Incorporating arugula and black radish into the soil and using black polyethylene as alternative control methods for field dodder in eggplant cultivation

Abstract

Background  Field dodder is a parasitic plant that continues to pose a significant challenge to both agricultural systems and natural ecosystems.

Objective  This experiment sought to evaluate some control methods for field dodder, assess their impact on eggplant growth, and analyze isothiocyanate content in arugula and black radish through GC-MS.

Methods  The experiment evaluated some control methods for managing field dodder, including arugula and black radish as cover crops, with and without mulch, and mulch alone. Two controls were used: one with and one without a field dodder. The key measurements included the number of infected plants, field dodder biomass, and control efficiency. Additionally, eggplant growth, yield, and losses were assessed, and GC-MS analysis identified isothiocyanate compounds in arugula and black radish.

Results  The control efficiency against field dodder in eggplant found to be 96% for arugula combined with mulch, 92% for black radish combined with mulch, 91% for mulch, 68% for arugula, and 63% for black radish. The arugula combined with mulch treatment had the highest positive impact on yield, producing 83.96 tons per hectare. Uncontrolled field dodder caused 82% yield loss, a 31% reduction in plant height, and a 59% decrease in fruit number. GC-MS analysis showed that arugula had the highest isothiocyanate content, comprising 36.23% of the total peak area of compounds detected in the sample, while black radish contained 29.20% isothiocyanates based on the same measure.

Conclusions  Arugula and black radish are alternative control methods for field dodder when incorporated into the soil to reduce the seed bank.

Eggplant; Field Dodder; Brassicaceae Plants; Isothiocyanates; Control Efficiency

1.Introduction

Eggplant (Solanum melongena L.), which belongs to the Solanaceae family, is considered one of the most important vegetables consumed by humans globally. The nutritional importance of eggplant is due to the fact that it is rich in vitamins and provides significant amounts of protein, fiber and carbohydrates (Ebrahimi et al., 2021). It is a source of essential minerals, as well as an important source of biologically active compounds such as antioxidants (Docimo et al., 2016; Butu, Rodino, 2019).

Eggplant, like all agricultural crops, is vulnerable to challenges resulting from various pests, including weeds. It was reported that the loss in eggplant yield reached 92.52% when weeds were left not controlled (Almhemed, Ustuner, 2022). Parasitic weeds are a major concern to eggplant farmers as they can cause yield losses that may reach 80% depending on the type of parasitic weed and the infestation severity (Aly, 2007; Zare, Donmez, 2013; Ustuner, 2018). Field dodder (Cuscuta campestris Yunck.) is considered one of the most destructive parasitic weeds due to its broad host range (Dawson et al., 1994; Nadler-Hassar, Rubin, 2003). It was reported that the yield losses caused by field dodder to some cultivated crops such as eggplant, tomato, potato, and pepper varies between 50 and 90% (Nadler-Hassar, Rubin, 2003; Lanini, Kogan, 2005; Lian et al., 2006). In Iraq, the yield loss in the Barcelona hybrid eggplant variety reached to 27.01% as a result of the damage caused by field dodder (Al-Gburi et al., 2019).

Field dodder is a parasitic weed that is difficult to control using traditional methods due to its close association with host plants. Additionally, its seeds are encased in a tough shell and exhibit prolonged dormancy, allowing them to remain viable in the soil for up to 30 years (Jayasinghe et al., 2004; Mishra, 2009). Many previous studies indicated the possibility of using the allelopathic effect of some plants to control weeds (Teasdale, Mohler, 2000; Bilalis et al., 2003; Younis et al., 2012; Aslam et al., 2017). For example, aqueous extract of stinkwort (Dittrichia graveolens L.) at a concentration of 10% reduced the germination rate of field dodder seeds by 76.2% under laboratory conditions (Almhemed et al., 2021). Many previous studies have reported that brassicaceae plants, especially those belonging to the Brassica genus, have allelopathic effects. These plants contain isothiocyanates, which are active compounds resulting from the hydrolysis of glucosinolates (Uremis et al., 2009; Jabran et al., 2015; Cipollini, 2016). It was reported that black polyethylene used as mulch achieved a control efficiency of 87.42% against weeds, including field dodder in eggplant (Almhemed, Ustuner, 2022).

