Prohexadione-calcium induces sunflower (Helianthus annuus) resistance against the root parasitic weed Orobanche cumana

Prohexadione-calcium (PHDC) is a plant growth retardant that inhibits gibberellin biosynthesis and transiently alters the spectrum of flavonoids and their phenolic precursors. In this study, root chamber and pot experiments were conducted to evaluate the effects of PHDC on Orobanche cumana seed germination and induction of sunflower resistance to this root parasitic weed. Root chamber experiments indicated that PHDC did not interfere with the progress of Orobanche seed germination, but retarded O. cumana tubercle formation and development. In pot experiments, control of O. cumana by PHDC depended on its dose, method of application and sunflower cultivar. In sunflower cv. HA89, PHDC at 10 mg LS⁻¹ (litre soil) as two drenches or at 1 m m as two foliar sprays significantly reduced the total number and dry matter of O. cumana without influencing flower, leaf and root development. In sunflower cv. Albena, PHDC at 20 and 30 mg LS⁻¹, but not at 10 mg LS⁻¹, as two drenches significantly reduced O. cumana infection. Sunflower cv. HA89 was less susceptible to O. cumana and more inducible by PHDC than sunflower cv. Albena. The biochemical analysis of root extracts revealed a significantly higher accumulation of free phenolics in sunflower cv. HA89 after PHDC soil drench, but not in Albena. No significant lignification was observed after PHDC treatments. The results suggest that PHDC reduces O. cumana infection in sunflower by inducing host resistance, not by directly interfering with the parasite. Free phenolics play an important role in sunflower response to the parasite.     

Molecular analysis of resistance mechanisms to Orobanche cumana in sunflower

Resistance to the dicotyledenous parasite Orobanche cumana in sunflower is characterized by a low number of parasitic attachments and a confinement of the parasite in host tissues leading to its necrosis. To help understand what determines such resistance mechanisms, molecular, biochemical and histological approaches were employed before (early response) and after (late response) attachment of the broomrape parasite to susceptible (2603) and resistant (LR1) sunflower genotypes. The expression patterns of 11 defence-related genes known to be involved in different metabolic pathways (phenylpropanoids, jasmonate, ethylene) and/or in resistance mechanisms against microorganisms were investigated. RT-PCR and cDNA blot experiments revealed that the resistant genotype exhibited a stronger overall defence response against O. cumana than the susceptible one, involving marker genes of the jasmonate (JA) and salicylic acid (SA) pathways. Among them, the SA-responsive gene, def. (defensin), appeared to be characteristic of LR1 sunflower resistance. However, no JA accumulation and similar SA contents (250–300 ng g⁻¹ FW) were measured by GC/MS in both genotypes, parasitized or not. In addition, three cDNAs, isolated by a suppression-subtractive hybridization, were shown to be strongly induced only in the resistant genotype 8 days post-inoculation, when the first O. cumana attachments occurred. These genes, putatively encoding a methionine synthase, a glutathione S-transferase and a quinone oxidoreductase, might be involved in detoxification of reactive oxygen species, suggesting the occurrence of an oxidative burst during the incompatible interaction. Finally, host cell-wall modifications leading to parasite-confinement were correlated with more intense callose depositions in the resistant genotype, concomitant with over-expression of the callose synthase cDNA HaGSL1 .     

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.     

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.     

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。     

Effect of broomrape (Orobanche cumana Wallr.) on some agro-morphological and biochemical traits of Tunisian and some reference sunflower (Helianthus annuus L.) accessions

Journal of Plant Diseases and Protection - Orobanche cumana Wallr. is an important new problem for sunflower crop in Tunisia. Little information is available on the behavior of sunflower to O....     

