and promote seedling growth under salt stress by improving enzymatic antioxidant activities and gene expression.

Exogenous naphthaleneacetic acid alleviated alkalinity-induced morpho-physio-biochemical damages in Cyperus esculentus L. var. sativus Boeck

Cyperus esculentus L. var. sativus Boeck (commonly called Chufa) is a perennial species that produces nutritious underground tubers and contributes to the diet and health of human worldwide. However, it is salt-sensitive and its adaptation to salinity stress remains an enigma. Naphthaleneacetic acid (NAA) plays a vital role in regulating plant salt stress tolerance. Thus, we aimed to investigate the impact of NAA (150 mg/L) application on growth and physio-biochemical response mechanisms of Chufa plants to different levels of salinity stress (0-, 90-, and 180 mM of alkaline stress ([1:1 ratio of Na₂CO₃ and NaHCO₃]). In response to increasing stress levels, shoot-root growth decreased, whereas malondialdehyde (MDA), hydrogen peroxide (H₂O₂), osmolytes (soluble protein, proline, and soluble sugars), and activities of superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) significantly increased. Alkalinity led to significant increase in Na⁺ and Cl^-, but decrease in Mg²⁺ concentration in both roots and leaves; however, K⁺ decreased significantly in leaves under both stresses. Additionally, NO 3 - and. levels, nitrate reductase (NR) activities, and glutamate synthase (GOGAT) decreased significantly. However, glutamine synthetase (GS) increased non-significantly at 90 mM but declined at 180 mM. Foliar NAA application reduced Na⁺ and Cl^-, MDA, and H₂O₂ but increased photosynthetic pigments, K⁺ and Mg²⁺, osmolytes, nitrogen (N) metabolism, and upregulating the enzymatic antioxidant system to reduce oxidative stress under alkaline conditions. Hence, our findings manifest that NAA application is an effective strategy that can be utilized to enhance tolerance of chufa plants to alkaline stress. Future studies should explore whether NAA can positively alter the nutrient composition of chufa tubers at deeper molecular levels, which might offer solutions to nutritious problems in developing countries.

Transcriptome Analysis of Leaf Senescence Regulation Under Alkaline Stress in Medicago truncatula

In plants, the leaf is an essential photosynthetic organ, and is the primary harvest in forage crops such as alfalfa (Medicago sativa). Premature leaf senescence caused by environmental stress can result in significant yield loss and quality reduction. Therefore, the stay-green trait is important for improving the economic value of forage crops. Alkaline stress can severely damage leaf cells and, consequently, cause leaf senescence. To understand the molecular regulatory mechanisms and identify vital senescence-associated genes under alkaline stress, we used high-throughput sequencing to study transcriptional changes in Medicago truncatula, a model plant for forage crops. We identified 2,165 differentially expressed genes, 985 of which were identical to those in the dark-induced leaf senescence group. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses showed that the 985 genes were mainly enriched in nutrient cycling processes such as cellular amino acid metabolic processes and organic substance catabolic processes, indicating nutrient redistribution. The other 1,180 differentially expressed genes were significantly enriched in the oxidoreductase complex, aerobic respiration, and ion transport. Our analysis showed the two gene sets guiding the coupled physiological and biochemical alterations play different roles under alkaline stress with a coordinated and integrated way. Many transcription factor families were identified from these differentially expressed genes, including MYB, WRKY, bHLH, and NAC which have particular preference involved in stress resistance and regulation of senescence. Our results contribute to the exploration of the molecular regulatory mechanisms of leaf senescence in M. truncatula under alkaline stress and provide new candidate genes for future breeding to improve the biomass and quality of forage crops.

Hydrogen Sulfide Promotes Adventitious Root Development in Cucumber under Salt Stress by Enhancing Antioxidant Ability

As a gas signal molecule, hydrogen sulfide (H₂S) can enhance plant stress resistance. Here, cucumber (Cucumis sativus 'Xinchun NO. 4') explants were used to investigate the role of H₂S in adventitious root development under salt stress. The results show that sodium chloride (NaCl) at 10 mM produced moderate salt stress. The 100 µM sodium hydrosulfide (NaHS) treatment, a H₂S donor, increased root number and root length by 38.37% and 66.75%, respectively, indicating that H₂S effectively promoted the occurrence of adventitious roots in cucumber explants under salt stress. The results show that under salt stress, NaHS treatment reduced free proline content and increased the soluble sugar and soluble protein content during rooting. Meanwhile, NaHS treatment enhanced the activities of antioxidant enzymes [peroxidase (POD), superoxide dismutase (SOD), ascorbate peroxidase (APX) and catalase (CAT)], increased the content of ascorbic (ASA) and glutathione (GSH), reduced the content of hydrogen peroxide (H₂O₂) and the rate of superoxide radical (O^2-) production, and decreased relative electrical conductivity (REC) and the content of malondialdehyde (MDA). However, the NaHS scavenger hypotaurine (HT) reversed the above effects of NaHS under salt stress. In summary, H₂S promoted adventitious root development under salt stress through regulating osmotic substance content and enhancing antioxidant ability in explants.

