A synthetic phytosiderophore analog, proline-2′-deoxymugineic acid, is efficiently utilized by dicots

Purpose Phytosiderophores (PS) from grasses solubilize sparingly soluble iron (Fe), and the resultant PS-Fe is an Fe source even for dicots. Recently, the synthetic PS proline-2′-deoxymugineic acid (PDMA) has been developed as a moderately biodegradable Fe fertilizer for grasses. We aimed to investigate whether PDMA-Fe is also a good Fe source for dicots. Methods The availability of PDMA-Fe to cucumber was evaluated in a calcareous substrate and hydroponic cultures at pH 7.0–9.0 by determining chlorophyll level, PSII activity, and Fe uptake. EDDHA-Fe, EDTA-Fe, and citrate-Fe were used as controls. The reducibility of Fe chelates by roots was measured to determine the mechanism underlying differences in availability. Expressions of Fe deficiency-inducible genes were analyzed to estimate the Fe status in plants. Results The application of PDMA-Fe and EDDHA-Fe to a calcareous substrate reduced Fe-deficient chlorosis to a similar extent; however, the shoot Fe concentration was higher in the PDMA-Fe treatment. In the hydroponic culture, the availability of PDMA-Fe was higher than that of the other chelates at all pH levels, and this was confirmed by higher PSII activity and lower expression of Fe deficiency-inducible genes. The reducibility assay revealed that the reduction level of PDMA-Fe was greater than that of EDTA-Fe and citrate-Fe under alkaline pH. Conclusions PDMA-Fe is utilized by cucumber roots more efficiently than traditional synthetic chelates in both calcareous substrate and hydroponic cultures. The higher availability of PDMA-Fe may be attributed to its higher reducibility. Our findings suggest that PDMA-Fe could be a good Fe fertilizer for dicots.

Synthetic Phytosiderophore, Proline-2′-Deoxymugineic Acid, is Efficiently Utilized by Dicots

Purpose: Phytosiderophores (PS) from grasses solubilize sparingly soluble iron (Fe), and the resultant PS-Fe is an Fe source, even for dicots. Recently, the synthetic PS proline-2′-deoxymugineic acid (PDMA) has been developed as a moderately biodegradable Fe fertilizer for grasses. We aimed to investigate whether PDMA-Fe is also a good Fe source for dicots.Methods: The availability of PDMA-Fe to cucumber was evaluated in calcareous soil and hydroponic cultures under pH 7.0–9.0 by determining chlorophyll concentration, PSII activity, and Fe uptake. EDDHA-Fe, EDTA-Fe, and citrate-Fe were used as controls. The reducibility of Fe chelates by roots was measured to determine the mechanism underlying differences in availability. Expressions of Fe deficiency-inducible genes (CsFRO1 and CsIRT1) were analyzed to estimate the Fe status in plants. Results: Application of PDMA-Fe and EDDHA-Fe to calcareous soil reduced Fe-deficient chlorosis to a similar extent; however, shoot Fe concentration was higher in the PDMA-Fe treatment. In the hydroponic culture, PDMA-Fe had higher availability than the other chelates at every pH, which was confirmed by higher PSII activity and lower expression of Fe deficiency-inducible genes. The reducibility assay revealed that the reduction level of PDMA-Fe was greater than that of EDTA-Fe and citrate-Fe under alkaline pH.Conclusion: PDMA-Fe is utilized by cucumber roots more efficiently than traditional synthetic chelates in both calcareous soil and hydroponic cultures. The higher availability of PDMA-Fe may be attributed to its higher reducibility. Our findings suggest that PDMA-Fe could be a good Fe fertilizer for dicots.

Whole Genome Sequencing and Root Colonization Studies Reveal Novel Insights in the Biocontrol Potential and Growth Promotion by Bacillus subtilis MBI 600 on Cucumber

Bacillus spp. MBI 600 is a gram-positive bacterium and is characterized as a PGPR strain involved in plant growth promotion and control of various plant pathogens which has recently been introduced into the agricultural practice. In this study we performed a Next Generation Sequencing analysis, to analyze the full genome of this microorganism and to characterize it taxonomically. Results showed that MBI 600 strain was phylogenetically close to other Bacillus spp. strains used as biocontrol agents and identified as B. subtilis. GOG analysis showed clusters contributed to secondary metabolites production such as fengycin and surfactin. In addition, various genes which annotated according to other plant-associated strains, showed that play a main role in nutrient availability from soil. The root colonization ability of MBI 600 strain was analyzed in vivo with a yellow fluorescence protein (yfp) tag. Confocal laser scanning microscopy of cucumber roots treated with yfp-tagged MBI 600 cells, revealed that the strain exhibits a strong colonization ability of cucumber roots, although it is affected significantly by the growth substrate of the roots. In vitro and in planta experiments with MBI 600 strain and F. oxysporum f.sp. radicis cucumerinum and P. aphanidernatum, showed a high control ability against these soilborne pathogens. Overall, our study demonstrates the effectiveness of MBI 600 in plant growth promotion and antagonism against different pathogens, highlighting the use of this microorganism as a biocontrol agent.

