Non-treated Plants Research Articles

Impact of UV-C Radiation Applied during Plant Growth on Pre- and Postharvest Disease Sensitivity and Fruit Quality of Strawberry.

Ultraviolet-C (UV-C) radiation is efficient in reducing the development of diseases in many species, including strawberry (Fragaria × ananassa). Several studies suggest that UV-C radiation is effective not only because of its disinfecting effect but also because it may stimulate plant defenses. In this study, the effect of preharvest UV-C radiation applied during strawberry cultivation on plant growth, fruit quality, and susceptibility to major fungal diseases such as gray mold, powdery mildew, and soft rot was evaluated. UV-C treatments had an impact on flowering initiation and fruit development. Flowering occurred earlier for UV-C-treated plants than for nontreated plants. At harvest, a larger amount of fruit was produced by treated plants despite their slight decrease in leaf area. UV-C treatment did not improve strawberry shelf life but did not alter the physical integrity of strawberry fruit. Natural infection of leaves to powdery mildew and of fruit to Rhizopus spp. strongly decreased in response to UV-C treatment.

Bacillus licheniformis strain POT1 mediated polyphenol biosynthetic pathways genes activation and systemic resistance in potato plants against Alfalfa mosaic virus

Alfalfa mosaic virus (AMV) is a worldwide distributed virus that has a very wide host range and causes significant crop losses of many economically important crops, including potato (Solanum tuberosum L.). In this study, the antiviral activity of Bacillus licheniformis strain POT1 against AMV on potato plants was evaluated. The dual foliar application of culture filtrate (CF), 24 h before and after AMV-inoculation, was the most effective treatment that showed 86.79% reduction of the viral accumulation level and improvement of different growth parameters. Moreover, HPLC analysis showed that a 20 polyphenolic compound was accumulated with a total amount of 7,218.86 and 1606.49 mg/kg in POT1-treated and non-treated plants, respectively. Additionally, the transcriptional analysis of thirteen genes controlling the phenylpropanoid, chlorogenic acid and flavonoid biosynthetic pathways revealed that most of the studied genes were induced after POT1 treatments. The stronger expression level of F3H, the key enzyme in flavonoid biosynthesis in plants, (588.133-fold) and AN2, anthocyanin 2 transcription factor, (97.005-fold) suggested that the accumulation flavonoid, especially anthocyanin, might play significant roles in plant defense against viral infection. Gas chromatography-mass spectrometry (GC-MS) analysis showed that pyrrolo[1,2-a]pyrazine-1,4-dione is the major compound in CF ethyl acetate extract, that is suggesting it acts as elicitor molecules for induction of systemic acquired resistance in potato plants. To our knowledge, this is the first study of biological control of AMV mediated by PGPR in potato plants.

Microbiome Management by Biological and Chemical Treatments in Maize Is Linked to Plant Health.

The targeted application of plant growth-promoting rhizobacteria (PGPR) provides the key for a future sustainable agriculture with reduced pesticide application. PGPR interaction with the indigenous microbiota is poorly understood, but essential to develop reliable applications. Therefore, Stenotrophomonas rhizophila SPA-P69 was applied as a seed coating and in combination with a fungicide based on the active ingredients fludioxonil, metalaxyl-M, captan and ziram. The plant performances and rhizosphere compositions of treated and non-treated maize plants of two field trials were analyzed. Plant health was significantly increased by treatment; however, overall corn yield was not changed. By applying high-throughput amplicon sequencing of the 16S rRNA and the ITS genes, the bacterial and fungal changes in the rhizosphere due to different treatments were determined. Despite the fact that treatments had a significant impact on the rhizosphere microbiota (9–12%), the field site was identified as the main driver (27–37%). The soil microbiota composition from each site was significantly different, which explains the site-specific effects. In this study we were able to show the first indications how PGPR treatments increase plant health via microbiome shifts in a site-specific manner. This way, first steps towards a detailed understanding of PGPRs and developments of consistently efficient applications in diverse environments are made.

