Cucumber Roots Research Articles

Plant seedlings of peas, tomatoes, and cucumbers exude compounds that are needed for growth and chemoattraction of Rhizobium leguminosarum bv. viciae 3841 and Azospirillum brasilense Sp7.

This study characterizes seedling exudates of peas, tomatoes, and cucumbers at the level of chemical composition and functionality. A plant experiment confirmed that Rhizobium leguminosarum bv. viciae 3841 enhanced growth of pea shoots, while Azospirillum brasilense Sp7 supported growth of pea, tomato, and cucumber roots. Chemical analysis of exudates after 1 day of seedling incubation in water yielded differences between the exudates of the three plants. Most remarkably, cucumber seedling exudate did not contain detectable sugars. All exudates contained amino acids, nucleobases/nucleosides, and organic acids, among other compounds. Cucumber seedling exudate contained reduced glutathione. Migration on semi solid agar plates containing individual exudate compounds as putative chemoattractants revealed that R. leguminosarum bv. viciae was more selective than A. brasilense, which migrated towards any of the compounds tested. Migration on semi solid agar plates containing 1:1 dilutions of seedling exudate was observed for each of the combinations of bacteria and exudates tested. Likewise, R. leguminosarum bv. viciae and A. brasilense grew on each of the three seedling exudates, though at varying growth rates. We conclude that the seedling exudates of peas, tomatoes, and cucumbers contain everything that is needed for their symbiotic bacteria to migrate and grow on.

Serratia marcescens LYGN1 Reforms the Rhizosphere Microbial Community and Promotes Cucumber and Pepper Growth in Plug Seedling Cultivation.

The vegetable plug seedling plays an important role in improving vegetable production. The process of plug seedling contributes to high-quality vegetable seedlings. The substrate composition and chemical fertilizer are widely studied to promote seedling growth. However, little is known about the effect of beneficial bacteria in the rhizosphere microbial community and vegetables' growth during plug seedling. The use of beneficial microbes to promote vegetable seedling growth is of great potential. In this study, we showed that the Serratia marcescens strain LYGN1 enhanced the growth of cucumber and pepper seedlings in plug seedling cultivation. The treatment with LYGN1 significantly increased the biomass and the growth-related index of cucumber and pepper, improving the seedling quality index. Specifically, LYGN1 also improved the cucumber and pepper root system architecture and increased the root diameter. We applied high-throughput sequencing to analyze the microbial community of the seedlings' rhizosphere, which showed LYGN1 to significantly change the composition and structure of the cucumber and pepper rhizosphere microbial communities. The correlation analysis showed that the Abditibacteriota and Bdellovibrionota had positive effects on seedling growth. The findings of this study provide evidence for the effects of Serratia marcescens LYGN1 on the cucumber and pepper rhizosphere microbial communities, which also promoted seedling quality in plug seedling cultivation.

Do DEEPER ROOTING 1 Homologs Regulate the Lateral Root Slope Angle in Cucumber (Cucumis sativus)?

The architecture of the root system is fundamental to plant productivity. The rate of root growth, the density of lateral roots, and the spatial structure of lateral and adventitious roots determine the developmental plasticity of the root system in response to changes in environmental conditions. One of the genes involved in the regulation of the slope angle of lateral roots is DEEPER ROOTING 1 (DRO1). Its orthologs and paralogs have been identified in rice, Arabidopsis, and several other species. However, nothing is known about the formation of the slope angle of lateral roots in species with the initiation of lateral root primordia within the parental root meristem. To address this knowledge gap, we identified orthologs and paralogs of the DRO1 gene in cucumber (Cucumis sativus) using a phylogenetic analysis of IGT protein family members. Differences in the transcriptional response of CsDRO1, CsDRO1-LIKE1 (CsDRO1L1), and CsDRO1-LIKE2 (CsDRO1L2) to exogenous auxin were analyzed. The results showed that only CsDRO1L1 is auxin-responsive. An analysis of promoter-reporter fusions demonstrated that the CsDRO1, CsDRO1L1, and CsDRO1L2 genes were expressed in the meristem in cell files of the central cylinder, endodermis, and cortex; the three genes displayed different expression patterns in cucumber roots with only partial overlap. A knockout of individual CsDRO1, CsDRO1L1, and CsDRO1L2 genes was performed via CRISPR/Cas9 gene editing. Our study suggests that the knockout of individual genes does not affect the slope angle formation during lateral root primordia development in the cucumber parental root.

