This treatment in the lab mimics the soil conditions in climatically suitable regions for broomrape such as Mediterranean non-irrigated agrosystems where the onset of warm and wet season coincides with the growth of juvenile stages of many annual crops (Lpez-Granados and Garca-Torres, 1996; Grenz and Sauerborn, 2007). Bacterial inhibition of Orobanche aegyptiaca and Orobanche cernua radical elongation. Though, the effect of L-methionine on internal crop resistance was not studied and requires further investigation. Weed Res. Broomrape seed bank remains viable in the soil for many years until germination is triggered by the coincidence of several physical and chemical factors that are indicative of environmental conditions for successful seedling establishment: i.e., the nearby growth of a host plant in a physiological stage susceptible for broomrape invasion and subsequent parasitic reproductive growth (Linke and Saxena, 1991; Lpez-Granados and Garca-Torres, 1996, 1999). J. Agric. 12, 722865. Strigolactone analogs derived from ketones using a working model for germination stimulants as a blueprint. Intercropping with cereals reduces infection by Orobanche crenata in legumes. Ann. This approach is based on the selection of naturally occurring mutants that overproduce and excrete an enhanced amount of specific amino acid with broomrape inhibition properties on seed germination and radicle growth (Vurro et al., 2006; Sands and Pilgeram, 2009). 19, 753758. Abbasher A. Hanson is part of a team of UC researchers enlisted by the processing tomato sector to work on a plan to contain the damage caused by branched broomrape, should it become established enough that the California Department of Food and Agriculture zero-tolerance quarantine strategy is replaced by management programs. Bot. Careful selection of the non-host component in the intercrop is, however, required as some plant species can act as non-host facilitators and therefore increase the severity of broomrape infection in the host component (Gibot-Leclerc et al., 2013). Rev. and transmitted securely. Like most seeds, broomrape seeds are resistant to rapid microbial degradation due to phenols located in its testa (Cezard, 1973). Therefore, it may be possible to achieve broomrape control by fooling the parasite with the delivering to the soil of synthetic analogs of the original host-derived germination-inducing factors such as strigolactones (Johnson et al., 1976). If left uncontrolled during one or a few seasons, broomrape weeds build a hardly destructible seed bank in agricultural soils that further renovates at a rate of millions of seeds per ha each year a susceptible crop is infested. Curr. Germinating seeds of the root parasite Orobanche aegyptiaca Pers. J. Appl. Processing tomato growers are struggling to contain a potentially devastating parasitic weed that had not been seen since growers waged a successful eradication campaign four decades ago. Bot. Euphytica 186, 897905. Few days after host vascular connection, the part of the broomrape seedling that remains outside the host root develops into a storage organ called tubercle. In addition long lived seed banks under physiological dormancy ensure that germination will occur when a suitable host in its correct stage of development is present nearby (Rubiales et al., 2009b). 72, 564574. In those cases, broomrape displays a pathogenic nature promoting disease in the crop mainly through negative effects on the crop photosynthetic machinery and hormonal balance (Stewart and Press, 1990; Mauromicale et al., 2008). doi: 10.1080/09583150903340544, Barker, E. R., Press, M. C., Scholes, J. D., and Quick, W. P. (1996). (2007). with Phytomyza orobanchia, a review. Differential response of pea (Pisum sativum) to Orobanche crenata, Orobanche foetida and Phelipanche aegyptiaca. A., Charnikhova, T., Fernandez, I., Bouwmeester, H., and Pozo, M. J. Nitrate reductase is not detectable (Lee and Stewart, 1978) and activity of glutamine synthetase is very low (McNally et al., 1983). Barry M. Goldwater Range (BMGR), West Cultural Affiliation Study. 