Sunflower Broomrape Research Articles

Virulence and aggressiveness of sunflower broomrape (Orobanche cumana Wallr.) populations in Romania

The pathogenic composition of broomrape populations in Eastern Europe, Turkey and Spain has changed over the years, slowly at first and then rapidly. In Romania, there are three important areas infested with broomrape (Orobanche cumana Wallr.). These areas differ in infestation degree and presence of different virulence groups. A new, highly virulent population of broomrape attacked sunflower in Romania in 2006. Many commercial hybrids belonging to different companies or to research institutes lost their resistance to the parasite in a heavily infested area near the Black Sea. The sunflower differentials set for the different races of the parasite have permited to identify a new, highly virulent population of broomrape in this area. The parasite infestation degree on the hybrids resistant to the old races has showed that this population is very aggressive. Several genotypes fully resistant to this new broomrape population have been identified in the sunflower germplasm collection of Fundulea institute. These genotypes (lines) can be used as sources of resistance genes as well as for obtaining resistant hybrids.

Interactions of sunflower ( Helianthus annuus) and sunflower broomrape ( Orobanche cumana) as affected by sowing date, resource supply and infestation level

The holoparasitic weed Orobanche cumana (sunflower broomrape) constrains sunflower ( Helianthus annuus) production in many countries. The development of efficient control strategies requires an understanding of the processes underlying the complex environment–host–parasite interrelations. Growth and development of O. cumana and sunflower were quantified under field conditions in southeastern Romania. Sunflower hybrid Florom 350 was sown at two dates, in plots infested with 0, 50, 200 and 1600 viable O. cumana seeds kg −1 dry soil, under low-input (rainfed, low nitrogen supply) and high-input (irrigated, high nitrogen supply) conditions. Sunflower shoot biomass reached peak values of 760–1287 g m −2 between the end of anthesis and physiological maturity. Seed yield varied from 221 to 446 g m −2. Sunflower biomass and yield were affected by all experimental factors. Seed yield responded positively to delaying sowing from early April to late May as well as to irrigation and fertilisation, and negatively to O. cumana infestation. Yield reductions, which were a product of reduced seed number and size, amounted to 13%, 25% and 37% at parasite seed densities of 50, 200 and 1600 viable seeds kg −1 soil, respectively. Maximum O. cumana attachment numbers, recorded in late-sown high-input crops in 2004, ranged from 11 m −2 in plots with 50 parasite seeds kg −1 soil to 188 m −2 with 1600 seeds kg −1 soil. Parasite attachment number was a function of crop sowing date, water and nutrient supply, seedbank density, and sunflower biomass and root length density, via mechanisms of parasite seed stimulation, host carrying capacity and intraspecific competition. Delayed sowing and improved water and nitrogen supply were associated with increases in parasite number that neutralised yield-boosting effects of irrigation and fertilisation at the highest infestation level. Sunflower shoot biomass was significantly reduced by O. cumana infection, with reductions affecting organs in the order head > stem > leaves. Most of the discrepancy between infected and non-infected plants was accounted for by O. cumana biomass. Parasites mainly acted as an extra sink for assimilates during sunflower generative growth and impaired host photosynthesis to a much lesser degree. Results suggest that similar mechanisms govern infection level and host–parasite biomass partitioning across different Orobanche–host systems.

Update on breeding for resistance to sunflower broomrape

Update on breeding for resistance to sunflower broomrape

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

SummaryDifferent 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.

Pre-haustorial resistance to broomrape (Orobanche cumana) in sunflower (Helianthus annuus): cytochemical studies