Trichoderma longibrachiatum (TG1) Enhances Wheat Seedlings Tolerance to Salt Stress and Resistance to Fusarium pseudograminearum

Salinity is abiotic stress that inhibits seed germination and suppresses plant growth and root development in a dose-dependent manner. Fusarium pseudograminearum (Fg) is a plant pathogen that causes wheat crown rot. Chemical control methods against Fg are toxic to the environment and resistance has been observed in wheat crops. Therefore, an alternative approach is needed to manage this devastating disease and the effects of salinity. Our research focused on the mycoparasitic mechanisms of Trichoderma longibrachiatum (TG1) on Fg and the induction of defenses in wheat seedlings under salt and Fg stress at physiological, biochemical and molecular levels. The average inhibition rate of TG1 against Fg was 33.86%, 36.32%, 44.59%, and 46.62%, respectively, in the four NaCl treatments (0, 50, 100, and 150 mM). The mycoparasitic mechanisms of TG1 against Fg were coiling, penetration, and wrapping of Fg hyphae. In response to inoculation of TG1 with Fg, significant upregulation of cell wall degrading enzymes (CWDEs) was observed. The expression of β-1, 6-glucan synthase (PP4), endochitinase precursor (PH-1), and chitinase (chi18-15) increased by 1. 6, 1. 9, and 1.3-fold on day 14 compared with day 3. Wheat seedlings with combined TG1 + Fg treatments under different NaCl stress levels decreased disease index by an average of 51.89%; increased the superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) activity by an average of 38%, 61%, and 24.96%, respectively; and decreased malondialdehyde (MDA) and hydrogen peroxide (H2O2) content by an average of 44.07% and 41.75% respectively, compared with Fg treated seedlings. The combined TG1 + Fg treatment induced the transcription level of plant defense-related genes resulting in an increase in tyrosin-protein kinase (PR2), chitinase class I (CHIA1), and pathogenesis-related protein (PR1-2) by an average of 1.15, 1.35, and 1.37-fold, respectively compared to Fg treatment. However, the expression levels of phenylalanine ammonia-lyase (PAL) increased 3.40-fold under various NaCl stresses. Our results suggest that TG1 enhances wheat seedling growth and controls wheat crown rot disease by strengthening the plant defense system and upregulating the expression of pathogenesis-related genes under both Fg and salt stress.

Choline Chloride Mediates Salinity Tolerance in Cluster Bean (Cyamopsis tetragonoloba L.) by Improving Growth, Oxidative Defense, and Secondary Metabolism

Choline chloride (CC) application enhanced the tolerance of cluster bean (Cyamopsis tetragonoloba L.) against salinity stress. The aim of the study was to determine the protective role of CC on plant growth, photosynthesis, and biochemical indicators of oxidative stress. The seeds of BR-99 (tolerant) and BR-2017 (sensitive) were surface sterilized and sown in plastic pots containing river sandy soil. The design of the experiments was completely randomized with 4 replicates per treatment. Three weeks after germination, salinity (150 mM) was imposed. Then plants were sprayed with different concentrations of CC (3, 5, and 10 mM), while normal plants were sprayed with distilled water. Salinity decreased growth attributes, relative water contents, photosynthetic attributes, total soluble proteins, total free amino acids, phenolic, flavonoids, ascorbic acid, proline, and glycine betaine and increased the levels of oxidative stress indicators. However, the application of CC (particularly 5 mM) improved growth attributes, photosynthetic pigments, and activities of antioxidant compounds by reducing the levels of H2O2, malondialdehyde in salt-stressed plants in both cluster bean varieties. BR-99 variety showed more tolerance to salinity stress than that of BR-2017 in the form of greater oxidative defense and osmotic adjustment and clear from greater plant dry masses. Thus, our results showed that the application of CC (5 mM) is an efficient strategy for field use in the areas, where salt stress soils limit agriculture production.

