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 .     

Orobanche cumana race F: performance of resistant sunflower hybrids and aggressiveness of populations of the parasitic weed

The production of sunflower is threatened by Orobanche cumana (broomrape) infections in many countries of southern and eastern Europe. The most virulent race of this parasitic weed, race F, is widespread in Spain. Most of the current commercial hybrids of resistant sunflower do not completely prevent broomrape emergence in the field. The performance (broomrape incidence and severity, final yields and oil contents) of four resistant and two susceptible sunflower hybrids was studied in different years in several O. cumana – infested locations. O. cumana – sunflower interactions were characterised by low severity and intermediate incidence in the resistant hybrids; both depended on the environment. An increase in sunflower yield because of the use of resistant hybrids was most noticeable under heavy field infestations and under drought. Characterisation of 20 populations of O. cumana classified as race F in terms of the standardised area under the degree of attack progress curve (SAUDC) and O. cumana incidence (BI) suggested differential intrinsic pathogenicities. These results highlight the variability within race F of O. cumana , mirroring the environmentally dependent horizontal resistance in sunflower.     

Phelipanche aegyptiaca management in tomato

Phelipanche and Orobanche species (broomrapes) are root holoparasitic plants that cause severe damage to economically important crops. Phelipanche and Orobanche spp. are widespread in Mediterranean areas, in Asia and in Southern and Eastern Europe, attacking dicotyledonous crops and depending entirely on their hosts for all nutritional requirements. Phelipanche aegyptiaca , Phelipanche ramosa and Orobanche cernua are extremely troublesome weeds on tomatoes. These noxious parasites exert their greatest damage prior to their shoot emergence and flowering; therefore, the majority of field loss may occur before diagnosis of infection. This review summarises the four main control measures for the weedy root parasites Phelipanche and Orobanche in tomato, namely chemical and biological control, resistant varieties and sanitation. Some of these methods are commercially widely used by farmers in Israel (chemical control), some are in the final stages of development towards commercialisation (resistant varieties and sanitation), and some still require further development and improvement before commercial implementation (biological control). The review presents an up-to-date summary of the available knowledge on their use for broomrape management in processing tomatoes.     

Effect of sowing date and host resistance on the establishment and development of Orobanche crenata in faba bean and common vetch

The effect of early and late sowing dates on the establishment of Orobanche crenata Forsk. (crenate broomrape) in resistant and susceptible cultivars of faba bean (Vicia faba L.) and vetch (Vicia sativa L.) were studied over four seasons in southern Spain. Differences in establishment, development and shoot emergence of the parasite were compared. With resistant faba bean and vetch cultivars, there was reduced attachment and shoot emergence of O. crenata with all sowing dates. Susceptible cultivars were more severely affected by the parasite with early sowing. Orobanche crenata development was also delayed in resistant cultivars. Crop yield, estimated by the number of pods per plant, decreased with late sowings. The combined use of resistant cultivars and early sowing is a useful tool as part of an integrated control strategy. Resistant cultivars allow early sowing (with low O. crenata attack), thus avoiding yield losses due to the short crop cycle with late sowing.     

Pathogenic diversity within field populations of Orobanche cumana and different reactions on sunflower genotypes

Different races of the parasitic Orobanche cumana (sunflower broomrape) have been reported in Spain, race F being the most virulent. Full resistance in sunflower to races A–E is achieved with each of the single major genes Or₁ to Or₅ respectively. However, parasitised hybrids allegedly resistant to race F were observed in early 2002. The purpose of this study was to verify broomrape incidences (BI) on resistant sunflower genotypes, to assess the mixture of races within field populations and to test for partial resistance to race F in the sunflower hybrids showing a low degree of attack (DA) by the weed. Tests were conducted under field conditions in two locations of southern Spain. While no significant differences were found for yield and BI between locations, the DA on the cultivars depended on the location. With high infection levels and significantly lower yield in susceptible controls, marked differences in BI and DA were found within resistant cultivars, but all of them showed similar crop yield. When artificially inoculated with several populations of race F, line P96 and mainly line L86, were consistently slightly infected, suggesting they were inbred lines responsible for horizontal resistance in infested fields. L86 was extremely susceptible to race E populations, which is unusual as sunflower resistance to one race provided resistance to all the previously described races of O. cumana. No different virulences were detected within two groups of subpopulations (races E and F) inoculated onto resistant sunflower genotypes. However, race F subpopulations showed significant differences in aggressiveness, which seems to be related to horizontal (multigenic) resistance of the crop to the parasitic weed.     