Chia: Host Status for Meloidogyne incognita and Activity of Plant Extracts

Chia (Salvia hispanica L.) seeds are used for food, drinks, oil, and animal feed, and all plant parts are employed in traditional medicine. The growing demand for the seed has created a need for improved disease management. Plant-parasitic nematodes have been found on other Salvia spp., but none have been reported from S. hispanica. Chia has also not been tested for production of compounds active against these nematodes. Therefore, aqueous extracts from shoots and roots of six chia lines, Brad’s Organic, Cono, E2, G3, G5, and W13.1, were tested in laboratory assays. Some concentrations of all extracts were nematotoxic, killing about one-third of Meloidogyne incognita (Kofoid & White) Chitwood second-stage juveniles (J2s) in shoot extracts and up to nearly half of J2s in root extracts. Hatch was generally not affected by the extracts. In greenhouse trials, all six chia lines were hosts of M. incognita. Chia line G3 had approximately two times or more eggs per gram of root than Brad’s Organic or Cono. When cucumber seedlings were transplanted into soil amended with chopped chia shoots (2.3 or 2.5% weight of fresh shoots/weight of dry soil), galling and egg production on cucumber roots were not suppressed. To our knowledge, this is the first report that chia is a host to M. incognita (or any phytoparasitic nematode) and that chia shoots and roots produce compounds active against a nematode.

Assessment of plant defence induction and biocontrol potential of Bacillus megaterium wr101 against Meloidogyne javanica

Summary The aim of this study was to evaluate biological control ability and induction of plant defence by Bacillus megaterium wr101, isolated from wheat rhizosphere, on disease severity induced by Meloidogyne javanica on cucumber. In addition, changes in some plant defence compounds (such as peroxidase, polyphenol oxidase, catalase, hydrogen peroxide (H2O2) and accumulation of total phenolic compounds) induced by B. megaterium wr101 and M. javanica were also evaluated. Results showed that application of B. megaterium wr101 reduced nematode disease indices compared to non-treated controls. Inoculation of cucumber roots with B. megaterium wr101 increased peroxidase and polyphenol oxidase activities in root tissue from the first day after inoculation (DAI), with maximum levels of these enzymes recorded 4 DAI and then reduced gradually. Catalase activity and H2O2 accumulation showed two peaks on 1 and 5 DAI, respectively, but the presence of nematodes in the plant significantly increased the activity level of catalase enzyme even in the presence of the bacterium. Bacillus megaterium wr101 also stimulated the accumulation of total phenolic compounds in cucumber roots.

Synthesis and bioactivity of benzohydrazide derivatives

N'-[4-(Hydroxyimino)-cyclohexa-2,5-dien-1-ylidene]-benzohydrazides have been synthesized by reaction of 4-(hydroxyimino)-cyclohexa-2,5-dien-1-one with different benzohydrazides in one stage. N'-(4-[(Aroyloxy)imino]cyclohexa-2,5-dien-1-ylidene)-benzohydrazides were obtained in reaction of 4-[(aroyloxy)imino]cyclohexa-2,5-dien-1-ones with corresponding benzohydrazides in one step too. Biological activities of the synthesized compounds were studied. N'-[4-{[(4-nitrobenzoyl)oxy]imino}cyclohexa-2,5-dien-1-ylidene]benzo-hydrazide showed high insecticidal activity against house fly and rice weevil. 3,4-Dichloro-N'-[4-(hydroxyimino)cyclohexa-2,5-dien-1-ylidene]benzohydrazide and N'-{4-[(benzoyloxy)imino]-cyclohexa-2,5-dien-1-ylidene}-2-bromobenzohydrazide showed excellent anti-nematode activity: decrease in gall formation on the cucumber roots was 93 and 91%, respectively.