37, 3751. Original article from AgAlert, California Farm Bureau Federation.). In order to achieve such synchrony they evolved mechanisms that release seed from dormancy triggering germination upon detection of specific molecules contained in host root exudates (Vaucher, 1823). Effective broomrape control should target the underground mechanisms of crop parasitism in order to meet both the short-term productivity expectations of the farmer and reduction of soil bank in the long run (Figure 1). Once broomrape germination has occurred, chemicals that reduce the growth of broomrape radicle reduce the chances of reaching the host and therefore parasitism. doi: 10.1146/annurev.py.19.090181.001235, Kebreab, E., and Murdoch, A. J. 133, 637642. Biol. Evaluation of the pathogenicity of microorganisms isolated from Egyptian broomrape (Orobanche aegyptiaca) in Israel. Jan 08, 2016. Soyasapogenol B and trans-22-dehydrocamposterol from common vetch (Vicia sativa L.) root exudates stimulate broomrape seed germination. This is a crop phyto trial, and so far, so good, Fatino said as he looked over tomato plots in test fields on the UC Davis campus that had been treated with very low rates of a number of weed killers. A member of the tropical Silky Flycatcher family, males are a shiny black and females a charcoal grey. High osmotic potential in roots and drop in amino acid levels in the phloem has been reported in tolerant varieties of faba bean in response to broomrape parasitism. In addition it promotes the development of a layer of papillae at the radicle apex in the absence of host contact, morphology that resembles the attachment organ (Joel and Losner-Goshen, 1994; Cimmino et al., 2015). However, it is a long-term strategy due to the long viability of seed bank (Rubiales et al., 2009b), which requires at least a nine-course rotation in order to prevent broomrape seed bank increases (Grenz et al., 2005). 60, 295306. Role of the sucrose synthase encoding PrSus1 gene in the development of the parasitic plant Phelipanche ramosa L. (Pomel). In general, parasitized crops suffer from reductions in total biomass at the greatest expense to the reproductive tissue (Barker et al., 1996; Manschadi et al., 1996; Lins et al., 2007). 6, 11511166. Weed Sci. The host range of broomrape, in addition to tomato, covers a number of economically important rotational crops in the Central Valley: safflower, sunflower, carrot, bell pepper, several Brassica species, lettuce, several bean crops, melon, potato, olive and many common weeds, according to Bagley. These plants are best known by their straw-yellow stems, which are completely free of chlorophyll and have blue, white, or yellow dragon-like flowers. Inter-cropping with berseem clover (Trifolium alexandrinum) reduces infection by Orobanche crenata in legumes. and other fungi as biological control agents of broomrape (Orobanche ramosa). Fernndez-Aparicio, M., Soto, M. J., Rubiales, D., Ocampo, J. Seed conditioning and its role in Orobanche seed germination: inhibition by paclobutrazol, in Progress in Orobanche Research. Phytochemistry 72, 624634. doi: 10.1093/pcp/pcr031, Nandula, V. K., Foster, J. G., and Foy, C. L. (2000). Responsiveness of Orobanche ramosa L. seeds to GR24 as related to temperature, oxygen availability and water potential during preconditioning and subsequent germination. Seed respiration patterns during conditioning indicate a strong activation of metabolism. The economic importance of the phytoparasites Orobanche and Striga, in Proceedings of the Fifth Symposium on Parasitic Weeds, Nairobi, eds J. K. Ransom, L. J. Musselman, A. D. Worsham, and C. Parker (Nairobi: CIMMYT), 137143. Imidazolinone-tolerant crops: history, current status and future. They are attempting to learn if a timely application of an herbicide at a rate high enough to stunt the broomrape, but low enough to spare the tomatoes, can be an effective strategy to minimize crop losses. Solarization, a physical control method for weeds and parasitic plants (Orobanche spp.) 61, 246257. Foy, C. L., Jain, R., and Jacobsohn, R. (1989). control. doi: 10.1614/WS-D-11-00113.1. Dormancy and germination of Orobanche seeds in relation to control methods, in Proceedings of a Workshop in Wageningen: Biology and Control of Orobanche, ed. Dor, E., and Hershenhorn, J. Weed Sci. 45, 467476. 63, 53115322. Appl. doi: 10.1002/ps.1740, Rubiales, D., Fernndez-Aparicio, M., Wegmann, K., and Joel, D. (2009b). 45, 379387. 