Orobanche Cumana Wallr Research Articles

Use of Blue-Green Fluorescence and Thermal Imaging in the Early Detection of Sunflower Infection by the Root Parasitic Weed Orobanche cumana Wallr.

Although the impact of Orobanche cumana Wallr. on sunflower (Helianthus annuus L.) becomes evident with emergence of broomrape shoots aboveground, infection occurs early after sowing, the host physiology being altered during underground parasite stages. Genetic resistance is the most effective control method and one of the main goals of sunflower breeding programmes. Blue-green fluorescence (BGF) and thermal imaging allow non-destructive monitoring of plant diseases, since they are sensitive to physiological disorders in plants. We analyzed the BGF emission by leaves of healthy sunflower plantlets, and we implemented BGF and thermal imaging in the detection of the infection by O. cumana during underground parasite development. Increases in BGF emission were observed in leaf pairs of healthy sunflowers during their development. Lower BGF was consistently detected in parasitized plants throughout leaf expansion and low pigment concentration was detected at final time, supporting the interpretation of a decrease in secondary metabolites upon infection. Parasite-induced stomatal closure and transpiration reduction were suggested by warmer leaves of inoculated sunflowers throughout the experiment. BGF imaging and thermography could be implemented for fast screening of sunflower breeding material. Both techniques are valuable approaches to assess the processes by which O. cumana alters physiology (secondary metabolism and photosynthesis) of sunflower.

Racial characterization and genetic diversity of sunflower broomrape populations from Northern Spain

In Spain, sunflower broomrape ( Orobanche cumana Wallr.) has been restricted to Cuenca province in Central Spain, and the Guadalquivir Valley in Southern Spain, that represent different gene pools of the species. This pathogenic plant has now spread to other areas such as Castilla y Leon region in Northern Spain. The racial status and genetic diversity were investigated in six populations of sunflower broomrape collected in several provinces of Castilla y Leon. Evaluation of virulence to a set of differential host genotypes classified three of the populations as race F, while the other three populations were classified as a race below F, probably race E. Genetic diversity analysis using a set of 20 SSR markers showed that the broomrape populations from new areas of Northern Spain are mainly derived from the Guadalquivir Valley gene pool. Introgression from the Cuenca gene pool was observed in one of the populations, in which the percentage of polymorphic loci was 31%, Shanon´s diversity index was 0.17, and the average number of pairwise differences was 1.69, compared to zero for the three parameters in the other five populations. The absence of race F individuals in the populations classified as race below F indicated that seed migration took place, probably before the generalized expansion of race F in the Guadalquivir Valley area, at the beginning of the 1990s.

Dostignuća u oplemenjivanju suncokreta na otpornost prema volovodu

Parasitic plant broomrape (Orobanche cumana Wallr.) is a major problem in sunflower (Helianthus annuus L.) production. Yield losses can be up to 100% when susceptible genotypes are grown. Eight known races of broomrape in sunflower have been identified and designated by letters from A to H. Five races have been identified (A, B, C, D and E) in the past, while more virulent races have recently appeared in the countries around the Black Sea and Spain. The race E has been predominant in Serbia for many years, although in some places a new race has appeared. Broomrape can be confined using chemical control, but growing resistant genotypes appears to be the most efficient and reliable way of control. The sources of resistance have mainly been found in the wild species of the genus Helianthus. Sunflower resistance to broomrape is controlled by Or genes. The system of resistance control depends on the race of broomrape and sources of resistance material. Over the last five decades, significant results have been achieved in sunflower breeding for the resistance to broomrape. Five dominant genes (Or1-Or5), which provide resistance to five races of broomrape (A-E), have been identified, establishing a set of five differential lines. The set was later supplemented with lines resistant to race F. Intensive work has been done at the Institute of Field and Vegetable Crops (IFVC) on: (1) finding the source of resistance towards races which overcome races E and F, in the wild species and cultivated sunflower, (2) determining the gene effects and mode of inheritance of this trait; as well as (3) research on the molecular level, focused on finding markers closely linked to Or genes. Genotypes were tested in naturally infested fields in Serbia, where race E is fully dominant; Spain, where race F is predominant; and in Romania and Turkey, where very virulent races (over race F) of broomrape are present. The results have indicated that several genotypes were selected as potentially resistant or highly tolerant to virulent races of broomrape present in these locations. Intensive research on the molecular level was focused on the development of specific DNA markers, in order to facilitate and accelerate the introduction of resistance into cultivated sunflower. By comparing the molecular profile of resistant and susceptible genotype, a polymorphism was observed on LG3 of the SSR map. The identification of closely related molecular markers will facilitate the introgression of the gene into different sunflower lines. Another way to control broomrape is the cultivation of sunflower hybrids tolerant to imidazolinone herbicides. This measure solves the problem of broomrape regardless of its racial composition.

