Strigolactone deficiency confers resistance in tomato line SL-ORT1 to the parasitic weeds Phelipanche and Orobanche spp

The parasitic flowering plants of the genera Orobanche and Phelipanche (broomrape species) are obligatory chlorophyll-lacking root-parasitic weeds that infect dicotyledonous plants and cause heavy economic losses in a wide variety of plant species in warm-temperate and subtropical regions. One of the most effective strategies for broomrape control is crop breeding for broomrape resistance. Previous efforts to find natural broomrape-resistant tomato (Solanum lycopersicon) genotypes were unsuccessful, and no broomrape resistance was found in any wild tomato species. Recently, however, the fast-neutron-mutagenized tomato mutant SL-ORT1 was found to be highly resistant to various Phelipanche and Orobanche spp. Nevertheless, SL-ORT1 plants were parasitized by Phelipanche aegyptiaca if grown in pots together with the susceptible tomato cv. M-82. In the present study, no toxic activity or inhibition of Phelipanche seed germination could be detected in the SL-ORT1 root extracts. SL-ORT1 roots did not induce Phelipanche seed germination in pots but they were parasitized, at the same level as M-82, after application of the synthetic germination stimulant GR24 to the rhizosphere. Whereas liquid chromatography coupled to tandem mass spectrometry analysis of root exudates of M-82 revealed the presence of the strigolactones orobanchol, solanacol, and didehydro-orobanchol isomer, these compounds were not found in the exudates of SL-ORT1. It can be concluded that SL-ORT1 resistance results from its inability to produce and secrete natural germination stimulants to the rhizosphere.     

Parasitic weeds of the Orobanchaceae family and their natural hosts in Jordan

A field survey of the Orobanchaceae family members and their hosts in Jordan was carried out from 2003 to 2007. The intensity of parasite infection on different hosts and the severity of the infestation were evaluated. The results showed the presence of seven species of Orobanche and three species of Cistanche . The Orobanche species were found parasitizing 86 plant species belonging to 24 botanical families. Most of the species attacked by Orobanche were from the Compositae (20 species), Solanaceae (11 species), Leguminosae (nine species), Umbelliferae (seven species), Cruciferae (seven species), Cucurbitaceae (four species), Labiatae (four species), and Rosaceae (four species) families. Other families were represented by one-to-three species. Cistanche attacked 20 species of forage wild shrubs, fruit trees, and forest trees of seven families, mostly belonging to the Chenopodiaceae (seven species) and Leguminosae (three species) families. Previously unreported hosts for both genera include: Amygdalus communis , Olea europaea , and Quercus coccifera , which were parasitized by Orobanche palaestina ; A. communis , O. europaea , Prunus armeniaca , and Prunus persica , which were parasitzed by Orobanche cernua ; O. europaea and A. communis , which were parasitzed by Orobanche schultzii ; Haloxylon persicum , which was parasitzed by Cistanche lutea ; Punica granatum , Alhagi maurorum , Casuarina equisetifolia , Centaurea postii , and Prosopis farcta , which were parasitzed by Cistanche tubulosa ; and Achillea spp., Anabasis syriaca , H. persicum , Haloxylon salicornicum, Suaeda spp., and Zilla spinosa , which were parasitzed by Cistanche salsa . Certain Orobanche species were completely destructive to the cultivated crops. The results indicated the high potential of both parasitic genera to spread and to attack new hosts, while the threat they impose to agriculture in Jordan will probably result from poor management and deficiences in farmers' training.     

Proteomic analysis reveals suppression of bark chitinases and proteinase inhibitors in citrus plants affected by the citrus sudden death disease

Citrus sudden death (CSD) is a disease of unknown etiology that greatly affects sweet oranges grafted on Rangpur lime rootstock, the most important rootstock in Brazilian citriculture. We performed a proteomic analysis to generate information related to this plant pathogen interaction. Protein profiles from healthy, CSD-affected and CSD-tolerant stem barks, were generated using two-dimensional gel electrophoresis. The protein spots were well distributed over a pI range of 3.26 to 9.97 and a molecular weight (MW) range from 7.1 to 120 kDa. The patterns of expressed proteins on 2-DE gels made it possible to distinguish healthy barks from CSD-affected barks. Protein spots with MW around 30 kDa and pI values ranging from 4.5 to 5.2 were down-regulated in the CSD-affected root-stock bark. This set of protein spots was identified as chitinases. Another set of proteins, ranging in pI from 6.1 to 9.6 with an MW of about 20 kDa, were also suppressed in CSD-affected rootstock bark; these were identified as miraculin-like proteins, potential trypsin inhibitors. Down-regulation of chitinases and proteinase inhibitors in CSD-affected plants is relevant since chitinases are well-known pathogenesis-related protein, and their activity against plant pathogens is largely accepted.     

