Abstract
Invasive species of Euphorbia peplus and Euphorbia geniculata weeds compete with the crops and act as hosts for other pests, consequently interfering with the livestock. Therefore, a comprehensive allelopathic screening of Euphorbia spp. was implemented via aqueous extracts and decayed residues against Triticum aestivum and their associated weeds. Aqueous and ethyl acetate extracts of E. peplus and E. geniculata were suppressed by the target weeds. The effects were influenced by plant types and concentrations. The Brassica nigra weeds were very susceptible, while T. aestivum was slightly sensitive. The phytotoxicity of Euphorbia spp. decayed residues correlated with the used concentrations and soil properties. Euphorbia spp. extracts were tested against Sclerotina sclerotiorum, Alternaria alternata, and Fusarium oxysporum fungi. E. peplus at 2000 µg/mL decreased fungal growth by 57.1% (S. sclerotiorum), 63.1% (A. alternata), and 63.0% (F. oxysporum), while E. geniculata at 2000 µg/mL decreased fungal growth by 73.0% (S. sclerotiorum), 64.8% (A. alternata), and 72.7% (F. oxysporum). Euphorbia spp. allelochemicals were analysed by HPLC, which indicated the differential in secondary metabolite concentrations between the two species. These substances have a positive potential as natural pesticides that are used in the management of these species.
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Implications of Euphorbia peplus and Euphorbia geniculata Allelopathy on Some Plant Species and Phytopathogenic Fungi
Mohamed A. El-Sakhawy 
,a,b Abeer Ali El-Sherbiny Ateya ,a,* and Mohamed Abdelaziz Balah ,c
Invasive species of Euphorbia peplus and Euphorbia geniculata weeds compete with the crops and act as hosts for other pests, consequently interfering with the livestock. Therefore, a comprehensive allelopathic screening of Euphorbia spp. was implemented via aqueous extracts and decayed residues against Triticum aestivum and their associated weeds. Aqueous and ethyl acetate extracts of E. peplus and E. geniculata were suppressed by the target weeds. The effects were influenced by plant types and concentrations. The Brassica nigra weeds were very susceptible, while T. aestivum was slightly sensitive. The phytotoxicity of Euphorbia spp. decayed residues correlated with the used concentrations and soil properties. Euphorbia spp. extracts were tested against Sclerotina sclerotiorum, Alternaria alternata, and Fusarium oxysporum fungi. E. peplus at 2000 µg/mL decreased fungal growth by 57.1% (S. sclerotiorum), 63.1% (A. alternata), and 63.0% (F. oxysporum), while E. geniculata at 2000 µg/mL decreased fungal growth by 73.0% (S. sclerotiorum), 64.8% (A. alternata), and 72.7% (F. oxysporum). Euphorbia spp. allelochemicals were analysed by HPLC, which indicated the differential in secondary metabolite concentrations between the two species. These substances have a positive potential as natural pesticides that are used in the management of these species.
DOI: 10.15376/biores.20.3.5633-5649
Keywords: Euphorbia species; Invasive species; Allelopathy; Antifungal; Biological control
Contact information: a: Department of Medical Laboratory, College of Applied Medical Sciences, Prince Sattam bin Abdulaziz University, Al-Kharj 11942, Saudi Arabia; b: Department of Medicinal and Aromatic Plants, Desert Research Center, Cairo, Egypt; c: Desert Research Center, El-Matriya, Cairo, Egypt;
* Corresponding author: abeeraliateya@gmail.com
INTRODUCTION
Across both tropical and temperate climates, the genus Euphorbia is one of the three richest genera of flowering plants. The spurge family (Euphorbiaceae) includes four giant genera, with a combined total of over 5000 species (Webster 1994; Steinmann and Porter 2002; Stejnmann and Porter 2002; Bruyns et al. 2006). One of the biggest and oldest plant families in the world, the Euphorbiaceae family includes about 300 genera, including approximately 8,000 species (Webster 1987). Many species of Euphorbia have been used in alternative and traditional medicine to treat a range of illnesses, including amaurosis, dropsy, deafness, paralysis, wounds, and skin warts (Benjamaa et al. 2022). The pharmacological qualities of Euphorbia spp. are widely utilized in medicine all over the world (Toudert et al. 2021). The extract (ethanolic) of Euphorbia helioscopia can be employed as a promising complementary and alternative therapy for diabetes mellitus (Beltagy et al. 2020). Essential oils from Euphorbia milii produce insecticidal activity against Periplaneta americana and Tettigonia viridissima, which may exert their insecticidal efficacy through physiological disruption of ionic composition (Okonkwo and Ohaeri 2018). Many Euphorbia spp. have been reported to have a range of phytochemicals with widely diverse biological effects, including polyphenol compounds, flavonoids, and terpenoids (Saleh et al. 2019).
