Extracts of Senecio brasiliensis and Solanum viarum as Potential Antifungal and Bioherbicidal Agents

Abstract

Ultrasound-assisted extraction is an interesting tool for obtaining bioactive compounds from plant matrices applicable as agricultural bio-inputs, as it increases the extraction efficiency, reducing the process time and the use of solvents. This technique uses ultrasonic waves to break down plant cell walls, releasing bioactive compounds quickly and effectively and promoting a sustainable path to obtaining bio-inputs. Accordingly, this research study reports pioneering results regarding the herbicidal and fungicidal potential of different extracts obtained from Senecio brasiliensis (samples from flowers, leaves, and stalks) and Solanum viarum (samples from fruits and roots), two weeds typically found in rural areas of South America. The fungicidal activity of the samples was tested on two fungi, i.e., Fusarium graminearum and Sclerotinia sclerotiorum, while the herbicidal action of the extracts was evaluated in pre-emergence tests in cucumber (Cucumis sativus) seeds. The successful results indicated a high antifungal and herbicidal potential of the extracts obtained for both weeds, with the inhibitory effect against both fungi achieving up to 82%, and the inhibition of C. sativus seed germination reaching 100% for all samples.

1. Introduction

Senecio spp. and Solanum spp. are plant genera widely known in South America for their weedy characteristics, especially in southern Brazil and Uruguay [1,2]. Particularly, Senecio brasiliensis Less., also known as “maria-mole” and “maçanilha”, is a weed belonging to the Asteraceae family found in a variety of habitats including pastures and roadsides [3]. With the possibility to grow up to one meter in height, its leaves are alternate, oblong, and have a rough texture, with small daisy-shaped flowers (yellow) grouped in inflorescences. Its ability to develop quickly and spread easily through seeds makes this vegetable species competitive with native plants, suppressing the growth and development of local vegetation [4]. Furthermore, it is known that species of the genus Senecio, such as S. brasiliensis, contain toxic chemical compounds, such as pyrrolizidine alkaloids, which can pose a health risk to cattle and other animals that feed on them [5].

Similarly, the species Solanum viarum Dunal., known as “joá-bravo”, is a perennial plant that grows vigorously and belongs to the Solanaceae family, reaching up to two meters in height [6]. Its leaves are large and oval in shape and have serrated edges, with small flowers (white or violet) grouped in inflorescences. Its fruits are small and yellowish in color when ripe, and each fruit can contain numerous seeds, which contributes to the rapid spread of the plant [7]. Consequently, one of the most worrying characteristics of S. viarum is its ability to reproduce and disperse quickly with the aid of birds, mammals, and even water. Moreover, this plant is resistant to adverse weather conditions, which provides it with a competitive advantage over native species. In this panorama, the control of the weed species S. brasiliensis and S. viarum is quite challenging, mainly due to their invasive nature and ability to adapt to a diversity of environments [8,9].

The well-known toxicity of the weed species S. brasiliensis and S. viarum is commonly associated with the accumulation of high levels of alkaloids in their cell structure [6]. Plant metabolism consists of a diversity of reactions that occur in each vegetable cell and aim to produce energy through adenosine triphosphate and the biosynthesis of substances essential for survival [10]. Accordingly, plants can synthesize a wide range of secondary metabolites comprising a variety of compounds that have evolved to promote plant survival [11,12]. This process protects plants against general stresses, such as environmental factors, insects, herbivores, predators, pathogens, and ultraviolet radiation [13]. Contextually, some secondary metabolites can interfere in the growth and development of biological systems, being thus considered allelopathic compounds. The action of allelopathic compounds capable of interfering in biological systems is usually attributed to different mechanisms that can range from inhibiting the growth of weeds and pests through the interruption of metabolic processes capable of causing biochemical disturbances that affect their survival and growth to even altering the soil microbiome, influencing the competition between beneficial and pathogenic microorganisms [14,15,16]. Therefore, these allelochemical compounds can be used directly for the formulation of pesticides or altered to improve their biological action.