A novel strain of Fusarium oxysporum from Germany and its potential for biocontrol of Orobanche ramosa

A newly isolated Fusarium oxysporum strain was investigated for its biocontrol potential against the root parasitic weed Orobanche ramosa (branched broomrape). The fungus was found to affect all developmental stages of the parasite. Orobanche seed germination was reduced by 40% in the presence of fungal conidia in vitro . The number of underground tubercles and shoots of the weed was reduced by the fungus by 55% compared with the control and 92% of tubercles were recorded as diseased in root chambers. In pot experiments, soil application of a granular formulation of the fungus resulted in a reduction of number and dry matter of Orobanche shoots by more than 90%. Spraying of a conidial suspension on aboveground Orobanche shoots caused the death of 75% of them within 2 weeks. Data from initial host-range experiments indicate that the isolate is very host-specific, not even attacking shoots of other Orobanche species. Because of these promising results, we conclude that the fungal isolate should be investigated under field conditions and be compared with other Fusarium isolates proposed for biocontrol of O. ramosa .     

Benzothiadiazole Activates Resistance in Sunflower (Helianthus annuus) to the Root-Parasitic Weed Orobanche cuman

ABSTRACT The study was conducted to evaluate the potential of induced resistance to infestation of sunflower (Helianthus annuus L.) by the parasitic weed Orobanche cumana Wallr. Treatment of sunflower seeds with 40 ppm of benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester (BTH) for 36 h completely prevented infection in root chambers. In pot studies using 2.86 x 10(-4) g of Orobanche seeds per gram of soil as inoculum, the total number of O. cumana shoots was reduced by 84 and 95% in the 60-ppm BTH treatment in the first and second trial, respectively. Evaluation of the disease incidences revealed that attachment of O. cumana at the sunflower root and the stage of early penetration was reduced in the BTH-treated plants. Chemical analysis of root extracts revealed synthesis of the phytoalexin scopoletin and of hydrogen peroxide in the BTH-treated sunflower roots, but no increase in lignification. Western blot analysis demonstrated accumulation of the pathogenesis-related protein chitinase in roots and stems of induced resistant plants. These results show that the phenomenon of induced resistance is not restricted to viral, bacterial, and fungal disease and demonstrate the great potential of this protection strategy as an effective component of future plant production systems.     

Investigation of wheat as a trap crop for control of Orobanche minor

Orobanche minor is a parasitic weed that attaches to the roots of red clover (Trifolium pratense) and a number of other broad‐leaved plant species in the Pacific Northwest USA. Orobanche minor seed must be stimulated by host plant exudates for germination and attachment to occur. However, plant species called false‐hosts can stimulate parasitic seed germination without attachment. These species could be utilized as trap crops to reduce the amount of parasitic seed in infested soil. Wheat (Triticum aestivum), was found to be a false‐host of O. minor; therefore, growth chamber, glasshouse and field soil experiments were conducted to evaluate the effect of six soft white winter wheats (T. aestivum), one durum wheat (Triticum turgidum), and one triticale (Triticale hexaploide) on O. minor germination. In growth chamber experiments, wheat and triticale induced 20–70% of O. minor seeds to germinate. In glasshouse studies, O. minor attachment was minimal on red clover plants grown in pots previously planted to wheat or triticale. In pots that did not receive a false‐host treatment, red clover plants averaged 4.2 O. minor attachments per plant. Red clover plants also had fewer O. minor attachments when grown in field soil taken from the plots where wheat or triticale were grown compared with plants grown in soil where no wheat or triticale were previously grown. Our results demonstrate that wheat may have the potential to be effectively integrated into an O. minor management system.     

