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1.
Phelipanche ramosa (Branched broomrape) is an obligate root parasitic plant that is a major pest of oilseed rape in France. Knowledge on seed viability and dormancy under field conditions is crucial to understand how to control P. ramosa, but is as yet unknown. Our study aimed to quantify these processes with a 2‐year seed burial experiment. Two genetically distinct populations of P. ramosa were studied, collected on winter oilseed rape (population O) and hemp (population H). Seed mortality was very low in both populations (4–7% per year). Although obligate parasitic seeds are assumed to germinate only after exposure to germination stimulants from host root exudates, a high proportion of population H seeds germinated spontaneously (up to 90%). Seeds of both populations displayed seasonal dormancy, with timing and magnitude depending on the population. Dormancy was low at the time each native host crop is usually sown. Populations differed in germination dynamics, with seeds of population H germinating faster. The difference in behaviour that we observed between populations is consistent with reported adaptations of pathovars to their preferred hosts. The results indicate that the parasitic plant management requires targeting at the populations concerned. For example, delayed sowing is more promising against population O than against population H.  相似文献   

2.
Salinity and Orobanche or Phelipanche spp. infection are important crop stress factors in agricultural areas. In this study, we investigated the effect of salt stress on Phelipanche ramosa seed germination and its attachment onto Arabidopsis thaliana roots. We also evaluated the effect of both stresses on the expression of genes regulated by abiotic and biotic stresses. According to our results, high concentration of NaCl delayed P. ramosa seed germination in the presence of a strigolactone analogue (GR24). A similar pattern was observed in the presence of A. thaliana plants. Furthermore, we found that salt‐treated A. thaliana seedlings were more sensitive to P. ramosa attachment compared with the untreated plants, indicating that there was a positive correlation between salt sensitivity and the ability of P. ramosa to infect A. thaliana plants. At the molecular level, a synergystic effect of both salt and P. ramosa stresses was observed on the cold‐regulated (COR) gene expression profile of treated A. thaliana seedlings. Our data clarify the interaction between parasitic plants and their hosts under abiotic stress conditions.  相似文献   

3.
Various Orobanche species are weedy and cause severe reduction in the yields of many important crops. The seeds of these parasitic weeds may remain dormant in the soil for many years until germination is stimulated by the release of a chemical signal from a host plant. In order to determine the effects of fenugreek root exudate on the induction of Orobanche crenata, Orobanche ramosa and Orobanche foetida seed germination, root exudate was collected from hydroponically grown fenugreek seedlings. Fractionation patterns obtained from column and thin layer chromatography of the fenugreek root exudate showed a set of metabolites differing in their polarity with stimulatory activity on Orobanche seed germination. The crude root exudate stimulated both O. ramosa and O. crenata seed germination to the same level caused by the synthetic germination stimulant GR24 at 10 mg L?1. It also stimulated O. foetida seed germination which did not respond to GR24. Active fractions of root exudate stimulated the germination of Orobanche species differentially.  相似文献   

4.
The root parasitic weeds Phelipanche ramosa (branched broomrape) and P. aegyptiaca have the widest host range among Orobanche and Phelipanche species. In Western Europe, P. ramosa attacks, with increasing aggressiveness, crops such as oilseed rape, tobacco, hemp, and tomato. The unique biology of root parasites, establishes a closed link with their host plant, thus reducing the possibility to successfully control them. Control measures include (a) physical processes (such as weeding, solarization, deep ploughing, burning off, flooding), (b) chemical (like soil fumigation, use of herbicides, germination stimulants) and (c) biological methods (e.g. resistant varieties, use of fungi and insects as antagonists, trap and catch crops). German tobacco growers rely mostly on the herbicide method. They apply glyphosate in very low concentrations, when the first tubercles are formed. Also a fungal antagonist against the parasitic weed on tobacco was found in Germany, but until now has not been developed into a commercial mycoherbicide. After hemp production lost its significance as a crop in Germany, tobacco remained as the main host for P. ramosa. In the past 10 years, branched broomrape has spread out and currently it can be found in areas where previously were free of it. Since the elimination of EU subsidies, some tobacco growers began to cultivate on their land parsley instead of tobacco. As a result, parsley has now been infected with P. ramosa. When used 10 years ago as catch crop, parsley had a rather small effect on branched broomrape. This potential danger, especially by other potential host plants, such as oilseed rape, tomato and potato or even weeds should not be underestimated. Spread and expansion of the host plant spectrum of branched broomrape in Germany might be reduced by the introduction of appropriate phytosanitary measures and improved information policies.  相似文献   