Klebsiella variicola improves the antioxidant ability of maize seedlings under saline-alkali stress

Background

Saline-alkali soil is mainly distributed in the northern and coastal areas of China. The Songnen Plain, located in the northeast of China, is a region with a relatively high concentration of saline-alkali soil and is also one of the more at-risk areas in the country. Every year, the increasing spread of saline-alkali soil areas has a serious impact on the growth of agricultural crops. The maize crop is sensitive to saline-alkali stress, which seriously affects its growth and development. Our previous study determined that Klebsiella variicola performs a variety of biological functions, as well as improves the rhizosphere microenvironment and promotes the growth and development of maize seedlings in saline-alkali soil environments. The present study further analyzed the mechanism that enables K. variicola to alleviate saline-alkali stress at the level of the antioxidant system.

Methods

The accumulation of O₂⁻ was observed directly via histochemical staining. The activities of several antioxidant enzymes were determined using the nitro blue tetrazolium and the guaiacol methods. The contents of non-enzymatic antioxidants were determined using the dithionitrobenzoic acid method.

Results

The contents of the superoxide anion and hydrogen peroxide in leaves and roots of maize seedlings increased under saline-alkali stress conditions. The higher level of reactive oxygen species increased the degree of membrane lipid peroxidation. There were differences in the degree of oxidative damage and performance of the antioxidant defence system in maize seedlings under saline-alkali stress. Following the application of increasing concentrations of K. variicola, the activity of antioxidant enzymes increased by 21.22%–215.46%, and the content of non-enzymatic antioxidants increased as well, the ratios of ASA/DHA and GSH/GSSG in leaves increased by 4.97% and 1.87 times, respectively, and those in roots increased by 3.24% and 1.60 times, respectively. The accumulation of reactive oxygen species was reduced, and the content of H₂O₂ decreased by 26.07%–46.97%. The content of O₂⁻ decreased by 20.18%–37.01%, which alleviated the oxidative damage to maize seedlings caused by saline-alkali stress.

Conclusion

K. variicola reduced ROS-induced peroxidation to membrane lipids and effectively alleviated the damage caused by saline-alkali stress by increasing the activities of antioxidant enzymes in maize seedlings, thus enhancing their saline-alkali tolerance. A bacterial concentration of 1×10⁸ cfu/mL was optimal in each set of experiments.

Saline-alkaline stress in growing maize seedlings is alleviated by Trichoderma asperellum through regulation of the soil environment

A significant proportion of the land area of Heilongjiang Province, China, is composed of saline-alkaline soil, which severely inhibits maize growth. Although Trichoderma treatment is widely regarded as a promising strategy for improving the soil environment and promoting plant growth, the mechanism through which Trichoderma asperellum enhances maize resistance to saline-alkaline stress is not clear. In this study, we explored the effect of T. asperellum application at different concentrations to soil saline-alkaline environment on the seedlings of two maize cultivars, assessing the biochemical parameters related to oxidation resistance. Increasing spore densities of T. asperellum suspension effectively regulated the soil ion balance in the rhizosphere of maize seedlings, reduced the soil pH by 2.15-5.76% and sodium adsorption ratios by 22.70-54.13%, increased soil nutrient content and enzyme activity, and improved the soil environment for seedling growth. Additionally, T. asperellum treatment increased the maize seedling content of osmo-regulating substances and rate of glutathione:oxidised glutathione (43.86-88.25%) and ascorbate:oxidised ascorbate (25.26-222.32%) by affecting the antioxidant enzyme activity in the roots, increasing reactive oxygen species scavenging, and maintaining the osmotic balance and metabolic homeostasis under saline-alkaline stress. T. asperellum also improved the saline-alkaline tolerance of maize seedlings by improving the root growth characteristics. Moreover, results showed that Trichoderma applied at high concentration had the greatest effect. In conclusion, improvement in the saline-alkaline tolerance of maize seedlings by T. asperellum under saline-alkaline soil conditions may be achieved through diverse effects that vary among maize cultivars.

Trichoderma asperellum Inoculation as a Tool for Attenuating Drought Stress in Sugarcane

Drought stress is an important concern worldwide which reduces crop yield and quality. To alleviate this problem, Trichoderma asperellum has been used as a plant growth-promoting fungus capable of inducing plant tolerance to biotic and abiotic stresses. Here, we examined the effect of T. asperellum inoculation on sugarcane plant above and belowground development under drought stress and investigated the role of this fungus on inducing tolerance to drought at physiological and biochemical levels. The experiment was performed in pots under greenhouse conditions, with four treatments and four replicates. The treatments consisted of sugarcane plants inoculated or not with T. asperellum and grown under drought stress and adequate water availability. Drought-stressed sugarcane plants inoculated with T. asperellum changed the crop nutrition and chlorophyll and carotenoid concentrations, resulting in increased photosynthesis rate, stomatal conductance, and water use efficiency compared to the non-inoculated plants. In addition, the antioxidant metabolism also changed, increasing the superoxide dismutase and peroxidase enzyme activities, as well as the proline concentration and sugar portioning. These cascade effects enhanced the root and stalk development, demonstrating that T. asperellum inoculation is an important tool in alleviating the negative effects of drought stress in sugarcane. Future studies should be performed to elucidate if T. asperellum should be reapplied to the sugarcane ratoons.