烟草及向日葵上列当Orobanche cumana的发生及其生物防治

 近年,在河北省部分烟草和向日葵种植地发现大量寄生性杂草列当发生并造成严重为害。经鉴定为向日葵列当Orobanche cumana Wallr.。向日葵、烟草、番茄和黄瓜等作物的根分泌物能够刺激向日葵列当O. cumana种子萌发,而油葵根的分泌物则不能刺激向日葵列当种子萌发。利用列当致病镰刀菌L2菌株进行田间生物防治,防治效果达到92.4%。L2菌株对小麦、玉米、棉花、烟草和向日葵等作物生长无影响,L2菌株粗毒素能够抑制列当种子萌发,并造成列当种子萌芽管损伤。     

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.     

我国向日葵列当发生危害现状调查

向日葵列当是危害我国向日葵最严重的杂草。为明确我国向日葵田列当的发生危害情况及防治现状,采用对角线5点取样法对新疆、内蒙古、吉林和河北等主要向日葵种植区进行调查,对向日葵列当的寄生率和寄生强度等数据进行分析。结果表明,向日葵列当在向日葵产区广泛分布,严重危害向日葵的生产,其对食葵的寄生率高于油葵,对抗性品种的寄生率较低。在所有调查地区中内蒙古地区向日葵列当发生最严重,寄生率高达100%,寄生强度达到38.5,单株寄生数量最高,达118株;新疆地区的向日葵列当寄生率居中,吉林、河北向日葵列当发生相对较轻。通过实地调研结合文献报道,对目前国内外向日葵列当的研究进展进行了综述,研究结果为指导向日葵列当防治提供参考。     

Pathogenic and molecular diversity in highly virulent populations of the parasitic weed Orobanche cumana (sunflower broomrape) from Europe

The parasitic weed Orobanche cumana (sunflower broomrape) constrains sunflower production in eastern and southern Europe and in the Middle East. Although genetic resistance is the most effective control method, new parasite races evolve overcoming sunflower resistance. In this work, highly virulent populations of O. cumana were analysed for pathogenicity and genetic diversity. The virulence of 11 populations from Hungary, Romania, Spain and Turkey was assessed and compared after infection of sunflower inbred lines to differentiate races of the parasite under glasshouse conditions. Molecular diversity among and within 27 parasite populations was studied by RAPD‐PCR, UPGMA and amova analyses. Highly virulent race F was identified in Hungary, Spain and Turkey. The most virulent race (G) was also found in Turkey. The molecular analysis among highly virulent populations of O. cumana identified four molecular clusters, respectively, grouping populations from Central Spain, Hungary, South Spain and Turkey. The genetic homogeneity within parasite populations was confirmed, since no molecular divergences were found within them. This work constitutes the first geographical study of O. cumana together with pathogenicity and molecular traits inherent to each geographical group, and provides useful information for possible phylogenetic analyses of O. cumana. In addition, molecular markers associated with geographical origin could be developed and used as diagnostic tools to track new broomrape introductions into areas free of virulent races where they might represent a threat to sunflower production.     