Induced in vitro adaptation for salt tolerance in date palm (Phoenix dactylifera L.) cultivar Khalas

BackgroundSoil salinity causes huge economic losses to agriculture productivity in arid and semiarid areas worldwide. The affected plants face disturbances in osmotic adjustment, nutrient transport, ionic toxicity and reduced photosynthesis. Conventional breeding approaches produce little success in combating various stresses in plants. However, non-conventional approaches, such as in vitro tissue culturing, produce genetic variability in the development of salt-tolerant plants, particularly in woody trees.ResultsEmbryogenic callus cultures of the date palm cultivar Khalas were subjected to various salt levels ranging from 0 to 300 mM in eight subcultures. The regenerants obtained from the salt-treated cultures were regenerated and evaluated using the same concentration of NaCl with which the calli were treated. All the salt-adapted (SA) regenerants showed improved growth characteristics, physiological performance, ion concentrations and K+/Na+ ratios than the salt non-adapted (SNA) regenerants and the control. Regression between the leaf Na+ concentration and net photosynthesis revealed an inverse nonlinear correlation in the SNA regenerants. Leaf K+ contents and stomatal conductance showed a strong linear relationship in SA regenerants compared with the inverse linear correlation, and a very poor coefficient of determination in SNA regenerants. The genetic fidelity of the selected SA regenerants was also tested using 36 random amplified polymorphic DNA (RAPD) primers, of which 26 produced scorable bands. The primers generated 1–10 bands, with an average of 5.4 bands per RAPD primer; there was no variation between SA regenerants and the negative control.ConclusionThis is the first report of the variants generated from salt-stressed cultures and their potential adaptation to salinity in date palm cv. Khalas. The massive production of salt stress-adapted date palm plants may be much easier using the salt adaptation approach. Such plants can perform better during exposure to salt stress compared to the non-treated date palm plants.

The Phytochemical, Antifungal, and First Report of the Antiviral Properties of Egyptian Haplophyllum tuberculatum Extract.

In this study, ethanol whole plant extract (WPE) of Haplophyllum tuberculatum was characterized and tested for its antifungal and antiviral activities against Fusarium culmorum, Rhizoctonia solani and tobacco mosaic virus (TMV). High Performance Liquid Chromatography (HPLC) analysis showed that the main phytochemical constituents of H. tuberculatum WPE were resveratrol (5178.58 mg/kg), kaempferol (1735.23 mg/kg), myricetin (561.18 mg/kg), rutin (487.04 mg/kg), quercetin (401.04 mg/kg), and rosmarinic acid (387.33 mg/kg). By increasing H. tuberculatum WPE at concentrations of 1%, 2%, and 3%, all of the fungal isolates were suppressed compared to the two positive and negative controls. Under greenhouse conditions, WPE-treated Chenopodium amaranticolor plants strongly inhibited TMV infection and significantly reduced TMV accumulation levels when compared to non-treated plants. Moreover, the induction of systemic resistance with significant increases in the transcriptional levels of the pathogenesis-related protein-1 (PR-1), chalcone synthase (CHS), and hydroxycinnamoyl-CoA quinate transferase (HQT) genes for treated plants were noticed at 3 and 5 days post-inoculation (dpi) for both assays. To the best of our knowledge, this is the first reported observation of the antiviral activity of H. tuberculatum extract against plant viral infections. Finally, the results obtained suggest that H. tuberculatum WPE can be considered a promising source of both antifungal and antiviral substances for practical use and for developing plant-derived compounds for the effective management of plant diseases.

Silicon (Si) enhances the resistance in finger millet genotypes against blast disease

Finger millet (Eleusine coracana) leaf blast caused by Pyricularia grisea is a common disease and results in severe yield losses. Noble element silicon (Si) effectively mitigates both biotic and abiotic stresses and is known to enhance plant resistance against fungal and bacterial pathogens. The results revealed that there are potential positive effects of silicon application in soil to suppress the blast disease in finger millet genotypes. Among various treatments, 3 g calcium silicate/kg of soil was found to be most effective in enhancing resistance to blast followed by 2 g calcium silicate/kg of soil and 1 g calcium silicate/kg of soil treatments. Silicon content in leaf, stem, and root increased significantly over non-treated plants. A significant negative correlation was observed between silicon accumulation in the plants (leaf, stem, and root) and percent disease index. Both principal component analysis and cluster analysis revealed that among 40 genotypes tested, six genotypes such as ‘Suvra’, ‘GE-2740’, ‘NO-2836’, ‘GE-320’, ‘OEB-532’, and ‘GE-1135’ showed higher silicon accumulation with enhanced plant resistance along with the desired traits. Therefore, silicon accumulating genotypes can be used for the breeding program. Further, this study confirmed the positive effect of Si in enhancing the blast resistance in finger millets through the physical barrier mechanism by inhibiting the fungal penetration and colonization in cell and it can provide an alternative eco-friendly disease management strategy.

