Ambrosia grayi as a new alien causal species in Israel: plant biology and chemical management.

BACKGROUND: Ambrosia grayi is a perennial weed native to northern Mexico, which can also be found in the Great Plains of the US. Outside the Americas, A. grayi has only been documented in Israel, where it is currently categorized as a casual species at advanced eradication stages. Here, we studied the plant biology and chemical weed management options of A. grayi. RESULTS: Only large achenes of A. grayi (~5% of all achenes) contain seeds; moreover, the viability of seeds extracted from large achenes was ~25%. Examination of plant anatomy revealed that underground vegetative segments show an anatomical structure of stems (rhizomes) with anomalous secondary growth. The optimal (night/day) temperature for the emergence of A. grayi rhizomes was 20/30 °C, and the emergence rate increased under elevated temperatures. Emergence may occur at different soil moisture content (25-60%); rhizomes were able to emerge even after 1 month of drought conditions (20%, 25% and 30%). Herbicide combinations, such as fluroxypyr + glufosinate, fluroxypyr + glyphosate, and glyphosate + saflufenacil + surfactant, were tested under quarantine conditions and showed high efficacy for the control of A. grayi. However, the efficiency of these treatments was highly correlated with plant growth stage. CONCLUSION: In Israel, the spread of A. grayi occurs mainly via rhizomes that can emerge under a wide range of temperatures and soil moisture conditions. Data regarding herbicide efficacy will aid in improving the eradication efforts taken by Israel's Plant Protection and Inspection Services. © 2024 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Solanum elaeagnifolium and S. rostratum as potential hosts of the tomato brown rugose fruit virus.

Invasive weeds cause significant crop yield and economic losses in agriculture. The highest indirect impact may be attributed to the role of invasive weeds as virus reservoirs within commercial growing areas. The new tobamovirus tomato brown rugose fruit virus (ToBRFV), first identified in the Middle East, overcame the Tm-22 resistance allele of cultivated tomato varieties and caused severe damage to crops. In this study, we determined the role of invasive weed species as potential hosts of ToBRFV and a mild strain of pepino mosaic virus (PepMV-IL). Of newly tested weed species, only the invasive species Solanum elaeagnifolium and S. rostratum, sap inoculated with ToBRFV, were susceptible to ToBRFV infection. S. rostratum was also susceptible to PepMV-IL infection. No phenotype was observed on ToBRFV-infected S. elaeagnifolium grown in the wild or following ToBRFV sap inoculation. S. rostratum plants inoculated with ToBRFV contained a high ToBRFV titer compared to ToBRFV-infected S. elaeagnifolium plants. Mixed infection with ToBRFV and PepMV-IL of S. rostratum plants, as well as S. nigrum plants (a known host of ToBRFV and PepMV), displayed synergism between the two viruses, manifested by increasing PepMV-IL levels. Additionally, when inoculated with either ToBRFV or PepMV-IL, disease symptoms were apparent in S. rostratum plants and the symptoms were exacerbated upon mixed infections with both viruses. In a bioassay, ToBRFV-inoculated S. elaeagnifolium, S. rostratum and S. nigrum plants infected tomato plants harboring the Tm-22 resistant allele with ToBRFV. The distribution and abundance of these Solanaceae species increase the risks of virus transmission between species.

Distinctive foliar features and volatile profiles in three Ambrosia species (Asteraceae).

MAIN CONCLUSION: Ambrosia species differ both in their trichome types and in metabolic profiles of leaf volatiles. The current study provides tools for easier taxonomic identification of ragweed species. The genus Ambrosia (Asteraceae) includes some of the most noxious allergenic invasive weeds in the world. Due to high polymorphism in this genus, identification of species is often difficult. This study focuses on microscopic investigation of foliar features and GC-MS identification of the main leaf volatile components of three Ambrosia species currently found in Israel-invasive species Ambrosia confertiflora and A. tenuifolia, and transient A. grayi. A. confertiflora and A. tenuifolia have three trichome types: non-glandular trichomes, capitate glandular trichomes and linear glandular trichomes. Their non-glandular trichomes and capitate trichomes have distinct structures and can serve as taxonomic characters. A. grayi (the least successful invader) has only very dense covering trichomes. All three Ambrosia species have secretory structures in their leaf midrib. A. confertiflora, the most problematic invasive plant in Israel, had a ten times higher volatiles content than the other two species. In A. confertiflora, the most abundant volatiles were chrysanthenone (25.5%), borneol (18%), germacrene D and (E)-caryophyllene (both around 12%). In A. tenuifolia, the most abundant volatiles were ß-myrcene (32.9%), (2E)-hexenal (13%) and 1,8-cineole (11.7%). In A. grayi, the most abundant volatiles were ß-myrcene (17.9%), germacrene D (17.8%) and limonene (14%). The three examined species have distinct trichome types and metabolic profiles. Non-glandular trichomes show structural diversification between species and are a good descriptive character. Considering the anthropocentric significance of this highly problematic genus, the current study provides tools for easier identification of ragweed species.