5.
Xanthomonas campestris pathovars are widely distributed throughout the globe and have a broad host range, causing severe economic losses in the food and ornamental crucifers markets. Using an approach based on multilocus sequence typing, phylogenetic diversity and population structure of a set of 75 Portuguese and other Xanthomonas campestris isolates from several cruciferous hosts were assessed. Although this population displayed a major clonal structure, neighbour‐net phylogenetic analysis highlighted the presence of recombinational events that may have driven the ecological specialization of X. campestris with different host ranges within the Brassicaceae family. A high level of genetic diversity within and among X. campestris pathovars was also revealed, through the establishment of 46 sequence types (STs). This approach provided a snapshot of the global X. campestris population structure in cruciferous host plants, correlating the existing pathovars with three distinct genetic lineages. Phylogenetic relationships between the founder genotype and remaining isolates that constitute the X. campestris pv. campestris population were further clarified using goeBURST algorithm. Identification of an intermediate link between X. campestris pv. campestris and X. campestris pv. raphani provided new insights into the mechanisms driving the differentiation of both pathovars. Wide geographic distribution of allelic variants suggests that evolution of X. campestris as a seedborne pathogen was not shaped by natural barriers. However, as Portuguese isolates encompass 26 unique STs and this country is an important centre of domestication of Brassica oleracea crops, a strong case is made for its role as a diversification reservoir, most probably through host–pathogen coevolution.  相似文献   

6.
Eighteen toxins produced byFusarium species were tested at different concentrations onOrobanche ramosa seeds to evaluate their effectiveness in inhibiting germination. Many of the toxins were active at the highest concentration used. Seven of them,viz. fusarenon X, nivalenol, deoxynivalenol, T-2 toxin, HT-2 toxin, diacetoxyscirpenol and neosolaniol, were highly active at 10μM, causing 100% inhibition of germination. Many of them were still active when assayed at a concentration ten times lower, with T-2, HT-2, nivalenol, neosolaniol and diacetoxyscirpenol still able to cause total inhibition; the last mentioned was very active also at 0.1μM, causing more than 90% inhibition. The results show that the use of toxic secondary metabolites could represent a useful alternative strategy in the management of parasitic weeds, by interfering with the induced germination process, and that fungal culture extracts could be an interesting source of new compounds acting as natural and original herbicides. http://www.phytoparasitica.org posting Sept. 18, 2002.  相似文献   

7.
Broomrapes (Orobanche spp.) are parasitic weeds that cause significant losses of crop yield. Experiments were conducted to investigate the seed response to the artificial germination stimulant GR24 in three species of Orobanche subjected to preconditioning under various temperatures, water potentials and with plant growth regulators. The highest germination percentages were observed in Orobanche ramosa, Orobanche aegyptiaca and Orobanche minor seeds conditioned at 18°C for 7 days followed by germination stimulation at 18°C. With the increase of the conditioning period (7, 14, 21 and 28 days), the germination percentage of O. ramosa and O. aegyptiaca progressively decreased. When conditioned at −2 MPa, the germination percentage was lower than at 0 and −1 MPa, especially at 13 and 28°C. Orobanche minor seeds could retain relatively high germination if conditioned at 18, 23 or 28°C, even after significantly extended conditioning periods (up to 84 days). GA3 (30–100 mg L−1), norflurazon and fluridone (10–100 mg L−1), and brassinolide (0.5–1.0 mg L−1) increased seed germination, while 0.01 mg L−1 uniconazole significantly reduced germination rates of all three Orobanche spp. The promotional effects of GA3 and norflurazon and the inhibitory effect of uniconazole were evident, even when they were treated for 3 days. Germination of Orobanche seeds was much lower when the unconditioned seeds were directly exposed to GR24 at 10−6 m . This early GR24-induced inhibition was however alleviated or even eliminated by the inclusion of GA3 or norflurazon (10–50 mg L−1) in the conditioning medium. On the contrary, the inclusion of uniconazole increased the inhibitory effect of GR24, particularly in the case of O. ramosa.  相似文献   