The Alleviation of Photosynthetic Damage in Tomato under Drought and Cold Stress by High CO2 and Melatonin.

The atmospheric CO2 concentration (a[CO2]) is increasing at an unprecedented pace. Exogenous melatonin plays positive roles in the response of plants to abiotic stresses, including drought and cold. The effect of elevated CO2 concentration (e[CO2]) accompanied by exogenous melatonin on plants under drought and cold stresses remains unknown. Here, tomato plants were grown under a[CO2] and e[CO2], with half of the plants pre-treated with melatonin. The plants were subsequently treated with drought stress followed by cold stress. The results showed that a decreased net photosynthetic rate (PN) was aggravated by a prolonged water deficit. The PN was partially restored after recovery from drought but stayed low under a successive cold stress. Starch content was downregulated by drought but upregulated by cold. The e[CO2] enhanced PN of the plants under non-stressed conditions, and moderate drought and recovery but not severe drought. Stomatal conductance (gs) and the transpiration rate (E) was less inhibited by drought under e[CO2] than under a[CO2]. Tomato grown under e[CO2] had better leaf cooling than under a[CO2] when subjected to drought. Moreover, melatonin enhanced PN during recovery from drought and cold stress, and enhanced biomass accumulation in tomato under e[CO2]. The chlorophyll a content in plants treated with melatonin was higher than in non-treated plants under e[CO2] during cold stress. Our findings will improve the knowledge on plant responses to abiotic stresses in a future [CO2]-rich environment accompanied by exogenous melatonin.

Isolation and Characterization of Mesophilic Rhizobacteria from Gilgit-Baltistan and their Impact on the Growth of Triticum aestivum L.

ABSTRACT:The basic aim of this work is the isolation of mesophilic rhizobacteria from Gilgit- Baltistan region of Pakistan to study their impact on growth promotion of plants. Plant growth promoting rhizobacteria (PGPR) play their part in enhancing overall plant growth and can serve as potential bio-fertilizers. These isolated bacterial strains were screened by checking out their capability to produce auxin. Morphological and physiological characterization was also done. Plant growth-stimulating activities of these isolates were assessed through biological assay. Triticum aestivum seeds were inoculated with these isolates and the effect of these isolates was studied on the growth of wheat. Auxin producing ten bacterial strains were selected and used for the current study. Bacterially treated plants have shown significant enhancement in growth parameters as compared to non-treated plants. All bacterial strains have shown variable behavior. However, bacterial strain Mi5 performed most efficiently. In this case increment of 12.09, 68.82 and 39.89 % have been recorded in plant shoot, root and fresh weight as compared to control. Improvement in various plant growth parameters have shown that these indigenous bacterial strains can be used as biofertilizers in areas like with low temperature.

Recovery of humic acids from anaerobic sewage sludge: Extraction, characterization and encapsulation in alginate beads

Wastewater production is rising all over the world and one of the most difficult problems is the disposal of sewage sludge (SS). It is known that SS contains certain quantities of added-value compounds, such as humic acids (HA) which in turn have beneficial effects on soil quality and plant growth. On the other hand, SS can retain many pollutants, such as heavy metals. The present work aimed to implement an HA alkaline extraction protocol from anaerobic sewage sludge (ASS). Subsequently, the HA were quantified in ASS, in HA extract and in commercial HA, used as a benchmark, which gave results of 12.53%, 26.87% and 77.87% (on dry matter basis), respectively. FESEM and EDX analyses on lyophilized HA extract confirmed that no heavy metals had passed into the extract. Afterwards, in order to allow controlled release of the HA in soils, alginate beads containing the HA extract were created. Finally, a pot experiment in a greenhouse was performed using Chilean lettuce plants (Lactuca sativa L.) treated with alginate-HA extract beads. At the end of the greenhouse experiments, the hypogean dry biomass of the treated plants was significantly higher than for non-treated plants. The relevance of this study relies not only on the exploitation of green chemistry principles, by converting a waste stream into a high-value product, but also on the application of an approach following a circular economy model.