The genus Euphorbia is one of the biggest in the Egyptian flora and is found in Upper Egypt as well as the Nile Delta (Batanouny et al. 1991). This genus grows in different life forms, such as herbs, shrubs, and trees. It is characterized by the presence of milky latex (Boulos 1999). The genus Euphorbia is considered the largest one in the Egyptian flora, represented in Egypt by 42 species (El-Karemy 1994). Some species of this genus occur as noxious weeds and invasive plants in several types of cultivated areas such as rangelands, pastures, and fields and are hosts for certain pests and diseases (Tedford and Fortnum 1988; Tanveer et al. 2010; Pahlevani 2007). The interaction between Euphorbia species and crop plants is a crucial factor in agricultural productivity (Deepti et al. 2023). The checklist of the alien species of Euphorbiaceae in the Egyptian flora is Euphorbia heterophylla, Euphorbia hyssopifolia, Euphorbia hirta, Euphorbia inaequilatera, Euphorbia lasiocarpa, Euphorbia mauritanica, Euphorbia prostrata, Euphorbia serpens, and Euphorbia nutans (Shaltout 2016; El-Beheiry et al. 2020), some of which are introduced to the cultivated land as weeds and invasive plants. Commonly, invasive spurges are noxious perennials with milky white latex sap that have variable poisonous effects depending on dose, mode of exposure, and species. In pastures and rangelands, leafy spurge is a persistent, aggressive weed that easily supplants good, desirable vegetation (Messersmith 1983). E. peplus is initially native to Europe and North Africa (Zhi-Qin et al. 2010). Grazed rangelands with leafy spurge densities of 50 or above have a minimum 35% reduction in annual herbage output. Once established in pasture and rangeland environments, it tends to supplant all other plants (Lym and Kirby 1987). Many Euphorbia-feeding insects accept as host plants most of the species in one subgenus and reject species in the other subgenera (Pemberton 1984).
The Euphorbia species exhibit allelopathic activity on cereals, vegetables, forage plants, and oilseeds due to the behavior of secondary metabolites. Most Euphorbia species are also fungicides or natural insecticides, and they inhibit 10 to 100% of foliage production (Deepti et al. 2023). The invasiveness of E. hypericifolia could be explained by its allelopathic potential at variable concentrations on five indicator plants (Ndam et al. 2021). Aqueous extracts of stems and leaves of leafy spurge (Euphorbia esula) inhibited radicle elongation and germination of tomato and crabgrass (Digitaria sanguinalis L. Scop.) when 0.1 to 1.0% (w/w) of leafy spurge roots or leaves were added to the soil (Steenhagen and Zimdahl 1979). The allelopathic effect of Euphorbia granulata on different plant species (Hussain 1980). E. heterophylla has allelopathic activity of extracts from roots inhibiting 100% of germination, root, and shoot growth of the indicator Sorghum bicolor and Lactuca sativa plants (da Silva et al. 2019).
Allelopathic inhibitory substances included in the water extract of E. heterophylla are responsible for the inhibition, which harms the growth and germination of mustard (Sinapis arvensis), wheat (Triticum durum), and cucumber (Cucumis sativus) (Fandah et al. 2020). The most active constituents in several members of the genus Euphorbia include myricitrin, afzelin, quercitrin, rutin, quercitin, 2,4,6-tri-O-galloyl-β-D-glucose, euphorbin (A to D), kaempferol, 1,3,4,6-tetra-O-galloyl-β-D-glucose, protocatechuic acid, gallic acid, 24-methylenecycloartenol, β-sitosterol, β-amyrin, nonacosane, shikimic acid, heptacosane, tinyatoxin, choline, camphol, rhamnose acid, and other quercitol derivatives (Kumar et al. 2010).