This experiment evaluated some control methods for field dodder. The control methods employed in the experiment included the use of arugula and black radish as cover crops, both with and without black plastic mulch, as well as black plastic mulch alone. Additionally, the experiment included two control plots: control 1 (which was free of field dodder) and Control 2 (which included field dodder). Determine how they affect field dodder growth, and to understand the effect of field dodder on some morphological and productive characteristics of eggplant. As well, the study aimed to determine the isothiocyanate content of arugula and black radish plants using gas chromatography-mass spectrometry (GC-MS).

2.Material and Methods

This experiment was implemented at the trial area of the East Mediterranean Transitional Zone Agricultural Research Institute in Kahramanmaras, Turkey (37.53564°N, 36.91800°E) during the years 2020 and 2021.

2.1 Soil characteristics and climate pattern

Soil analysis was performed by collecting samples from eight randomly selected points within the experimental area at a depth of 0–30 cm. The samples were subsequently analyzed at the laboratory of Kahramanmaras Sutcu Imam University, Center for University and Industry Collaboration (USKIM) (Table 1).

Table 1
Soil properties of the trial area

Parameter	Analysis results value	Analysis method
Saturation (%)	52.80	TS 8333
pH	7.36	TS 8332
Total salt (%)	0.15	TS 8334
Lime (%)	15.22	TS 8335 ISO 10693
Organic substances (%)	3.49	TS 8336
K (mg/kg)	231.70	Olsen method
P (mg/kg)	54.19	Olsen method

Utilizing meteorological records obtained from the Kahramanmaras Province Meteorological Station during the two years encompassing the duration of the experiment, it was ascertained that July and August were the warmest months, whereas January and February were the coldest. Additionally, the month of January had the most substantial levels of precipitation, while the months of June, July, August, and September recorded notably less precipitation levels (Figure 1).

Figure 1
Temperature, humidity, and precipitation in Kahramanmaras province for 2020 and 2021

2.2 Experiment design and treatments

A randomized complete block design (RCBD) with three replications was used. Each block consisted of 7 treatments; arugula (0.72 kg/m² dry weight) and black radish (1.01 kg/m² dry weight) as cover crops, arugula (0.72 kg/m² dry weight) and black radish (1.01 kg/m² dry weight) as cover crops covered with black polyethylene mulch, and black polyethylene mulch with a thickness of 100 microns. In addition, the experiment included two control plots: control 1 (free of field dodder) and control 2 (with field dodder), where all the field dodder plants were removed manually from control 1 whenever they appeared and control 2 was left to grow field dodder without any intervention. The experimental plot dimension was 10 m² (2×5 m), with 1 m between the plots, 2 m between blocks, and a 3 m buffer zone surrounding the entire experiment.

2.3 Experiment implementation methodology

Arugula (Eruca vesicaria subsps. Sativa Mill.) and black radish (Raphanus sativus L. var. niger J. Kern) plants were cultivated as cover crops in the experimental plots allocated to each one according to the experiment design. Arugula (Istanbul rokasi variety) and black radish (Siyah inci variety) seeds were sown on 10 Feb 2020 and on 11 Feb 2021. Agricultural practices (fertilization, irrigation, and pest prevention) were provided in accordance with the Directorate of Agriculture recommendations in Kahramanmaras province. These cover crops were left in the field until the flowering stage then were incorporated into the soil. Before incorporating plants into the soil, samples were taken from an area of 1 m2 for each plant species. The samples included the entire plant, were dried in the laboratory to determine dry biomass that was incor porated into the soil for each plant species. The cover crops were incorporated into the soil to a depth of 20 cm using a tractor equipped with a disc plow. In addition, samples of arugula and black radish were prepared for GC-MS analysis to determine the content of isothiocyanate compounds (ITCs).