8.
Emex spinosa and Emex australis are invasive dicotyledonous weeds. The effects of various environmental factors on the germination of these weeds were investigated under laboratory and glasshouse conditions. Germination response of both species was lower at warmer temperature, and maximum germination was recorded at 20/12°C (day/night). Light stimulated germination in both species, but considerable germination also occurred under darkness. More than 80% of E. spinosa seeds germinated at pH between 6 and 9, whereas E. australis seeds germination was considerably decreased at pH 9. Emex spinosa was fairly tolerant to salinity as compared with E. australis and germination (21%) of E. spinosa occurred even at 200 mm NaCl. Both species were sensitive to osmotic stress, but E. spinosa tolerated more osmotic stress than E. australis. Temperature above 20/12°C (day/night) and low osmotic potential increased time to start germination and mean germination time (MGT), as well as decreased germination index (GI) of both species. Darkness resulted in increased MGT and decreased GI in both species when compared with 10 h photoperiod. Salt stress strongly increased time to obtain 50% germination and reduced GI of both species. In both species, an increasing burial depth decreased emergence percentage and emergence index and increased time to start emergence, although some seed emerged even at 10 cm burial depth. It was concluded that both species can germinate over a wide range of environmental conditions. However, E. australis was more sensitive under adverse environmental conditions compared with E. spinosa. This information on germination ecology may aid in developing tools and strategies for management.  相似文献   

9.
Resistant annual and herbaceous perennial plant species were identified as key hosts which allow Phytophthora cinnamomi to persist on severely impacted black gravel sites within the Eucalyptus marginata (jarrah) forest of southwest Western Australia. Of the annual and herbaceous perennial plant species present on black gravel sites, 15 out of 19 species were found to be hosts of P. cinnamomi, and 10 of these were symptomless hosts. In particular, the native annual Trachymene pilosa and the two native herbaceous perennials Stylidium diuroides and Chamaescilla corymbosa were commonly found to be hosts of the pathogen. Species from 12 new genera including three from new families (Crassulaceae, Droseraceae and Primulaceae) are reported for the first time to be hosts of P. cinnamomi. The species from which P. cinnamomi was recovered were the native species: Chamaescilla corymbosa, Crassula closiana, Drosera erythrorhiza, Hydrocotyle callicarpa, Levenhookia pusilla, Paracaleana nigrita, Podotheca angustifolia, Pterochaeta paniculata, Rytidosperma caespitosum, Siloxerus multiflorus, Stylidium diuroides and Trachymene pilosa, and the introduced annual weeds Hypochaeris glabra, Lysimachia arvensis and Pentameris airoides.  相似文献   

10.
庞智黎  席真 《农药学学报》2017,19(3):273-281
独脚金属（Striga spp.）及列当属（Orobanche spp.和Phelipanchce spp.）杂草是世界范围内对农业生产危害严重的根寄生杂草,主要依靠寄生茄科、豆科、谷类等作物获得水分和营养。根寄生杂草种子只有在合适的萌发诱导物（如独脚金内酯）刺激下才能萌发。文章从根寄生杂草的分类、分布及危害,种子萌发剂类型及适用范围,种子萌发剂独脚金内酯的生物合成及分离鉴定,根寄生杂草种子萌发诱导剂的作用机制以及种子萌发过程中激素间协同调控作用等方面进行了综述,并展望了种子萌发剂设计筛选及其在根寄生杂草化学防控中的潜在应用前景。  相似文献   