The main constraints facing crop production and its future development in newly cultivated land are weeds, especially invasive weed infestation. Through their disruption of water and mineral intake and their impact on photosynthetic partitioning, they are the cause of significant losses in agricultural yields. Invasive Euphorbia plants release biochemical compounds that can inhibit the growth of native plants and play crucial roles in ecosystem health and plant disease dynamics. However, there still is a need to confirm and evaluate the impact of Euphorbia species as the most common invasive plants in newly cultivated land on important crops. Moreover, the largest gap is the shift from evaluating their damage to crops to evaluating their impact on other weeds and their impact on phytopathogenic fungi.
Therefore, the research aimed to characterise the allelopathic potentials of two Euphorbia species in the environment against the nearby important plants from weeds and crops. Furthermore, a goal was to find natural products in these species that deal with the major pestilence issues that have become apparent in agricultural organisms, such as weeds and fungi. Additionally, the bioactive components were evaluated to optimise their application settings in crop productivity.
EXPERIMENTAL
Plant Materials
Euphorbia peplus and Euphorbia geniculata were identified by plant taxonomists in 2023 at the Desert Research Centre in Egypt after being gathered during the flowering stage from Borg El-Arab Alexandria Governorate, Egypt. Weed seeds were collected from Marryot Research Station–Desert Research Center, while the Agriculture Research Centre in Cairo provided 193 Giza wheat (seeds.
Extraction
Aqueous extraction
The dried shoot parts, weighing 25 g, were shaken on a rotary shaker for five h at room temperature after being soaked in 100 mL distilled water. Before being employed in bioassays, the mixture was filtered to remove debris and run through Whatman #4 paper, then preserved at -20 °C until use. The concentrations of 1.25, 2.5, 5, and 10 g/100 mL of the aqueous extract were achieved by diluting it with distilled water. The filter paper was placed on top of ten seeds, which were surface-sterilized in 9 cm diameter Petri dishes. Each experiment contained four replications. After that, 10 mL of extract was added, and 10 mL of distilled water was used as the control. Seven days were spent incubating petri dishes at 25 °C for 12 h of day and 12 h of darkness. The percentage of germination (G %), shoot, and root length were measured. The assays were repeated independently three times.
Organic extraction
Two hundred grams of soaking dried vegetative parts were macerated in 1000 mL of distilled water and shaken on a shaker at room temperature for five h. Following collection and filtering, the solution was successfully extracted three times with equal volume using ethyl acetate partitioning. After filtering the mixture, a rotary evaporator was used to remove the solvent. The resultant crude extracts (50 mg) were used in bioassays after being dissolved in aqueous methanol and then replaced with sterile distilled water after the evaporation of methanol before bioassay.
Plant Bioassays
Pre-emergence activity and phytotoxicity bioassays
The ethyl acetate extract on the target plant seeds was tested at 0, 200, 400, 800, and 1200 µg/mL in DMSO. Ten seeds were put in Petri dishes with two layers of filter paper that had been wet with 10 mL of extract concentration. The control treatment was planted on filter paper that was soaked with extract-free DMSO. Germination and plant seedling length were measured following 7 days of incubation at 25 °C with a photo period of 12/12 h (dark/light).
Assays against seedlings in liquid media
After surface sterilizing by sodium hypochlorite 0.05%, Avena fatua, Brassica nigra, and Triticum aestivum seeds were cultivated on static Murashige and Skoog (MS) basal media for seven days or until roots and shoots appeared. The seedlings were placed in a tissue culture tube with 5 mL of liquid MS medium containing extracts at concentrations of 0, 200, 400, 800, and 1200 µg/mL. The same volume of DMSO with extract-free was used in control treatment. At 25°C, plant cultures were kept in incubators with a photo period of 12 h of light and 12 h of darkness. After 10 days of treatment, the seedlings’ total biomass was measured. All experiments were designed with four replicates and repeated as needed.