The plots were infested with field dodder. Despite this, field dodder seeds were added to the soil at a rate of 2 g/m². The dormancy of field dodder seeds was broken by exposing them to concentrated sulfuric acid (98%) for 5 minutes, then rinsing the seeds with running water for 10 minutes (Almhemed et al., 2020). After incorporating the cover crops into the soil and plowing the field land, the black polyethylene mulch was used on the plots allocated to it and for the cover crops according to the experiment design. Eggplant seedlings of Adana variety (S. melongena var. esculentum) were cultivated on 11 May 2020 and on 12 May 2021, with row spacing of 70 cm and plant spacing of 40 cm. The field was irrigated on a weekly basis, fertilizers were applied, and pest prevention services were performed according to the guidelines of the Agriculture Directorate in the study area. All weed species were removed from the experimental plots manually, and the field dodder was left to grow except for the control plots that were free of field dodder.

2.4 Main study components and measurements

At the end of the experiment, the number of infected plants per square meter and the number of infected branches for each plant were calculated. In order to calculate the percentage of infected branches, the following formula was used:

$\text{Infected branches percentage}\left(\%\right)=\left[\right(x-y\left)/x\right]\times 100$

Where, x: the total number of eggplant branches per plant, y: the number of infected branches per plant.

At the end of the experiment, field dodder plants were collected from 1m². This process was performed for all treatments and for each replication. The samples were placed in nylon bags and transported to the laboratory, where the biomass were calculated (at 0.01g accuracy). The samples were left to dry at room temperature (25±2 °C), then the dry biomass weights were calculated.

The control efficiency was calculated based on the effectiveness of each method in reducing the dry biomass weight of field dodder using the formula proposed by Abbott (1925):

$CE\%=\left[\right(WNC-WNT\left)/WNC\right]\times 100$

Where, CE: is the control efficiency; WNC: is the dry biomass weight of the field dodder in the control 2; WNT: is the dry biomass weight of the field dodder in the treatment x.

At the end of the eggplant harvest season, 10 plants were randomly selected from each experimental plot, and the average plant height was calculated. To calculate the reduction in plant height due to field dodder infection, the following formula was used:

$\text{The decrease in eggplant height}=[1-(\mathrm{Lx}/L0\left)\right]\times 100$

Where, Lx: is the eggplant height in the treatment x, L0: is the eggplant height in the control 2.

From the same random sample 10 plants, the number of branches per plant was calculated.

At the beginning of the eggplant flowering season, 10 plants were randomly selected, and the number of flowers was recorded before each harvest for all treatments and for each replication, thus obtaining the cumulative total number of flowers per plant. At the same time, the number of fruits for each plant was recorded with each harvesting process, and thus the cumulative number of fruits for each plant was obtained. In order to calculate the rate of reduction in the number of eggplant fruits due to field dodder infection, the following formula was used:

$\begin{array}{cc}& \text{The reduction in the number of eggplant fruits =}\\ & [1-(\mathrm{Nx}/\mathrm{NO}\left)\right]\times 100\end{array}$

Where, Nx: is the number of eggplant fruits in the treatment x, N0: the number of eggplant fruits in the control 2.

The eggplant yield was calculated by aggregating the yields from all harvesting activities within a 1 m² area for each replication in each treatment. Following this, the yield was converted into tons per hectare. To evaluate the impact of field dodder on eggplant yield, the yield loss was determined by comparing the yield of each treatment with that of the control 2 using the formula below:

$\text{Eggplant yield loss rate}=[1-(\mathrm{Yx}/\mathrm{YO}\left)\right]\times 100$

Where, Yx: Yield in x treatment, Y0: Yield in the control 2.

The brassicaceae plants were sampled at the flowering stage. Arugula and black radish samples were prepared for GC-MS analysis in the laboratory of the Plant Protection Department at Kahramanmaras Sutcu Imam University following the method outlined by Vaughn and Berhow (2005). Initially, 10 grams of plant powder were weighed. The powder samples underwent a 24-hour defatting process using hexane in a Soxhlet extractor. Subsequently, the plant powders were dried completely in a fume hood. The defatted powders were mixed with 30 ml of 0.05M potassium phosphate buffer in separate flasks. To each mixture, 50 ml of dichloromethane was added, and the flasks were agitated at 25°C and 200 rpm for 8 hours. Afterward, 10 g of NaCl and 10 g of Na2SO4 were added and thoroughly mixed. The mixtures were filtered with additional dichloromethane during the filtration process. The resulting dichloromethane solutions were transferred to labeled ampoules according to the respective plants for GC-MS analysis.