Mechanisms involved in plant growth promotion by Enterobacter cloacae DJ under salinity-alkalinity stress

BackgroundPlant-promoting bacteria are safer alternatives to pesticides and fertilizers, reduce environmental pollution, and increase crop yields. We isolated an Enterobacter cloacae strain DJ with plant-promoting effects from the rhizosphere soil of a plant (Leymus chinensis (Trin.) Tzvel) in the western region of Jilin Province of China and investigated the mechanisms underlying the adaptation of the DJ bacteria to salinity-alkalinity environments and the molecular mechanisms of the cross-talk between DJ bacteria and cucumber seedlings.ResultsThe average diameter of the colonies on the salinity-alkalinity medium after incubation for 24 h was 3.3 cm, and this was significantly higher than the 1.9 cm diameter in ADF medium (p < 0.01). Comparative proteomic analysis revealed that 188 differentially expressed proteins, comprising 116 upregulated and 72 downregulated proteins, significantly changed in salinity-alkalinity groups compared to the control groups. The top one upregulated pathway of KEGG enrichment was bacterial chemotaxis, DJ bacteria adapted to salinity-alkalinity environments by upregulating the genes associated with bacterial chemotaxis. The contents of putrescine in salinity-alkalinity and control groups were 4.73 μg/mL and 3.02 μg/mL, whereas the contents of spermidine were 46.18 ng/mL and 0.34 ng/mL, respectively. Comparing to the control cohorts, the concentrations of both polyamines in the experimental cohorts exhibited statistically significant increases (p < 0.01). The expression of Pt gene encoding polyamine transporter protein was sharply up-regulated in cucumber roots after treatment with DJ bacteria under salinity-alkalinity stress; the expression was more than tenfold higher than that in the control groups. The enzyme activities of POD, SOD, and CAT in cucumber seedlings were higher compared to those in the control groups (p < 0.01). The stem height, number of lateral roots, and fresh weight of cucumber seedlings in the DJ treatment groups were 6.0 cm, 17 roots, and 0.42 g, respectively, whereas those of the control groups were 3.8 cm, 14 roots, and 0.28 g, respectively, with a notable difference between two cohorts (p < 0.01).ConclusionsDJ bacteria can live in salinity-alkalinity conditions by upregulating the expression of genes associated with chemotaxis. The resistance of cucumber seedlings under salinity-alkalinity conditions through the antioxidant pathway was increased by polyamines produced by DJ bacteria.Graphical

Foliar application of glycine-functionalized nanopesticides for effective prevention and control of root-knot nematodes via a targeted delivery strategy.

Root-knot nematodes (RKNs) are the highly damaging pests for various crops, and the prevalence of RKNs has posed serious threats to worldwide agricultural harvest, severely affecting global food security and ecosystem health. Traditional pesticide systems on controlling RKNs generally cause environmental hazards and phytotoxicity due to the excessive use of pesticides resulted from low utilization efficiency. And effective approaches with biosafe and efficient features are highly demanded to break away from the dilemma caused by RKNs. In this research, a nanopesticide system with root-targeted delivery function was developed to achieve effective prevention and control of RKNs. The nanocarriers (MSN-KH560-Gly) and the obtained nanopesticides (EB@MSN-KH560-Gly) were proved to be biosafe. Also, this nanopesticide system demonstrated sustained release behavior. The grafting of glycine (Gly) significantly improved the pesticide contents translocating to cucumber roots (about 304.7%). Besides, such root-targeted delivery function resulted in no root nodule in cucumber plants after the foliar application of these nanopesticides (prevention rate of 100%). In addition, the root nodule numbers of the infected cucumber plants decreased by 71.67%. Foliar application of these Gly-functionalized nanopesticides achieved effective prevention and control of RKNs due to the root-targeted delivery property inherent in this nanopesticide system, and such root-targeted delivery strategy opens a novel and efficient method to protect crops from RKN invasion and thus facilitates the development of sustainable agriculture. © 2023 Society of Chemical Industry.