Decayed Residues of Euphorbia peplus and Euphorbia geniculata in Soil
Decayed shoot materials of Euphorbia peplus and Euphorbia geniculata were tested for their phytotoxic potentials and on soil properties. The used soil was collected from Wadi Al Natroun, Egypt. Soil mechanical composition was (80.2%) sand, (14.1%) silt, and (5.6%) clay, respectively with a pH of 7.95 and electrical conductivity of 670 µS/m and contained (1.31 meq/L) sodium, (0.73 meq/L) potassium, (0.98 meq/L) calcium, and (0.62 meq/L) magnesium cations, as well as the anions (1.46 meq/L) HCO3, (1.35 meq/L), chloride, and (1.05 meq/L) sulfate. In the greenhouse, dry plant materials were combined with soil at varying concentrations (0.0, 1.0, 2.0, 3.0, 4.0, and 5.0% (DW/100 g soil). Ten T. aestivum seeds were sown in the pots to test for phytotoxicity. The T. aestivum plant was harvested two weeks after germination, and the fresh and dry weight of the entire biomass, shoot, and root lengths, and the numbers of germinated plants were recorded. Using a Spectrophotometer, the pigments of chlorophyll A and B (Chl a and Chl b) and carotenoids were quantitatively identified. 5 g of soil from each pot were taken to determine the pH and EC values.
Bioassay against Fungi
Before usage, 50 µg of ethyl acetate crude extracts were dissolved in DMSO, and then exactly 1 mL of concentrations of 0, 250, 500, 1000, and 200 µg/mL was put into each 9 cm petri dish containing PDA media (20 mL) before it solidified. After that, the dishes were slowly turned to ensure that the crude extract was dispersed equally. One centimeter diameter (punched by sterilized Cork borer) of pathogenic Sclerotinia sclerotiorum, Alternaria alternata, and Fusarium oxysporum fungal growths isolated from the Vigna unguiculata field in Egypt was placed in the center of the dishes. After four days, data on fungal growth was collected from the dishes placed in a growth chamber with five replications at 25 °C.
Phenolic Compounds Determination
The phenolic content of the plant ethyl acetate was determined using an Agilent-1100 HPLC system with a quaternary gradient pump unit, an ultraviolet (UV) detector at 320 nm, and a C18 analytical column (Agilent, Santa Clara, CA, USA) measuring 150 × 406 mm with a particle size of 5 µm. Elution was done at 23 °C with a flow rate of 0.075 mL/min. The mobile phase contained 8% acetonitrile, 22% isopropyl alcohol, and 70% formic acid solution (1%). A 0.22 μm syringe filter was used to filter all dissolved standards and samples before HPLC analysis. Weed extracts were frozen for 24 h at -20 °C. The residues were then dissolved in HPLC-grade methanol and injected into the HPLC in a 20 μL volume.
Statistics
A randomized complete block design with four repetitions was used for all trials. To choose a significant difference (P ≥ 0.05), an analysis of variance was performed using the ANOVA test. Duncan multiple ranges were then performed using IPM SPSS, 19 Software (SPSS, Chicago, IL, USA).
RESULTS AND DISCUSSION
The dose-response relationship of Euphorbia spp. shoot part aqueous extracts and the target plants exhibited that E. peplus achieved EC50 values of 8.80, 7.55, and 8.96 µg/ mL in T. aestivum root length, shoot length, and germination, respectively. The moderate response plant was A. fatua, which showed values of 5.85, 4.90, and 5.65 µg/mL for root length, shoot length, and germination, respectively. However, the most vulnerable was B. nigra, which had EC50 values of 4.88, 3.95, and 6.14 µg/mL for root length, shoot length, and germination, respectively.
Similarly, the extracts of E. geniculata showed that T. aestivum was a low-sensitivity plant, as indicated from EC50 values of 7.99, 5.59, and 6.31 µg/mL for their root length, shoot length, and germination, respectively. The EC50 values in A. fatua were 7.99, 5.59, and 6.31 µg/mL for root length, shoot length, and germination, respectively. This was followed by B. nigra, the most vulnerable plant, with EC50 values of 3.98, 2.85, and 4.22 µg/mL for root length, shoot length, and germination respectively.
The dose-response relationship of ethyl acetate extracts revealed that the E. peplus EC50 value was 745 µg/mL in T. aestivum total biomass fresh weight. This was followed by A. fatua seedlings, for which the total biomass with EC50 value reached 458 µg/mL. However, B. nigra seedlings were the most vulnerable plant, which had EC50 values of 405 µg/mL in total biomass fresh weights. The maximum concentration of E. peplus presented reduction in the fresh total biomass by 87.1% (T. aestivum), 66.4% (A. fatua), and 82.2% (B. nigra), respectively.