11.
Some species of the genusOrobanche are among the most devastating parasitic weeds, causing extensive damage in agricultural fields. Considering the difficult control due to seed longevity in the soil, small seed size, high fecundity and a subterranean phase that allows them to parasitize the host before they emerge and become evident, the development of diagnostic markers is highly recommended. In our study we identified potential molecular diagnostic markers from the plastid genome in order to distinguish among the most importantOrobanche species attacking crops in Andalusia, the southern region of the Iberian Peninsula. The study has consideredO. crenata, O ramosa andO. cumana causing serious losses in legumes, solanaceous crops and sunflower fields, respectively, andO. minor that, although abundant in Andalusia, has to our knowledge not yet been found parasitizing agricultural hosts. We amplified a non-coding region from the plastid genome, studied sequence differences among the amplified fragments and digested those of the same length with selected restriction enzymes. Here, we propose a molecular protocol to distinguish the main parasitic plants in crop fields of southern Spain. Different applications such as identification ofOrobanche seeds in soil or crop seed lots are discussed in order to offer right crop recommendations or to prevent new infestation of parasite-free fields. Recommendations for further development of these diagnostic markers are also considered. http://www.phytoparasitica.org posting Jan. 15, 2007.  相似文献   

12.
Strigolactones, plant‐secreted underground signalling molecules, play an important role in agricultural ecosystems, because they mediate the interaction of crops with symbiotic AM fungi and parasitic weeds like Striga hermonthica. Cereal host plants secret these signalling molecules particularly under nutrient‐deficient conditions and especially when phosphate (P) is limiting. The objective of the present study was to see the potential of P seed priming for S. hermonthica management in cereals in relation to strigolactone production. It has been demonstrated that P fertiliser application down‐regulates the production of these signalling molecules in the rhizosphere, which results in lower S. hermonthica infection of cereals. The laboratory study showed maximum production of strigolactones from dry and water‐soaked seeds, while seed soaking in P solution reduced their production. Similarly, maximum S. hermonthica infection was observed under control treatments with dry sowing or water soaking, while P seed soaking decreased S. hermonthica germination, emergence and dry biomass in all cereal crops. Our study shows that P seed priming resulted in lower exudation of strigolactones, which induced less S. hermonthica seeds germination and hence may lead to lower S. hermonthica infection. P‐based seed priming could prove to be an effective and affordable strategy to reduce S. hermonthica infection in cereals. Further research for practical field application is needed.  相似文献   

13.
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14.
Parasitic weeds of the genera Striga and Orobanche spp. cause severe yield losses in agriculture, especially in developing countries and the Mediterranean. Seeds of these weeds germinate by a chemical signal exuded by the roots of host plants. The radicle thus produced attaches to the root of the host plant, which can then supply nutrients to the parasite. There is an urgent need to control these weeds to ensure better agricultural production. The naturally occurring chemical signals are strigolactones (SLs), e.g. strigol and orobanchol. One option to control these weeds involves the use of SLs as suicidal germination agents, where germination takes place in the absence of a host. Owing to the lack of nutrients, the germinated seeds will die. The structure of natural SLs is too complex to allow multigram synthesis. Therefore, SL analogues are developed for this purpose. Examples are GR24 and Nijmegen‐1. In this paper, the SL analogues Nijmegen‐1 and Nijmegen‐1 Me were applied in the field as suicidal germination agents. Both SL analogues were formulated using an appropriate EC‐approved emulsifier (polyoxyethylene sorbitol hexaoleate) and applied to tobacco (Nicotiana tabacum L.) fields infested by Orobanche ramosa L. (hemp broomrape), following a strict protocol. Four out of 12 trials showed a reduction in broomrape of ≥95%, two trials were negative, two showed a moderate result, one was unclear and in three cases there was no Orobanche problem in the year of the trials. The trial plots were ca 2000 m2; half of that area was treated with stimulant emulsion, the other half was not treated. The optimal amount of stimulant was 6.25 g ha?1. A preconditioning prior to the treatment was a prerequisite for a successful trial. In conclusion, the suicidal germination approach to reducing O. ramosa in tobacco fields using formulated SL analogues was successful. Two other options for weed control are discussed: deactivation of stimulants prior to action and biocontrol by Fusarium oxysporum. © 2016 Society of Chemical Industry  相似文献   