The combination of Bacillus amyloliquefaciens and Purpureocillium lilacinum in the control of Meloidogyne enterolobii

Nowadays, numerous microorganisms have been identified as effective agents against plant-parasitic nematodes (PPNs) when applied individually. However, under field conditions, the combination of biocontrol agents is a desirable strategy to improve control efficacy against soil-borne pathogens. Since, as different biogents species possess different mechanisms, the combination of strains is an alternative to improve the biocontrol effects. The present study aimed to investigate in planta the efficacy of the association of two commercial bionematicides against M. enterolobii. Here, the combination of Purpureocillium lilacinum strain PL251 (PL) and Bacillus amyloliquefaciens strains D747 (Ba) simultaneously inoculated on cucumber roots, in Florida (USA) soil, significantly reduced (p<0.05) the number of eggs per gram of roots (84%) and gall index compared to negative control. Contrasting with the mixture, the application of each microorganism alone didn’t show any difference to the negative control. In in vitro assays, the combined cell-free supernatants cultures of these microorganisms were also effectiveness on increasing Meloidogyne enterolobii second-stage juvenile (J2) toxicity and inhibit the eggs hatching. Also in in vitro assays, the chemotaxis of M. enterolobii J2 showed to be repellent to both microorganisms. M. enterolobii (J2) repellence was also obtained when root exudates of cucumber were simultaneously inoculated with both microorganisms. On the other side, the exudate of cucumber roots free of those microorganisms was highly attractive to the J2. Despite the notable toxicity of Ba's volatile organic compounds (VOCs) to M. enterolobii J2 compared to the control, the impact of VOCs from Ba alone was significantly more pronounced (P<0.05) when the combined microorganisms were examined. Hence, the enhanced nematode control observed in in vivo experiments is substantiated by the combined impact of the mixture.

Uptake, Translocation, and Subcellular Distribution of Strobilurin Fungicides in Cucumber (Cucumis sativa L.).

The absorption, transport, and subcellular distribution of strobilurin fungicides (azoxystrobin, pyraclostrobin, and trifloxystrobin) have been studied in cucumbers. Under hydroponic laboratory conditions, pyraclostrobin and trifloxystrobin mainly accumulated in cucumber roots whereas azoxystrobin accumulated in cucumber leaves. In the subcellular distribution experiment, azoxystrobin mainly accumulated as a soluble component. Pyraclostrobin and trifloxystrobin accumulated more in the organelles and cell walls. Azoxystrobin and pyraclostrobin enter the root primarily through the apoplast pathway, whereas trifloxystrobin enters the root through the symplastic pathway. Azoxystrobin can be transported in cucumber through anion and cation channels, whereas pyraclostrobin and trifloxystrobin can be transported only through anion channels. This study has great significance in evaluating environmental risks and food safety.

Microplastics alter Cr accumulation and fruit quality in Cr(VI) contaminated soil-cucumber system during the lifecycle: Insight from rhizosphere bacteria and root metabolism

Both microplastics and Cr(VI) potentially threaten soil and crops, but little is known about their interaction in the soil-plant system. This study investigated the effect and mechanism of polyethylene (PE), polyamide (PA), and polylactic acid (PLA) microplastics on Cr bioaccumulation and toxicity in a Cr(VI) contaminated soil-cucumber system during the lifecycle. The results show that microplastics had a greater effect on Cr accumulation in cucumber roots, stems, and leaves than in fruits. PE microplastics increased, but PA and PLA microplastics decreased the Cr accumulation in cucumber. Microplastics, especially high-dose, small, and aged microplastics, exacerbated the effects of accumulated Cr in cucumber on fresh weight and fruit yield. The nutrient contents in fruits except soluble sugars were reduced by microplastics. The random forest regression model shows that the microplastic type was the most important factor causing changes in the soil-cucumber system except for Cr(VI) addition. Under Cr(VI) and microplastic co-exposure, bacteria that could simultaneously tolerate Cr(VI) stress and degrade microplastics were enriched in the rhizosphere soil. The partial least squares path model shows that microplastics reduced the beneficial effect of the bacterial community on cucumber growth. Microplastics, especially PLA microplastics, alleviated the adverse effects of Cr(VI) stress on root metabolism.

Silicon alleviates autotoxicity by regulating membrane lipid peroxidation and improving photosynthetic efficiency in cucumber seedlings (Cucumis sativus L.)