As for E. geniculata shoot part extracts, the EC50 value was 765 µg/mL for total biomass fresh weight of T. aestivum seedlings. This was followed by A. fatua seedlings, with the total biomass coming in second and an EC50 value that reached 574 µg/mL. However, B. nigra seedlings were the most vulnerable plant with EC50 values of 493 µg/mL biomass fresh weight. The fresh total biomass was reduced at the highest concentration by 86.5% (T. aestivum), 58.0%), (A. fatua), and 76.3% (B. nigra) in that order.
Table 1. Bioassay of Euphorbia spp. Aqueous Extract (EC50) Against Some Plant Germination and Seedling Growth in Petri-dishes
Table 2. Petri-dish Bioassay of Euphorbia spp. Ethyl Acetate Extracts Against the Tested Plants Seedling Total Biomass Fresh Weights (g)
Table 3. Post-emergence Activity (EC50) of Euphorbia spp. Ethyl Acetate Extracts Against Plant Seedlings
Under the greenhouse conditions, the post-emergence activities of E. peplus and E. geniculata ethyl acetate extracts at 2500 and 5000 µg/mL were evaluated on T. aestivum and associated weeds of A. fatua, and B. nigra at 4-leaf stage seedlings (Table 3). Concerning to application of spraying E. peplus extracts at the maximum concentration, fresh weights, dry weights, carotenes, and Chl A and Chl B were reduced by 75.2, 24.8, 51.3, 55.3, and 35.8% (T. aestivum), 55.4, 41.0, 42.6, 49.6, 49.6, and 29.4% (A. fatua), and 66.0, 33.3, 40.8, 48.6, and 34.9% (B. nigra), respectively, in comparison to the untreated control. As for E. geniculata extracts at the maximum concentration, it resulted in reduction in fresh weights, dry weights, and carotenes of 81.7, 25.1, 42.6, 53.5, and 26.6% (T. aestivum), 65.9, 41.1, 42.3, 49.4, and 31.3% (A. fatua), and 66.0, 32.6, 40.6, 48.3, and 25.2% (B. nigra) in comparison to the control. Statically, there were significant interactions between species × concentration in fresh weights (F=313.4, p ≤ 0.00), fresh weights (F=11.60, p ≤ 0.00), carotenoids (F=31.3, p ≤ 0.00), Chl A (F=4.1, p ≤ 0.000), and Chl B (F=42.1, p ≤ 0.00) respectively for E. peplus. Meanwhile, there was a significant interaction effect in fresh weight (F=340.7, p ≤ 0.000), dry weight (F=12.60, p ≤ 0.00), carotenoids (F=34.00, p ≤ 0.000) Chl A, (F=11.40, p ≤ 0.00) Chl B, and (F=45.80, p ≤ 0.00) respectively for E. geniculata.
In soil, decayed residues of Euphorbia species were tested using T. aestivum seeds at concentrations of 2, 3, 4, and 5% (W/W) for two weeks after germination (Table 4). The concentration of 1% stimulated growth, but other concentrations reduced T. aestivum growth parameters. The greater reduction reached its peak at 5% concentration of E. peplus decayed residues, in shoot length, root length, fresh weight, dry weight, Chl A, Chl B, carotenes by 21.3%, 17.1%, 27.9%, 24.9%, 11.8%, 24.8 and 21.5% respectively. At the highest concentration (5%) of E. geniculata decayed residues, reduction was achieved in shoot length, root length, fresh weight, dry weight, Chl A, Chl B, carotenes by 12.1%, 20.2%, 25.0%, 20.0%, 6.0%, 3.6%, and 16.9%, respectively. As for soil parameters, the decayed residues of E. peplus and E. geniculata caused a reduction in soil pH; however, a little increase was detected in soil EC values, which reached 2.8 and 2.7%, respectively. These results pointed out that E. peplus had a greater impact on soil and T. aestivum seedling characteristics than E. geniculata. Statically, there were significant interactions between species × concentration in shoot length (F=3.66.4, p ≤ 0.037), root length (F=12.92, p ≤ 0.00), fresh weights (F=2.99, p ≤ 0.035), dry weights (F=3.02, p ≤ 0.025), carotenoids (F=4.09, p ≤ 0.029), Chl A (F=4.12, p ≤ 0.025), and Chl B (F=12.1, p ≤ 0.00), respectively.