Sunflower broomrape (Orobanche cumana Wallr.) is a root holoparasitic angiosperm considered as one of the major constraints for sunflower production in Mediterranean areas. Breeding for resistance is regarded as the most effective, feasible, and environmentally friendly solution to control this parasite. However, the existing sources of genetic resistance are defeated by the continuous emergence of new more virulent races of the parasite. In this work, the interaction between sunflower and O. cumana has been analysed in order to gain insights into the mechanisms involved in resistance. Two sunflower genotypes were selected showing different behaviour against the new race F of O. cumana, HE-39998 (susceptible) and HE-39999 (resistant), and both compatible and incompatible interactions were compared. Pot and Petri dish bioassays revealed that only HE-39998 plants were severely affected, supporting a high number of successfully established broomrapes to mature flowering, whereas in HE-39999 root tubercles were never observed, resistance being associated with browning symptoms of both parasite and host tissues. Histological aspects of the resistance were further investigated. Suberization and protein cross-linking at the cell wall were seen in the resistant sunflower cells in contact with the parasite, preventing parasite penetration and connection to the host vascular system. In addition, fluorescence and confocal laser microscopy (CLM) observations revealed accumulation of phenolic compounds during the incompatible reaction, which is in agreement with these metabolites playing a defensive role during H. annuus-O. cumana interaction.

Effects of Broomrape Parasitism on Sunflower Plants: Growth, Development, and Mineral Nutrition

ABSTRACT Sunflower broomrape (Orobanche cumana Wallr.) is a parasitic plant that infects sunflower (Helianthus annuus L.) plants. In this work, sunflower plants were grown under greenhouse conditions in pots with the substrate infested or non-infested with broomrape seeds. At different numbers of days after sowing, plant height, internode lengths, number of leaves, head diameter, mineral composition of leaves, and potassium (K) concentration in stem were measured. The negative effects of broomrape parasitism were assessed from 57 d after sowing, when broomrape started to emerge. Parasitized plants exhibited lower shoot dry weight, height, and head diameter than control plants. The reduction in internode lengths was associated with a decrease in the gradient of K concentration from basal to apical stem. The mineral composition of leaves was also affected in parasitized plants. The concentrations of calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn) in leaves of parasitized plants were lower than those of the control plants, while there were few differences for K, phosphorus (P), iron (Fe), and copper (Cu). The effects of parasitism are discussed in relation to their competition for resources and to perturbations of the host physiology such as hormonal and water balance.

First Report of a New Race of Sunflower Broomrape (Orobanche cumana) in Israel

The genus Orobanche includes chlorophyll-lacking root parasites that parasitize many dicotyledonous species and causes severe damage to vegetable and field crops worldwide. Sunflower broomrape (Orobanche cumana Wallr.) is known in Eurasia as a specific parasite of sunflower, which differs from the nodding broomrape (O. cernua Loefl) in host specificity and morphological characteristics (3). Together with Egyptian broomrape (O. aegyptiaca Pers.), it seriously parasitizes sunflower (Helianthus annuus L.) in Israel (1). Prior to 2000, the local confectionary sunflower cvs. Ambar and Gitit proved to be resistant to the local O. cumana populations in Israel (2). A preliminary study, which we conducted in 1995 using the Vranceanu's differentials (4), indicated that O. cumana populations in Israel behave like the known race C. Using random amplified polymorphic DNA analysis, we also found a very low intraspecific diversity of this species in Israel at that time. However, in 2000, infection of the sunflower cvs. Ambar and Gitit was reported in two fields (Gadot and Afek) in northern Israel. In 2001 and 2002, O. cumana parasitized these cultivars in three more locations as much as 50 km apart (Tel-Adashim, Mevo-Hama, and Bet-Hilel). To determine the virulence of O. cumana populations on sunflower cultivars under controlled conditions, O. cumana seeds were collected in the above mentioned sunflower fields. In addition, we also used seeds from an O. cumana population collected in Alonim in 1997. This latter population did not infect the above mentioned 'resistant' sunflower cultivars in the field (2,); therefore, represented the previously known O. cumana populations in Israel. Resistant (Ambar) and susceptible (D.Y.3) sunflower cultivars were planted in separate pots that were differentially filled with soil that was inoculated with O. cumana seeds of the different populations. The experiment was performed in a full factorial arrangement with six replications. As expected, O. cumana from Alonim failed to attack the resistant sunflower. However, the O. cumana populations that were collected in the five other fields seriously attacked both sunflower cultivars, indicating higher virulence. O. cumana from all five new populations proved more virulent than the Alonim population on cvs. Ambar and D.Y.3. The occurrence of these new virulent populations could have several reasons including: (i) importation of virulent parasite seeds from abroad; or (ii) local development of virulence from previously avirulent populations. The latter could be favored by the continuous and repeated use of the available resistant varieties that are all based on a single resistance response (2).