The potential of foxtail millet as a trap crop for sunflower broomrape

Heavy infestation of large areas in China by the root parasitic sunflower broomrape (Orobanche cumana Wallr.) constitutes a major threat to sunflower production. This study was conducted to investigate the potential of foxtail millet as a trap crop for the management of sunflower broomrape (SB). To assay the ability of foxtail millet to stimulate germination of SB seeds, the rhizosphere soil of six foxtail millet cultivars cultured in various sand/soil ratios and fertilizer levels were employed to directly induce SB germination. Among all sand/soil treatments, Hong Guzi grown in a 1:1 sand/soil ratio induced the highest germination of SB (30.1%). Phosphorus resulted in a small but significantly higher germination of SB compared with the control without any fertilizer, while in contrast, nitrogen greatly suppressed the germination inducing capacity of foxtail millet even at concentrations as low as 28 mg kg−1 soil (based on N). Cropping rotation experiment was undertaken to quantify the effect of foxtail millet on SB infection in a subsequent sunflower crop. All foxtail millet rotation treatments reduced broomrape infection and gave higher shoot and flower disk dry mass of sunflowers than the control grown without a fore-rotating crop. These results suggest that efficacious cultivars of foxtail millet reduce SB parasitism and increase sunflower yields and that using foxtail millet as trap crop is probably an effective way to reduce the broomrape weed problem in China, especially in the dry, infertile, and sandy soils of the Loess Plateau.

Conditioning duration and agents involved in broomrape seeds responding to germination stimulants

Weedy broomrape species, such as sunflower broomrape (Orobanche cumana Wallr.) and Egyptian broomrape [Phelipanche aegyptiaca Pers. (syn. O. aegyptiaca)], require a period of pre-conditioning before they can respond to germination stimulants. Thus, the sensitivity of weedy broomrape seeds to germination stimulants could be an important factor for broomrape control. In this study, the influence of conditioning agents, conditioning period (0–21 days) and germination stimulants on the germination of sunflower broomrape and Egyptian broomrape seeds was analyzed. Without conditioning, the sunflower and Egyptian broomrape seeds exhibited negligible germination responses to the stimulants. The germination rate of the broomrape seeds increased rapidly with conditioning period and reached a maximum under a conditioning period of 4–10 days; further prolonged conditioning resulted in a decrease in the germination rate. Gibberellic acid (GA3) could not only break the dormancy of the sunflower and Egyptian broomrape seeds but also maintained the high sensitivity of these seeds even after 21 days of conditioning. Furthermore, 100 µM of GA3 induced the germination of the Egyptian broomrape seeds. The stimulants that induced Egyptian broomrape germination were ranked in decreasing order as GR24 (76.8 %), strigol (76.1 %), tobacco root exudates (49.5 %), dehydrocostus lactones (DCL, 39.2 %), and maize root exudates (18 %). In contrast, GA3 did not directly induce sunflower broomrape seed germination, which responded to strigol (62.8 %) > maize root exudates (58.2 %) > GR24 (57.9 %) > tobacco root exudates (41.6 %) > DCL (41.3 %). These results indicate specialized recognition of germination stimulants by sunflower and Egyptian broomrape. This study may contribute to a better understanding of parasitic weed germination and may lead to improved control strategies.