31, 2730. These connections are probably developed from simultaneous differentiation of adjacent host and parasite cells to xylem elements (Drr, 1997). Haustorium 53, 13. doi: 10.1111/j.1366-9516.2005.00179.x, Parker, C. (2009). Pest Manag. Plant Dis. Paris: Mmoires du Museum dHistoire Naturelle, 261273. A., and Rubiales, D. (2008b). Instead, broomrapes are in current state of intensification and spread due to lack of broomrape-specific control programs, unconscious introduction to new areas and may be decline of herbicide use and global warming to a lesser degree. GA acts positively on germination in dormant non-parasitic species by counteracting ABA (Seo et al., 2009). (2008). hellofresh stock concentrate packets. The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. A Comprehensive Approach to Evaluate Durum Wheat-Faba Bean Mixed Crop Performance. Bot. (2002). Expression of sarcotoxin IA gene via a root-specific tob promoter enhanced host resistance against parasitic weeds in tomato plants. Gain of host sensitivity in broomrape seeds at the end of the conditioning phase is mediated by demethylation of PrCYP707A1 promoter. Weed Sci. control in pea (Pisum sativum L.) by foliar applications of benzothiadiazole (BTH). Control of Egyptian Broomrape in Processing Tomato: A Summary of 20 Years of Research and Successful Implementation. Appl. Corrections? This approach would inhibit parasitism by killing the young seedling before it attaches to the host root. doi: 10.1111/nph.12692, Logan, D., and Stewart, G. R. (1995). doi: 10.1111/j.1365-3180.2009.00739.x, Hershenhorn, J., Goldwasser, Y., Plakhine, D., Lavan, Y., Blumenfeld, T., Bucsbaum, H., et al. doi: 10.1614/WS-04-088R1, Gozzo, F. (2003). Figure 2. How Striga parasitizes its host: a TEM and SEM study. doi: 10.1046/j.1365-3040.1999.00462.x, Hiraoka, Y., Ueda, H., and Sugimoto, Y. The Broomrape takes its food, nutrients, and water from the roots of the Bursage which weakens the Bursage. doi: 10.1006/anbo.1998.0847, Toh, S., Kamiya, Y., Kawakami, N., Nambara, E., McCourt, P., and Tsuchiya, Y. (2015). 41, 127151. Synthetic analogs of growth regulators can be successfully used to reduce parasitism by hampering the synchronization of the parasitic seed bank with the growth of the host. A., and Garca-Garrido, J. M. (2009c). Although hard seed coat has been described as dormancy mechanism in newly formed broomrape seeds (Lpez-Granados and Garca-Torres, 1996), water uptake and imbibition are performed quickly by mature seeds through the micropyle without the need of scarification (Bar-Nun and Mayer, 1993; Joel et al., 2012). Jain, R., and Foy, C. L. (1992). Lins, R. D., Colquhoun, J. The moths lay their eggs in the flowers. S. J. Ter Borg (Wageningen: LH/VPO), 2534. 62, 1048510492. 50, 69556958. Biol. 22, 937947. Simulation of integrated control strategies for Orobanche spp. Colonization of field pea roots by arbuscular mycorrhizal fungi reduces Orobanche and Phelipanche species seed germination. Phosphorous and nitrogen have been described to down regulate strigolactones exudation in some crop species (Yoneyama et al., 2007a,b, 2012). This is a short and delicate stage where the parasite either connects with the host or dies due to nutrient exhaustion. Successful reduction of broomrape parasitism in the current crop is obtained by intercropping host species with inhibitory species of cereals, fenugreek, or berseem clover (Fernndez-Aparicio et al., 2007, 2008b, 2010a). Direct application of strigolactones to the soil has been the subject of intense research. Characterization of resistance in chickpea to crenate broomrape (Orobanche crenata). doi: 10.1051/agro:2001167. B., and Mallory-Smith, C. A. Abbes, Z., Kharrat, M., Pouvreau, J. Parker, C., and Riches, C. R. (1993). TABLE 1. In addition, the biological similarity between host and parasite characterizing broomrape-crop interactions is higher than in other plant pathosystems, which complicates the development of selective methods to control broomrape, without harmful effect in the crop from which it is feeding (Eizenberg et al., 2006; Hearne, 2009; Yoder and Scholes, 2010; Prez-Vich et al., 2013). Broomrape (Orobanche cumana Wallr.) Pesta granule trials with Aspergillus alliaceus for the biocontrol of Orobanche spp. Such target-site resistance is also available in other broomrape-susceptible crops but remains to be tested and registered to control broomrape. 