Some compatible Rhizobium leguminosarum strains in peas decrease infections when parasitised by Orobanche crenata

Orobanche crenata (crenate broomrape) produces serious damage to many legume crops and particularly becomes a limiting factor for pea production in the Mediterranean basin. Nodulation effects on pea–broomrape relationships were studied using the commercial pea cultivar Douce de Provence and different Rhizobium strains using pot and Petri dish experiments. First, the benefit of bacterial inoculation on plant growth and efficiency of N incorporation were demonstrated for two isolates, P.SOM and P.1236. These isolates did not influence parasite germination induced by the artificial stimulant, GR24. In contrast, pea root inoculation with P.SOM and P.1236 isolates led to a reduced root infection by O. crenata , resulting from a lower Orobanche germination rate close to pea roots and a limited capacity of the parasitic seedlings to develop tubercles. Broomrape necrosis was observed both before and after parasite attachment to inoculated pea roots. Concomitantly, reduction in infection was accompanied by enhanced peroxidase activity and constantly high phenylalanine ammonia lyase activity in pea roots. These data suggest the involvement of these enzymes in pea resistance to crenate broomrape induced by the compatible rhizobia. Management of Orobanche via crop selection based on these enzyme systems is a viable option.     

Herbicides for control of broomrape (Orobanche ramosa L.) in tobacco (Nicotiana tabacum L.)

In field tests conducted on oriental and flue-cured tobacco, six herbicides were evaluated for their effect on broomrape (Orobanche ramosa L.) control and on tobacco growth, yield and chemical composition. Imazaquin+pendi-methalin (1:6) at 0.09+0.55 kg a.i. ha^?1 soil in corporated before transplanting controlled broomrape effectively only in 1990 and signifi cantly reduced tobacco yield. Glyphosate (as Roundup 360 ga.e.1^?1 and Armada (90 ga.e.l^?1) and sulfosate, each at 0.2+0.3 kg a.e. ha^?1 and imazaquinat 0.07+0.1 kg a.i. ha^?1 foliar applied at 40 days and 60 days after transplanting gave excellent control of broomrape, with no adverse effect on tobacco growth or yield; however, the 9% formulation of glyphosate was damaging. Maleic hydrazide gave moderate to good (up to 80%) control of broomrape. Reducing sugars in flue-cured tobacco and nicotine in both oriental and flue-cured tobacco were higher where a her bicide was used. Des herbicides pour lutter contre Orobanche ramosa L. dans le tabac (Nicotiana tabacum L). Dans des expérimentations au champ conduites sur du tabac oriental et ‘flue cured’, six herbicides ont étéévalués pour leur effet sur Orobanche ramosa L. ainsi que sur la croissance, le rendement et la composition chimique du tabac. Le mélange imazaquin+pendiméthalin (1:6 à 0.09+0.55 kg ha^?1, incorporé avant le repiquage, n'a permis de détruire l'orobanche qu'en 1990 et réduisait de manière significative le rendement du tabac. Le glyphosate (Roundup, 360 m.a. 1^?1 et Armada, 90 g m.a. l^?1) et le sulfosate chacun aux doses 0.2+0.3 kg m.a. ha^?1 et l'imazaquin 0.07+0.1 kg m.a. ha^?1 appliqués en post-levée 40 et 60 jours après le repiquage donnaient d'excellents résultats contre l'orobanche, sans effet sur la croissance du tabac et sur son rendement, si l'on excepte la formulation de giyphosate 9%. L'hydrazide maléique donnait des résultats moyens à bons (jusqu'à 80% d'efficacité). Les teneurs en sucres réducteurs chez le tabac ‘flue cured’ et en nicotine chez les tabacs ‘flue cured’ et oriental étaient plus élevées lorsqu'un herbicide avait été utilisé. Herbizide zur Bekämpfung von Orobanche ramosa L. in Tabak (Nicotiana tabacum L.) In Freilandversuchen wurden in Orient- und Vir-gin-Tabak 6 Herbizide hinsichtlich der Bekämpfung der Sommerwurz Orobanche ramosa sowie des Wachstums, des Ertrags und der chemischen Zusammensetzung des Tabaks geprüft. Mit einer Mischung von Imazaquin mit Pendimethalin zu 0,09+0,55 kg AS ha^?1, vor dem Pflanzen in den Boden eingearbeitet, konnte die Sommerwurz nur 1990 wirkungsvoll bekämpft werden, aber der Tabakertrag wurde signifikant reduziert. Glyphosat (als Roundup [360 g AS 1^?1] und als Armada [90 g AS 1^?1) mit Sulfosat zu 0,2+0,3 kg AS ha^?1 und Imazaquin zu 0,07 sowie 0,1 kg AS ha^?1, 40 bzw. 60 Tage nach dem Pflanzen angewandt, wirkten hervorragend, ohne Wuchs und Ertrag des Tabaks zu beeinträchtigen, ausgenommen bei der 9% igen Glyphosatformulierung. Mit Maleinhydazid ließ sich die Sommerwurz befriedigend bis gut (bis zu 80 %) bekämpfen. Der Gehalt an reduzierenden Zuckern im Virgin-Tabak und Nikotin in beiden Tabaken war erhöht, wenn ein Herbizid angewandt worden war.     