Accordingly, in an attempt to reduce the use of synthetic pesticides, extensive investigations have been accomplished into the possible exploitation of these plant compounds as natural commercial products that are safe for humans and the environment. The investigation of natural compounds and management methods as alternatives to conventional pesticides has become an intense and productive field of research [17]. Due to their structural diversity and the biological activities developed, these compounds can be used for the development of organic biochemical pesticides based on the structure of natural phytotoxins [18]. Appropriately, an interesting range of scientific studies has reported this efficiency against distinct pathogens [19,20,21,22,23,24].

Therefore, considering the negative effects of the use of herbicides and fungicides on the environment, the growth of organic agriculture, the control of weeds with alternative methods, and the herbicide and fungicide potential of S. brasiliensis and S. viarum, this paper reports data on the effects of extracts from different matrices of the considered weeds on the in vitro mycelial growth of Fusarium graminearum and Sclerotinia sclerotiorum. In addition, the herbicidal action of the extracts in pre-emergence tests on seeds of cucumber (Cucumis sativus)—a plant indicative of allelopathic activity—is also disclosed. To our knowledge, the results presented throughout the text involve a pioneering approach for the use of extracts from S. brasiliensis and S. viarum in agricultural management.

2. Materials and Methods

2.1. Samples

Plant samples of S. brasiliensis (flowers, leaves, and stalks) and S. viarum (fruits and roots) were collected from natural fields/pasture areas in the north of the state of Rio Grande do Sul (27°55′39.43 S, 52°7′37.14 W), Brazil, during spring in the year 2023 (first week of November). The samples were initially stored in plastic packaging at room temperature (23 ± 1 °C) for no more than two days until they were subjected to a drying process. The material was dried at 40 °C until constant mass and then ground in a knife mill (Model MA885, Marconi LTDA., Piracicaba, Brazil), after which, samples with particle diameters between 48 and 8 mesh (0.3 and 2 mm, Tyler) were selected for extraction. Finally, the samples were stored at −4 °C until extraction to avoid their degradation.

2.2. Extraction Step

Extracts were obtained from different parts of S. brasiliensis (flowers, leaves, and stalks) and S. viarum (fruits and roots) by ultrasound-assisted extraction (UAE, using an ethanolic solution of 60 vol.%) using a high-intensity ultrasound processor of 400 W and 24 kHz (Model UP 400S, Hielscher Ultrasonics GmbH, Teltow, Germany) and following the methodology described by Confortin et al. [9]. Preliminary tests were performed to define the operational conditions that would lead to the highest concentrations and yields of the extracts, resulting in the selection of ultrasound intensity of 85 W m⁻², pulse of 0.75 for 30 min, and temperature of 40 °C. The liquid phase was collected, and the solvent was completely removed by vacuum evaporation at 40 °C. The yields obtained for each botanical part of the substrates considered were calculated by Equation (1).

$$\mathrm{Y}\mathrm{i}\mathrm{e}\mathrm{l}\mathrm{d}\left(\mathrm{\%}\right)=\frac{\mathrm{m}\mathrm{a}\mathrm{s}\mathrm{s} \mathrm{o}\mathrm{f} \mathrm{e}\mathrm{x}\mathrm{t}\mathrm{r}\mathrm{a}\mathrm{c}\mathrm{t}\left(\mathrm{g}\right)}{\mathrm{i}\mathrm{n}\mathrm{i}\mathrm{t}\mathrm{i}\mathrm{a}\mathrm{l} \mathrm{m}\mathrm{a}\mathrm{s}\mathrm{s} \mathrm{o}\mathrm{f} \mathrm{t}\mathrm{h}\mathrm{e} \mathrm{d}\mathrm{r}\mathrm{y} \mathrm{m}\mathrm{a}\mathrm{t}\mathrm{r}\mathrm{i}\mathrm{x}\left(\mathrm{g}\right)}\times 100$$

(1)

2.3. Antifungal Activity

To determine the antifungal activity of the extracts obtained from different matrices of S. brasiliensis and S. viarum, extract solutions (100 mg mL⁻¹) were prepared using ethanol as a solvent. For the control solution, ethanol and distilled water were used at the same concentration. The fungitoxic action of the extracts was evaluated on the development of two important phytopathogens, Fusarium graminearum (strain ATCC 46779) and Sclerotinia sclerotiorum (strain ATCC 18683), obtained from the Department of Phytosanitary Defense of the Federal University of Santa Maria, Brazil. The culture medium used in the experimental assays was Potato Dextrose Agar (PDA, Himedia^®, Thane, India), prepared according to the manufacturer’s instructions (39 g L⁻¹).