Autotoxicity is one of the main causes of cucumber continuous cropping obstacles. Cinnamic acid (CA), a phenolic acid derivative, acts as an autotoxin found in cucumber root exudates. The autotoxicity mimicked by CA significantly increases membrane lipid peroxidation in root and leaf cells, resulting in damage to the structure and function of root tip cells and leaf cells. It also injures the activity of photosystem PSII, reducing the photosynthetic rate and inhibiting the growth of cucumber plants. Supplementing Si alleviates CA-mimicked autotoxicity by increasing the thickness and smoothness of root tip cell walls, inhibiting the absorption and accumulation of CA, as well as relieving osmotic stress and membrane lipid peroxidation caused by CA in cucumber roots and leaves. Additionally, Si promotes grana lamella (GL) stacking and increases thylakoid numbers in chloroplasts. It also enhances the chlorophyll content in cucumber leaves and improves the energy conversion efficiency of photosystem PSII. These effects lead to an improvement in both photosynthetic efficiency and dry matter accumulation, as well as increased the resistance to CA-induced autotoxicity in cucumber plants. The same concentration of Si had no significant effect on the growth of cucumber seedlings, indicating that Si plays an important role in improving the tolerance to autotoxicity in cucumbers. These findings provide an effective theoretical basis and methods for research regarding the alleviation of continuous cropping obstacles.

Volatile organic compounds produced by Paenibacillus polymyxa J2-4 exhibit toxic activity against Meloidogyne incognita.

Root knot nematodes cause great damage to crops worldwide. Due to the negative effects of the application of fumigant and old chemical nematicides, biological nematicides have drawn increasing attention in recent years. Here we tested the fumigant activity of the volatile organic compounds (VOCs) blends emitted from Paenibacillus polymyxa and pure commercial VOCs against M. incognita. In this study, we investigated whether P. polymyxa strain J2-4 could produce VOCs that exhibit nematicidal activity. In vitro assays indicated that J2-4 VOCs were highly toxic to second stage juveniles (J2s) and could inhibit egg hatching. Three-layered pot experiments showed that the number of nematodes that penetrating in cucumber roots was reduced by 69.27% after the application of J2-4 VOCs under greenhouse conditions. We identified 14 volatiles using solid-phase micro-extraction gas chromatography-mass spectrometry. The efficacy of six commercially available VOCs, namely 2-isobutyl-3-methylpyrazine, 2,4-dimethoxybenzaldoxime, 2-dodecanone, 2-tridecanol, 2-tridecanone, and 2-tetradecanol, against M. incognita were examined. Except for 2,4-dimethoxybenzaldoxime, the remaining five VOCs showed strong direct-contact nematicidal activity against J2s of M. incognita, and only 2-isobutyl-3-methylpyrazine showed strong fumigant activity against J2s of M. incognita. In pot experiments, 2-isobutyl-3-methylpyrazine and 2-dodecanone reduced the number of root galls by about 70%, and 2-tridecanone reduced the number of root galls and egg masses by about 63% compared with controls. Paenibacillus polymyxa strain J2-4 exhibited high fumigant activity against M. incognita. Our results provide evidence for the use of J2-4 and its VOCs as biocontrol agents in the management of root-knot nematodes. © 2023 Society of Chemical Industry.

Cucumber malate decarboxylase, CsNADP-ME2, functions in the balance of carbon and amino acid metabolism in fruit

Abstract Central metabolism produces carbohydrates and amino acids that are tightly correlated to plant growth and thereby crop productivity. Malate is reported to link mitochondrial respiratory metabolism with cytosolic biosynthetic pathways. Although the function of malate metabolism-related enzymes in providing carbon has been characterized in some plants, evidence for this role in the fleshy fruit of cucumber is lacking. Here, radiolabeled bicarbonate fed into the xylem stream from the cucumber roots was incorporated into amino acids, soluble sugars, and organic acids in the exocarp and vasculature of fruits. The activities of decarboxylases, especially decarboxylation from NADP-dependent malic enzyme (NADP-ME), were higher in cucumber fruit than in the leaf lamina. Histochemical localization revealed that CsNADP-ME2 was mainly located in the exocarp and vascular bundle system of fruit. Radiotracer and gas-exchange analysis indicated that overexpression of CsNADP-ME2 could promote carbon flux into soluble sugars and starch in fruits. Further studies combined with metabolic profiling revealed that the downregulation of CsNADP-ME2 in RNA interference (RNAi) lines caused the accumulation of its substrate, malate, in the exocarp. In addition to inhibition of glycolysis-related gene expression and reduction of the activities of the corresponding enzymes, increased amino acid synthesis and decreased sugar abundance were also observed in these lines. The opposite effect was found in CsNADP-ME2-overexpressing lines, suggesting that there may be a continuous bottom-up feedback regulation of glycolysis in cucumber fruits. Overall, our studies indicate that CsNADP-ME2 may play potential roles in both central carbon reactions and amino acid metabolism in cucumber fruits.