15.
Damage caused by Orobanchaceae root parasitic weeds is a substantial agricultural problem for global food security. Many studies have been conducted to establish practical methods of control, but efforts are still required for successful management. Seed germination of root parasitic weeds requires host-derived germination stimulants including strigolactones (SLs). Studies on SLs have revealed that a butenolide ring is the essential moiety for SL activity as a germination stimulant. Interestingly, recent studies have revealed that butenolide hormones regulate the biosynthesis of secondary metabolites and mediate communication in actinomycete bacteria. Because of the structural similarity between SLs and the bacterial butenolides, we evaluated the germination stimulatory activity of butenolides isolated from Streptomyces albus J1074 on root parasitic weeds. These butenolides were found to specifically induce seed germination of Orobanche minor. Our findings contribute to understanding the molecular mechanisms of germination stimulant perception and to the development of a method for their biological control.  相似文献   

16.
Striga asiatica and Rhamphicarpa fistulosa are important parasitic weeds of rain‐fed rice, partly distributed in similar regions in sub‐Saharan Africa (SSA). It is not evident whether their ecologies are mutually exclusive or partially overlapping. In Kyela, a rice‐growing area in south Tanzania where both parasites are present, three transects of about 3 km each across the upland–lowland continuum were surveyed in June 2012 and 2013. A total of 36 fields were categorised according to their position on the upland–lowland continuum as High, Middle or Low and soil samples were taken. In each field, parasitic and non‐parasitic weed species were identified in three quadrats. Additionally, in two pot experiments with four different moisture levels ranging from wilting point to saturation, influence of soil moisture on emergence and growth of parasites was investigated. Striga asiatica was observed in higher lying drier fields, while R. fistulosa was observed in the lower lying wetter fields. Furthermore, non‐parasitic weed species that were exclusive to S. asiatica‐infested fields are adapted to open well‐drained soils, while species that were exclusive to R. fistulosa fields are typical for wet soils. The experiments confirmed that S. asiatica is favoured by free‐draining soils and R. fistulosa by waterlogged soils. These results imply that changes in climate, specifically moisture regimes, will be crucial for future prevalence of these parasitic weeds. The non‐overlapping ecological range between their habitats suggests that their distribution and associated problems might remain separate. Thus, management strategies can be focused independently on either species.  相似文献   

17.
We developed 20 microsatellite markers to genotype over 100 populations of the parasitic weed Phelipanche ramosa, which covers a wide host crop and geographic range. A representative core collection of 15 populations was also used in cross‐infestation assays to study host preference during germination, attachment and shoot formation. We observed low genetic differentiation within most of the populations, but high genetic differentiation between populations partitioned into 3 genetic groups with different host preferences and geographic distributions. Genetic group 1 is detected exclusively in western France and on various host crops, notably winter oilseed rape (WOSR) and not hemp. Cross‐infection assays confirmed its incompatibility with hemp and showed its preference for WOSR and tobacco in terms of germination and attachment success. The group 2 populations share a large geographic distribution in France and Europe, low germination success with WOSR and high germination success, attachment success and shoot formation with hemp, tobacco or tomato. The subclades 2a and 2b include most of the French populations in hemp crops in eastern France and in tobacco fields in several European countries respectively. The genetic analyses revealed the potential of the three groups to increase their geographic range in the future. Intermediate genetic groups showed higher intrapopulation diversity and represent potential stocks for new host race emergence. Those findings argue in favour of the existence of host races in P. ramosa and should be considered for appropriate management strategies, notably in breeding programmes for resistance against this parasitic weed.  相似文献   