列当杂草及其防除措施展望

根寄生杂草列当Orobanche spp.每株可产生大量细小的种子,易于传播,且在出苗前已经对寄主作物造成危害,使列当的防除成为一个世界性难题。本文详述了列当的生活史、为害现状以及防除措施,并突出了生物防除的生态效益与经济效益。基于＂诱捕＂作物及＂捕获＂作物诱导列当种子＂自杀发芽＂理论的防除机制,本文提出了新型可持续生态防除思想,为列当科杂草防除提供参考。     

麦红吸浆虫滞育不同时期幼虫蛋白质双向电泳分析

为筛选与麦红吸浆虫滞育相关的蛋白,采用双向电泳及图像分析技术分析了麦红吸浆虫滞育前、后和滞育期的蛋白质图谱及其变化。结果表明,在滞育前幼虫的双向电泳图谱上平均可检测到蛋白质点约300个,其它时期约275个,其中多数分布在分子量8.0～50.0kD、等电点4.0～9.0的区域。在所检测到的蛋白质点中,26个在滞育前特异表达;3个在滞育前缺失,其它阶段表达;2个在滞育后200天特异表达;3个在滞育前和滞育解除后表达,滞育期缺失;34个在所有时期均表达,但各时期的表达量存在显著差异。     

室内条件下向日葵列当和弯管列当在三种不同寄主上寄生能力的比较

以向日葵列当Orobanche cumana Wallr.和弯管列当O.cernua Loefl.为研究对象,利用已有的室内寄生体系来研究两种列当在向日葵、烟草、番茄3种寄主上的寄生能力。结果表明,向日葵列当在室内条件下不仅能够寄生在向日葵上,同时也可以在烟草与番茄上寄生;但其寄生效率在上述不同的寄主之间存在显著差异,而在相同寄主的不同品系间没有差异。交互侵染的结果表明,在寄主番茄上,弯管列当平均每株寄生的瘤结数量为16.3个,向日葵列当只有2.5个;在寄主向日葵上,向日葵列当的平均寄生瘤结数量为25.2个,弯管列当为27.6个,预示着弯管列当在番茄上寄生效率均显著高于向日葵列当,而在寄主向日葵上,二者寄生效率差异不显著,均能高效寄生在向日葵根系上。上述研究结果将为向日葵列当和弯管列当发生严重地区作物轮作对象的选择提供理论依据。     

Parasitic plant infection is partially controlled through symbiotic pathways

Legumes are unique in interacting with Rhizobium , arbuscular mycorrhizal (AM) fungi, and parasitic plants. To dissect common parts of these three plant–organism interactions, infection by Orobanche crenata was studied in mutants with altered symbiotic phenotypes of Medicago truncatula and Pisum sativum . Orobanche crenata inoculation of mutant lines carrying defective mutation in the genes dmi2 / sym19 and dmi3 resulted in an increase in O. crenata establishment. Similarly, inoculation of mutants carrying mutation in the gene sunn / sym29 that controls the autoregulation mechanism of the symbiosis, also lead to a significant increase in haustoria formation. Altogether, our results suggest that parasitic plant infection is partly controlled by both the conserved symbiotic pathway that mediates symbiont recognition and establishment and the autoregulation mechanism that regulates the extent of colonisation by Rhizobium and AM fungi.     

捕食线虫真菌酯酶同工酶谱和可溶性蛋白质谱分析

 本文对5个属14个种共33株捕食线虫真菌采用聚丙烯酰胺凝胶电泳技术进行了酯酶同工酶谱和可溶性蛋白质谱分析。结果表明,酯酶同工酶谱带少,但各属的特征谱带是明显的,在同属不同种之间,多数种都有自已的特征谱带与其它种相区别,同种不同菌株间没有明显差异;蛋白质谱带较多,在每个属中均有1~2条特征谱带,属间的谱带差异明显,同属不同种和同种不同菌株间蛋白质谱带都表现出多型性。     

Seed viability determination in parasitic broomrapes (Orobanche and Phelipanche) using fluorescein diacetate staining