Antifungal Activity of E. peplus and E. geniculata Ethyl Acetate Extracts against Some Plant Pathogenic Fungi
The ethyl acetate extracts of E. peplus and E. geniculata impact on the growth of S. sclerotiorum, A. alternata, and F. oxysporum were demonstrated in Table 5. E. peplus extracts were tested against the growth at concentrations of 250, 500, 1000, and 2000 µg mL. They dramatically decreased fungal growth by 4.8, 21.4, 40.5, and 57.2%, (S. sclerotiorum) 19.0, 23.8, 33.3, and 63.1% (A. alternata), 13.6, 41.0, 58.9, and 63.0%, (F. oxysporum), respectively, in comparison to its control. Meanwhile, when E. geniculata extracts were tested against the growth at concentrations of 250, 500, 1000, and 2000 µg mL, they dramatically decreased fungal growth reaching 19.6, 56.8, 59.2, and 73.0% (S. sclerotiorum), respectively, 22.0, 39.9, 61.3, and 64.8% (A. alternata), and 14.8, 38.1, 59.5, and 72.7%, (F. oxysporum) respectively, compared to the control.
Table 4. Effect of Euphorbia spp. Ethyl Decayed Residues on Wheat Seedling Growth and Soil Parameters
Table 5. Activity of Euphorbia spp. Ethyl Acetate Extract Against the Tested Fungi Growth (cm)
Table 6. Euphorbia spp. Ethyl Acetate Extracts Quantitative Determination Using HPLC-UV
According to analysis by HPLC-UV, the ethyl acetate extracts of Euphorbia species that were qualitatively present contained twelve free chemicals based on their relative retention times that were identified as hydroxycinnamic acid, p-hydroxybenzoic acid, syringic acid, gallic acid, chlorogenic acid, vanillic acid, caffeic acid, coumaric acid, kaempferol, ferulic acid, citric acid, and salicylic acid substances. The quantitative analysis revealed that the amounts of coumaric acid in E. peplus and E. geniculata reached approximately 47.0 and 48.0 µg g-1 DW, respectively. However, small amounts of vanillic acid 19.2 and 18.6% μg g-1 DW were found in E. peplus and E. geniculata, respectively. The results showed these weeds are abundant in physiologically active substances (Table 6).
DISCUSSION
Euphorbia species are important to agriculture because they compete with crops for nutrients, CO2, and water resources and serve as hosts for several pests. However, few studies on the allelopathic effects of E. peplus and E. geniculata have been conducted. Therefore, the allelopathic effects of E. peplus and E. geniculata were assayed against wheat crop (T. aestivum) and associated weeds (A. fatua and B. nigra) via aqueous leachate and on their soil chemistry via decayed residues. Additionally, the antifungal effect of these species was tested on S. sclerotiorum, A. alternata, and F. oxysporum. In the Euphorbiaceae family, great phytochemical varieties were found, including tannins (Giordani et al. 2001), terpenoids (Liu et al. 2002), and phenolics (Duarte et al. 2008). Genus Euphorbia members cover macrocyclic diterpenoid compounds that have analgesic, antimicrobial, anticancer, PGE2-inhibitory, and anti-HIV properties (Jassbi 2006). However, the Euphorbia hypericifolia plant showed that certain allelochemicals might be used to create natural compounds that promote plant growth and can served as bioherbicides (Ndam et al. 2021).
The dose-response relationship of Euphorbia species extracts offered important information about their allelopathic capabilities and specificity. It revealed that E. peplus and E. geniculata aqueous extracts have varying phytotoxic effects on test plant species, based on the concentration used in the current study. This aligns with Ndam et al. (2021), whose study found that variable allelopathic patterns depend on E. hypericifolia concentration against five indicator plants; this may be attributed to the increase of active constituents. The lowest sensitivity shown by the T. aestivum plant could be because of their variation in the allelopathic substances absorption, translocation, and physiological or biochemical response of the target species that detoxify the allelopathic molecules. Conversely, weeds’ high susceptibility could be caused by increased absorption, ineffective detoxification, or increased sensitivity to particular extract constituents, to which B. nigra was more sensitive than A. fatua to Euphorbia species allelochemicals. Similar patterns were shown in ethyl acetate extracts of E. peplus and E. geniculata, whereas more powerful activities were displayed from the extraction of ethyl acetate with a stronger impact as compared to water extracts. The root, leaf, stem, and fruit of E. helioscopia watery extract decreased the germination index and seed germination (lentils and chickpeas), while the leaf extract lengthened the average germination time for all tested plant crops (Tanveer et al. 2010). The extract of E. dracunculoides showed a significant reduction in the plumule and radicle length of Chickpea (Kil and Yun 1992). The stimulatory and inhibitory effects of Euphorbia hirta on germination rate and seedling growth in response to particular doses demonstrate its allelopathic action on sorghum (Mali et al. 2021).