18.
Broomrape (Orobanche ramosa L.) is a common root parasite of solanaceous, leguminous and other crops grown in the semi-arid regions of the world. The seeds germinate when root exudates from host plants are released in their immediate vicinity (Lindley, 1853; Koch, 1887; Chabrolin, 1934). Brown et al. (1951a) reported that non-host plants, such as flax (Linum usitatissimum L.) may stimulate Orobanche seed germination without being parasitized. The stimulating properties of flax exudate were studied by Brown et al. (1951b). They reported that the stimulant was unstable in alkaline solutions, but moderately stable in weakly acidic media, which may indicate the presence of an acidic (lactone) grouping. Nash & Wilhelm (1960) reported that gibberellic acid in agar media stimulated O. ramosa seed germination. Abu- Shakra, Miah & Saghir (1970) found that pre-treatment of 0. ramosa seeds with 100 ppm of gibberellic acid followed by incubation on a flax-root diffusate agar medium gave a high (81·7%) germination. The purpose of this study was to collect root exudates from three species of plants cultured under three experimental systems, namely (a) germ-free, (b) glasshouse (non-sterile), and (c) growth chamber (hydroponic, initially aseptic), and to evaluate their biological activity as germination stimulants for O. ramosa seeds. The plants used were tomato (Lycopersicon esculentum Mill.), sorghum (Sorghum vulgare Pers.) and flax. Exudate from marigold (Tagetes erecta L.) also was collected from germ-free culture.  相似文献   

19.
In Germany, sugar beet is often rotated with 2 years of cereal. Extensive fallow periods between cereal harvest and autumn primary tillage allow for a weed flora to develop. Broad‐leaved weeds could potentially be alternate hosts for the common nematode Heterodera schachtii, one of the most important pests of sugar beet. Between 2009 and 2012, annual weeds developing in cereal stubble fields during July to mid‐October in the season prior to sugar beet were surveyed, including known hosts of H. schachtii. Yearly weather patterns and agronomic practices possibly impacted weed species composition and weed population densities. During September, Chenopodium album, Cirsium arvense, Convolvulus arvensis, Mercurialis annua, Polygonum spp., Solanum nigrum and Sonchus spp. occurred at the highest frequencies. Weed hosts of H. schachtii were present, but densities, frequencies and uniformity were limited. In 2010 and 2011, staining for nematodes in roots revealed juvenile penetration of some weeds but few adult stages. No indication of nematode reproduction of H. schachtii was found on these weed hosts. A fairly stable weed flora was detected on stubble fields that could provide some carry over for weed species. An elevated risk for nematode population density build‐up on these weeds was not found and management of these weeds at the observed densities during the stubble period for nematological reasons appeared unnecessary.  相似文献   

20.
Alternative hosts of Spongospora subterranea may allow multiplication and survival of the pathogen over time; thus, host range is important from an epidemiological aspect. Weeds and rotational crops, such as wheat and barley, were sampled from potato fields with a history of powdery scab (PS) and examined for the presence of S. subterranea by root staining followed by microscopic observations and by qPCR analysis after DNA extraction. The pathogen was detected in plants of 16 weed species from eight families and in volunteer plants of potato and wheat. The ability of the pathogen to infect weeds and rotational crops was further examined by artificial inoculations with sporosori in pot experiments. Successful inoculations occurred with 13 weed species from eight families and with 12 rotational crops from five families. The findings of this study indicate a wide host range in Israel; the families Malvaceae and Zygophyllaceae and the following species are reported for the first time as S. subterranea hosts: Solanum elaeagnifolium, Triticum aestivum, Cynodon dactylon, Phalaris paradoxa, Phalaris minor, Setaria verticillata, Rostaria cristata, Sinapis nigra, Arachis hypogaea, Medicago sativa, Astragalus hauraensis, Amaranthus albus, Chenopodium murale, Chenopodium opulifolium, Salsola soda, Malva nicaeensis, Chrysanthemum segetum, Verbesina encelioides, Ammi majus and Tribulus terrestris. Controlling weeds and avoiding the relevant rotational crops observed to be S. subterranea-positive and thus potential hosts, should be taken into consideration in the management of PS, to reduce pathogen inoculum build-up.  相似文献   

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