Fluorescein diacetate (FDA) was investigated as a potential viability stain for seeds of holoparasitic broomrapes Orobanche and Phelipanche (Orobanchaceae), using four weedy and two non-weedy taxa. FDA viabilities were compared with the currently used 2,3,5-triphenyl tetrazolium chloride (TTC) test, and in vitro germination induced by the strigolactone analogue GR-24. Viable FDA-stained seeds were characterised by bright yellow–green fluorescence under 450–490 nm blue light. These viable seeds could be discriminated from non-viable seeds, in which low levels of fluorescence, similar to non-stained control seeds were observed. FDA viabilities were not significantly different from those obtained using the TTC stain; however, viability values for both stains were consistently higher than levels of artificially induced germination. Positive TTC-staining showed continuous variation that was difficult to interpret. Nevertheless, the TTC test does not involve grinding seeds, and therefore probably remains a practical alternative to FDA for screening soil samples contaminated with Orobanche and Phelipanche seeds, which indicates different applications for the two viability tests. Interestingly, the strigolactone analogue GR-24 only induced germination in O. crenata , P. ramosa and O. minor , suggesting a high specificity towards this germination inducer among the species investigated. We suggest that FDA-staining provides a potential alternative to the currently used TTC test for seed viability assays for Orobanche and Phelipanche , and other parasitic weeds which are an obstacle to crop cultivation.     

外源茉莉酸甲酯诱导的水稻叶片蛋白质差异表达分析

 以抗稻瘟病水稻近等基因系C101LAC及CO39为材料,应用差异蛋白组学技术对外源茉莉酸甲酯（MeJA）诱导8 h和12 h后的水稻叶片蛋白质差异表达变化进行了分析。采用PEG 4000预沉淀法提取水稻叶片总蛋白,经双向电泳、凝胶染色和图像分析,结果表明：与对照相比MeJA处理后的2个水稻品系中共有21个蛋白质表现为2倍以上的表达差异。其中,MeJA处理8 h后,CO39中的差异表达蛋白质点有5个,C101LAC中有8个,U5为2个品系中均新增的蛋白质点。MeJA处理12 h后,CO39中有6个差异表达蛋白质点,C101LAC中则有5个。经胶内酶解、MALDI TOF/TOF质谱分析及数据库检索,成功对21个差异表达蛋白质进行了鉴定,其中新增的蛋白质点U5被鉴定为内切β 1,3 1,4 葡聚糖酶。依据GO数据库和UniProtKB数据库提供的蛋白质注释信息,按照功能可将21个差异表达蛋白质分为8类,分别在植物抗性、氨基酸代谢、信号转导、光合作用、光呼吸、糖代谢、蛋白质合成与分解及细胞代谢等方面发挥作用。     

不同向日葵播期、磷肥用量及除草剂对向日葵列当寄生的影响

以高感列当的食用向日葵品种"SH363"为试验材料,采用随机区组试验,研究不同播期、磷肥施用量和化学除草剂对向日葵列当寄生的影响。结果表明:随着播期推迟,列当寄生程度呈现先升高后降低的趋势,6月14日和6月21日播种,向日葵列当寄生数量明显减少,适时晚播可以减轻向日葵列当的危害;磷肥施用量为337.5 kg/hm2时,相对对照及其他处理,列当寄生数量最少;不同剂量的48%仲丁灵、48%氟乐灵和72%金都尔处理对列当寄生均具有一定的抑制作用,其中效果最好的为72%金都尔(用量为5400 m L/hm2),在减少列当寄生方面有很好的应用前景。     

茄青枯拉尔氏菌Rs-T02在3,4,5-三羟基苯甲酸甲酯作用下的差异蛋白分析

为探明3,4,5-三羟基苯甲酸甲酯(MG)抑制茄青枯拉尔氏菌的机制,利用二维电泳技术,分析了MG作用下茄青枯拉尔氏菌Rs-T02菌株的差异蛋白。结果发现在MG作用下的菌体中检测出29个差异蛋白点。采用质谱技术鉴定出22个差异蛋白,其中新增蛋白11种、缺失蛋白5种、表达上调蛋白1种和表达下降蛋白5种。这些蛋白参与能量代谢、信号转导、物质运输和DNA修复等途径。我们推测,与能量代谢相关的新增蛋白spot 9和缺失蛋白spot 65可能与MG抑制茄青枯拉尔氏菌的机制有关。     

农作物寄生线虫的初步调查鉴定

从1974～1979年,作者先后在广东、广西、湖南、湖北、江西、福建等省对农作物寄生线虫进行调查工作,调查的作物包括水稻、柑桔、茶、桑、麻类、香蕉、芭蕉、菠萝、马铃薯、甘薯、花生、大豆、菜豆、蚕豆、豇豆、西瓜、丝瓜、南瓜、冬瓜、黄瓜、辣椒、茄子、番茄、白菜、胡椒、花卉、药材、烟草、橡胶、树木、苗木等30多种。共收集样本300多标号,已鉴定的植物寄生线虫共38属80余种。     