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.     

Extent and pattern of genetic differentiation within and between European populations of Phelipanche ramosa revealed by amplified fragment length polymorphism analysis

The extent and pattern of genetic differentiation between Phelipanche ramosa populations colonising tobacco in different European regions were investigated by amplified fragment length polymorphism (AFLP) analysis, in order to determine levels of variation for tobacco resistance breeding and management programmes. Four different AFLP primer pairs amplified a total of 1050 clear and reproducible bands, of which 962 (91.62%) were polymorphic among the 35 individuals taken from four P. ramosa populations collected in Spain, Italy, Bulgaria and Germany. Cluster analysis based on the AFLP data categorised the plants into distinct groups, in line with their geographical origin, denoting clear genetic differentiation among the four populations. This differentiation was supported by both high bootstrap values and significant results of the analysis of molecular variance. The most divergent population was the one from Bulgaria. The majority of the genetic diversity was attributable to differences among populations (77.80%), as expected from the predominant autogamous behaviour of this species. Populations differed significantly in within-population diversity, as measured by Shannon's information index. The German population presented the lowest genetic diversity and the Italian population harboured the highest level of within-population genetic diversity. There are significant differences in genetic diversity level among the studied P. ramosa populations and clear population-specific genetic diversity structures. These need to be taken into account, together with the potential differences in parasite aggressiveness, when planning breeding and management strategies for P. ramosa control in tobacco cultivation.     

Research onOrobanche crenata management in sicily from the 19 th to the early 20 th century

In order to offer hints for new research, the agronomic techniques used to manageOrobanche crenata in Sicily in the late 19 ^th and early 20 ^th Century are examined; the publications in which they were originally described can be obtained only with difficulty. Hand pulling, resistant cultivars and late sowing are the techniques used nowadays. Screening for resistance to broomrape of the traditional cultivars of broad bean, and for the influence of sowing density on broomrape infestations, is still to be done.     

A study of assimilation and translocation in Cuscuta hyalina Heyne ex Roth., Orobanche ramosa L. and Striga hermonthica Benth.

Quantitative determinations of chlorophyll showed that Cuscuta hyalina and Striga hermonthica possess chlorophyll. No trace of chlorophyll was found in Orobanche ramosa. Autoradiographic evidence showed that both radiocarbon and radiophosphorous moved from host to parasite in alt three species. Photosynthesis occurs in S. hermonthica when the parasite is isolated from its host. The adventitious roots of S. hermonthica and O. ramosa appear to be functional in absorbing a proportion of the required inorganic substances and water. S. hermonthica is a hemiparasite, O. ramosa is a holoparasite but C. hyalina is best described as a partial parasite.     

