Pomegranate (Punica granatum) as Host of the Broomrapes Phelipanche aegyptiaca and Orobanche crenata in Israel.

Orobanche and Phelipanche, commonly known as broomrape, are dicotyledonous holoparasitic flowering plants that cause heavy economic losses in a wide variety of plant species. Egyptian broomrape (Phelipanche aegyptiaca Pomel.) parasitizes more than 30 food and ornamental crops, including tomato, sunflower, tobacco, chickpea and many others in different parts of the world. Crenate broomrape (Orobanche crenata Forsk.) parasitizes important legume crops, such as lentil, faba bean, chickpea, pea, vetches, and grass pea, as well as some apiaceous crops, such as carrot (4). This is the first report of pomegranate (Punica granatum L.) as a new host for broomrape. This is also the first report of broomrape parasitism on a Lythraceae family member. Because of their high value for human health, the demand for pomegranate fruits has increased tremendously in the last few years and the extent of pomegranate growth has increased significantly in many regions throughout the world. In March 2013, heavy broomrape infection of a 10-year-old pomegranate orchard near the village Kfar Pines was reported. The infected area of about 2 ha was located in the middle of a big pomegranate orchard (variety 116). Broomrape inflorescence counts in the infected area revealed 14 and 0.6 P. aegyptiaca and O. crenata shoots per m2, respectively. Both broomrape species were uniformly distributed over all the infected area. No differences of infection rate between the pomegranate trees could be observed. The inflorescences of the two species were normal and healthy and produced germinable seeds. Digging up the inflorescences verified a direct connection between the parasites and the pomegranate roots. The parasite species were identified morphologically according to Flora Europea (2) and Flora Palaestina (3). Detailed description of the two parasites may be found in (4). Identification was confirmed using unique DNA marker based on the photosynthetic gene rbcL of O. crenata. rbcL primers were able to distinguish between the above two species according to differences in PCR products yielding 390 bp for P. aegyptiaca and 300 bp for O. crenata (1). This was the first time that broomrapes had appeared in the orchard since its establishment, on fields that had been intensively used for processing tomato. No legume cropping history in the infected areas is known. It may be hypothesized that the broomrape seeds were dormant in the soil for over 10 years (4).The extremely wet and hot weather conditions of winter 2012/13 induced their germination. A total of 730 mm of rainfall was measured for that year as compared to the annual average of 560 mm for the region. High-level infestations with P. aegyptiaca and O. crenata were also reported from two other pomegranate orchards, Givat Ada and Evron, 11 km west and 81 km north of Kfar Pines, respectively. Neither symptoms nor visible qualitative or quantitative damage could be observed on the infected vs. non-infected pomegranate trees. However, pomegranate appears to be an alternate host for P. aegyptiaca and O. crenata serving as a seed inoculum source for nearby sensitive field crops. References: (1) R. Aly et al. Joint Workshop of the EWRS Working Groups, 29 September - 3 October, Chania, Crete, Greece, 2013. (2) A. O. Chater and D. A. Webb. Orobanche. Page 285 in: Flora Europaea, Vol. 3. T. G. Tutin et al., eds. University Press, Cambridge, 1972. (3) N. Feinbrun-Dothan. Page 210 in: Flora Palaestina, Vol. 3. Israel Academy of Sciences and Humanities, Jerusalem, 1978. (4) D. M. Joel et al., eds. Parasitic Orobanchaceae: Parasitic Mechanisms and Control Strategies. Springer Verlag Berlin Heidelberg, 2013.

First Report of Orobanche crenata Parasitism on Ornamental Anemone (Anemone coronaria) in Israel.