Increased Virulence in Sunflower Broomrape (Orobanche cumana Wallr.) Populations from Southern Spain Is Associated with Greater Genetic Diversity.

Orobanche cumana Wallr. (sunflower broomrape) is a holoparasitic weed that infects roots of sunflower in large areas of Europe and Asia. Two distant O. cumana gene pools have been identified in Spain, one in Cuenca province in the Center and another one in the Guadalquivir Valley in the South. Race F has been hypothesized to have arisen by separate mutational events in both gene pools. In the Guadalquivir Valley, race F spread in the middle 1990’s to become predominant and contained so far with race F hybrids. Recently, enhanced virulent populations of O. cumana have been observed in commercial fields parasitizing race F resistant hybrids. From them, we collected four independent populations and conducted virulence and SSR marker-based genetic diversity analysis. Virulence essays confirmed that the four populations studied can parasitize most of the race F resistant hybrids tested, but they cannot parasitize the differential inbred lines DEB-2, carrying resistance to race F and G, and P-96, resistant to F but susceptible to races G from other countries. Accordingly, the new populations have been classified as race GGV to distinguish them from other races G. Cluster analysis with a set of populations from the two Spanish gene pools and from other areas, mainly Eastern Europe, confirmed that race GGV populations maintain close genetic relatedness with the Guadalquivir Valley gene pool. This suggested that increased virulence was not caused by new introductions from other countries. Genetic diversity parameters revealed that the four populations had much greater genetic diversity than conventional populations of the same area, containing only alleles present in the Guadalquivir Valley and Cuenca gene pools. The results suggested that increased virulence may have resulted from admixture of populations from the Guadalquivir Valley and Cuenca followed by recombination of avirulence genes.

Simplified strigolactams as potent analogues of strigolactones for the seed germination induction of Orobanche cumana Wallr.

Strigolactones play an important role in the rhizosphere as signalling molecules stimulating the seed germination of parasitic weed seeds and hyphal branching of arbuscular micorrhiza, and also act as hormones in plant roots and shoots. Strigolactone derivatives, e.g. strigolactams, could be used as suicidal germination inducers in the absence of a host crop for the decontamination of land infested with parasitic weed seeds. We report the stereoselective synthesis of novel strigolactams, together with some of their critical physicochemical properties, such as water solubility, hydrolytic stability, as well as their short soil persistence. In addition, we show that such strigolactams are potent germination stimulants of O. cumana parasitic weed seeds and do not affect the seed germination and the root growth of sunflower. The novel strigolactam derivatives described here compare favourably with the corresponding GR-28 strigolactones in terms of biological activity and physicochemical properties. However, we believe strigolactone and strigolactam derivatives require further structural optimisation to improve their soil persistence to demonstrate a potential for agronomical applications. © 2016 Society of Chemical Industry.

Research on resistance to sunflower broomrape: an integrated vision

Sunflower broomrape ( Orobanche cumana Wallr.) parasitization on sunflower was first observed at the end of the 19th century and has continued since then jeopardizing sunflower cultivation in many areas of Europe and Asia. A distinctive characteristic of the O. cumana -sunflower parasitic system is that it is mainly governed by a gene-for-gene interaction. This determines complete resistance in the host controlled by dominant alleles at a single locus, which facilitates the management of the resistance for hybrid seed production. But on the other hand avirulence in the parasite is also controlled by dominant alleles at a single gene. Monogenic, dominant resistance exerts a strong selection pressure on the parasite that maximizes the probability of overcoming resistance mechanisms in a short period of time. This has in fact resulted in a number of physiological races that periodically surpass all the available resistance sources. The spread of populations to new areas and the subsequent hybridization between populations is another mechanism creating genetic diversity in sunflower broomrape and allegedly recombination of avirulences genes. After more than one century of coexistence, genetic resistance to broomrape in sunflower has to be focused under an integrated approach that considers not only the characterization of resistance mechanisms in the host, but also the genetic and physiological bases of avirulence in the parasite. From the perspective of genetic resistance in sunflower, most important is not relying only on single dominant genes, but following instead pyramiding strategies. These should give priority to combining complementary mechanisms of resistance under both qualitative (vertical) and quantitative (horizontal) genetic control. These aspects are discussed in the paper.

