Caffeic Acid, an Allelochemical in Artemisia argyi, Inhibits Weed Growth via Suppression of Mitogen-Activated Protein Kinase Signaling Pathway and the Biosynthesis of Gibberellin and Phytoalexin

Artemisia argyi is widely distributed in Asia, and it often becomes the dominant population in the field because of its strong ecological niche competitiveness. Allelochemicals secreted by plants are generally considered an important reason for their dominance in ecological competition. In this study, the allelochemicals in A. argyi were screened by a series of experiments and their mechanisms were explored via transcriptomics. First, the inhibitory effects of A. argyi on Echinochloa crusgalli, Setaria viridis, Portulaca oleracea and Amaranthus retroflexus were evaluated. Then, we carried out a qualitative and quantitative analysis of the chemical composition of the aqueous extract of A. argyi to screen for potential allelochemicals that can inhibit weed growth. Four potential allelochemicals were quantified: neochlorogenic acid (5-CQA), chlorogenic acid (3-CQA), cryptochlorogenic acid (4-CQA), and caffeic acid (CA). Coincidentally, their allelopathic effects on weeds seemed to be identical to their content, in the order CA>4−CQA>5−CQA>3-CQA. These findings suggested that CA might be the main allelopathic compound in the aqueous extract of A. argyi. Subsequently, the allelopathic effect and molecular mechanism of CA on S. viridis leaves were investigated. The physiological results showed that CA significantly induced reactive oxygen species (ROS) production, led to malondialdehyde (MDA) accumulation, and disrupted enzyme activities (POD, SOD, CAT) in S. viridis leaves. Moreover, transcriptome results revealed that CA inhibited S. viridis growth by downregulating multiple genes involved in gibberellin (GA) and phytoalexin biosynthesis and Mitogen-activated protein kinase (MAPK) signaling pathways. In addition, differentially expressed genes (DEGs) related to the biosynthesis and signaling pathways of phytohormones were verified by Quantitative Real-Time PCR (RT-qPCR). Taken together, this study may be the first to identify allelochemicals and explore their molecular mechanism about A. argyi. Importantly, the ecological advantages of A. argyi could be applied to ecological regulation and the development of botanical herbicides.

Allelopathic Effect of Aqueous Extracts of Stinkwort (Dittrichia graveolens L.) on Germination and Growth of Some Weed Species

The experiment was implemented by CRD design with three replications and lasted for 40 days, from 5 October until 15 November 2020. Four extract concentrations of D. graveolens 0, 2, 6, and 10% were used. The concentration of 0% was considered as control. The allelopathic effect has been studied on five weed species; Amaranthus retroflexus L., Portulaca oleracea L., Lolium multiflorum Lam., Sorghum halepense L., and Cuscuta campestris Yunck. The research also aimed to determine the effect of Stinkwort extract on the growth of tomato seedlings. All concentrations affected seed germination for all studied weeds. The concentration of 10% was more influential in growth-related indicators compared to other concentrations. The seeds of L. multiflorum and rhizomes of S. halepense were more tolerant to D. graveolens allelochemicals in germination rate than A. retroflexus, P. oleracea, and C. campestris. All concentrations led to a reduction in the weed heights and the wet and dry weights compared with the controls. The effect of the extract with various concentrations was catalytic for the growth of tomato seedlings, as the average height of tomato seedlings was in direct proportion to the concentration.

Allelopathic Effect of Aqueous Extracts of Stinkwort (Dittrichia graveolens L.) on Germination and Growth of Some Weed Species

The experiment was implemented by CRD design with three replications and lasted for 40 days, from 5 October until 15 November 2020. Four extract concentrations of D. graveolens 0, 2, 6, and 10% were used. The concentration of 0% was considered as control. The allelopathic effect has been studied on five weed species; Amaranthus retroflexus L., Portulaca oleracea L., Lolium multiflorum Lam., Sorghum halepense L., and Cuscuta campestris Yunck. The research also aimed to determine the effect of Stinkwort extract on the growth of tomato seedlings. All concentrations affected seed germination for all studied weeds. The concentration of 10% was more influential in growth-related indicators compared to other concentrations. The seeds of L. multiflorum and rhizomes of S. halepense were more tolerant to D. graveolens allelochemicals in germination rate than A. retroflexus, P. oleracea, and C. campestris. All concentrations led to a reduction in the weed heights and the wet and dry weights compared with the controls. The effect of the extract with various concentrations was catalytic for the growth of tomato seedlings, as the average height of tomato seedlings was in direct proportion to the concentration.