Trichoderma asperellum xylanases promote growth and induce resistance in poplar

Xylanase secreted by Trichoderma asperellum ACCC30536 can stimulate the systemic resistance of host plants against pathogenic fungi. Following T. asperellum conidia co-culture with Populus davidiana × P. alba var. pyramidalis Louche (PdPap) seedlings, the expression of xylanases TasXyn29.4 and TasXyn24.2 in T. asperellum were upregulated, peaking at 12 h, by 106 (2^6.74) and 10.1 (2^3.34)-fold compared with the control, respectively. However, the expression of TasXyn24.4 and TasXyn24.0 was not detected. When recombinant xylanases rTasXyn29.4 and rTasXyn24.2 were heterologously expressed in Pichia pastoris GS115, their activities reached 18.9 IU/mL and 20.4 IU/mL, respectively. In PdPap seedlings induced by rTasXyn29.4 and rTasXyn24.2, the auxin and jasmonic acid signaling pathways were activated to promote growth and enhance resistance against pathogens. PdPap seedlings treated with both xylanases showed increased methyl jasmonate contents at 12 hpi, reaching 122 % (127 μg/g) compared with the control. However, neither of the xylanases could induce the salicylic acid signaling pathway in PdPap seedlings. Meanwhile, both xylanases could enhance the antioxidant ability of PdPap seedlings by improving their catalase activity. Both xylanases significantly induced systemic resistance of PdPap seedlings against Alternaria alternata, Rhizoctonia solani, and Fusarium oxysporum. However, the xylanases could only be sensed by the roots of the PdPap seedlings, not the leaves. In summary, rTasXyn29.4 and rTasXyn24.2 from T. asperellum ACCC30536 promoted growth and induced systemic resistance of PdPap seedlings, which endowed the PdPap seedlings broad-spectrum resistance to phytopathogens.

Assessment of Acidic Biochar on the Growth, Physiology and Nutrients Uptake of Maize (Zea mays L.) Seedlings under Salinity Stress

The application of an acidic biochar can improve plant growth and soil properties in saline conditions. In this study, we investigated the effect of acidic biochar on plant growth and nutrients contents in saline soil. Seven treatments were arranged in a complete randomized design, including control (CK), 0, 30, and 45 g biochar added to a soil having 1% and 1.5% salts; these treatments were termed as B0S1, B30S1, B45S1 and B0S1.5, B30S1.5, B45S1.5 respectively. Experimental results showed that the plant height, leaves plant−1, leaf area, and shoot fresh and dry biomass, and root fresh and dry biomass were increased for the B45S1.5, respectively. Similarly, the highest total nitrogen (TN), total phosphorus (TP), total potassium (TK), and total sodium (Na) concentration in maize shoot were observed for B30S1, B0S1.5, CK, and B0S1.5, respectively. The highest concentrations of TN, TP, TK, and Na in root were obtained with the treatments B0S1, B0S1, B45S1, and B0S1, respectively. Soil pH, and EC decreased and nutrients concentration improved by the addition of acidic biochar. We conclude that the use of acidic biochar can be a potential source for the improvement of maize plant growth as well as mitigate the adverse effect of salt stress.

Hydrogen sulfide priming can enhance the tolerance of artichoke seedlings to individual and combined saline-alkaline and aniline stresses