The antifungal activity was evaluated by the agar dilution method, which involves the incorporation of the desired concentration of the antimicrobial agent into an agar medium (molten agar medium), followed by the inoculation of a defined microbial inoculum onto the agar plate surface [25]. Accordingly, Petri dishes were filled with the prepared PDA medium and each extract that was tested. After natural solidification, a 7 mm diameter mycelium disk of each microorganism was transferred from a seven-day pure culture to the center of a dish. The Petri dishes were then incubated at 28 °C and the diameter of the mycelial growth was measured through two diametrically opposite measurements of the colonies when the control (PDA without the addition of extract) reached its maximum growth. The inhibition percentage (IP) of mycelial growth was determined using the control concentration growth (Petri dish with PDA medium only) as a reference and calculated using Equation (2), as suggested by Zabka et al. [26]. The experiments were performed according to a randomized design in triplicate, using five plant matrices (fruits and roots of S. viarum as well as leaves, flowers, and stalks of S. brasiliensis), one concentration of extract, and two fungi. Data analysis was conducted performing a mean comparison test by the Tukey method (p < 0.05) using the software Statistica, version 8.0 (Statsoft Inc., Tulsa, OK, USA)

$$\mathrm{I}\mathrm{P}\left(\mathrm{\%}\right)=\left(\frac{\mathrm{D}\mathrm{C}-\mathrm{D}\mathrm{T}}{\mathrm{D}\mathrm{C}}\right)\times 100$$

(2)

where DC is the colony diameter of the control concentration, and DT is the colony diameter in the presence of the different extracts evaluated.

2.4. Analytical Procedure

Additional bioassays were performed in pre-emergence tests on cucumber (C. sativus) seeds. The assays were conducted in Petri dishes previously disinfected with alcohol 70 vol.%, covered with two filter paper sheets (Germitest^®) moistened with the respective extracts (treatment) in a volume 2.5 times the paper’s weight, according to the Rules for Seed Analysis (RAS) [27]. The control assays were performed replacing the extract with distilled water. Afterward, three replicates of 10 seeds were applied, totaling 30 seeds per treatment, conditioned in a biological oxygen demand incubator at 25 °C and with a photoperiod of 12/12 h of light and darkness. Subsequently, these data were expressed as percentage of inhibition of germination or abnormal plants (plants that did not have normal growth). The first evaluation of the number of germinated seeds was performed on the third day after the start of the experiment, followed by two evaluations on the seventh day. Here, the seeds that presented a growth of the radicle superior to 2 mm were considered germinated, as described in the RAS [27]. Germination inhibition (GI) was calculated using Equation (3), analyzing the data using a mean comparison test following the Tukey method (p < 0.05) and the software Statistica, version 8.0 (Statsoft Inc., Tulsa, OK, USA)

$$\mathrm{G}\mathrm{I}\left(\mathrm{\%}\right)=\left[\frac{\sum n_i}{\mathrm{A}}\right]\times 100$$

(3)

where n_i is the number of seeds germinated in each repetition, and A is the total number of seeds.

3. Results and Discussion

3.1. Antifungal Activity

The yields obtained for each botanical part of the substrates considered are presented in

Table 1. Yields and main compounds obtained from S. viarum and S. brasiliensis extracted by UAE.

Botanical Part	Yield (wt.%)	Compounds with Biological Activity 1
S. viarum
		Salsodine
		Cydine
Fruit	19.15	Quinic acid
Root	10.20	Piperazine
		Mannofuranoside
		1,8 Diazabicyclo [5.4.0] undec-7-ene
S. brasiliensis
		Integerrimine
		Senecionine
		Propanetriol
		Cinerin
Leaf	10.68	Celidoniol
Flower	6.52	Hexadecanoic acid
Stalk	5.57	Phenol
		Octadecenoic acid
		2-Methoxy-4-vinyl phenol
		Guanosine
		5H-1-Pyridinol

¹ According to Confortin et al. [8,9].