Genetic study of recessive broomrape resistance in sunflower

Genetic resistance to broomrape (Orobanche cumana Wallr.) in sunflower is mainly monogenic and dominant. Massive use of vertical resistance has led to the progressive extension of increasingly virulent races of the parasite. Additional introduction of horizontal resistance genes is crucial to develop more durable resistance. The objective of this research was to study the inheritance of resistance to broomrape race F in sunflower line K-96 and to identify QTL of potential value for marker assisted pyramiding of resistance genes. The inheritance of broomrape resistance was studied in crosses with the susceptible line P-21 and the line P-96, with oligogenic recessive resistance. Crosses with P-96 revealed broad transgressive segregation for susceptibility in the F2, indicating that both lines possess different resistance alleles. Crosses with P-21 suggested that the trait is mainly controlled by a dominant-recessive epistasis at two loci. Additionally, segregation for plant height was identified and measured in a non-inoculated F2 population. Five QTL on LG 2, 3, 4, 5, and 6 were associated with broomrape resistance traits. Two of them at LG 4 and 5 were also associated with plant height, suggesting an alleged pleiotropic effect of plant height on broomrape resistance. The latter two QTL had been previously identified in the cross P-21 × P-96, whereas the other QTL seem to be involved in K-96 but not in P-96 resistance. This study concluded that K-96 and P-96 have complementary QTL with minor effect on broomrape resistance. They are, therefore, good donor sources for marker-assisted pyramiding programs.

New sunflower hybrids tolerant to tribenuron-methyl

The creation of sunflower hybrids tolerant to tribenuron-methyl enabled the use of wider palette of herbicides to control effectively weeds during the growing season. Moreover, thanks to this tolerance, chemical control of broad-leaves weeds in sunflower, especially Cirsium arvense, is more efficient. The Institute of Field and Vegetable Crops offers four new hybrids tolerant to tribenuron-methyl: NS SUMO SUN, NS SUMO STAR, NS SUMO SjAj and NS SUMO SOL, released in 2016. Hybrids belong to early and medium-early maturity groups; have high yield potential and high oil content. They are adapted for cultivation in different environmental conditions. All hybrids are resistant to broomrape (Orobanche cumana Wallr) races from A-E and have a high level of tolerance to Phomopsis, white rot (Sclerotinia sclorotiorum), rust (Puccinia helianthi) and others. The paper presents the results of seed and oil yield from the official trials of the Department of variety registration within the Ministry of Agriculture and Environmental Protection of the Republic of Serbia.

The Virulence of Broomrape (Orobanche cumana Wallr.) in Sunflower Crop in Braila Area, in Romania

AbstractBroomrape

Stimulating effect of the root exudates of sorghum, millet, and Sudan grass on the seed germination of broomrape (Orobanche cumana Wallr.) infesting sunflowers in Russia

Broomrape (Orobanche cumana Wallr.) is a harmful obligate parasite of sunflower. We found that the negative effect of broomrape on the cultivation of this crop can be eliminated by planting the crops that stimulate the germination of broomrape seeds but do not serve as its hosts. Under laboratory conditions, the root exudates of eight samples of grain sorghum, three samples of sugar sorghum, two samples of Sudan grass, and five cultivars of common millet stimulated the germination of broomrape seeds in different ways. It was observed that Gureeva millet, Sudan grasses Anastasia and Aleksandrina, grain sorghum Khasine 28, and sugar sorghum Listvenit are the most suitable provocative crops for the elimination of O. cumana seeds.