Regulatory roles of hydrogen sulfide (H₂S) under saline-alkaline and/or aniline stress have not been studied yet. In this study, we investigated the insights into saline-alkaline and/or aniline stresses-induced toxicity in artichoke plants and its alleviation by H₂S priming. Individual saline-alkaline or aniline stress and their combination reduced plant growth and photosynthetic pigments. Principal component analysis (PCA) revealed that these detrimental impacts were caused by the higher oxidative damage and disruption of osmolyte homeostasis. Interestingly, only aniline stress (25 mg L^-1) caused neither oxidative nor osmotic stress thus almost slight growth retarding effects had ensued. On the other hand, the presence of aniline in saline-alkaline conditions exacerbated stress-induced deleterious effects on plants, as evidenced by PCA and heatmap. However, H₂S priming markedly eased the stress-induced deleteriousness as evident by enhanced chlorophyll, soluble proteins, soluble carbohydrates and up-regulated water relation in H₂S-primmed plants compared with only stressed plants resulting in improved plant phenotypic features. Furthermore, H₂S priming enhanced endogenous H₂S content, phenylalanine ammonia-lyase, non-enzymatic antioxidants (ascorbic acid, flavonoids, glutathione, α-tocopherol, and anthocyanins) and enzymatic antioxidants (superoxide dismutase, catalase, and ascorbate peroxidase), whereas reduced oxidative stress markers (superoxide, hydrogen peroxide, hydroxyl radical, malondialdehyde, and methylglyoxal) compared with only stressed plants, indicating a protective function of H₂S against oxidative damage. The PCA also clarified that H₂S-mediated saline-alkaline and/or aniline stress tolerance strongly connected with the improved antioxidant system. Overall, our finding proposed that H₂S priming could be an effective technique to mitigate saline-alkaline and/or aniline stress in artichoke, and perhaps in other crop plants.

Response Mechanisms of Plants Under Saline-Alkali Stress

As two coexisting abiotic stresses, salt stress and alkali stress have severely restricted the development of global agriculture. Clarifying the plant resistance mechanism and determining how to improve plant tolerance to salt stress and alkali stress have been popular research topics. At present, most related studies have focused mainly on salt stress, and salt-alkali mixed stress studies are relatively scarce. However, in nature, high concentrations of salt and high pH often occur simultaneously, and their synergistic effects can be more harmful to plant growth and development than the effects of either stress alone. Therefore, it is of great practical importance for the sustainable development of agriculture to study plant resistance mechanisms under saline-alkali mixed stress, screen new saline-alkali stress tolerance genes, and explore new plant salt-alkali tolerance strategies. Herein, we summarized how plants actively respond to saline-alkali stress through morphological adaptation, physiological adaptation and molecular regulation.

The interactions of Trichoderma at multiple trophic levels: inter-kingdom communication

Trichoderma spp. are universal saprotrophic fungi in terrestrial ecosystems, and as rhizosphere inhabitants, they mediate interactions with other soil microorganisms, plants, and arthropods at multiple trophic levels. In the rhizosphere, Trichoderma can reduce the abundance of phytopathogenic microorganisms, which involves the action of potent inhibitory molecules, such as gliovirin and siderophores, whereas endophytic associations between Trichoderma and the seeds and roots of host plants can result in enhanced plant growth and crop productivity, as well as the alleviation of abiotic stress. Such beneficial effects are mediated via the activation of endogenous mechanisms controlled by phytohormones such as auxins and abscisic acid, as well as by alterations in host plant metabolism. During either root colonization or in the absence of physical contact, Trichoderma can trigger early defense responses mediated by Ca²⁺ and reactive oxygen species, and subsequently stimulate plant immunity by enhancing resistance mechanisms regulated by the phytohormones salicylic acid, jasmonic acid, and ethylene. In addition, Trichoderma release volatile organic compounds and nitrogen or oxygen heterocyclic compounds that serve as signaling molecules, which have effects on plant growth, phytopathogen levels, herbivorous insects, and at the third trophic level, play roles in attracting the natural enemies (predators and parasitoids) of herbivores. In this paper, we review some of the most recent advances in our understanding of the environmental influences of Trichoderma spp., with particular emphasis on their multiple interactions at different trophic levels.

Application of Trichoderma asperellum T34 on maize (Zea mays) seeds protects against drought stress

Coating maize seeds with the microbial plant protection product Trichoderma asperellum strain T34 is an effective form of inoculation that enhances plant performance when faced with drought stress, and it improves nutrient and kernel parameters differently in drought and non-stressed conditions. Drought is currently one of the biggest threats to maize production. Trichoderma spp. is mainly used in agriculture as plant protection product with secondary beneficial effects on plants: improved growth, nutrient uptake and plant immunity. Here, we studied the physiological performance of maize plants under two different water regimes (fully irrigated and drought conditions) and three different seed treatments: application of Trichoderma asperellum strain T34, application of a chemical fungicide (CELEST XL) or the combination of both. Regardless of water regime, T34 treatment improved kernel P and C, kernel number and dry weight. Higher populations of T34 on the rhizosphere (T34 treatment) alleviated water stress better than lower T34 populations (T34+Q treatment). Under drought, T34 treatment improved leaf relative water content, water use efficiency, PSII maximum efficiency and photosynthesis. T34-treated maize seeds maintained sufficient T34 populations to alleviate drought throughout crop development suggesting an optimal dose of 10⁴ and 10⁵ colony forming units g^-1 dry weight of rhizosphere under the studied conditions. This work helps to demonstrate the beneficial interaction between T. asperellum strain T34 and maize plants under drought.