Effect of Herbicides on the Management of the Invasive Weed Solanum rostratum Dunal (Solanaceae).

Solanum rostratum Dunal is an invasive weed species that invaded Israel in the 1950s. The weed appears in several germination flashes, from early spring until late summer. Recently, an increase in its distribution range was observed, alongside the identification of new populations in the northern part of Israel. This study aimed to investigate the efficacy of herbicide application for the control of S. rostratum using two field populations originated from the Golan Heights and the Jezreel Valley. While minor differences in herbicide efficacy were recorded between populations, plant growth stage had a significant effect on herbicide response. Carfentrazone-ethyl was found to be highly effective in controlling plants at both early and late growth stages. Metribuzin, oxadiazon, oxyfluorfen and tembutrione showed reduced efficacy when applied at later growth stage (8-9 cm height), as compared to the application at an early growth stage (4-5 cm height). Tank mixes of oxadiazon and oxyfluorfen with different concentrations of surfactant improved later growth stage plant control. Taken together, our study highlights several herbicides that can improve weed control and may be used as chemical solutions alongside diversified crop rotation options. Thus, they may aid in preventing the spread and further buildup of S. rostratum field populations.

Subcritical water extraction as a circular economy approach to recover energy and agrochemicals from sewage sludge.

Global population growth is creating severe pressure on wastewater treatment plants, and specifically on sludge management. Meanwhile, the global challenge of achieving food-security requires the development of green pest control practices that maximize crop productivity. The hydrothermal technology, using subcritical water as the conversion media has been intensively studied, mostly for energy recovery purposes. Here, we focused on the aqueous phase by-product of this process and studied the subcritical water extraction of sewage sludge to recover valuable agrochemicals, with high potential of pre-emergent herbicidal activity. Full characterization of hydrothermal extracts from different reaction temperatures (200-300 °C) and times (30-120 min) highlighted the formation of pyrazine derivatives. Seed germination bioassays with three different species suggested a positive correlation between reaction temperature and extract herbicidal activity. Moreover, differences in seed viability and final root elongation between the tested crop (Trriticum aestivum) and weeds (Lapidium sativum and Amaranthus palmeri) may indicate the competitive abilities that can play a key role in weed management. Our results suggest that subcritical water can be applied as a green solvent for extracting a valuable agrochemical from sewage sludge and improving the circular economy for wastewater treatment.

Broomrape infestation in carrot (Daucus carota): Changes in carotenoid gene expression and carotenoid accumulation in the parasitic weed Phelipanche aegyptiaca and its host.

Carotenogenesis has been intensively studied in carrot roots, and transcriptional regulation is thought to be the major factor in carotenoid accumulation in these organs. However, little is known about the transcriptional regulation of carotenoid biosynthetic genes concerning carotenoid accumulation during infestation by the obligate parasite Phelipanche aegyptiaca. HPLC analysis revealed a decrease in carotenoid levels of the different carrot cultivars when parasitized by P. aegyptiaca. Besides, we isolated and analyzed P. aegyptiaca tubercles parasitizing the various carrot root cultivars and show that they accumulate different carotenoids compared to those in non-infested carrot roots. Expression analysis of PHYTOENE SYNTHASE (PSY1) and CAROTENOID ISOMERASE (CRTISO) as well as the strigolactone apocarotenoid biosynthetic genes DWARF27 (D27), CAROTENOID CLEAVAGE DIOXYGENASE 7 (CCD7) and CCD8 revealed that their transcript levels showed significant variation in P. aegyptiaca infested carrot roots. After parasite infestation, the expression of these genes was strongly reduced, as were the carotenoid levels and this was more pronounced in the uncommon non-orange varieties. We also analyzed the parasite genes encoding D27, CCD7 and CCD8 and show that they are expressed in tubercles. This raises important questions of whether the parasite produces its carotenoids and apocarotenoids including strigolactones and whether the latter might have a role in tubercle development.

Use of a visible reporter marker- myb-related gene in crop plants to minimize herbicide usage against weeds.