The decomposed residues of Euphorbia species in the soil emphasized the unique impacts of their allelopathic abilities against other plants and soil properties. The differences between E. peplus and E. geniculata were found in E. peplus’ decayed process compared to remarkable inhibitory effects during the decayed process than E. geniculata against T. aestivum seedling development and soil characteristics. These impacts of Euphorbia species could serve for a better understanding of invasion and impacts in both agriculture and soil systems. The decayed effect of E. peplus was higher than E. geniculata. These findings are proven by Singh et al. (2003), who informed the reduction in the dry weight of wheat grown in soil infested with E. helioscopia. Abu-Romman et al. (2010) found that Euphorbia hierosolymitana exhibited an allelopathic effect on wheat seedling growth, seed germination, chlorophyll, and protein. According to Choudhary et al. (2023), researchers divided the allelochemical mode of action into direct and indirect categories, including functional and genuine (true) allelopathy. Allelochemicals have two possible effects: direct allelopathy, which affects the target directly, and secondary degradation products, which are discharged into the soil and can either damage plant development or alter the microenvironment, which affects growth indirectly. Moreover, the allelochemicals released from weeds, most of them water-soluble chemicals, into the soil have allelopathic effects on wheat seed germination and growth (Al-Qthanin et al. 2024).
The plant pathogen of S. sclerotiorum, A. alternata, and F. oxysporum fungi are among the most dangerous diseases in many crops. They lead to huge decreases in the growth parameters and losses in crop yield. Therefore, the current study investigated the antifungal potential of E. peplus and E. geniculata ethyl acetate extracts under laboratory conditions with a series of concentrations. The results showed that E. peplus and E. geniculata ethyl acetate extracts have antifungal activity against S. sclerotiorum, A. alternata, and F. oxysporum significantly by reducing fungal growth compared with the control. E. peplus extract has significantly inhibited the growth of S. sclerotiorum and F. oxysporum, while extracts of E. geniculata show broad-spectrum action and successfully prevented the growth of F. oxysporum, A. alternata, and S. sclerotiorum. Differences in the fungi’s susceptibility based on the bioactive chemicals in the extracts of E. peplus and E. geniculata’s vary in efficacy against particular fungal species. Chemical analysis points to their capacity to prevent the growth of fungi, particularly when combined. However, the potential of Euphorbia species as a source of naturally occurring antifungal chemicals is supported by earlier research that found Euphorbia species hydroalcoholic extract of this species showed antimicrobial activity against pathogenic bacteria, including Gram-negative (K. pneumonia, S. typhi, P. aeruginosa, and E. coli) and Gram-positive bacteria such as Staphylococcus aureus and Candida albicans yeast (Bahy et al. 2022). Euphorbia spp. active metabolites, including lathyrane diterpenoids, especially Euphorbia factor L3 have excellent inhibitory effects against Phytophthora capsica plant pathogen. Plant-derived terpenoids’ antifungal properties have been partially ascribed to their damaging effects on the cell membrane as well as the cell wall of pathogens (Wang et al. 2023). Moreover, Euphorbia factor L3 compound has anticancer activity and induces apoptosis by loss of mitochondrial pathway and release of cytochrome c (Zhang et al. 2011).