(a total of five samples were obtained from the extractions and used for determining their bioactivities). Table 1 also shows the typical distribution of phytochemicals extracted from these plants, according to works already published by our research group [8,9].

The antifungal activity of the extracts obtained by UAE of S. viarum and S. brasiliensis against F. graminearum and S. sclerotiorum is presented in

Table 2. Inhibition of mycelial growth of F. graminearum and S. sclerotiorum by extracts of S. brasiliensis and S. viarum.

IP (%)
	S. brasiliensis			S. viarum
	Flowers	Leaves	Stalks	Fruits	Roots
F. graminearum	60.18 ± 0.14 bG	75.02 ± 0.17 aD	58.75 ± <0.1 cH	62.02 ± 0.11 bF	65.01 ± 0.15 aE
S. sclerotiorum	74.27 ± 0.10 cG	82.01 ± 0.31 aD	77.65 ± 0.24 bF	77.05 ± 0.15 bF	81.15 ± 0.12 aE

^a–c Different letters in the same column indicate a significant difference of 95% (p < 0.05—Tukey test) between the tests for each species and for each fungus, separately. ^D–H Different letters in the same column indicate a significant difference of 95% (p < 0.05—Tukey Test) between the tests on the two species for each fungus, separately.

. For the in vitro tests, it was possible to verify that all matrices of both plants presented promising antifungal activity against the two species of fungi considered, with an IP ranging from 58.75% to 75.02% for F. graminearum and from 74.27% to 82.01% for S. sclerotiorum.

Specifically, for the S. brasiliensis extracts, the matrix with the better results was the leaves, with the highest IP for both tested fungi (75.02% and 82.01% of inhibition for F. graminearum and S. sclerotiorum, respectively). Similarly, for S. viarum, the matrix that presented the highest IP was the roots (65.01% and 81.15% for F. graminearum and S. sclerotiorum, respectively). Figure 1 shows images collected after the 7th day of applying the extracts onto the fungal samples. Given the scarcity of studies that evaluated the antifungal activity of extracts from S. brasiliensis and S. viarum on fungi of the species F. graminearum and S. sclerotiorum, comparing the results obtained with data from the literature was not simple. However, it was possible to emphasize the data obtained by highlighting similar results reported by other authors who used plant extracts to inhibit fungal growth [23,24,28,29,30]. Interestingly, Seepe et al. [31] reported the application of extracts from Combretum erythrophyllum, Quercus acutissima, and Melia azedarach (2.5 mg mL⁻¹) on samples of F. proliferatum, indicating an antifungal activity ranging from 68% to 98%. Similarly, Hernández-Ceja et al. [32] obtained an IP of 100% when testing the effect of extracts of Lantana hirta (at a concentration of 5.0 mg mL⁻¹) on the growth of Pichia clavispora, Colletotrichum gloeosporioides, and Alternaria ochroleuca.