Evaluating the combined effect of a systemic phenylpyrrole fungicide and the plant growth-promoting rhizobacteria Paraburkholderia phytofirmans (strain PsJN::gfp2x) against the grapevine trunk pathogen Neofusicoccum parvum.

A new chemical control strategy for grapevine trunk diseases (GTDs) is to develop site-targeted fungicides to protect grapevine vascular tissues. Due to the complexity of GTDs, the effectiveness of a single method is limited. Investigation of the interactions between chemical and biological agents is an essential requirement for integrated control strategies. The effect of a phloem-mobile derivative of the fungicide fenpiclonil (SM 26) in combined use with the plant growth-promoting rhizobacteria, Paraburkholderia phytofirmans PsJN on the Neofusicoccum parvum strain Bourgogne (NpB) was evaluated. SM 26 was found to be translocated to the shoot apices and roots of grapevines through both xylem and phloem after foliage application. In vitro studies demonstrated that SM 26 exhibited no inhibitory effect on the growth of PsJN and could be largely absorbed into the bacterial cells. In vivo evaluation showed that the combined use of SM 26 and PsJN was the most effective following artificial inoculation of NpB on the stems of rooted Chardonnay and Sauvignon cuttings. Finally, the expression of defence-related genes, including the genes associated with secondary metabolism (ANTS, PAL, STS, Vv17.3), defence proteins (GLUC, PR1, PGIP), redox status (GTS1) and ethylene synthesis (ACC), was found to be strongly upregulated in PsJN + SM 26 cotreated plants compared to non-treated plants (controls), especially for Chardonnay. The systemic profungicide SM 26 interacts with the biocontrol agent PsJN to stimulate some plant defence responses, and their combined use may present a potential integrated control strategy against GTDs. © 2020 Society of Chemical Industry.

Flue-cured tobacco tolerance to S-metolachlor

AbstractCurrently, there are seven herbicides labeled for U.S. tobacco production; however, additional modes of action are greatly needed in order to reduce the risk of herbicide resistance. Field experiments were conducted at five locations during the 2017 and 2018 growing seasons to evaluate flue-cured tobacco tolerance to S-metolachlor applied pretransplanting incorporated (PTI) and pretransplanting (PRETR) at 1.07 (1×) and 2.14 (2×) kg ai ha−1. Severe injury was observed 6 wk after transplanting at the Whiteville environment in 2017 when S-metolachlor was applied PTI. End-of-season plant heights from PTI treatments at Whiteville were likewise reduced by 9% to 29% compared with nontreated controls, although cured leaf yield and value were reduced only when S-metolachlor was applied PTI at the 2× rate. Severe growth reduction was also observed at the Kinston location in 2018 where S-metolachlor was applied at the 2× rate. End-of-season plant heights were reduced 11% (PTI, 2×) and 20% (PRETR, 2×) compared with nontreated control plants. Cured leaf yield was reduced in Kinston when S-metolachlor was applied PRETR at the 2× rate; however, treatments did not impact cured leaf quality or value. Visual injury and reductions in stalk height, yield, quality, and value were not observed at the other three locations. Ultimately, it appears that injury potential from S-metolachlor is promoted by coarse soil texture and high early-season precipitation close to transplanting, both of which were documented at the Whiteville and Kinston locations. To reduce plant injury and the negative impacts to leaf yield and value, application rates lower than 1.07 kg ha−1 may be required in these scenarios.

Exogenously applied proline enhances growth and productivity of drought stressed onion by improving photosynthetic efficiency, water use efficiency and up-regulating osmoprotectants

Drought and salinity are the main limiting factors negatively affect plant growth and productivity. Proline is recently reported to play a positive role in plants exposed to various abiotic stresses. A two year field experiment was implemented consecutively to assess the potential effect of exogenously applied proline (1 and 2 mM) under different irrigation water regimes (IWR) (120 %, 100 %, 80 % and 60 % of ETc.) on growth, plant defense system, physio-biochemical attributes, bulb yield and water use efficiency of onion cultivated in saline calcareous soil. Results showed that, exogenously-applied proline significantly enhanced growth as well as, plant water status, photosynthetic efficiency, and osmoprotectants of drought-stressed onion which consequently reflected in increased bulb yield. Treatments of 80 % and 60 % of ETc had increased water use efficiency (WUE) by 32.0 % and 26.5 % respectively, compared to full irrigation (100 % of ETc). The effect of proline was negligible on unstressed plants, but when applied under deficit irrigation (DI) treatments (80 and 60 % of ETc), WUE reached 50 % higher than control. These plants also had a higher content of total soluble sugars but a lower content of proline and amino acids. Exogenous proline application markedly enhanced onion growth traits compared to non-treated plants due to increased cell membrane integrity (MSI) and leaf water content (RWC), also improved photosynthetic efficiency and up-regulated osmoprotectants contents. Results revealed that proline foliar application on onion plants might attenuate drought stress by increasing their sugar content and via improving plant self-defense system. Consequently, combination of DI at 80 % and 1−2 mM proline is highly recommended to attain optimal yield with the opportunity of saving 20−40 % of irrigation water during onion growing season.