The phytochemical screening of E. peplus and E. geniculata extracts revealed the presence of phenolic and flavonoids. The biological activity against plants and fungi is highlighted by the varying amounts of secondary constituents in both E. peplus and E. geniculata. The E. peplus had higher quantities of flavonoids and phenolic acids, which makes it a more potent allelopathic competitor to E. geniculata. However, E. geniculata is a more potent antifungal agent than E. peplus due to its higher concentrations of flavonoids and phenolic acids. Strong antifungal and allelopathic effects are well-known for phenolic acids, such as coumaric, ferulic, and caffeic acids. Since caffeic and ferulic acids can break down fungal cell walls and prevent spore germination (Macías et al. 2007; Simonetti et al. 2020). Phenolic compounds and their derivatives have been frequently cited as chemical sources of allelopathy (Rice 1984). E. peplus displayed higher amounts of chlorogenic acid, hydroxycinnamic acid, and citric acid, which may account for its superior allelopathic effectiveness. On the other hand, E. geniculata has greater concentrations of other chemicals, which are mostly linked to antioxidant properties and may not be as efficient against fungus. These variations imply that E. geniculata and E. peplus had higher concentrations of non-specific phenolic and a flavonoid that is responsible for allelopathic and antifungal properties. Whereas, the presence of citric acid may help to modify the pH of the environment, which may not directly have an antifungal effect but may indirectly affect microbial activity. Salicylic acid, coumaric acid, and hydroxycinnamic acid are essential for allelopathy. E. peplus may have a competitive advantage because of its greater levels of chlorogenic acid, hydroxycinnamic acid, and citric acid, which may prevent nearby plants from germinating and growing. Since E. geniculata has fewer of these allelopathic substances, it probably has less of the inhibiting chemicals. Possible synergistic or antagonistic interactions between the chemicals may be bioactivity constituents and between the target plants. This result validates previous findings by Ndam et al. (2014), who found that the presence of phenolics in the leaf extracts of E. hypericifolia could thus have significantly advanced the suppression of germination, growth, and biomass production in this study’s targeted plants. Katemas (Euphorbia geniculata Ortega) toxicity exhibited the highest mortality at 5% concentration in armyworm larvae (Spodoptera litura). While spectroscopy analysis identified a type of pentacyclic triterpenoid compound, namely lupeol acetate (Eliza et al. 2016). In addition, non-polar secondary metabolites of Euphorbia peplus may serve as potential therapeutic candidates for leishmaniasis (Amin et al. 2017).
CONCLUSIONS
- The results of this work highlight the significant effectiveness of Euphorbia species on plants and fungi and the great convergence between the two laboratory plants (T. aestivum, A. fatua, and B. nigra). These results may be due to the closest relationship of the genetic diversity observed between E. geniculata and E. aphylla; and E. pulcherrima and E. peplus using RAPD-PCR.
- These findings demonstrated that E. peplus and E. geniculata extracts were effective due to their allelochemicals, which give them their allelopathic capabilities. These potentials are concentration-dependent and demonstrate stimulatory and phytotoxic effects on germination and growth traits in the sensitivity order of B. nigra > A. fatua > T. aestivum of targeted plants.
- The findings demonstrate the potential of the bioactive chemicals in Euphorbia species as natural substitute antifungal agents for the control of F. oxysporum > S. sclerotiorum > A. alternata of target fungi. Therefore, these plants are a source of extracts with suppressive properties as potential natural pesticides.
Finally, the allelopathic effects of two invasive Euphorbia species, Euphorbia peplus and Euphorbia geniculata, significantly impact other weed species and phytopathogenic fungi. This dual action not only holds promise for competing with other weed plant species and control of some phytopathogenic fungi as potential natural pesticides, but it also may have promising usage in other agriculture. These results highlight the necessity of taking action to manage these invasive weeds to achieve sustainable agriculture and establish a baseline for economic crop productivity away from the use of chemically manufactured pesticides.
ACKNOWLEDGMENTS
The authors extend their appreciation to Prince Sattam bin Abdulaziz University for funding this research work through the project number (PSAU/2024/03/29884).
Author Contributions
Conceptualization, Investigation, Methodology (A.A.E. Ateya), Analysis, investigation, methodology, writing ± original draft (M. A. El-Sakhawy), Data analysis, Methodology, writing and review (M. Balah).
Conflict of Interest
The authors confirm that this article’s content has no conflict of interest.
Data Availability Statement
All data generated or analyzed during this study are available from the corresponding author upon justified request.
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Article submitted: January 20, 2025; Peer review completed: March 9, 2025; Revised version received and accepted: May 13, 2025; Published: May 22, 2025.
DOI: 10.15376/biores.20.3.5633-5649