The Effect of the Timing of Manure Application in Combination with Mineral Fertilizers and Planting Density on the Weediness of Potato Plantings

Potatoes are one of the most responsive crops for grooming techniques since in the period from seedlings before closing rows are easily suppressed by weeds that take away nutrients, water, light from it. The factor that causes high harm to potatoes is weed. By absorbing a large number of nutrients and moisture from the soil, weeds inhibit the growth and development of plants, reducing their potential productivity. The purpose of the study was to establish the effect of the timing of the introduction of bedding manure in conjunction with mineral fertilizers and planting density on the weediness of potato plantings. Studies were provided to identify the impact of the timing of bedding manure together with mineral fertilizers and planting density for weed planting potatoes. Experiments were laid by the systematic method with a tiered arrangement of variants in the experiment with a 3-fold repetition. We used cattle manure on straw bedding for autumn-winter harvesting. The following types of fertilizers were used: ammonium nitrate, double superphosphate, potassium chloride. Determination of the amount and biomass of weeds in potato plantings was carried out in the flowering phase and before harvesting. The application of manure was accompanied by an increase in the number and weight of weeds. Annual weeds predominated in potato plantings: Amaranthus retroflexus L., 1753 and Amaranthus blitoides S. Watson, 1877, Chenopodium album L. Chenopodium album L., 1753, Setaria P. Beauv, 1812 and Setaria viridis (L.) P. Beauv, 1812, Echinochloa crus-galli (L.) BEAUV., 1812 and others, perennials included Cirsium arvense (L.) SCOP. 1772 and Sonchus arvensis L., 1753, (Elytrigia repens (L.) DESV. ex NEVSKI, 1933 and others. Planting density also has a definite effect on the development of weeds. When manure was applied in autumn under the plow, the number of weeds increased in comparison with other options, where only mineral fertilizers were applied. The application of manure over frozen plow and in winter over snow leads to a slight decrease (2.3-2.5 pcs/m2) of weeds. The greatest number of weeds is observed during the spring application of manure for plowing the fall plow. Nevertheless, studies aimed at clarifying the composition and structure of weediness, the number and weight of weeds in potato plantings are of great practical importance for local agricultural producers. These data should contribute to the development of an effective weed control system and high yields of potatoes in the region

Phytotoxic effects of essential oils from Nepeta glocephalata Rech.f. and N. ispahanica Boiss. on se-lected weed species

<p class="042abstractstekst">In the present study the bioherbicidal activity of essential oils hydrodistilled from <em>Nepeta glocephalata </em>Rech.f and <em>N</em>. <em>ispahanica</em> Boiss were investigated on four weed species (barnyard grass (<em>Echinochloa crus-galli</em> (L.) Beauv), redroot pigweed (<em>Amaranthus retroflexus </em>L.), lambsquarters (<em>Chenopodium album </em>L.) and canary grass (<em>Phalaris canariensis </em>L.)). A total of 37 components were identified from the essential oils of <em>N. glocephalata and N. ispahanica</em> constituting approximately 98.61 % and 96.1 % of the oils, respectively. In laboratory bioassay different concentrations (0, 1, 2, 4 and 8 μl ml^-1) of two <em>Nepeta </em>essential oils on germination, root and shoot length were studied. Results showed by increasing the concentration of oils, all studied traits of the weeds were decreased compared with control. In a glass house bioassay post-emergence application of <em>Nepeta</em> essential oils (1.25 %, 2.5 %, 5 % and 10 %, v/v) on 3-week-old weed plants caused visible injury (7-days after spray) ranging from chlorosis to necrosis of plant weeds. In foliar application under glasshouse conditions, both<em> Nepeta</em> essential oils reduced the seedling dry mass and concentrations of chlorophyll a chlorophyll b. The study concludes that <em>Nepeta</em> essential oils have phytotoxic effects and could be used as bioherbicides but the selectivity of these compounds should be considered also.</p>

Weed Control in Sunflower (Helianthus annuus L.) with Soil-applied Herbicides Affected by a Prolonged and Limited rainfall