The antifungal (as well as antimicrobial) capacity of extracts from plants of the Senecio genus has been evaluated and reported in interesting scientific studies. Galvez et al. [33] investigated the antifungal action of extracts from the aerial parts of Senecio nutans and Senecio viridis against toxigenic species of Fusarium and Aspergillus. The authors reported 27.6 wt.% of sabinense and 15.7 wt.% of α-phellandrene in S. nutans samples and 92.7 wt.% 9,10-dehydrofukinone in S. viridis extracts. The extracts presented a reasonable antifungal effect against Fusarium species (0.6 < minimal inhibitory concentration (MIC) < 1.2 mg mL⁻¹) and a slight action against Aspergillus species. The authors also described the synergy for S. viridis extracts between fungicidal action and food preservation properties in relation to the fungus F. verticillioides. Similarly, Singh et al. [34] evaluated the antifungal action of extracts from the roots of Senecio amplexicaulis Kunth. against the phytopathogenic fungi Sclerotium rolfsii, Macrophomina phaseolina, Rhizoctonia solani, Pythium debaryanum, and F. oxysporum. The extracts, obtained by hydrodistillation, were mainly composed of α-phellandrene (48.6 wt.%), o-cymene (16.8 wt.%), and β-ocimene (7.61 wt.%), and the authors reported interesting antifungal activities (157.0 < EC₅₀ < 199.3 μg mL⁻¹) against the five microorganisms indicated. Elhidar et al. [35] reported data concerning the chemical composition and activities of extracts obtained from the aerial parts of Senecio anteuphorbium, a weed commonly found in Morocco. Using a hydrodistillation process, discrete yields of 0.15% (v w⁻¹) were obtained, and the extracts were predominantly composed of γ-selinene (27.2 wt.%), cyperene (21.7 wt.%), γ- cadinene (11.4 wt.%), and α-cyperone (8.1 wt.%). Nevertheless, the S. anteuphorbium extracts showed interesting antimicrobial action against Candida strains, with minimal bactericidal/fungicidal values ranging between 2.05 and 4.10 mg mL⁻¹. The microorganism C. albicans (L4) was more sensitive to the action of the extract—with an inhibition diameter of 27 mm—than C. glabrata (L7) and C. parapsilosis (L18), which presented higher resistance, with inhibition diameters of 21 mm (including 6 mm of disc diameters) for each strain. Finally, Basaid et al. [36] evaluated the antifungal action of extracts from Senecio glaucus subsp. coronopifolius against Botrytis cinerea. The extracts from the stem, leaves, flowers, and roots of the plant were also obtained by hydrodistillation, and the main compounds detected were α-pinene (26.2 wt.%), myrcene (11.4 wt.%), and p-cymene (9.9 wt.%). Interestingly, the extracts showed an IP of 83% at 16 μL mL⁻¹, highlighting the potential of extracts from plants of the Senecio genus as antifungal bio-inputs.

Contextually, interesting research that evaluated the antimicrobial action of extracts obtained from plants of the genus Solanum is described in the literature. Ajaib et al. [37] reported data regarding the antimicrobial activity of extracts obtained from S. erianthum via the Soxhlet system (four solvents were tested: chloroform, petroleum ether, methanol, and water) against the fungi F. solani and Aspergillus niger. In terms of mass yield, the variation of the solvents had little impact on the results, with values between 4.6% (water) and 11.7% (methanol), and the extracts presented concentrations higher than 15 wt.% of alkaloids and than 12 wt.% of phenolic compounds. Concerning the antifungal activity, the authors reported the best results for the extracts from the process using methanol as the solvent against F. solani (zone of inhibition of 40 mm), whereas for A. niger, the maximum zone of inhibition was achieved with the aqueous extract (43 mm). Similarly, Senizza et al. [38] studied the phenolic and alkaloid profiles as well as the biological properties of S. erianthum and S. torvum extracts, obtained by Soxhlet extraction with methanol. The authors reported that for both plants, the stem bark was the main source of phenolic compounds (12.6 mg g⁻¹), while the leaves of S. erianthum were the main sources of alkaloids (2.1 mg g⁻¹). The antifungal action of the extracts was tested against A. fumigatus, A. ochraceus, A. niger, A. versicolor, Trichoderma viride, Penicillium funiculosum, P. ochrochloron, and P. verrucosum var. cyclopium. The highest inhibitory activity was reported against P. funiculosum (MIC < 0.3 mg mL⁻¹), while all the extracts from S. erianthum and S. torvum presented antifungal activity higher than the control samples. In another interesting study, Cabanillas et al. [39] investigated the antifungal activity of extracts obtained from the fruits of S. mammosum L. against Trichophyton mentagrophytes and Candida albicans. The extracts were obtained via maceration in methanol. Solamargine was the main glycoalkaloid found in the samples, a compound that, although still little explored for its antifungal actions, is known for its anti-cancer properties, as described by the authors. Regarding the antifungal action, the authors reported a MIC < 256 μg mL⁻¹ for both fungi evaluated, which is a discrete result, considering the values typically reported for extracts from this type of plant genus. Finally, Pinto et al. [40] reported data regarding the antifungal activity of extracts from the leaves and fruits of S. asperum against T. rubrum, T. mentagrophytes, Microsporum canis, and M. gypseum. The authors reported a strong antifungal action of the extracts against the genera Microsporum and Trichophyton (MIC < 0.24 μg mL⁻¹), a result that was associated with the presence of the glycoalkaloids solamargine and solasonine, recognized for their antimicrobial action.