Weeds, a main threat to agricultural productivity worldwide, are mostly controlled by herbicides. To minimize herbicide usage by targeting only weedy areas, we developed a new methodology for robust weed detection that relies on manipulating the crop plant's leaf hue, without affecting crop fitness. We generated transgenic tobacco (Nicotiana tabacum Xanthi) lines overexpressing the anthocyanin pigment as a traceable marker that differentiates transgenes from the surrounding weeds at an early stage. Transformation with the anthocyanin VlmybA1-2 gene produced purple-colored leaves. Subsequent gene silencing with vector pTRV2:VlmybA1-2 significantly reduced anthocyanin pigments in tobacco leaves 40 days after agroinfiltration, with a concomitant reduction in VlmybA1-2 transcript levels. Purple hue faded gradually, and there were no fitness costs in terms of plant height or leaf number in the silenced vs. non-silenced tobacco transgenes. These results could lead to a new sustainable weed-control method that will alleviate weed-related ecological, agricultural and economic issues.

Enhanced Host-Parasite Resistance Based on Down-Regulation of Phelipanche aegyptiaca Target Genes Is Likely by Mobile Small RNA.

RNA silencing refers to diverse mechanisms that control gene expression at transcriptional and post-transcriptional levels which can also be used in parasitic pathogens of plants that Broomrapes (Orobanche/Phelipanche spp.) are holoparasitic plants that subsist on the roots of a variety of agricultural crops and cause severe negative effects on the yield and yield quality of those crops. Effective methods for controlling parasitic weeds are scarce, with only a few known cases of genetic resistance. In the current study, we suggest an improved strategy for the control of parasitic weeds based on trans-specific gene-silencing of three parasite genes at once. We used two strategies to express dsRNA containing selected sequences of three Phelipanche aegyptiaca genes PaACS, PaM6PR, and PaPrx1 (pma): transient expression using Tobacco rattle virus (TRV:pma) as a virus-induced gene-silencing vector and stable expression in transgenic tomato Solanum lycopersicum (Mill.) plants harboring a hairpin construct (pBINPLUS35:pma). siRNA-mediated transgene-silencing (20-24 nt) was detected in the host plants. Our results demonstrate that the quantities of PaACS and PaM6PR transcripts from P. aegyptiaca tubercles grown on transgenic tomato or on TRV-infected Nicotiana benthamiana plants were significantly reduced. However, only partial reductions in the quantity of PaPrx1 transcripts were observed in the parasite tubercles grown on tomato and on N. benthamiana plants. Concomitant with the suppression of the target genes, there were significant decreases in the number and weight of the parasite tubercles that grew on the host plants, in both the transient and the stable experimental systems. The results of the work carried out using both strategies point to the movement of mobile exogenous siRNA from the host to the parasite, leading to the impaired expression of essential parasite target genes.

Gene silencing of CCD7 and CCD8 in Phelipanche aegyptiaca by tobacco rattle virus system retarded the parasite development on the host.

Strigolactones are phytohormones that stimulate seed germination of parasitic plants including Phelipanche aegyptiaca. Strigolactones are derived from carotenoids via a pathway involving the carotenoid cleavage dioxygenases CCD7 and CCD8. We report here identification of PaCCD7 and PaCCD8 orthologous genes from P. aegyptiaca. Expression analysis of PaCCD7 and PaCCD8 genes showed significant variation in their transcript levels in seeds and tubercles of P. aegyptiaca at different developmental stages. These two parasitic PaCCD7 and PaCCD8 genes were silenced in P. aegyptiaca using a trans-silencing approach in Nicotiana benthamiana. The transient knock-down of PaCCD7 and PaCCD8 inhibited tubercle development and the infestation process in host plants. Our results suggest an important role of the strigolactone associated genes (PaCCD7 and PaCCD8) in the parasite life cycle.

Biological activity of natural phytoecdysteroids from Ajuga iva against the sweetpotato whitefly Bemisia tabaci and the persea mite Oligonychus perseae.

BACKGROUND: Ecdysteroids are steroid hormones that control moulting and govern several changes during metamorphoses in arthropods. The discovery of the same molecules (phytoecdysteroids) in several plant species displayed a wide array of rather beneficial agricultural impact. Many representatives of the genus Ajuga plants contain phytoecdysteroids with a 5ß-7-ene-6-one system exhibiting physiological activities in insects. RESULTS: By means of chromatographic (silica gel column, TLC) and LC-MS, two major ecdysteroids (20-hydroxyecdysone and cyasterone) have been isolated and identified from Israeli carpet bugle Ajuga iva (L.) Schreber (Lamiales: Lamiaceae) plants. Ajuga iva extract fractionated on the silica gel column yielded two fractions that showed high activity against the sweetpotato whitefly Bemisis tabaci and the persea mite Oligonychus perseae. A dose of 5 mg AI L(-1) of the purely identified A. iva ecdysterone significantly reduced fecundity, fertility and survival of these pests, while commercial 20-hydroxyecdysone at the same dose had lesser effects. CONCLUSION: The results demonstrate considerable efficacy of natural phytoecdysteroids against major agricultural pests, and suggests that these materials should be considered for potential development of friendly control agents.