Accumulation potential and tolerance response of Typha latifolia L. under citric acid assisted phytoextraction of lead and mercury

Chelate-assisted phytoextraction by high biomass producing macrophyte plant Typha latifolia L. commonly known as cattail, is gaining much attention worldwide. The present study investigated the effects of Lead (Pb) and Mercury (Hg) on physiology and biochemistry of plant, Pb and Hg uptake in T. latifolia with and without citric acid (CA) amendment. The uniform seedlings of T. latifolia were treated with various concentrations in the hydroponics as: Pb and Hg (1, 2.5, 5 mM) each alone and/or with CA (5 mM). After four weeks of treatments, the results revealed that Pb and Hg significantly reduced the plant agronomic traits as compare to non-treated plants. The addition of CA improved the plant physiology and enhanced the antioxidant enzymes activities to overcome Pb and Hg induced oxidative damage and electrolyte leakage. Our results depicted that Pb and Hg uptake and accumulation by T. latifolia was dose depend whereas, the addition of CA further increased the concentration and accumulation of Pb and Hg by up to 22 & 35% Pb and 72 & 40% Hg in roots, 25 & 26% Pb and 85 & 60% Hg in stems and 22 & 15 Pb and 100 & 58% Hg in leaves respectively compared to Pb and Hg treated only plants. On other hand, the root-shoot translocation factor was ≥1 and bioconcentration factor was also ≥2 for both Pb & Hg. The results also revealed that T. latifolia showed greater tolerance towards Hg and accumulated higher Hg in all parts compared with Pb.

Response of tomato transplants to varying soil residual levels of preplant herbicides

ABSTRACT Processing-tomato (Lycopersicon esculentum L.) cultivation in California has transitioned to the use of transplants, subsurface drip irrigation (SDI), and shallow tillage from direct-seeded, flood-irrigated, deep-tillage systems. Observation of stunted tomato plants in fields treated with preplant herbicides suggests that the herbicides may not be disintegrating as rapidly in the newer system. Greenhouse studies were conducted to assess plant response to trifluralin, S-metolachlor, and pendimethalin at soil-residue levels of 0, 0.03, 0.06, 0.12, 0.25, and 0.5 ppm (0, 0.03, 0.06, 0.12, 0.25, and 0.5 mg l-1, respectively; 1 ppm = 1 mg l-1). Plants grown for 45 days after transplanting showed that all three herbicides at levels as low as 0.03 ppm (0.03 mg l-1) reduced shoot and root growth. Therefore, appropriate methods need to be developed to reduce soil carryover effects of these herbicides in tomatoes grown with SDI system. All herbicides resulted in some reduction in shoot and root biomass of the tomato plants at the higher doses (>0.12 ppm) compared to the non-treated plants. Both S-metolachlor and trifluralin caused significant reductions in shoot and root biomass at 0.5 ppm and the potential of the plants to recover from herbicide injury is unknown. Pendimethalin had a lower potential to cause injury than the other two herbicides. Although the effect of shoot and root biomass reduction on fruit yield and quality was not recorded, this study suggests that preplanting soil tests and appropriate management to reduce soil carryover of these herbicides may be necessary in processing tomatoes grown with SDI.

Imidazolium salts as alternative compounds to control diseases caused by plant pathogenic bacteria.