Comparative transcriptome analysis reveals gene expression differences between two peach cultivars under saline-alkaline stress

BACKGROUND

Saline-alkaline stress is a major abiotic stress that is harmful to plant growth worldwide. Two peach cultivars (GF677 and Maotao) display distinct phenotypes under saline-alkaline stress. The molecular mechanism explaining the differences between the two cultivars is still unclear.

RESULTS

In the present study, we systematically analysed the changes in GF677 and Maotao leaves upon saline-alkaline stress by using cytological and biochemical technologies as well as comparative transcriptome analysis. Transmission electron microscopy (TEM) observations showed that the structure of granum was dispersive in Maotao chloroplasts. The biochemical analysis revealed that POD activity and the contents of chlorophyll a and chlorophyll b, as well as iron, were notably decreased in Maotao. Comparative transcriptome analysis detected 881 genes with differential expression (including 294 upregulated and 587 downregulated) under the criteria of |log2 Ratio| ≥ 1 and FDR ≤0.01. Gene ontology (GO) analysis showed that all differentially expressed genes (DEGs) were grouped into 30 groups. MapMan annotation of DEGs showed that photosynthesis, antioxidation, ion metabolism, and WRKY TF were activated in GF677, while cell wall degradation, secondary metabolism, starch degradation, MYB TF, and bHLH TF were activated in Maotao. Several iron and stress-related TFs (ppa024966m, ppa010295m, ppa0271826m, ppa002645m, ppa010846m, ppa009439m, ppa008846m, and ppa007708m) were further discussed from a functional perspective based on the phylogenetic tree integration of other species homologues.

CONCLUSIONS

According to the cytological and molecular differences between the two cultivars, we suggest that the integrity of chloroplast structure and the activation of photosynthesis as well as stress-related genes are crucial for saline-alkaline resistance in GF677. The results presented in this report provide a theoretical basis for cloning saline-alkaline tolerance genes and molecular breeding to improve saline-alkaline tolerance in peach.

Carbon metabolic profiling of Trichoderma strains provides insight into potential ecological niches

Many Trichoderma species are cosmopolitan and widespread free-living fungi in various ecological environment, and many are economically important in the fields of agriculture and industry. However, carbon metabolism profiles of Trichoderma species have not been characterized in detail. In this study, Biolog FF MicroPlates were used to contrast carbon utilization and the differences among five Trichoderma species, each representing a unique phenotype. Their metabolic abilities varied greatly. Species producing cellulases and chitinases and with phosphate-solubilizing activities exhibited high efficiency of substrate utilization, whereas low efficiency was shown by saline-alkaline-tolerant species that metabolized simple carbon sources. Species producing cellulases at high levels may be specified to decompose and assimilate cellulose and hemicellulose in woody substrates, and those producing chitinases may have mycoparasitic roles. Species with plant growth-promoting traits are good at uptake of exudates from plant roots. Overall, metabolic models reflect nutritional adaptation of Trichoderma to diverse niches in nature.

Effects of Foliar Treatment with a Trichoderma Plant Biostimulant Consortium on Passiflora caerulea L. Yield and Quality

The influence of spore concentration on the ability of a Trichoderma consortium to colonize the Passiflora caerulea phyllosphere was evaluated by determining the effects of foliar treatments with two spore concentrations, in two repeated treatments, on the morphological, physiological, and ultrastructural characteristics, and on the yield and quality of P. caerulea. The studied crop quality features were related to its nutraceutical use: the accumulation of polyphenols and flavonoids, antioxidant activity, and effects on mouse fibroblast L929 cells. The Trichoderma consortium consisted of two strains, T. asperellum T36b and T. harzianum Td50b, and the concentrations used were 106 colony forming units (cfu)/mL and 108 cfu/mL. As a reference treatment, a commercial product that was based on herbs and algal extracts was used. As compared to the negative control, the treatment with the Trichoderma consortium at 108 cfu/mL concentration determines the accumulation of higher level of polyphenols and flavonoids and increased antioxidant activity. This enhancement of P. caerulea quality characteristics after treatment with the higher concentration of Trichoderma consortium was associated with larger leaves, increased number and size of chloroplasts, improved plant physiology characteristics, and an increased yield. The treatment with high concentration of Trichoderma consortium spores promotes phyllosphere colonization and benefits both crop yield and quality.