Exogenous Putrescine Modulates Nitrate Reductase-Dependent NO Production in Cucumber Seedlings Subjected to Salt Stress.

Polyamines (PAs) are small aliphatic compounds that participate in the plant response to abiotic stresses. They also participate in nitric oxide (NO) production in plants; however, their role in this process remains unknown. Therefore, the study aimed to investigate the role of putrescine (Put) in NO production in the roots of cucumber seedlings subjected to salt stress (120 mM NaCl) for 1 and 24 h. In salinity, exogenous Put can regulate NO levels by managing NO biosynthesis pathways in a time-dependent manner. In cucumber roots exposed to 1 h of salinity, exogenous Put reduced NO level by decreasing nitrate reductase (NR)-dependent NO production and reduced nitric oxide synthase-like (NOS-like) activity. In contrast, during a 24 h salinity exposure, Put treatment boosted NO levels, counteracting the inhibitory effect of salinity on the NR and plasma membrane nitrate reductase (PM-NR) activity in cucumber roots. The role of endogenous Put in salt-induced NO generation was confirmed using Put biosynthesis inhibitors. Furthermore, the application of Put can modulate the NR activity at the genetic and post-translational levels. After 1 h of salt stress, exogenous Put upregulated CsNR1 and CsNR2 expression and downregulated CsNR3 expression. Put also decreased the NR activation state, indicating a reduction in the level of active dephosphorylated NR (dpNR) in the total enzyme pool. Conversely, in the roots of plants subjected to 24 h of salinity, exogenous Put enhanced the NR activation state, indicating an enhancement of the dpNR form in the total NR pool. These changes were accompanied by a modification of endogenous PA content. Application of exogenous Put led to an increase in the amount of Put in the roots and reduced endogenous spermine (Spm) content in cucumber roots under 24 h salinity. The regulatory role of exogenous Put on NO biosynthesis pathways may link with plant mechanisms of response to salt stress.

Regulation of V-ATPase by Jasmonic Acid: Possible Role of Persulfidation.

Vacuolar H+-translocating ATPase (V-ATPase) is a proton pump crucial for plant growth and survival. For this reason, its activity is tightly regulated, and various factors, such as signaling molecules and phytohormones, may be involved in this process. The aim of this study was to explain the role of jasmonic acid (JA) in the signaling pathways responsible for the regulation of V-ATPase in cucumber roots and its relationship with other regulators of this pump, i.e., H2S and H2O2. We analyzed several aspects of the JA action on the enzyme, including transcriptional regulation, modulation of protein levels, and persulfidation of selected V-ATPase subunits as an oxidative posttranslational modification induced by H2S. Our results indicated that JA functions as a repressor of V-ATPase, and its action is related to a decrease in the protein amount of the A and B subunits, the induction of oxidative stress, and the downregulation of the E subunit persulfidation. We suggest that both H2S and H2O2 may be downstream components of JA-dependent negative proton pump regulation. The comparison of signaling pathways induced by two negative regulators of the pump, JA and cadmium, revealed that multiple pathways are involved in the V-ATPase downregulation in cucumber roots.