Broomrapes (Orobanche spp.) are obligatory parasitic weeds that infect roots of vegetables and field crops worldwide, resulting in severe damage. Orobanche crenata Forsk is common in agricultural fields in the Mediterranean Basin, Southern Europe, and the Middle East and is known as an important scourge of grain and forage legumes and of some Apiaceous crops such as carrot (Daucus carota L.) and celery (Apium graveolens L.) (3,4). To our knowledge, in this note, we report for the first time on Anemone coronaria L. (Ranunculaceae) as a new host for O. crenata and this is also the first report of Orobanche parasitism on a geophytic crop. Anemone (Anemone coronaria L.) is a high-value ornamental crop, which is commercially grown for cut flowers. Four anemone cultivars (Meron Red, Galil White, Jerusalem Blue, and Jerusalem Pink) were planted in September 2006 in a 2-ha field in Israel. The previous crop, broad bean (Vicia faba L.), was heavily infected during 2005 by O. crenata. In February 2007, O. crenata parasitized the anemone plants and developed numerous fertile flowering stalks throughout the field. The four anemone cultivars were equally infected by the parasite. Additional flowering stalks were still emerging on anemone plants during July 2007. Washing the root system clearly verified direct connection between the parasite and anemone roots. The parasite species was identified morphologically after Flora Europea (1) and Flora Palaestina (2). In addition, the stem had the fragrance typical of O. crenata. Neither symptoms nor visible qualitative or quantitative damage could be detected on infected anemone plants compared with noninfected plants. However, anemone appears to be an alternate host on which O. crenata can produce additional seed for the parasite seed bank. References: (1) A. O. Chater and D. A. Webb. Orobanche. Page 285 in: Flora Europaea. T. G. Tutin et al., eds. Vol. 3. University Press, Cambridge, 1972. (2) N. Feinbrun-Dothan. Page 210 in: Flora Palaestina. Vol. 3. Israel Academy of Sciences and Humanities, Jerusalem, 1978. (3) D. M. Joel et al. Hortic. Rev. 33:267, 2007. (4) C. Parker and C. R. Riches. Page 111 in: Parasitic Weeds of the World: Biology and Control. CAB International, Wallingford, Great Britain, 1993.

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). References: (1) H. Eizenberg and D. M. Joel. Orobanche in Israeli agriculture. Workshop of COST Action 849, Parasitic Plant Management in Sustainable Agriculture, 2001. (2) H. Eizenberg et al. Plant Dis. 88:479, 2003. (3) D. M. Joel. Phytoparasitica 16:375, 1988. (4) A. V. Vranceanu et al. Proc. 9th Sunflower Conf. 1:74-82, 1980.

Variation in Responses of Sunflower Cultivars to the Parasitic Weed Broomrape.

Development of four Orobanche species, O. cumana, O. aegyptiaca, O. ramosa, and O. cernua, was compared on resistant and susceptible sunflower cultivars. Sunflower plants were infected by O. cumana, O. aegyptiaca, and O. ramosa, but not by O. cernua, in field and greenhouse studies. However, cultivating the hosts and parasites in a polyethylene bag system allowed the observation that sunflower induced O. cernua seed germination. This difference demonstrates that O. cernua is unique from the other three species. O. cumana, O. aegyptiaca, and O. ramosa attached to and developed tubercles on the susceptible sunflower 'Adi.' On the resistant 'Ambar' sunflower, a greater percentage of tubercles were degenerated or dead than on the susceptible cultivar. Thus, resistance of Ambar appears to manifest during tubercle development. Seed production of Adi sunflower was greatly reduced with infection by O. cumana.

Resistance to broomrape (Orobanche spp.) in sunflower (Helianthus annuus L.) is temperature dependent.

The effects of various temperature regimes in the range 29-17/21-9 degrees C day/night on each stage of the parasitism process of Orobanche cumana and O. aegyptiaca on sunflower were studied under controlled conditions in polyethylene bags. The response of the resistant sunflower variety 'Ambar' was expressed as the degeneration of the parasite tissues after its establishment in the plant roots, and this stage was found to be temperature dependent. The degeneration rate of Orobanche tubercles in the resistant sunflower variety was also found to be temperature dependent and was about five times as great as that in the sensitive variety in the highest temperature regime tested of 29/21 degrees C day/night. The ability to reject the parasite by causing its degeneration and death is the main factor that determines the resistance. As the temperature rises, more tubercles degenerate and die, that is the sunflower plant expresses higher levels of resistance.