Effects of Exogenous Spermidine on Root Metabolism of Cucumber Seedlings under Salt Stress by GC-MS

To investigate the effects of exogenous spermidine (Spd) on metabolism changes under salt stress in cucumber roots, a gas chromatography-mass spectrometry (GC-MS) was performed. The results showed that most of the 142 metabolites responded to salt stress or exogenous Spd treatment. Salt stress reduced carbon consumption, resulted in the transformation of glycolysis and the tricarboxylic acid (TCA) cycle to the pentose phosphate pathway (PPP), and meanwhile increased salicylic acid (SA) and ethylene synthesis, and, thus, inhibited the growth of seedlings. However, exogenous Spd further improved the utilization of carbon, the energy-saving pattern of amino acid accumulation, and the control of hydroxyl radicals. In conclusion, Spd could promote energy metabolism and inhibit SA and ethylene synthesis in favor of root growth that contributes to higher salt tolerance. This study provides insight that may facilitate a better understanding of the salt resistance by Spd in cucumber seedlings.

Community Structures and Antifungal Activity of Root-Associated Endophytic Actinobacteria in Healthy and Diseased Cucumber Plants and Streptomyces sp. HAAG3-15 as a Promising Biocontrol Agent

Microorganisms related to plant roots are vital for plant growth and health and considered to be the second genome of the plant. When the plant is attacked by plant pathogens, the diversity and community structure of plant-associated microbes might be changed. The goal of this study is to characterize differences in root-associated endophytic actinobacterial community composition and antifungal activity between Fusarium wilt diseased and healthy cucumber and screen actinobacteria for potential biological control of Fusarium wilt of cucumber. In the present research, three healthy plants (also termed “islands”) and three obviously diseased plants (naturally infected by F. oxysporum f. sp. cucumerinum) nearby the islands collected from the cucumber continuous cropping greenhouse were chosen as samples. Results of culture-independent and culture-dependent analysis demonstrated that actinomycetes in the healthy roots were significantly more abundant than those of diseased roots. Moreover, there were seven strains with antifungal activity against F. oxysporum f. sp. cucumerinum in healthy cucumber roots, but only one strain in diseased cucumber roots. Out of these eight strains, the isolate HAAG3-15 was found to be best as it had the strongest antifungal activity against F. oxysporum f. sp. cucumerinum, and also exhibited broad-spectrum antifungal activity. Thus, strain HAAG3-15 was selected for studying its biocontrol efficacy under greenhouse conditions. The results suggested that the disease incidence and disease severity indices of cucumber Fusarium wilt greatly decreased (p < 0.05) while the height and shoot fresh weight of cucumber significantly increased (p < 0.05) after inoculating strain HAAG3-15. On the basis of morphological characteristics, physiological and biochemical properties and 100% 16S ribosomal RNA (rRNA) gene sequence similarity with Streptomyces sporoclivatus NBRC 100767T, the isolate was assigned to the genus Streptomyces. Moreover, azalomycin B was isolated and identified as the bioactive compound of strain HAAG3-15 based on analysis of spectra using a bioactivity-guided method. The stronger antifungal activity against F. oxysporum f. sp. cucumerinum, the obvious effect on disease prevention and growth promotion on cucumber seedlings in the greenhouse assay, and the excellent broad-spectrum antifungal activities suggest that strain HAAG3-15 could be developed as a potential biocontrol agent against F. oxysporum f. sp. cucumerinum used in organic agriculture. These results suggested that the healthy root nearby the infected plant is a good source for isolating biocontrol and plant growth-promoting endophytes.

EFFECT OF BETA-AMINOBUTYRIC ACID ON ACTIVITY OF PEROXIDASE AND POLYPHENOL OXIDASE ENZYMES IN CUCUMBER INFECTED WITH NEMATODE MELOIDOGYNE JAVANICA

Beta-amino-butyric acid is introduced as an inducer of resistance in plants against plant pathogens. In this research, the induction of some defensive compounds including peroxidase and polyphenol oxidase enzymes by this compound against the rootstock node-producing nematode Meloidogyne javanica in cucumber was investigated. The results showed that inoculation of cucumber roots infected with root-knot nematode with the chemical composition of BABA from the first day after inoculation increased the activity of peroxidase enzyme and reached its maximum on the fourth day of this activity. Induction of the activity of polyphenol oxidase enzyme showed a gradual increase with a significant difference in comparison to the control and healthy plants and reached the maximum on the fourth day. The electrophoresis of peroxidase isozymes showed that isozyme peroxidase forms in cucumber roots induced by BABA were much more potent than pathogen-induced isozymes. In plants treated with nematode plus BABA, two isozymes were Rf = 00.31 and Rf = 34/0, which were stronger than control (inoculated with nematode).