Natural variation of an EF-hand Ca2+-binding-protein coding gene confers saline-alkaline tolerance in maize

Sodium (Na⁺) toxicity is one of the major damages imposed on crops by saline-alkaline stress. Here we show that natural maize inbred lines display substantial variations in shoot Na⁺ contents and saline-alkaline (NaHCO₃) tolerance, and reveal that ZmNSA1 (Na⁺Content under Saline-Alkaline Condition) confers shoot Na⁺ variations under NaHCO₃ condition by a genome-wide association study. Lacking of ZmNSA1 promotes shoot Na⁺ homeostasis by increasing root Na⁺ efflux. A naturally occurred 4-bp deletion decreases the translation efficiency of ZmNSA1 mRNA, thus promotes Na⁺ homeostasis. We further show that, under saline-alkaline condition, Ca²⁺ binds to the EF-hand domain of ZmNSA1 then triggers its degradation via 26S proteasome, which in turn increases the transcripts levels of PM-H⁺-ATPases (MHA2 and MHA4), and consequently enhances SOS1 Na⁺/H⁺ antiporter-mediated root Na⁺ efflux. Our studies reveal the mechanism of Ca²⁺-triggered saline-alkaline tolerance and provide an important gene target for breeding saline-alkaline tolerant maize varieties.

Saline-alkaline stress affects worldwide crops production, but the tolerance mechanisms have not been fully elucidated. Here, the authors show that EF-hand Ca2 + -binding-protein coding gene ZmNSA1 can regulate root H + efflux, Na + homeostasis, and saline-alkaline tolerance in maize.

Effect of Straw Biochar on Soil Properties and Wheat Production under Saline Water Irrigation

Use of saline water for irrigation is essential to mitigate increasing agricultural water demands in arid and semi-arid regions. The objective of this study is to address the potential of using straw biochar as a soil amendment to promote wheat production under saline water irrigation. A field experiment was conducted in a clay loam soil from eastern China during 2016/2017 and 2017/2018 winter wheat season. There were five treatments: freshwater irrigation (0.3 dS m−1), saline water irrigation (10 dS m−1), saline water irrigation (10 dS m−1) combined with biochar of 10, 20, 30 t ha−1. Saline water irrigation alone caused soil salinization and decreased wheat growth and yield. The incorporation of biochar decreased soil bulk density by 5.5%–11.6% and increased permeability by 35.4%–49.5%, and improved soil nutrient status. Biochar also reduced soil sodium adsorption ratio by 25.7%–32.6% under saline water irrigation. Furthermore, biochar alleviated salt stress by maintaining higher leaf relative water content and lower Na+/K+ ratio, and further enhanced photosynthesis and relieved leaf senescence during reproductive stages, leading to better grain formation. Compared to saline water irrigation alone, biochar application of 10 and 20 t ha−1 significantly increased wheat grain yield by 8.6 and 8.4%, respectively. High dose of biochar might increase soil salinity and limit N availability. In the study, biochar amendment at 10 t ha−1 would be a proper practice at least over two years to facilitate saline water irrigation for wheat production. Long-term studies are recommended to advance the understanding of the sustainable use of straw biochar.

Investigating Maize Yield-Related Genes in Multiple Omics Interaction Network Data

Zea mays (maize) is the highest yielding food crop globally, feeding large numbers of people across the planet. It is thus especially important to explore the key genes that affect maize production with prior knowledge. Merging multiple datasets of different types can improve the accuracy of candidate genes prediction results, so we constructed interaction networks using gene, mRNA, protein, and expression profile datasets. A network propagation schedule was used considering combined scores obtained by integrating both network scores and significance scores for each candidate gene based on the guilt-by-association principle. An SVM model was used to optimize the weighted parameters to achieve more reliable results, according to the accuracy of label classification. We found that integrating multiple omics data with more data types improves the reliability of the results. We investigated the GO terms particularly associated with the top 100 candidate genes and the known genes, and analyzed the roles that these genes play in determining the phenotype of maize. We hope that the candidate genes identified here will provide a biological perspective and contribute to maize breeding research.