IAA production during germination of Orobanche spp. seeds

Broomrapes ( Orobanche spp.) are parasitic plants, whose growth and development fully depend on the nutritional connection established between the parasite and the roots of the respective host plant. Phytohormones are known to play a role in establishing the specific Orobanche–host plant interaction. The first step in the interaction is seed germination triggered by a germination stimulant secreted by the host-plant roots. We quantified indole-3-acetic acid (IAA) and abscisic acid (ABA) during the seed germination of tobacco broomrape ( Orobanche ramosa) and sunflower broomrape ( O. cumana). IAA was mainly released from Orobanche seeds in host–parasite interactions as compared to non-host–parasite interactions. Moreover, germinating seeds of O. ramosa released IAA as early as 24 h after the seeds were exposed to the germination stimulant, even before development of the germ tube. ABA levels remained unchanged during the germination of the parasites’ seeds. The results presented here show that IAA production is probably part of a mechanism triggering germination upon the induction by the host factor, thus resulting in seed germination.

Dominance relationships for genes conferring resistance to broomrape (Orobanche cumana wallr) in sunflower

The holoparasitic angiosperm sunflower broomrape (Orobanche cumana Wallr) is currently regarded as one of the most important constraints of sunflower production in many areas in Southern Europe and the Black Sea region. Breeding for resistance is considered to be the most effective and feasible method of controlling sunflower broomrape. Commercial hybrids cultivated in Spain carry the Or1 to Or5 genes that confer resistance to races A to E. However, a new race, designated F, has been identified. Germplasm with race F resistant genes derived from wild and cultivated sunflowers has been developed. Dominance reaction of these genes is an essential feature that determine the breeding method to produce race F resistant sunflower hybrids. Crosses between different sources of race F resistant lines, including those derived from wild and cultivated sunflower, and different susceptible parental lines were made. Allelic crosses between race F resistant lines, as well as crosses between race F resistant lines and race E resistant lines were also carried out. F1 plants, F2 plants, and their parental lines were evaluated for their disease reaction to race F or race E of broomrape. Different dominance reactions and inheritance mechanisms for broomrape resistance were observed. These depended on the race of broomrape, the source of race F resistance, and also the susceptible parental line used for the cross. The relevance of the results obtained for sunflower breeding for resistance to sunflower broomrape is discussed.

Effect of temperature on susceptibility of sunflower varieties to sunflower broomrape (Orobanche cumana) and Egyptian broomrape (Orobanche aegyptiaca)

Sunflower broomrape and Egyptian broomrape are two holoparasites of sunflower that cause severe yield loss. The aim of the current study was to clarify the relationship between temperature and sunflower broomrape and Egyptian broomrape parasitism of the resistant sunflower variety ‘Ambar’ (R) and the susceptible variety ‘Adi’ (S). Experiments were conducted in pots under controlled conditions in a multiclimate greenhouse at five temperature (day–night) regimes: 17:9 C, 20:12 C, 23:15 C, 26:18 C, and 29:21 C. The resistant confectionery sunflower variety (R) was susceptible to sunflower broomrape only at low temperature regimes of 17:9 C, whereas the S variety was highly susceptible from 29 to 9 C. Temperature correlated negatively with the number of sunflower broomrape and Egyptian broomrape shoots that emerged above the soil in the R variety, and positively in the S variety. The number of degenerated tubercles found on the roots of the resistant variety correlated positively with temperature in both sunflower broomrape and Egyptian broomrape. No such correlation could be found in the susceptible sunflower variety grown in the presence of these two parasites. The resistance response of the R variety to sunflower broomrape and Egyptian broomrape was similar regardless of temperature regime. Parasite seeds were successfully germinated and attached to the sunflower roots but the parasite at the infection site degenerated and died. On the other hand, the susceptible variety (S) was equally susceptible to Egyptian broomrape and sunflower broomrape in all the temperature regimes tested, and susceptibility increased as temperature increased.