Seed Structure Characteristics of Orobanche cumana Populations

AbstractSunflower broomrape Orobanche cumana Wallr. is a rapidly growing threat to the oil crop production in many countries. Fast adaptation to new environments and increasing host resistance suggests that phenotypically distinctive populations of the weed may have evolved. The classification of the species and the differentiation of such populations on the base of seed micromorphological characters were attempted. Morphometric measurements allowed the distinction of O. cumana from several other Orobanche and Phelipanche species. An irregularly thickened cell wall of the anticlinal testa cells differentiated O. cumana and O. cernua from O. caryophyllacea, O. crenata, O. minor, P. aegyptiaca, P. arenaria and P. ramosa. However, populations of sunflower broomrape from five European countries and China could not be separated from each other on the base of micromorphological seed characters. In contrast, length to width measurements indicated that the Asian samples had a slightly different seed shape which was less elongated than the European samples. However, this seemingly geographic effect may as well be a consequence of sampling which comprised a higher rate of the so-called modern races E-H in the European samples.

First Report of Race Composition and Distribution of Sunflower Broomrape, Orobanche cumana, in China.

Sunflower broomrape (Orobanche cumana Wallr.) is a holoparasitic plant that penetrates the vascular system of sunflower roots, absorbs plant nutrients and water, and thus causes stunting, reduced growth, and severe yield losses (3). To date, seven races of sunflower broomrape (O. cumana) have been identified by using international standard race differential hosts in Bulgaria, Serbia, Romania, Turkey, and Russia (4). However, the race types present in China are unknown. To identify the race composition of sunflower broomrape in China, race differential hosts of sunflower broomrape were received from Dr. Dragan Skoric (Serbian Academy of Sciences and Arts, Novi Sad, Serbia): Line AD66 has no resistant genes; Kruglik-41 contains resistant gene Or1; B-RO-02A has Or2; Record has Or3; LC1002B has Or4; LC1003B has Or5; LC-1093 has Or6, and Race-G-2 has Or7 (1). Eighteen sunflower broomrape samples were collected in August of 2011, 2012, and 2013 from different provinces/locations in China, including Xinjiang (Xinyuan, Shihezi, Tekesi, Beitun, Urumqi, and Yining), Inner Mongolia (Linhe, Xixiaozhao, Wuqianqi, Tuzuoqi, Keyouqianqi, and Aohanqi), Shanxi (Hunyuan, Shilou, Mizhi, and Dingbian), Jilin (Tongyu), and Hebei (Xuanhua). The differential hosts were each inoculated with the seeds of each broomrape isolate that was recovered, as described by Pancenko with minor modification (2). Briefly, two parts of field soil and one part of vermiculite were mixed together and used as potting mix. The mix was inoculated with broomrape seeds at 10 mg of seeds per 100 g of potting mix. The inoculated mix was placed in a 7-cm (diameter) × 11-cm (height) plastic pot to fill two-thirds of the pot volume. Three sunflower seeds were placed on the surface of the mix at an even distance from each other and covered with additional mix. The pots were kept in a greenhouse under a 16-h photoperiod at 10,000 lux of illumination intensity, temperature of 20-25°C, and 40% relative humidity. Forty days after incubation, sunflower seedlings were taken out from the pot and the roots washed with tap water. The number of tubercles was recorded on the root of each differential host. Race types were determined based on the reaction (tubercule formation on roots) of all the standard differential hosts to the test isolate. The results showed that races A, D, E, and G of O. cumana were present among the isolates. Race G was found in Wuqianqi, Xixiaozhao, and Linhe in the western part of Inner Mongolia. Race E was found only in Shihezi of Xinjiang. Race D was found in Aohanqi and Keyouqianqi (eastern part of Inner Mongolia); Xinyuan, Tekesi, Beitun, and Urumqi (northern part of Xinjiang); and Tongyu (northern part of Jilin). Race A was found in Mizhi, Shilou, and Hunyuan of Shanxi province and Xuanhua in Hebei province. Additionally, race A was also found in Tuzuoqi, the middle region of Inner Mongolia. Thus, races A, D, E, and G were the main race types of O. cumana in China. Race D was the predominant race type and had the widest distribution. Race G was the highest level race type in this study but was mainly limited to the western part of Inner Mongolia. This is the first report of race composition and distribution of sunflower broomrape (O. cumana) in China.