Influence of tomato waste composts on dry matter and heavy metals content in cucumber and summer squash seedlings

ABSTRACT Huge quantities of agricultural waste are available annually in Saudi Arabia, which are not well exploited, leading to large environmental pollution and health problems. The use of different proportions of tomato waste compost (TWC) mixed with commercial peat-moss as a natural, economical, cheap and environmentally friendly fertilizer for fertilizing vegetables is very important, therefore, this study is concerned with investigating and evaluating the dry matter content (DM) and the accumulated heavy metal contents (HMs) in the root and leaf seedlings tissues of cucumber and summer squash plants as a result of using this fertilizer. Five ratios of mixtures (vermiculite: peat moss: TWC by weight) used in the experiment, and the TWC in the mixture represents 0, 5, 10, 15 and 20% (by wieght). The results indicated that, the DM contents in the root and leaf tissues were relatively close between cucumber and summer squash seedlings. However, they were higher in the root than in leaf tissues, particularly under 20% TWC. A TWC application ratio of 20% reduced concentrations of the most HMs in the two vegetable species seedlings due to high EC and pH levels. The amounts of HMs in vegetable species were not high, which proves the that transfer of HMs from the TWC substrate to the seedlings is determined chiefly by metal bioavailability and by a vegetable species. DM, mineral and nutritional quality of vegetable seedlings showed that substrates containing 5% and 10% TWC appeared to be the most suitable growing medium for economic vegetable seedlings; and it is recommended for use in the nursery production. Implications: The idea of this research revolves around the use of different proportions of tomato waste compost in fertilizing cucumber and summer squash seedlings and investigate the effect of this compost on dry matter (DM) and heavy metal (HMs) contents in the root and leaf tissues of the seedlings, and fruit quality of cucumber and summer squash plants.

Evaluation of Biochars against Fusarium oxysporum f. sp. radicis-cucumerinum and their Impact on Growth Parameters of Cucumber in Pot Condition

The present study was conducted under greenhouse conditions to evaluate the efficacy of biochars prepared from different plant parts against the pathogen Fusarium oxysporum f. sp. radicis-cucumerinum causing root and stem rot of cucumber. Three types of raw materials were used to prepare the biochars (Eucalyptus wood, citrus wood, and greenhouse waste). The prepared biochar was collected and filled into pots at four concentrations (1%, 2%, 3%, and 4% W/W). All biochars were effective in reducing the incidence of the disease up to 3% concentration with minimum mortality (4.17%) obtained with Eucalyptus wood (EW) + Citrus wood (CW) + Greenhouse waste (GHW). The biochars also positively influenced the plant growth parameters like seed germination, root length, and shoot length. Maximum shoot length 7.73 cm and root length 12.10 cm was observed with 3% Eucalyptus wood (EW) + Citrus wood (CW) + Greenhouse waste (GHW) biochar treated seeds.

Biocontrol of cucumber Fusarium wilt by Trichoderma asperellum FJ035 dependent on antagonism and spatiotemporal competition with Fusarium oxysporum

Fusarium wilt is one of the major constraints of cucumber production worldwide and is difficult to control in production. This study selected a strain of Trichoderma asperellum FJ035 with a good antagonistic effect against Fusarium oxysporum f. sp. cucumerinum Owen (FOC) by plate confrontation test and secondary metabolites (volatile substances and non-volatile substances) antagonism tests. T. asperellum FJ035 inhibited spore germination of FOC and improved the germination potential of cucumber seeds. The spatiotemporal competition dynamics of T. sperellum FJ035 green fluorescence-labeled strain and FOC red fluorescence-labeled strain in the cucumber rhizosphere were monitored under a laser confocal microscope. The results showed that the vitality of FOC in the cucumber rhizosphere exceeded that of T. asperellum FJ035, but T. asperellum FJ035 exerted some inhibitory effects on FOC. When inoculation of T. asperellum FJ035 24 h before inoculation of FOC could significantly reduce the accumulation of FOC on the roots of cucumber, corresponding to the highest control efficiency against cucumber Fusarium wilt were 69.79% and 75.96% under hydroponic and potted conditions, respectively. T. asperellum FJ035 also significantly improved the root length, plant height, stem thickness, fresh weight, and area index of the first true leaves of cucumber seedlings, and effectively mitigating the adverse effects of FOC on cucumber growth.

Involvement of NO in V-ATPase Regulation in Cucumber Roots under Control and Cadmium Stress Conditions.