171, 501523. This is maintained by accumulation of solutes mainly potassium at higher concentrations than in the corresponding host tissues (Abbes et al., 2009). When they are applied in vitro to seeds of P. ramosa and O. minor, they bypass the effect of germination-inducing factors, promoting broomrape germination in absence of host or any germination stimulant (Cala et al., 2015). Figure 1. Suttle, J. C. (1983). The broomrape plant is small, from 10-60 cm tall depending on species. Crop Prot. Host plant resistance to parasitic weeds; recent progress and bottlenecks. The strigolactone story. Isr. Orobanche crenata in UK- an update. doi: 10.1111/j.1365-3180.1989.tb01310.x, Schneeweiss, G. M. (2007). The host reproductive sinks compete earlier and stronger against the parasitic sink and in consequence less nutritive resources are allocated to the parasite (Manschadi et al., 1996). There are not figures based on rigorous data for the total area affected by broomrape weeds (Parker, 2009). 49(Suppl. Inhibition of Orobanche crenata seed germination and radicle growth by allelochemicals identified in cereals. Ann. Weed Technol. doi: 10.1002/ps.1732. Joel, D. M., Back, A., Kleifeld, Y., and Gepstein, S. (1991). 65, 478491. Syst. List of Inert Pesticide Ingredients List 4b. On the contrary, weedy broomrape species are usually generalists attacking annual crops (Schneeweiss, 2007). This parasitic weed, unable to produce its own chlorophyll, survives only by attaching to the roots of a host plant, often with severe consequences. Omissions? Agric. Among the reviewed strategies are those aimed (1) to reduce broomrape seed bank viability, such as fumigation, herbigation, solarization and use of broomrape-specific pathogens; (2) diversion strategies to reduce the broomrape ability to timely detect the host such as those based on promotion of suicidal germination, on introduction of allelochemical interference, or on down-regulating host exudation of germination-inducing factors; (3) strategies to inhibit the capacity of the broomrape seedling to penetrate the crop and connect with the vascular system, such as biotic or abiotic inhibition of broomrape radicle growth and crop resistance to broomrape penetration either natural, genetically engineered or elicited by biotic- or abiotic-resistance-inducing agents; and (4) strategies acting once broomrape seedling has bridged its vascular system with that of the host, aimed to impede or to endure the parasitic sink such as those based on the delivery of herbicides via haustoria, use of resistant or tolerant varieties and implementation of cultural practices improving crop competitiveness. Therefore, decisions on the date of sowing has to be well-adjusted in order to balance the loss of productivity due to shorter growing period with gain of productivity due to reduced parasitism. A role for IAA in the infection of Arabidopsis thaliana by Orobanche aegyptiaca. Revisiting strategies for reducing the seedbank of Orobanche and Phelipanche spp. doi: 10.1006/anbo.1998.0629, Johnson, A. W., Rosebery, G., and Parker, C. (1976). doi: 10.1111/j.1365-3180.2009.00742.x, Rubiales, D., Fernandez-Aparicio, M., and Rodriguez, M. J. Plant. In the fields I am aware of, the crop was destroyed, the field disked under and methyl bromide applied. (1996). 52, 699715. doi: 10.1016/S0044-328X(83)80047-6. Sci. Phelipanche ramosa (L.) Pomel (branched broomrape) is a holoparasitic plant that reproduces on crops and also on weeds, which contributes to increase the parasite seed bank in fields. doi: 10.1016/S0031-9422(00)90779-9, Bar-Nun, N., and Mayer, A. M. (2002). Sci. (2010). Nature 435, 824827. Depending on the genetic background of the resistant host, the intrusive cells of broomrape seedling can be stopped at three different levels in their way of penetration through the root layers to achieve connection with the host vascular system. 4, 123152. Food Chem. Haustorium 65, 56. However, the overall productivity of the host-parasite system is also reduced due to the shorter growing period being detrimental for crop yield. Matvienko, M., Wojtowicz, A., Wrobel, R., Jamison, D., Goldwasser, Y., and Yoder, J. I. doi: 10.1093/molbev/msu343, Yoder, J. I., and Scholes, J. D. (2010). 38, 343349. doi: 10.1016/j.biocontrol.2005.09.017. 65, 453459. Edits and additions by Ann Filmer, Department of Plant Sciences, UC Davis; August 14, 2019.