Switchgrass (Panicum virgatum L.) has ability to induce germination of Orobanche cumana

Orobanche cumana Wallr. (sunflower broomrape) is a devastating root parasitic weed, causing enormous crop losses worldwide. The question was whether or not switchgrass has the potential to be a ‘trap crop’ for O. cumana control. To answer this question, the field experiments, pot experiments, and laboratory experiments were conducted in this study. The ability of nine switchgrass (Panicum virgatum L.) cultivars to induce O. cumana seeds germination was tested. Results indicated that root extracts shoot extracts, rhizosphere soil, and root exudates from switchgrass induced O. cumana germination. Ability to induce germination varied significantly among growing stages, with the earlier part of growing season (grown for 2 weeks) generally inducing the highest O. cumana germination rates. The methanol was a more suitable solvent than distilled water for extracting germination stimulants from switchgrass plants. Ten-fold dilutions of the extracts generally induced higher germination rates than either undiluted or 100-fold dilutions. The germination rates of O. cumana seeds in shoot extracts treatments were positively correlated with those in the root extracts (R2 = 0.6397; p < 0.01) and negatively correlated with those in the rhizosphere soil treatments ( R2 = 0.4433; p < 0.05). In conclusion, it is believed that switchgrass is a potential trap crop for the control of root parasitic weed O. cumana.

Genetic similarity and differences between the Orobanche cumana Wallr. Populations from Russia, Kazakhstan, and Romania revealed using the markers of simple sequence repeat

The molecular genetic diversity of the broomrape (O. cumana) populations, parasitizing on sunflower in Russia, Romania and Kazakhstan, was studied with codominant microsatellite markers. By means of cluster analysis, the populations of broomrape were divided into two clusters, regardless of their racial composition. In the first cluster, 19 samples from Russia and Kazakhstan, representing one gene pool are grouped; the second cluster consisted of five populations from Romania, united in another pool. According to Nei, the genetic distance between the clusters was 0.137. The analysis of molecular variance revealed that 22% of total variance were caused by differences between the genetic pools and 78% appeared due to differences between the samples within the each gene pool. The pairwise comparisons performed by Wright’s statistics showed that the differences between these two gene pools are sufficient (Fst = 21.9%) in order to make the conclusion about the existence of small genetic differentiation between the pools. The descriptive population genetic statistics for each pool indicate that the broomrape populations from Russia and Kazakhstan are characterized by a higher level of intrapopulation diversity than the populations from Romania.

Allelopathy of rice (Oryza sativa L.) root exudates and its relations with Orobanche cumana Wallr. and Orobanche minor Sm. germination

Allelopathy has been considered not only as an environmentally friendly approach for weed control but also a potential reason causing autotoxicity in crop production. In this study, the responses of seeds of lettuce, wheat, rice, clover broomrape (CB), and sunflower broomrape (SB) to the root exudates of rice cultivars were studied. Lettuce germination was promoted by root exudates of Yliangyou 3218 and I-Kung-Pao. Wheat seedling growth was inhibited by all nine rice species. I-Kung-Pao and Ganxin 203 exerted greater autotoxicity than other cultivars. Yongyou 15 and I-Kung-Pao induced the highest germination rate of CB, while Yongyou 13, Zhongzao 22, and I-Kung-Pao induced the highest germination rate of SB. A significantly correlation was noted between germination-inducing ability on broomrape seeds and allelopathic effects on target plants. It is suggested that using broomrape seeds germination is a better receptor for the identification of rice allelopathic potential.

Wild Sunflower Species as a Genetic Resource for Resistance to Sunflower Broomrape (Orobanche cumana Wallr.)

AbstractBroomrape (

Interpopulation Genetic Differentiation Orobanche cumana Wallr. from Russia, Kazakhstan and Romania Using Molecular Genetic Markers

AbstractBroomrape (

Broomrape (Orobanche Cumana Wallr.) Resistance Breeding Utilizing Wild Helianthus Species

AbstractWild