Granular Pesta formulation of Fusarium oxysporum f. sp. orthoceras for biological control of sunflower broomrape: efficacy and shelf-life

Formulation of fungal propagules encapsulated in a wheat-gluten matrix (termed ‘Pesta’) has proved to be a suitable technique for the development of Fusarium oxysporum f. sp. orthoceras (FOO) as a bioherbicide for sunflower broomrape ( Orobanche cumana ). To improve the efficacy of this fungus, 19 Pesta formulations, using two types of fungal spores and 8 adjuvants, used singly or in combinations, were examined for their shelf-life and for efficacy under greenhouse conditions. Amending Pesta with yeast extract reduced the loss of viability of microconidia and chlamydospores during production of the formulations by 40 and 100%, respectively. Sodium alginate and Water Lock also prevented loss of viability of chlamydospores during Pesta production. The longest shelf-life (inoculum viability) was obtained when granules were stored at 3 °C. In greenhouse experiments, there were no differences among the 19 Pesta treatments in disease severity (DS). In terms of the number of Orobanche attachments, Orobanche dry matter, and the number of Orobanche shoots that produced seeds, the most effective formulations were Pesta 14 (containing chlamydospores [PC] with yeast extract, glycerol, and sucrose as additives), Pesta 1 (containing microconidia [PM] with yeast extract and sucrose), Pesta 5 (PM with yeast extract, glycerol, and sucrose), Pesta 7 (PM with sodium alginate as an additive), and Pesta 15 (PC with stillage). These formulations produced 99, 98, 98, 97, and 97%, DS, respectively, and caused reduction in Orobanche biomass by 80, 76, 71, 80, and 67%, respectively. These Pesta formulations of FOO increased sunflower seed yield by 5–11 times in comparison with the negative control inoculated with fungus-free Pesta. In general, applications of the formulations of FOO in Pesta did not affect the number of leaves, stem diameter, plant height, or the dry matter of roots of sunflower or the rate of photosynthesis in sunflower plants.

Broomrape (Orobanche cumana) Control in Sunflower (Helianthus annuus) with Imazapic1

Field trials were conducted in 1997 and 1998 at two locations in Israel to evaluate the efficacy of imazapic applied postemergence (POST) to sunflower for broomrape control under irrigated and nonirrigated conditions. Two sequential treatments of imazapic at 1.5 followed by (FB) 3.0, 3.0 FB 4.5, or 4.5 FB 6.0 g ai/ha on sunflower plants 12 ± 3 and 55 ± 5 cm tall, respectively, reduced sunflower broomrape throughout the growing season under irrigated and nonirrigated conditions. Sunflower growth was not affected by imazapic treatments. It was confirmed, in accordance with an earlier report, that when sequential treatments of imazapic included an application at the sunflower inflorescence developmental stage, the herbicide decreased seed yield in proportion to the applied rate.Nomenclature: Imazapic; broomrape, Orobanche cumana Waller; sunflower, Helianthus annuus L.Additional index words: Parasitic weed, herbicide.Abbreviations: fb, followed by; POST, postemergence; PRE, preemergence.

Comparative studies on Orobanche cernua L. and O. cumana Wallr. (Orobanchaceae) in the Iberian Peninsula

The systematic treatment of Orobanche cumana Wallr. and O. cernua L. is controversial. Whereas some authors consider O. cumana as an infraspecific taxon of O. cernua, others treat it as a separate species. Furthermore, the nomenclature of the sunflower broomrape is unclear, and both names are found without qualification in the literature. The objective of the present study has been to evaluate the distribution, morphology, and ecology of O. cernua and O. cumana in the Iberian Peninsula, as well as their seed oil fatty acid profile, which is a trait of great chemotaxonomic value. O. cernua was found parasitizing wild Compositae, mainly Artemisia sppwhereas O. cumana was exclusively found on cultivated sunflower. Both species clearly differ in morphological traits, especially plant height and build, length and structure of the inflorescence, corolla length and colour. Both species are characterized by contrasting seed oil fatty acid profiles, with high oleic acid concentration in O. cernua and high linoleic acid concentration in O. cumana. The evaluation of both taxa in the Iberian Peninsula gives additional support to those authors that treat them as separate species.