The <Emphasis Type="Italic">Zea mays</Emphasis> b-32 ribosome-inactivating protein efficiently inhibits growth of <Emphasis Type="Italic">Fusarium verticillioides</Emphasis> on leaf pieces <Emphasis Type="Italic">in vitro</Emphasis>

In maize endosperm, a cytosolic albumin, b-32, with a molecular weight of 32 kDa is synthesised in temporal and quantitative coordination with the deposition of storage proteins. This protein has homology with several previously characterised Ribosome-Inactivating Proteins (RIPs). To verify if the maize plant expressing b-32 in various tissues has an increased tolerance to fungal pathogens, transgenic plants were obtained through genetic transformation using a chimeric gene containing the b-32 coding sequence downstream of a constitutive 35SCaMV promoter. A set of four independent homozygous progenies expressing b-32, were selected for a detailed analysis of b-32 expression in leaves and for pathogenicity tests. A differential b-32 content in leaf protein extracts was recorded in the transgenic progenies. Proteomic investigations on protein leaf extracts were carried out; the overlapping of the two-dimensional electrophoresis maps demonstrated the presence in a transgenic progeny, of additional spots, identified as b-32 and as a protein for herbicide resistance, in comparison to the negative control. Transgenic progenies were tested in bioassays to evaluate the response to Fusarium attack in leaf tissues. Preliminary experiments supported the choice of bioassay parameters for a reliable evaluation of transgenic progenies. The negative control was most susceptible to Fusarium verticillioides attack, compared to transgenic progenies. The data obtained indicate that maize b-32 was an effective antifungal protein by reducing Fusarium infection progression. Additionally, the reduction in Fusarium attack symptoms was related to b-32 concentration in leaf tissues.     

Revisiting strategies for reducing the seedbank of Orobanche and Phelipanche spp.

Weedy Orobanche and Phelipanche species are important in Southern and Eastern Europe, the Middle East and North Africa, and have recently been reported in the USA, Australia and some countries in South America. Rather than being controlled, the Orobanche and Phelipanche problem is increasing, both in intensity and in acreage. Large areas of new territory are at risk of invasion, if care is not immediately taken to limit the introduction of parasitic seeds and to educate farmers and others to be alert for new infestations. There is an urgent need to re-evaluate novel integrated Orobanche and Phelipanche management programmes that will allow a better control of the parasite species and limit their distribution. The main obstacle in the long-term management of Orobanche and Phelipanche infested fields is the durable seedbank, which may remain viable for decades in the field. Large quantities of long-lived seeds give the parasite genetic adaptability to changes in host resistance and cultural practices. As long as the seedbank is not controlled, the need to control the parasite will persist whenever a susceptible host is grown in the infested field. We discuss strategies for seedbank reduction, paying particular attention to cultural practices, whereas chemical and biological control methods are covered by other reviews in this issue.     

Purification of a Necrosis-Inducing, Host-Specific Protein Toxin from Spore Germination Fluid of Alternaria panax

ABSTRACT Spore germination fluid of Alternaria panax, the causal agent of Alternaria blight of American ginseng (Panax quinquefolius), collected from water droplets or aqueous ginseng leaf extracts produced visible water-soaked lesions on wounded, detached leaflets after incubation for 48 h. Maximum development of brown, necrotic spots occurred 4 to 5 days after inoculation on attached and detached ginseng leaflets. Of 15 plant species tested, only American ginseng was susceptible to applications of spore inoculum or spore germination fluid. The phytotoxic activity of the spore germination fluid was destroyed by heat and treatment with proteinase A. The phytotoxic factor was retained by an ultrafiltration membrane with a 30-kDa molecular mass cut-off. Purification of the phytotoxic protein, named AP-toxin, was performed by anion exchange and gel filtration chromatography. Bioactive fractions eluted as a single peak. By comparison with protein standards, a molecular mass of 35 kDa was estimated for the native protein. The denatured protein toxin also had a mass of 35 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis. Production of the protein toxin was induced on American ginseng leaflets and water extracts of ginseng leaves but not on leaves of other nonhost plants and their water extracts. The results show that A. panax produces a host-specific, proteinaceous toxin during colonization and pathogenesis of ginseng leaves.