2.5 Data analysis

The experiment was repeated in 2020 and 2021. To assess the consistency of the data within each year, the Levene test was employed to determine the standard deviation of each mean relative to the overall mean. Following the Levene test results, a T-test assuming equal variances was conducted to compare the means between the two years. The T-test indicated that there were no significant differences in means between the two years, leading us to accept the hypothesis of similarity. Consequently, the average results of both years were utilized when discussing the findings. For data analysis, ANOVA procedure with MSTAT-C software (Version 2.10) was employed. To compare means the Least Significant Difference (LSD) test was applied at a significance level of 0.05.

3.Results

3.1 Field dodder density

All treatments led to a reduction in the number of branches infected with field dodder compared to control 2. No significant differences were observed between the arugula combined with mulch and black radish combined with mulch treatments on the one hand and between the black radish combined with mulch and mulch treatments on the other hand, as this three treatments significantly outperformed other treatments. The number of infected branches was 2.03, 2.30, and 2.77 per plant in these three treatments, respectively. The percentage of branches infected with field dodder reached 94% in control 2, and this percentage decreased to 63%, 48%, 9%, 7%, and 6% in the treatments of black radish, arugula, mulch, black radish combined with mulch, and arugula combined with mulch, respectively and there were no statistically significant differences between the arugula combined with mulch, black radish combined with mulch, and mulch treatments. Likewise, the number of infected plants per 1 m² was 3.7 out of 4 plants in control 2, and this number decreased to 2.6, 1.9, 0.3, 0.3, and 0.2 in the treatments of black radish, arugula, mulch, black radish combined with mulch, and arugula combined with mulch, respectively with no differences between the arugula combined with mulch, black radish combined with mulch, and mulch treatments (Table 2).

Table 2
The number of infested branches, percentage of infected branches, and the number of infected plants

Treatments	The number of infected branches/plant	Percentage of infected branches per plant (%)	The number of infected plants/m2
Arugula with mulch	2.03b	6b	0.2b
Black radish with mulch	2.30bc	7b	0.3b
Mulch	2.77c	9 b	0.3b
Arugula	12.43d	48c	1.9c
Black radish	13.87e	63d	2.6d
Control 1	0.00a	0a	0.0a
Control 2	13.10f	94e	3.7f
LSD 0.05	0.5367	2.900	0.1258

• Values followed by the same letter(s) in the same column are not significantly different from each other at 0.05 level of probability

3.2 Fresh and dry weights of field dodder biomass

All treatments led to a reduction in fresh biomass of field dodder compared to control 2. However, the percentage reduction in the fresh biomass of field dodder was 93%, 92%, 91%, 65%, and 62% for treatments arugula combined with mulch, black radish combined with mulch, mulch, arugula, and black radish, respectively. No differences were observed between the arugula combined with mulch and black radish combined with mulch treatments and between the black radish combined with mulch and M treatments. The effect of treatments on the fresh biomass was reflected in the dry biomass of field dodder, which were 37.8, 43.1, 47.5, 190.9, and 208.9 g/m2 for the treatments arugula combined with mulch, black radish combined with mulch, mulch, arugula, and black radish, respectively, while it was 542.3 g/m2 in the control 2 (Table 3).

Table 3
Field dodder fresh and dry biomass and percent of fresh biomass reduction

Treatments	Field dodder fresh biomass g/m2	Percent of fresh biomass reduction (%)	Field dodder dry biomass g/m2
Arugula with mulch	122.7b	93b	37.8b
Black radish with mulch	141.3b	92bc	43.1b
Mulch	150.8b	91c	47.5b
Arugula	625.2c	65d	190.9c
Black radish	676.3d	62e	208.9d
Control 1	0.0a	100a	0.0a
Control 2	1774.0e	0f	542.3e
LSD 0.05	38.04	1.193	9.725

• Values followed by the same letter(s) in the same column are not significantly different from each other at 0.05 level of probability

3.3 Eggplant height and number of branches

Eggplant height ranged between a minimum of 78.00 cm in control 2 and a maximum of 113.2 cm in control 1. No differences were observed between treatments of arugula combined with mulch, black radish combined with mulch and mulch, and between treatments of arugula and black radish, as plant heights recorded 105.5, 104.7, 104.1, 90.93, and 89.70 cm for these five treatments, respectively. Field dodder caused a 31% decrease in eggplant height based on control 2. This percentage decreased to 21%, 20%, 8%, 8%, and 7% for treatments black radish, arugula, mulch, black radish combined with mulch, and arugula combined with mulch, respectively.