To evaluate the inhibitory effect of five structurally different imidazolium salts on the in vitro growth of plant pathogenic bacteria that belong to divergent taxonomic genera as well as their ability to reduce the severity of common bacterial blight of common bean caused by Xanthomonas axonopodis pv. phaseoli and bacterial speck of tomato caused by Pseudomonas syringae pv. tomato. Growth inhibition of Xanthomonas, Pseudomonas, Erwinia, Pectobacterium and Dickeya strains by imidazolium salts was assessed in vitro by radial diffusion on agar medium and by ressazurin reduction in liquid medium. The reduction of common bacterial blight and bacterial speck symptoms and the area under de disease progress curves were determined by spraying two selected imidazolium salts on healthy plants 48h prior to inoculation with virulent strains of the bacterial pathogens. All imidazolium salts inhibited the growth of all plant pathogenic bacteria when tested by radial diffusion on agar medium. The strength of inhibition differed among imidazolium salts when tested on the same bacterial strain and among bacterial strains when tested with the same imidazolium salt. In liquid medium, most imidazolium salts presented the same minimum inhibitory concentration (MIC) and minimum bactericidal concentration values (200µmoll-1 ), the most notable exception of which was the MIC (at least 1000µmoll-1 ) for the dicationic MImC10 MImBr2 . The imidazolium salts C16 MImBr and C16 MImCl caused significant reductions in the severity of common bacterial blight symptoms when compared with nontreated plants. Imidazolium salts inhibit the in vitro growth of plant pathogenic bacteria and reduce plant disease symptoms to levels comparable to an authorized commercial antibiotic product. New compounds exhibiting broad-spectrum antibacterial activity with potential use in agriculture were identified.

Exogenous salicylic acid mitigates the accumulation of some pesticides in cucumber seedlings under different cultivation methods.

Salicylic acid (SA) is a crucial signal molecule and phytohormone, regulating the biotic and abiotic stress responses as well as plant development. In this research, we comparatively examined the effects of exogenous SA on the behaviors of thiamethoxam (THIM), hymexazol (HMI) and chlorantraniliprole (CAP) in cucumber planting systems under soil pot and hydroponic cultivation. The cucumber seedlings were transplanted into soil or nutrient solution containing a target pesticide (1mg/kg) or a target pesticide with SA (1mg/kg) after the fourth leaf emerged. We examined the behaviors of pesticides both the SA treated and nontreated plants by analyzing cucumber root, stem and leaf samples taken on the 0-21 days following the root treatment. The root concentration factor (RCF), bioconcentration factor (BCF) and translocation factors (TFstem and TFleaf) were calculated for the comparison of the differences in the behaviors of pesticides. We found that the accumulation behaviors of pesticides in planting systems were related to the physicochemical properties of pesticides, exogenous SA and cultivation methods. Exogenous SA had a certain promoting effect on the degradation of pesticides in soil and nutrient solution, resulting in reduced half-lives. SA was able to block the accumulation of pesticides in roots and leaves and alleviated the accumulation ability of roots, the bioconcentration ability of plants, and the translocation ability from roots to leaves. Interestingly, SA had more distinct effects on the behaviors of pesticides under hydroponic experiments than under soil pot experiments. Furthermore, the behaviors of clothianidin (CLO), the main metabolite of THIM, were also assessed, indicating that THIM was mainly metabolized to CLO in leaves and stems, and SA facilitated this process. Our findings suggest that SA has a certain regulatory effect on the accumulation of pesticides in plants, and SA-blocked pesticide accumulation is practically rewarding for improving food safety.

Bio-stimulant, what is its promoting effect on the cultivation of safflower (Carthamus tinctorius L.)?

The present experimentation evaluated the potential of a bio-stimulant, made by indigenous strains of Trichoderma, on the performance of safflower plants cultivated in the region of Touggourt (Southeastern Algeria). The study was conducted according to seven (07) biometric measurements associated to growth and yield comparing treated and non-treated plants. Results revealed that the biological product has a stimulating efficiency towards all examined parameters. The percentage of germination in the treated plots (93.75%) was more than the non-treated (78.13%). After, it enhanced the growth of safflower plants either in the lifting, flowering, or the time of harvesting clumps and seeds. Furthermore, the treated plants were influenced by the applied bio-stimulant with significant differences in the diameter (2.6 cm; p = 0.01) and the number of principal branches (21.3 branch/plant; p = 0.07) comparing to the control plants. Besides, great efficiency of this bio-product was recorded with very highly significant differences on the weights of fresh (28.63 g; p = 0.000) and dry (1.31 g; p = 0.000) clumps per plant. Also, the statistical analyses applied on the productivity of safflower presented a significant difference (t 2.43, p = 0.018) between the treated plants (20.51 g/day) and the control (7.92 g/day). The present bio-stimulant was very efficient in promoting the growth of safflower crop so that it can be contributed in sustainable organic agriculture.