The field trials were carried out in the Bitola and Titov Veles regions during two sunflower growing seasons (2018 and 2019) to estimate a weed control in sunflower with the soil‒applied herbicides, influenced by a prolonged and limited rainfall. Polygonum aviculare L., Solanum nigrum L., Chenopodium album L., Amaranthus retroflexus L., Portulaca oleracea L., and Echinochloa crus-galli (L.) P. Beauv. were the most dominant weeds in both regions. The efficacy of PRE-em herbicides varied among the weed species, treatments, periods of efficacy estimation, regions, and years. The overall performances of the PRE-em herbicides were correlated with weather and soil conditions. The inconsistent weather patterns between the two years of the study likely influenced the weed control. All weeds in 2018 in the Bitola region were poorly controlled (<77% and <62%, 28 and 56 days after application, respectively) due to a higher amount of rainfall (57 mm) during the 10 days of the 1st decade after herbicide application. The herbicide efficacy has only produced a marginal control of weeds in 2019 in the Titov Veles region as well (<68% and <59%, 28 and 56 days after application, respectively), due to the drought conditions observed in this region in early spring and in mid-spring. A PREem application followed by a heavy rainfall resulted in a sunflower injury in the Bitola region in 2018, ranging from 9 to 28% across the PRE-em treatments seven days after emergence. The injuries by oxyfluorfen and dimethenamid-P were more serious (24 and 28%, respectively). The sunflower achene yields for each treatment in both regions generally reflected an overall weed control and crop injury.

Efficiency of herbicide ACRIS (dimethenamid-P + terbuthylazine) on sunflower

Trials with a herbicide Acris, SE (280 g/l of dimethenamid-P + 250 g/l of terbuthylazine) were carried out in the Astrakhan, Krasnodar and Altai regions. The aim of this work is studying biological and economic efficiency of pre-emergence treatment with the combined herbicide Acris, SE on sunflower. The treatment with the herbicide Acris, SE (2.0–3.0 l/ha) made it possible to prevent many annual dicotyledonous weeds: Chenopodium album, Amaranthus retroflexus, Fagopyrum tataricum, Abutilon theophrastii and Solanum nigrum. Ambrosia artemisiifolia, found in the Krasnodar region, is less sensitive to this herbicide. The herbicide Acris, SE was highly effective in suppressing annual monocotyledonous weeds: Echinochloa crusgalli and Panicum miliaceum. Efficiency of the herbicide ACRIS was at the level of the standard Gardo Gold, and at the maximum application rate (3.0 l/ha) exceeded the standard one. Pre-emergence soil treatment with the herbicide Acris, SE did not have a negative effect on the germination of sunflower. Significant increase of sunflower yield was noted in all regions of trials. The most significant values were observed on varieties Flagman and R 453 in the Krasnodar region (8.7–9.2 and 7.0–7.5 quintal/ha, respectively). The lowest yields of sunflower in untreated control (10.2 and 11.0 quintal/ha) were observed in the Altai region, but the relative increase in yield in variants with the herbicide Acris, SE application was maximum (from 29.1 to 67.6% in relation to yields in untreated control). In the Astrakhan region, application rates of the herbicide Acris, SE of 2.5 and 3.0 l/ha were characterized by statistical significance (increases up to 2.5 and 3.2 quintal/ha, respectively).

LIPIDS 0F SEEDS MEDICAGO SATIVA, AMARANTHUS CRUENTUS AND AMARANTHUS RETROFLEXUS, GROWING IN GEORGIA

There is studied chemical composition of neutral and polar lipids of the seeds of: Medicago sativa, Amaranlhus cmentus and Amaranthus retroflexus growing in Georgia. The composition of free fatty acids was determined with help GLC and HPLC. There is determined class and fatty acidal composition of them, qualitative and quantitative determination of phospholipids is carried. There is elaborated various medicinal forms from Medicago sativat.

The Joint Action of Some Broadleaf Herbicides on Potato (Solanum tuberosum L.) Weeds and Photosynthetic Performance of Potato

Herbicide mixtures are a modern weed management practice as they reduce herbicide application. This study aimes to evaluate the effect of metribuzin, halosulfuron and flumioxazin applied individually and as mixtures (metribuzin:halosulfuron and metribuzin:flumioxazin) on Chenopodium album, Amaranthus retroflexus, and potatoes on biomass and chlorophyll-a fluorescence in 21 experiments. The individual herbicide experimental design was a randomized completely block design with seven doses and three replications. The factorial experiments were performed on the basis of randomized completely block design in three replications for binary mixture experiments. Flumioxazin was very potent in controlling C. album, A. retroflexus, and injured potatoes with a 50% effective dose (ED50) of 1.21, 0.54, and 12.23 g ai·ha−1, respectively. Both mixtures of metribuzin:halosulfuron and metribuzin:flumioxazin generally showed an antagonistic effect on both weeds and potato in 12 independent experiments. Metribuzin, halosulfuron, and flumioxazin significantly decreased photosystem II activity by decreasing the maximum quantum efficiency (Fv/Fm). The metribuzin:halosulfuron mixtures almost followed the Additive Dose Model for Fv/Fm, whilst there was an antagonistic effect for the metribuzin:flumioxazin that was closely related to biomass. The results indicated that mixtures were generally antagonistic, and the endpoint choice is pivotal when assessing the joint action of mixtures.