No differences were observed between treatments arugula combined with mulch, black radish combined with mulch, and mulch in terms of the number of eggplant branches per plant, which ranged between 32.5 and 33.3. At the same time, the number of eggplant branches per plant was 26.1 and 21.9 for treatments arugula and black radish, respectively, and the differences between them were significant (Table 4).

Table 4
The eggplant height, the percentage decrease in the eggplant height, and the number of eggplant branches

Treatments	The eggplant height (cm)	The percentage decrease in the eggplant height (%)	The number of eggplant branches/plant
Arugula with mulch	105.5b	7b	33.3b
Black radish with mulch	104.7b	8b	32.5b
Mulch	104.1b	8b	32.7b
Arugula	90.93c	20c	26.1c
Black radish	89.70c	21c	21.9d
Control 1	113.2a	0a	37.8a
Control 2	78.00d	31d	13.9e
LSD 0.05	2.103	1.844	0.7049

• Values followed by the same letter(s) in the same column are not significantly different from each other at 0.05 level of probability

3.4 Eggplant flowers and fruits

The greatest number of flowers was recorded in control 1 at 34.0, and the least was 13.9 flowers per plant in control 2. The number of eggplant flowers was 28.1, 26.4, 25.7, 18.9, and 17.2 flowers per plant in the arugula combined with mulch, black radish combined with mulch, mulch, arugula, and black radish treatments, respectively.

The greatest number of eggplant fruit was recorded in control 1 at 32.0, and the least was 13.1 fruit per plant in control 2. The number of eggplant fruit was recorded 26.5, 25.3, 24.3, 17.9, and 16.3 fruit per plant in the arugula combined with mulch, black radish combined with mulch, mulch, arugula, and black radish treatments, respectively. Field dodder caused a 59% decrease in the number of eggplant fruits per plant based on control 2. This percentage decreased to 49%, 44%, 24%, 21%, and 17% for treatments black radish, arugula, mulch, black radish combined with mulch, and arugula combined with mulch, respectively (Table 5).

Table 5
The number of eggplant flowers, eggplant fruits, and the percentage decrease in the number of fruits

Treatments	The number of eggplant flowers/plant	The number of eggplant fruits/plant	The percentage decrease in the number of fruits per plant (%)
Arugula with mulch	28.1b	26.5b	17b
Black radish with mulch	26.4c	25.3c	21c
Mulch	25.7c	24.3c	24d
Arugula	18.9d	17.9d	44e
Black radish	17.2e	16.3e	49f
Control 1	34.0a	32.0a	0a
Control 2	13.9f	13.1f	59g
LSD 0.05	0.8532	0.9481	2.891

• Values followed by the same letter(s) in the same column are not significantly different from each other at 0.05 level of probability

3.5 Efficiency of control methods against field dodder

The control method efficiency against the field dodder was 96%, 92%, 91%, 68%, and 63% for treatments arugula combined with mulch, black radish combined with mulch, mulch, arugula, and black radish, respectively. Significant differences were observed between all treatments (Table 6).

Table 6
Efficiency of control methods, eggplant yield, and yield loss caused by field dodder

Treatments	Efficiency of control methods (%)	Eggplant yield ton/ha	Eggplant yield loss caused by field dodder (%)
Arugula with mulch	96b	83.96b	20b
black radish with mulch	92c	82.1c	22c
Mulch	91d	80.36d	24d
Arugula	68e	44.9e	57e
Black radish	63f	32.42f	69f
Control 1	100a	105.4a	0a
Control 2	0g	18.81g	82g
LSD 0.05	1.196	0.1949	1.897

• Values followed by the same letter(s) in the same column are not significantly different from each other at 0.05 level of probability

3.6 Eggplant yield and yield loss caused by field dodder

The greatest eggplant yield was recorded in control 1 at 105.4, and the least was 18.81 tons/ha in control 2. Differences were observed between all treatments in terms of the eggplant yield, which recorded 83.96, 82.1, 80.36, 44.9, and 32.42 tons/ha in the arugula combined with mulch, black radish combined with mulch, mulch, arugula, and black radish treatments, respectively.