列当(Orobanche spp. and Phelipanche spp.)种子的采集与预处理方法

列当(Orobanche spp.and Phelipanche spp.)是一种在世界范围内危害严重的根寄生杂草,防除列当的研究也越来越多。正确地采集和预培养列当种子是获得正确防除列当研究结果的前提。列出了大田正确采集列当种子的方法,以及对采集到的种子进行过筛提纯、加洗洁精和吐温20清洗后,再表面消毒和预培养,并通过发芽试验检验此方法的可行性。结果表明,经过处理的向日葵列当、瓜列当种子的发芽率最高分别为54.4%、59.1%。此方法可以应用于列当的采集和预处理过程中,可为列当研究和防除提供参考。     

Genetic diversity of Orobanche cumana populations from Spain assessed using SSR markers

Orobanche cumana (sunflower broomrape) is found in Spain as an allochthonous species parasitising exclusively sunflower. For many years, it was distributed in the Guadalquivir Valley and Cuenca province, but in recent years, it has spread to new areas. The objective of this research was to study genetic diversity of O. cumana populations from Spain using robust co‐dominant molecular markers. Cluster analysis on a set of 50 populations using 15 microsatellite markers revealed the existence of two distant gene pools, one in Cuenca province and another one in the Guadalquivir Valley. Within each gene pool, both inter‐ and intrapopulation variability were extremely low. This population structure probably reflects a founder effect, with the two genetically distant gene pools deriving from separate introduction events. Different races occurred within the same gene pool, suggesting that current races might have evolved through mutation from a common genetic background. Most of the populations from new areas were identical to the populations from the Guadalquivir Valley. Only a few populations showed larger intrapopulation variation. In these cases, our results suggested the co‐existence of both gene pools within the same population, as well as the occurrence of genetic recombination between them. Genetic recombination between distant gene pools is an important mechanism for creating new variation, which might also have an effect on race evolution. These results will contribute to the establishment of improved crop breeding and management strategies for O. cumana control.     

Indigenous highly virulent accessions of the sunflower root parasitic weed Orobanche cumana

Orobanche cumana (broomrape) is a severe constraint to sunflower production in southern and eastern Europe and the Middle East. Races A to E of this parasitic weed controlled by genes Or₁ to Or₅ have been described. A study of 38 seed accessions of O. cumana collected from different locations in Spain between 1983 and 2003 investigated the effect of long‐term storage in the laboratory on germination and infectivity and assessed their virulence on a number of sunflower cultivars. Only 18 infected the susceptible cultivar B117. Infectivity was maintained for up to 17 years of storage, but with a greatly decreased vigour as compared with that of recently collected seed. The 12 oldest viable accessions overcame the resistance of the gene Or₅ (in resistant line NR5). Seven out of them, in particular those collected in 1988 and 1989, were identified as race F. Three accessions were identified as race E allegedly holding components of higher virulence. Our results show evidence of the occurrence of race F prior to the use of sunflower hybrids resistant to race E, suggesting the former as indigenous to the country. This finding suggests the necessity of a continuous breeding of sunflower for resistance to O. cumana. The effectiveness and sustainability of genetic resistance must rely on the knowledge of the diverse virulence characteristics of O. cumana accessions.     

Broomrape control in faba bean (Vicia faba L.) with glyphosate and imazaquin

Field studies were carried out to evaluate the efficacy of imazaquin and glyphosate in controlling broomrape (Orobanche crenata Forsk. and O. aegyptiaca Pers.) in faba bean (Vicia faba L.) in Northern Syria. Several rates and times of application of the herbicides were tested. Nearly complete control of broomrape was achieved with both the herbicides when they were sprayed twice (when the broomrape attachments to the faba bean roots were at tubercle stage of develoment and 15 days later) at a rate of application of 80 g a.i. ha^?1 for glyphosate and 10 g a.i. ha^?1 for imazaquin. However, the yield of faba bean did not increase with these treatments, suggesting that the herbicides at these rates were still causing some physiological disorder in the plant that counteracted the beneficial effect of broomrape control on the performance of faba bean plants.