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。     

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。     

向日葵抗列当品种(系)筛选及其应用评价

为了全面评价不同向日葵品种(系)对列当的抗寄生性和其在生产中的应用价值,对‘TP3313’等50个食葵品种(系)、‘内蒙杂4号’等6个油葵品种(系)进行了田间自然寄生试验,结果表明:食葵‘TP3313’为对列当免疫的品种,且病虫害发生较轻,产量相对较高(261.11kg/667m~2),因而具有极高的推广应用价值;‘TP3314’为高抗列当品种,但是受向日葵菌核病危害较重,产量为219.64kg/667m~2;‘SH361-L’、‘SH338-M’等8个品种表现为中感,属耐列当品种(系),并且产量相对较高,在生产中具有一定的应用价值。     

内生黏质沙雷氏菌LIEH 92对向日葵菌核病的防治效果及其防病机制研究

本研究评价了从向日葵列当体内分离筛选得到的内生黏质沙雷氏菌(Serratia marcescens)LIEH 92对向日葵菌核病进行盆栽与大田防效评价,并测定了该菌株的生理特性和其在根际土与向日葵体内的定殖情况。结果表明,LIEH 92发酵液对向日葵菌核病的室内盆栽防效达73.35%,对大田根腐型菌核病和盘腐型菌核病防效分别达53.48%和38.64%。菌株LIEH 92可产生几丁质酶,并能在根际土和向日葵根、茎、叶内定殖与传导,定殖菌量达102~106 cfu/g。其在向日葵植株的根内定殖数量最大,茎中次之,叶中最少。在灭菌土中LIEH 92在根际土和向日葵根部的定殖菌量小于在自然土中其在相应部位的定殖菌量,而灭菌土中LIEH 92在向日葵茎部和叶部的定殖菌量则大于自然土中相应的定殖菌量。LIEH 92处理可提高向日葵植株PAL、POD和PPO等防御酶活性,从而诱导向日葵对菌核病的抗性。LIEH 92对向日葵菌核病具有生防潜力。     

Identification,characterisation and discriminatory power of microsatellite markers in the parasitic weed Orobanche cumana

Orobanche cumana is an obligate root parasite of sunflower. It represents a major agricultural problem in many countries of southern and eastern Europe. Information on O. cumana population genetics, structure and dynamics is scarce, particularly due to the lack of suitable molecular markers for such studies. The objective of this study was to identify and characterise simple sequence repeat (SSR) markers for O. cumana. Four thousand two hundred SSR‐containing candidate sequences were obtained from O. cumana using next‐generation sequencing, from which 298 SSR primer pairs were designed and 217 of them used for validation. Seventy nine SSR primers produced reproducible, high quality amplicons of the expected size that were polymorphic among 18 O. cumana populations from different geographical locations and hosts (sunflower, wild hosts from the Compositae family). The number of alleles per locus ranged from 2 to 10, with an average polymorphism information content value of 0.37. The O. cumana SSR markers were highly transferable to the closely related species Orobanche cernua. SSR markers showed high resolving power; UPGMA cluster analysis allowed proper classification of Orobanche spp. samples into species (O. cumana and O. cernua), geographical origin and host. The functional SSR markers reported in this study constitute a valuable tool for genetic analyses in O. cumana and related species and will contribute insights into the biology and genetics of this parasitic weed.     

Increasing control reliability of <Emphasis Type="Italic">Orobanche cumana </Emphasis>through integration of a biocontrol agent with a resistance-inducing chemical

Fusarium oxysporum Schlecht. f.sp. orthoceras (Appel & Wollenw.) Bilai is a potential biocontrol agent against the root-parasitic weed Orobanche cumana. In pot experiments with different sunflower cultivars, the application of F. oxysporum was combined with a treatment of BTH (Benzo(1,2,3)thiadiazole-7-carbothioic acid S-methyl ester), a product known to induce resistance against O. cumana in sunflower. The combined treatments resulted in highly reliable control and sometimes in increased control level compared to the Fusarium treatment alone. In laboratory experiments, no enhancing effect of BTH on virulence and growth of the fungus was observed. Future experiments should further investigate the basic mechanisms of the effect achieved by combining the two control strategies as well as the transfer of this innovative control approach into field experiments.     