<i>In vitro</i> alteration of artemisinin biosynthesis in <i>Artemisia annua</i> L during treatment with methyl jasmonate

Purpose: To investigate the in vitro effect of methyl jasmonate (MeJA) on artemisinin biosynthesis in Artemisia annua.Method: The effect of two concentrations of MeJA i.e. 2 μm (T2) and 5 μm (T5) on biomass, plant height and artemisinin content of Artemisia annua L. was investigated in vitro in MS medium.Results: Plant height (6.5 ± 1.8 cm), biomass (0.18 ± 0.02 g/plant) and artemisinin content (0.035 ± 0.002 % dry weight) were higher in T5 and T2 treatment groups than in non-treated control plants (C). Artemisinin content, biomass and plant height were positively correlated after 2 - 8 days of treatment, but remained unchanged on the 12th day of treatment.Conclusion: The observed effects of exogenous MeJA on the biosynthesis of artemisinin and other secondary metabolites may lead to elucidation of promising targets for further studies on metabolic engineering of Artemisia annua L.
 Keywords: Artemisia annua L. Methyl jasmonate, HPLC, Artemisinin

Nanostructured alumina as seed protectant against three stored-product insect pests

Nanoparticles represent a promising technology to enhance the efficacy of bioactive materials and a large number of studies showed the effectiveness of nanostructured materials against various arthropod species of economic importance. In this work nanostructured alumina (NSA) was prepared using sol-gel method and the effect of NSA was evaluated as seed protectant against the main seed-infesting insect pests Oryzaephilus surinamensis (L.) (Coleoptera: Silvanidae) Stegobium paniceum (L.) (Coleoptera: Anobiidae), and Tribolium confusum Jacquelin du Val (Coleoptera: Tenebrionidae). Besides, we tested the effects of NSA on seed germination and plant growth and finally, we assessed the presence of NSA as a contaminant in the leaves of bean plants germinated from NSA-treated seeds. The results showed significant insecticidal activity of NSA against the three tested species. After sixteen days, the percentage of insect mortality at the highest NSA concentration tested (400 mg kg−1) was 100.00% for S. paniceum followed by O. surinamensis (80.64%) and T. confusum (79.41%). Besides, in-vitro tests indicated that NSA has no effects on seeds germination and on radicle and shoot elongation. No effects of NSA were also observed in pot tests on the bean’s plants. No differences were recorded in the leaves area, stoma density and roots length. On the contrary, the shoot of plants from NSA-treated beans was about 66% higher than the one of the non-treated plants (shoot, 15.07 cm for the control and 22.76 cm for NSA-treated plants). Finally, no contamination by alumina particles was found by EDX-system coupled with Scanning Electron Microscopy (SEM) on the surface of the P. vulgaris leaves obtained from NSA-treated beans. Overall, the results showed that NSA could be an effective protective agent for the control insect pests during the seeds storage.

Potential Application of Crotalaria longirostrata Branch Extract to Reduce the Severity of Disease Caused by Fusarium

Fusarium are considered as the major plant pathogen fungi, that cause the majority of soil-borne diseases to more than 100 plant species in the world, including maize. Thus, there are emerging demands of biocontrol reagents, and Crotalaria longirostrata showed fungicidal activity. The C. longirostrata branch extract was phytochemically characterized and evaluated for efficacy for the control of Fusarium wilt in maize. The application of the extract reduced the percentage of disease incidence significantly caused by Fusarium verticillioides from 70.4% to 40.12% as compared to non-treated plants, and evenly the disease severity was reduced from 40.15% to 29.46%. The phytochemical components of the extract were cinnamic acids (caffeic acid and ferulic acid) and phenolic acid (gallic acid). Furthermore, multiple structures were detected through mass spectrometry such as: phenols, alkaloids, esters, terpene, ketones, and amides. The bioautography assay showed that to separate the compounds of C. longirostrata branch extract causes it’s the loss of fungicidal activity. This is due to the synergy or additive interactions of secondary metabolites present in the raw extract. Our results suggest that the application of C. longirostrata branch extract is a promising strategy to be applied to the soil as a preventive treatment.