Comparative studies on Orobanche cernua L. and O. cumana Wallr. (Orobanchaceae) in the Iberian Peninsula

The systematic treatment of Orobanche cumana Wallr. and O. cernua L. is controversial. Whereas some authors consider O. cumana as an infraspecific taxon of O. cernua , others treat it as a separate species. Furthermore, the nomenclature of the sunflower broomrape is unclear, and both names are found without qualification in the literature. The objective of the present study has been to evaluate the distribution, morphology, and ecology of O. cernua and O. cumana in the Iberian Peninsula, as well as their seed oil fatty acid profile, which is a trait of great chemotaxonomic value. O. cernua was found parasitizing wild Compositae, mainly Artemisia sppwhereas O. cumana was exclusively found on cultivated sunflower. Both species clearly differ in morphological traits, especially plant height and build, length and structure of the inflorescence, corolla length and colour. Both species are characterized by contrasting seed oil fatty acid profiles, with high oleic acid concentration in O. cernua and high linoleic acid concentration in O. cumana . The evaluation of both taxa in the Iberian Peninsula gives additional support to those authors that treat them as separate species.

R‐41, a sunflower restorer inbred line, carrying two genes for resistance against a highly virulent Spanish population of Orobanche cernua

AbstractThe inheritance of resistance to a highly virulent population of sunflower broomrape (Orobanche cernua) has been studied in R‐41, a Spanish sunflower restorer inbred line. Using the cytoplasmic male‐sterile inbred line HA‐89 (cms; very susceptible to this population of broomrape) as a female parent, progenies of the cross with R‐41, i.e. Fl, F2 and BC1 to both parents, as well as the parental lines, were analysed for their reaction to the broomrape population EC‐94. The goodness of fit of the observed vs expected segregation ratios indicated that the inheritance of resistance to broomrape in line R‐41 is conferred by two independent dominant genes.

Screening for resistance to broomrape (Orobanche cernua) in cultivated sunflower

AbstractRacial evolution of sunflower broomrape (Orobanche cernua) has been very rapid in Spain during recent years, in which resistance has been overcome several times and there has been an important increase in areas infested with this parasitic angiosperm. In order to find resistance to a highly virulent population of sunflower broomrape that could be used directly in breeding programmes, three different sets of cultivated plant material composed of 429 entries were tested by artificial inoculation. All evaluated inbred lines from Moden, Canada, were fully susceptible. Out of the 240 P.I. accessions tested, only 10 segregated for resistance to broomrape, the rest being susceptible. From the 160 USDA breeding lines evaluated, 5% were resistant and 19% segregated for resistance to O. cernua. These lines traced back mainly to crosses of RHA 274 and RHA 801 with Russian, Turkish and Romanian hybrids. The origin of P.I. accessions that segregated for resistance were primarily derived from the former USSR and from Romania.

Inheritance of Resistance toOrobanche cumanain Sunflower

The inheritance of resistance to Orobanche cumata (sunflower broom-rape) in the resistant sunflower lines SW-501 and RW-637 and the hybrid Sunbred-254 was studied in crosses with susceptible sunflower cultivars Aya and DI-1, in the field and in the growth chamber. Resistance in SW-501 and RW-637 was conferred by a single dominant gene. SW-501 was homozygously resistant, and RW-637 was heterozygously resistant, having one resistance allele and one susceptible allele. The testcross progeny of Sunbred-254 (SW-501 X RW-637) to the susceptible Aya segregated 3 resistant: 1 susceptible, indicating that Sunbred-254 is composed of two genotypically different subpopulations in equal parts, representing the genetic differences between RW-637 and SW-501 in the resistance to Orobanche cumana