It is important to emphasize that the fungi tested in the present research may demonstrate a high impact on agriculture management. Gibberella is one of the main fungal diseases in several grain crops caused by F. graminearum [41], against which, the most applied control method is based on the use of synthetic fungicides such as carbendazim. This agrochemical, besides being highly toxic, is also frequently inactive because of the fungus resistance to it [42]. Contextually, S. sclerotiorum, causing white mold in a wide range of hosts, can mainly attack crops such as beans, soybeans, and other vegetables [43]. Alves et al. [44] highlighted the importance of biological control for the management of this fungus, since resistant cultivars already exist.

The compounds usually identified in the extracts justify their antifungal potential [8,9]. Cytidine was described as responsible for the antifungal activity against A. niger and F. culmorum [45]. Walters et al. [46] reported that octadecenoic acid is a powerful antifungal agent against Crinipellis pernicosa and Pythium ultimum. Mannofuranoside [47], propanetriol [48,49], octadecane [50], farnesol [51,52,53], 2-propenoic acid [54], and pyrethroids [55] were also identified in the extracts and possess antifungal activity. Nevertheless, the mechanisms of action by which botanical products act still require further exploration, as the extracts contain a mixture of bioactive compounds, and thus, their allelopathic activity is often attributed, rather than to one single compound, to various compounds that act in synergy [56,57].

3.2. Herbicidal Activity in Pre-Emergence Tests

Table 3. Inhibition of C. sativus seed germination by extracts of S. brasiliensis and S. viarum.

GI (%) 1
	S. brasiliensis			S. viarum
	Flowers	Leaves	Stalks	Fruits	Roots
C. sativus	100 ± 0.14 aA	100 ± 0.17 aA	100 ± <0.01 aA	100 ± 0.11 aA	100 ± 0.15 aA

¹ Different letters in the same line indicate that the means differed significantly by the Tukey test (p ≤ 0.05); lowercase letters indicate “S. brasiliensis”, and capital letters indicate “S. viarum”.

presents the results of the germination test with different matrices on seeds of C. sativus, which is considered an indicative plant with allelopathic activity [58,59]. The use of this indicator plant made it possible to evaluate whether the extracts of S. brasiliensis and S. viarum have allelopathic activity, that is, whether they are capable of releasing compounds that would affect the germination and growth of other plants. If C. sativus seeds show inhibition of germination in response to bioherbicide application, this suggests that the examined product has allelopathic potential. Appropriately, the data reported in Table 3 are promising, since a substantial bioherbicidal effect was observed for all matrices. All matrices extracted from both substrates demonstrated 100% of germination inhibition, with no significant difference between the samples, as can be verified more clearly in Figure 2.

The data presented in this research clearly indicate that extracts from S. brasiliensis and S. viarum have a high allelopathic effect on seed germination. These results may be associated with the action of compounds such as 1,8-diazabicyclo[5.4.0]undec-7-ene and 2-propenoic acid, which have herbicide effects, as reported by Cao et al. [60] and Fraga et al. [54]. Nonetheless, the synergistic or antagonistic interaction of the compounds identified by Confortin et al. [8,9] should also be relevant due to their interesting bioactivities. In this respect, soalsodine was described with high toxicity [61,62]; quinic acid was reported to have anti-inflammatory potential [49,63]; celidoniol, has antibacterial, anti-inflammatory, and pesticidal action [64,65,66,67]; and integerrimine and senecionine are considered pyrrolizidine alkaloids [68]. However, the mode of action of allelochemicals, including the alkaloid compounds highlighted in this study, remains poorly comprehended. These secondary metabolites are absorbed by the plant seeds, causing damage to the cell membrane, DNA, mitosis, and amylase activity, as well as initiating other biochemical processes that could delay or inhibit seed germination [69]. Although this pioneer study demonstrates the fungicidal and herbicidal action of extracts from S. brasiliensis and S. viarum, it is suggested that further studies should be performed to evaluate distinct concentrations of the extracts, their toxicity to human health/environment, and the purification of the included compounds, to better understand their activities.