Field dodder caused an 82% loss in eggplant yield based on control 2. This percentage decreased to 69%, 57%, 24%, 22%, and 20% for treatments black radish, arugula, mulch, black radish combined with mulch, and arugula combined with mulch, respectively (Table 6).

3.7 Identification of ITCs in arugula and black radish

Four different isothiocyanate (ITC) compounds were detected in arugula, including Benzyl ITC, Phenethyl ITC, Sulforaphane, and 1-Naphthyl ITC. The cumulative ITC compounds constituted 36.23% of the total peak area of detected compounds in the sample, with 1-Naphthyl ITC being the most abundant, accounting for 13.76% of the total ITC compounds in the sample. In the case of black radish, five ITC compounds were found including Allyl ITC, Isobutyl ITC, Benzyl ITC, Raphasatin, and Phenethyl ITC. The collective ITC compounds comprised 29.20% of the total peak area of detected compounds in the sample, with Isobutyl ITC being the primary ITC compound, making up 10.28% of the total ITC compounds in the sample (Table 7).

Table 7
ITC compounds in arugula and black radish based on the GC-MS analysis

Brassicaceae plants	Isothiocyanate compounds	ITC percentage of the total peak area of detected compounds in the sample (%)
Arugula	Benzyl ITC	7.12
	Phenethyl ITC	4.32
	Sulforaphane	11.03
	1-Naphthyl ITC	13.76
	Total	36.23
Black radish	Allyl ITC	4.62
	Isobutyl ITC	10.28
	Benzyl ITC	7.52
	Raphasatin	3.24
	Phenethyl ITC	3.54
	Total	29.20

4.Discussion

According to the results obtained from the control 2, the number of infected plants was 3.7 of 4 plants, and the percentage of infected eggplant branches was 94% per plant. The different control methods achieved varying levels of control efficiency against field dodder in eggplant when compared to the control 2; 96% in arugula combined with mulch, 92% in black radish combined with mulch, 91% in mulch, 68% in arugula, and 63% in black radish treatments.

Previous studies have demonstrated the effectiveness of mulch as control method against field dodder. In chickpea fields, mulching achieved a control efficiency of 93% (Shamse et al., 2013). Similarly, when black plastic mulch was employed in eggplant fields to control narrow and broad-leaf weeds as well as field dodder, control efficiency ranging from 85.33% to 87.42% (Almhemed, Ustuner, 2022). As well, the application of black plastic mulch led to an 89% to 98% reduction in parasitic weed infestation in tomato crops (Johnson et al., 2007). Additionally, studies have shown that using black plastic mulch against weeds can substantially decrease their dry biomass, with reductions of 95% to 98% (Rajablariani et al., 2012). Our findings found that black plastic mulch alone achieved a control efficiency of 91%. When cover crops were covered with black plastic mulch, the control efficiency ranged from 92% to 96%, aligning with findings from previous studies.

This study illustrates that the incorporation of arugula and black radish plants into soil infested with field dodder seeds leads to a reduction in the soil’s field dodder seed bank. Consequently, there is a decrease in the number of germinated field dodder seeds, as evidenced by a reduced dry biomass of field dodder per 1 m². When arugula and black radish plants were incorporated into the soil before cultivating eggplant, the resulting control ranged from 63% in the black radish treatment to 68% in the arugula treatment. These findings align with previous studies, such as Kalinova (2010), which reported a 72% reduction in parasite seed bank when brassicaceae plants were integrated into the soil. This effect of brassicaceae plants on field dodder is attributed to the hydrolysis products of glucosinolates (GLSs), particularly ITCs, which form in the presence of Fe2+ ions and an acidic pH. The concentration of GLSs in brassicaceae plants, particularly those in the Brassica family, has been documented in various studies (Motmainna et al., 2021; Weston et al., 2013; Petersen et al., 2001). Our study observed the ready formation of ITCs in a slightly acidic soil with a pH of 7.36, consistent with other research indicating that GLS hydrolysis under neutral conditions in the presence of Fe2+ ions and at an acidic pH typically results in ITC formation (Bones, Rossiter, 1996). ITCs are known for their high bioactivity against weeds, underscoring their potential as a natural herbicide (Martins et al., 2004).