Trichoderma erinaceum Bio-Priming Modulates the WRKYs Defense Programming in Tomato Against the Fusarium oxysporum f. sp. lycopersici (Fol) Challenged Condition

The beneficial association and interaction of rhizocompetent microorganisms are widely used for plant biofertilization and amelioration of stress-induced damage in plants. To explore the regulatory mechanism involved in plant defense while associating with beneficial microbial species, and their interplay when co-inoculated with pathogens, we evaluated the response of tomato defense-related WRKY gene transcripts. The present study was carried out to examine the qRT-PCR-based relative quantification of differentially expressed defense-related genes in tomato (Solanum lycopersicum L.; variety S-22) primed with Trichoderma erinaceum against the vascular wilt pathogen (Fusarium oxysporum f. sp. lycopersici). The tissue-specific and time-bound expression profile changes under the four different treatments "(unprimed, Fol challenged, T. erinaceum primed and Fol+ T. erinaceum)" revealed that the highest upregulation was observed in the transcript profile of SlWRKY31 (root) and SlWRKY37 (leaf) in T. erinaceum bioprimed treated plants at 24 h with 16.51- and 14.07-fold increase, respectively. In contrast, SlWRKY4 showed downregulation with the highest repression in T. erinaceum bioprimed root (24 h) and leaf (48 h) tissue samples with 0.03 and 0.08 fold decrease, respectively. Qualitative expression of PR proteins (chitinases and glucanases) was found elicited in T. erinaceum primed plants. However, the antioxidative activity of tomato superoxide dismutase and catalase increased with the highest upregulation of SOD and SlGPX1 in Fol + T. erinaceum treatments. We observed that these expression changes were accompanied by 32.06% lesser H₂O₂ production in T. erinaceum bioprimed samples. The aggravated defense response in all the treated conditions was also reflected by an increased lignified stem tissues. Overall, we conclude that T. erinaceum bio-priming modulated the defense transcriptome of tomato after the Fol challenged conditions, and were accompanied by enhanced accumulation of defense-related WRKY transcripts, increased antioxidative enzyme activities, and the reinforcements through a higher number of lignified cell layers.

Transcriptome reprogramming, epigenetic modifications and alternative splicing orchestrate the tomato root response to the beneficial fungus Trichoderma harzianum

Beneficial interactions of rhizosphere microorganisms are widely exploited for plant biofertilization and mitigation of biotic and abiotic constraints. To provide new insights into the onset of the roots-beneficial microorganisms interplay, we characterised the transcriptomes expressed in tomato roots at 24, 48 and 72 h post inoculation with the beneficial fungus Trichoderma harzianum T22 and analysed the epigenetic and post-trascriptional regulation mechanisms. We detected 1243 tomato transcripts that were differentially expressed between Trichoderma-interacting and control roots and 83 T. harzianum transcripts that were differentially expressed between the three experimental time points. Interaction with Trichoderma triggered a transcriptional response mainly ascribable to signal recognition and transduction, stress response, transcriptional regulation and transport. In tomato roots, salicylic acid, and not jasmonate, appears to have a prominent role in orchestrating the interplay with this beneficial strain. Differential regulation of many nutrient transporter genes indicated a strong effect on plant nutrition processes, which, together with the possible modifications in root architecture triggered by ethylene/indole-3-acetic acid signalling at 72 h post inoculation may concur to the well-described growth-promotion ability of this strain. Alongside, T. harzianum-induced defence priming and stress tolerance may be mediated by the induction of reactive oxygen species, detoxification and defence genes. A deeper insight into gene expression and regulation control provided first evidences for the involvement of cytosine methylation and alternative splicing mechanisms in the plant-Trichoderma interaction. A model is proposed that integrates the plant transcriptomic responses in the roots, where interaction between the plant and beneficial rhizosphere microorganisms occurs.

Biocontrol potential of saline- or alkaline-tolerant Trichoderma asperellum mutants against three pathogenic fungi under saline or alkaline stress conditions

Salinity and alkalinity are major abiotic stresses that limit growth and development of poplar. We investigated biocontrol potential of saline- and alkaline-tolerant mutants of Trichoderma asperellum to mediate the effects of salinity or alkalinity stresses on Populus davidiana×P. alba var. pyramidalis (PdPap poplar) seedlings. A T-DNA insertion mutant library of T. asperellum was constructed using an Agrobacterium tumefaciens mediated transformation system; this process yielded sixty five positive transformants (T1-T65). The salinity tolerant mutant, T59, grew in Potato Dextrose Agar (PDA) containing up to 10% (1709.40mM) NaCl. Under NaCl-rich conditions, T59 was most effective in inhibiting Alternaria alternata (52.00%). The alkalinity tolerant mutants, T3 and T5, grew in PDA containing up to 0.4% (47.62mM) NaHCO₃. The ability of the T3 and T5 mutants to inhibit Fusarium oxysporum declined as NaHCO₃ concentrations increased. NaHCO₃ tolerance of the PdPap seedlings improved following treatment with the spores of the WT, T3, and T5 strains. The salinity tolerant mutant (T59) and two alkalinity tolerant mutants (T3 and T5) generated in this study can be applied to decrease the incidence of pathogenic fungi infection under saline or alkaline stress.