Quantitative aspects of Orobanche crenata infestation in faba beans as affected by abiotic factors and parasite soil seedbank

The interactions between the root parasitic weed Orobanche crenata Forsk. and its host plant faba bean ( Vicia faba L.) were quantified under controlled and field conditions at ICARDA's Tel Hadya research station. In the field experiments conducted in 1993–94 and 1994–95 faba beans were sown on two dates, in plots with 0, 50, 200 and 600 O. crenata seeds kg^–1 soil, under both limited and sufficient moisture supply. The effects of temperature on the duration of the early developmental stages of O. crenata were investigated in a growth chamber. The extent of O. crenata infestation was closely related to the number of parasite seeds in the soil. The seed-density treatment with 600 seeds kg^–1 soil resulted in complete crop failure. Furthermore, O. crenata infestation was higher under sufficient than under limiting water supply conditions, irrespective of sowing date. Only in the moderately infested plots, did shifting of the planting time of faba bean result in a significant decrease in parasite dry weight and an increase in crop seed yield. The timing of germination, attachment and further developmental stages of O. crenata was not related to faba bean growth stage and was affected primarily by soil temperature. The duration of O. crenata developmental stages was estimated using the thermal time concept. The relationship between total number of parasite attachments at the harvest of the faba bean crop and O. crenata seed density was dependent on maximum faba bean root-length density measured by the start of pod-filling in each treatment combination of sowing date and moisture supply. The results are discussed with reference to implications for the development of a dynamic simulation model for the prediction of faba bean yield losses caused by O. crenata .     

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.     

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。     

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.     

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.     

Orobanche crenata (Forsk) control in Vicia faba (L.) with glyphosate as affected by herbicide rates and parasite growth stages

The broomrape (Orobanche crenata Forsk) susceptibility to glyphosate applied on faba-bean (Vicia faba L.) as affected by the parasite growth stages at the time of application was studied under field conditions. Glyphosate treatments delayed O. crenata emergence. Single glyphosate application to faba-bean infected with O. crenata predominantly at the stage (a) (small nodule) and (b) (nodules with initial vestigial roots) resulted in a moderate to low control. When the stages (c) (shoot bud already visible) or (d) (shoot and vestigial roots well developed) were the predominant stages, an excellent control was achieved with a single glyphosate application at 60 g ha^?1. Increased development stages, with the shoot emerged from the shoot bud, decreased its susceptibility to glyphosate. La lutte contre Orobanche crenata en culture de férerole avec le glyphosate; influence des doses d'herbicide et du stade de développement du parasite     

Characterization of the Orobanche–Medicago truncatula association for studying early stages of the parasite–host interaction

There is an increasing interest in the legume species Medicago truncatula as a model plant for structural and functional genomic studies that can be used to identify agronomically important genes in legumes. Field screening has shown very high levels of resistance to Orobanche crenata in M. truncatula. However, in vitro studies with O. crenata, Orobanche foetida, Orobanche ramosa and Orobanche minor showed useful variation among accessions at early stages of the parasite–host interaction. Significant differences were observed in the levels of germination of O. crenata and O. foetida seeds induced by different accessions of M. truncatula. Only limited germination was observed on accession SA‐4327. All accessions induced little O. ramosa and O. minor germination. Accessions also varied in the number of O. crenata and O. foetida attachments supported, with few developing on accession SA‐27774. The variation observed for induction of germination and of subsequent attachment will be useful to isolating and characterizing genes involved in the early stages of Orobanche–host plant interaction and for the study of the biosynthetic pathways of production for germination stimulants.     

In vitro culture of Orobanche ramosa

Orobanche spp. (broomrapes) are holoparasites that subsist on the roots of many important crops and can considerably reduce yield. The control of Orobanche spp. includes physical, chemical and biological methods. Interactions between parasitic angiosperms and their hosts first occur at the level of parasite seed germination. The seeds of all Orobanchaceae germinate in soil under natural conditions only in response to specific chemical exudates from the host plant. This study describes the influence of different plant growth regulators and host plant root exudates on germination and development of calli from Orobanche seeds in vitro . The effect of indole-3-acetic acid, gibberellic acid and kinetin on the germination of Orobanche seeds varied with concentration. These plant growth regulators also affected the period of germination and the structure of calli and protrusions. An in vitro system for the collection of tobacco root exudates was established. Compounds released from the host roots of three different tobacco cultivars were found to provoke high levels of germination of the Orobanche seeds without any period of pre-conditioning. This study developed methods for the investigation of host–parasite interactions and the effect of germination stimulants in Orobanche spp.