Nitric oxide (NO) is a signaling molecule that participates in plant adaptation to adverse environmental factors. This study aimed to clarify the role of NO in the regulation of vacuolar H+-ATPase (V-ATPase) in the roots of cucumber seedlings grown under control and Cd stress conditions. In addition, the relationship between NO and salicylic acid (SA), as well as their interrelations with hydrogen sulfide (H2S) and hydrogen peroxide (H2O2), have been verified. The effect of NO on V-ATPase was studied by analyzing two enzyme activities, the expression level of selected VHA genes and the protein level of selected VHA subunits in plants treated with a NO donor (sodium nitroprusside, SNP) and NO biosynthesis inhibitors (tungstate, WO42- and N-nitro-L-arginine methyl ester, L-NAME). Our results indicate that NO functions as a positive regulator of V-ATPase and that this regulation depends on NO generated by nitrate reductase and NOS-like activity. It was found that the mechanism of NO action is not related to changes in the gene expression or protein level of the V-ATPase subunits. The results suggest that in cucumber roots, NO signaling interacts with the SA pathway and, to a lesser extent, with two other known V-ATPase regulators, H2O2 and H2S.

Developing a Subsurface Drip Irrigation Scheduling Mode Based on Water Evaporation: Impacts Studies on Cucumbers Planted in a Greenhouse in the North China Plain

China is a country short of water resources, and improving the water use efficiency (WUE) in agriculture has become the only way to ensure sustainable development. In this article, subsurface drip irrigation (SDI) experiments of cucumber were implemented with a randomized block design comprising two factors and three levels, and the two factors were depth of drip belt buried and irrigation amount, which were determined by a 20 cm diameter pan’s water evaporation times its coefficient (Kp). The effects of schedule of SDI on soil evaporation (Es), evapotranspiration (ET), Kp, root dry matters, yield, and WUE of cucumber were studied. The results indicated that the Es and the ET decreased along with increasing depth of drip belt buried or decreasing amount of irrigation water applied. The relationships between ET and its total irrigation amount were significant linear positive correlations. Proportions of plant transpiration accounting for the ET were about 41~69% in two years, and it became bigger along with the increase of ET within a year. The Kp became smaller along with the reducing of ET. The roots of cucumber were mainly concentrated in the soil layer of 0~20 cm, and the two factors could only influence root dry weights of 0~60 cm soil layers significantly. The relationships between yield and ET were quadratic polynomial correlations. At last, an ultimate SDI scheduling mode based on water evaporation was established.

Effectiveness of Selected Biological Agents, Chemical Inducers, and Fungicides in Managing Cucumber Root Rot Disease caused by Rhizoctonia solani

Effectiveness of Selected Biological Agents, Chemical Inducers, and Fungicides in Managing Cucumber Root Rot Disease caused by Rhizoctonia solani

Isolation and Identification Antagonistic Bacterium Paenibacillus tianmuensis YM002 against Acidovorax citrulli.

In this study, we aimed to screen antagonistic microorganisms against Acidovorax citrulli, the causal agent of bacterial fruit blotch, which is known to induce sever diseases in cucurbit crops. From 240 bacterial strains isolated, only one unknown bacterial isolate, named YM002, showed significant antagonistic activity against A. citrulli KACC17909. Further experiments revealed that YM002 shows antagonistic activity against all tested A. citrulli strains, including KACC17000, KACC17001 and KACC17005, to different degrees. The phylogenetic analysis of 16S rRNA sequences identified YM002 as Paenibacillus tianmuensis. Importantly, pretreatment of cucumber (Cucumis sativus) leaves with YM002 enhanced disease resistance as observed by significantly reduced necrotic symptom development and bacterial growth. YM002-induced resistance accompanied by enhanced expression of defense-related genes, such as PAL1, PR1-1a and CTR1. Importantly, culture filtrate of YM002 significantly suppressed biofilm formation and swimming motility of A. citrulli, which is indispensable for its full virulence. In addition to its antagonistic activity, YM002 showed a various plant growth promotion (PGP)-related traits, such as production of ammonia production, amylase production, ACC deaminase production, inodole-3-acetic acid production, extracellular protease production, siderophore production, and zinc solubilization activities. Indeed, treatment of cucumber roots with YM002 significantly enhanced plant growth parameters, such as fresh and dry weight of leaves or roots. This study suggests the potential of YM002 as an effective PGPR with biological control activity against Acidovorax citrulli in cucumber plants.