According to the results obtained from the GC-MS analysis in this study, arugula exhibited the highest content of ITC compounds, representing 36.23% of the total peak area of detected compounds in the sample. Furthermore, arugula contained four of ITC compounds; Benzyl ITC, Phenethyl ITC, Sulforaphane, and 1-Naphthyl ITC. In arugula, 1-Naphthyl ITC emerged as the predominant compound accounting for 13.76% of the total ITC compounds in the sample. Previous studies have substantiated the existence of Phenethyl ITC in arugula, originating from the enzymatic hydrolysis of gluconasturtiin (Ioannides et al., 2010). Moreover, three earlier research endeavors have identified the presence of four distinct ITC compounds within arugula, specifically Phenethyl ITC, Allyl ITC, Iberin, and Sulforaphane (Villatoro-Pulido et al., 2013; Rodrigues et al., 2016). In sum, the outcomes of the present study exhibit partial concordance with previous research findings.

Based on the results of the GC-MS analysis of black radish samples, revealing that the collective percentage of ITC compounds amounted to 29.20% of the total peak area of detected compounds in the sample. Five ITC compounds were identified; Allyl ITC, Isobutyl ITC, Benzyl ITC, Raphasatin, and Phenethyl ITC. Notably, Isobutyl ITC emerged as the dominant ITC compound in black radish, constituting 10.28% of the total ITC compounds in the sample. These findings closely align with those reported in one of the previous studies, which detected five ITC compounds in black radish, comprising Tert-butyl ITC, 2-propenyl ITC, Benzyl ITC, 4-methylthio-3-butenyl ITC, and 2-phenylethyl ITC. The cumulative ITC content in that study amounted to 40.39%, with 4-methylthio-3-butenyl ITC being the most prominent constituent, constituting 19.32% of the overall ITC compounds (Elsekran et al., 2023). In our study, there is a partial concurrence with the outcomes of a preceding investigation that evaluated the allelopathic influence of six brassicaceae plant species, encompassing round white radish, garden radish, black radish, little radish, turnip, and rapeseed, on johnsongrass. This particular research reported that black radish exhibited higher concentrations of Benzyl ITC and Allyl ITC in comparison to the other plants under scrutiny (Uremis et al., 2009). Furthermore, another study indicated that black radish contains two ITC compounds, namely Raphasatin and Sulforaphane, findings that are partially congruent with our study, given that Raphasatin was among the ITC compounds identified in black radish samples (Castro-Torres et al., 2013).

While allelopathy holds promise as a natural method for managing field dodder, demonstrating its presence and effectiveness, particularly under field conditions, presents significant challenges. As Duke (2015) pointed out the influence of biotic and abiotic factors in the field such as soil microflora, temperature fluctuations, and water stress are difficult to replicate in laboratory settings, making it challenging to prove allelopathy. However, emerging techniques, such as gene knockout technologies, may offer more robust evidence of allelopathy in the future.

5.Conclusion

Based on the results obtained from this study, it appears that black plastic mulch as a control method is effective against field dodder. Also, using arugula and black radish as a cover crops before cultivating eggplant was also effective in controlling field dodder. In conclusion, the integration between these two control methods gave better control efficiency against the field dodder than if each method was used alone. As a result, brassicaceae plants such as arugula and black radish can be used as environmentally friendly control methods against field dodder and as an alternative to herbicides.

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• Funding
  This work was supported by Kahramanmaras Sutcu Imam University Scientific Research Unit (Project No: 2019/6-15 D).

Edited by

• Approved by:
  Editor in Chief: Carol Ann Mallory-Smith
  Associate Editor: Aldo Merotto Junior

Publication Dates

• Publication in this collection
  28 Apr 2025
• Date of issue
  2025

History

• Received
  20 Aug 2024
• Accepted
  28 Feb 2025