To date, no research evaluating the pre-emergence effects of extracts from S. viarum and S. brasiliensis has been published. Nonetheless, distinct authors demonstrated the phytotoxic effect of plant extracts on seed germination [20,21,22,70]. In an interesting research, Scavo et al. [71] reported a GI of up to 80% when testing aqueous extracts of leaves from Cynara cardunculus L. on Mediterranean weed species. Similarly, Scavo et al. [72] evaluated the application of extracts from Stellaria media and Amaranthus arvensis in the inhibition of germination of A. retroflexus and Portulaca oleracea, reporting a GI of 100%. Kaab et al. [73], when testing plant extracts of C. cardunculus and Artemisia herba-alba (5 g L⁻¹), verified a phytotoxic effect on the growth of seedlings of Silybum marianum, with GI ranging between 80.9 and 100%.

The potential of extracts from plants of the genera Senecio and Solanum to act as agricultural bio-inputs has been reported in different studies. Interestingly, Macedo et al. [3] evaluated the pesticide action of S. brasiliensis on Drosophila melanogaster larvae. Different concentrations of the extracts were considered (from 0.01 to 1.00 mg mL⁻¹, mixed in agar medium), and the authors observed a substantial reduction in the rate of larval hatching at 1.00 mg mL⁻¹. After 20 days of exposure, the authors reported that 28 flies hatched from 50 eggs in the control group, while for samples exposed to 1.00 mg mL⁻¹ of extract, only 1 fly hatched from 50 eggs, indicating a 96.4% decrease in the hatching rate. Similarly, Basaid et al. [36] verified the nematicidal and acaricidal activity of an extract of S. glaucus subsp. coronopifolius on second-stage juveniles (J2) as well as the inhibition of the hatching of eggs of Meloidogyne javanica and Tetranychus urticae Koch. Interesting results were observed, where the authors reported 95% immobility of J2 and 92% inhibition of egg hatching using 16,000 ppm of the extract. In the case of mites, leaf immersion tests revealed 100% mortality in adult T. urticae, with 24% repellency after exposure to the extract at a concentration of 80 wt.%. Regarding extracts from plants of the Solanum genus, Ahmad et al. [74] evaluated the phytotoxic activity of S. surrattense extracts against Lemna minor L., an aquatic monocotyledonous plant that is extremely sensitive to bioactive compounds. Using 20 mg mL⁻¹ of an extract obtained via methanolic maceration, the authors reported a GI of 46.7%. Finally, Balah and Razek [75] reported data regarding the allelopathic potential of extracts from S. elaeagnifolium Cav., known as sliver nightshade, a weed species commonly found in Egyptian arable fields. The extracts obtained from the leaves of the plant by hydrodistillation were tested against a nematode suspension containing 100 freshly hatched juveniles of Meloidogyne incognita as well as on seeds of typical weeds (Convolvulus arvensis L., Polypogon monspeliensis L., Desfontainia minor, and Phalaris minor). The authors described that the use of 100 mg mL⁻¹ of the extracts was capable of causing mortality in 98.0% (J2) of the nematodes considered. Regarding the herbicidal effect, the S. elaeagnifolium extracts were able to powerfully suppress the growth of C. arvensis seeds and delaying the development of other weeds. The GI activities varied between 17.6 and 84.3%, according to the extract concentration used (400 and 2000 μg mL⁻¹). Accordingly, the research described reinforces the potential of plant extracts from the Senecio and Solanum genera as bio-inputs for agricultural management.

4. Conclusions

The results presented in this research demonstrated the antifungal and herbicidal power of extracts obtained by UAE from different weed matrices of the species S. brasiliensis and S. viarum. The samples extracted from the leaves of S. brasiliensis and roots of S. viarum returned the best results in relation to the inhibition of the fungi F. graminearum and S. sclerotiorum. Contextually, all matrices presented an excellent GI of 100% regarding the inhibition of germination of C. sativus seeds, a result that can be associated with the action of the bioactive compounds present in these matrices. In this panorama, it is suggested that knowledge of the presence of allelopathic compounds in the extracts to be applied as agricultural bio-inputs plays a crucial role in this area of research. Although additional investigations focusing on evaluating different extract concentrations and toxicity to human health and the environment, as well as compound purification is necessary to consolidate the convenience of an increase in production scale, the results reported indicate that the extracts of both weeds can be valuable when considered as an alternative option for organic agricultural management.