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.

Interaction between Orobanche crenata and its host legumes: unsuccessful haustorial penetration and necrosis of the developing parasite.

BACKGROUND AND AIMS: Orobanche species represent major constraints to crop production in many parts of the world as they reduce yield and alter root/shoot allometry. Although much is known about the histology and effect of Orobanche spp. on susceptible hosts, less is known about the basis of host resistance to these parasites. In this work, histological aspects related to the resistance of some legumes to Orobanche crenata have been investigated in order to determine which types of resistance responses are involved in the unsuccessful penetration of O. crenata. METHODS: Samples of resistance reactions against O. crenata on different genotypes of resistant legumes were collected. The samples were fixed, sectioned and stained using different procedures. Sections were observed using a transmission light microscope and by epi-fluorescence. KEY RESULTS: Lignification of endodermal and pericycle host cells seems to prevent parasite intrusion into the root vascular cylinder at early infection stages. But in other cases, established tubercles became necrotic and died. Contrary to some previous studies, it was found that darkening at the infection site in these latter cases does not correspond to death of host tissues, but to the secretion of substances that fill the apoplast in the host-parasite interface and in much of the infected host tissues. The secretions block neighbouring host vessels. This may interfere with the nutrient flux between host and parasite, and may lead to necrosis and death of the developing parasite. CONCLUSIONS: The unsuccessful penetration of O. crenata seedlings into legume roots cannot be attributed to cell death in the host. It seems to be associated with lignification of host endodermis and pericycle cells at the penetration site. The accumulation of secretions at the infection site, may lead to the activation of xylem occlusion, another defence mechanism, which may cause further necrosis of established tubercles.

In vitro infection of host roots by differentiated calli of the parasitic plant Orobanche.

Root parasites of the genus Orobanche are serious weeds in agriculture. An aseptic infection system of host roots using calli of three Orobanche species was developed for the study of host-parasite interaction. The response of calli to various hormonal combinations was studied, because a requirement for infection is the differentiation of root-like protrusions, which are capable of producing haustorial connections to the host. Infectious root-like protrusions develop under the influence of 0.5-1.0 mg l(-1) IAA, and under the combination of 0.2 mg l(-1) NAA with 5.0 mg l(-1) kinetin. These protocols produced root protrusions with pad-like structures that resembled attachment organs of Orobanche seedlings, and proved effective in parasitizing host roots. Direct contact with the medium inhibited haustorium development and prevented infection. To overcome this problem, certain root portions were isolated from the medium by inserting thin glass plates underneath. Calli were then placed on the raised root portions and successfully infected the roots and developed young Orobanche tubercles with vascular system that directly connected to the host.

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.

First Report of the Parasitic Plant Orobanche aegyptiaca Infecting Olive.

Broomrapes (Orobanche spp.) are obligatory parasitic plants that infect the root system of vegetables and field crops worldwide resulting in severe damage. Five broomrape species are known as significant parasites of crops in Israel: O. aegyptiaca Pers., O. cernua Loefl., O. cumana Wallr., O. crenata Forssk., and O. ramose L. (1,2). Recently, O. aegyptiaca was found to parasitize roots of young olive trees (Olea europaea) in a 1-year-old plantation located in Esdraelon Valley, Israel (voucher specimens deposited in Newe-Ya'ar Weed Herbarium, Ramat Yishay, Israel). To our knowledge, this is the first time that a tree in general and olive in particular has been reported to serve as host for O. aegyptiaca. Washing the root system clearly verified connections between the parasite and olive roots. Cross sections of an attachment site confirmed the development of functional haustoria. Trees were planted in a field where tomatoes had been previously parasitized by O. aegyptiaca for several years. In April 2001, many O. aegyptiaca plants emerged under each olive tree in a total area of 0.3 ha. Additional emergence of O. aegyptiaca was observed until July 2001. The high level of Orobanche infection did not lead to visible damage in the trees. However, the mature parasite developed massive amounts of seeds, serving to increase the population of O. aegyptiaca in the field. References: (1) D. M. Joel and H. Eizenberg. Three Orobanche species newly found on crops in Israel. Phytoparasitica 30:187, 2002. (2) C. Parker and C. R. Riches. Parasitic Weeds of the World. CAB International, Wallingford, UK, 1993.

Differential Expression and Turnover of the Tomato Polyphenol Oxidase Gene Family during Vegetative and Reproductive Development.

Polyphenol oxidases (PPOs) are encoded by a highly conserved, seven-member gene family clustered within a 165-kb locus on chromosome 8 of tomato (Lycopersicon esculentum). Using gene-specific probes capable of differentiating between PPO A/C, PPO B, PPO D, and PPO E/F, we examined the spatial and temporal expression of this gene family during vegetative and reproductive development. RNA blots and in situ hybridization using these probes showed that although PPO expression is primarily confined to early stages of development, the steady-state mRNA levels of these genes are subject to complex patterns of spatial and temporal regulation in vegetative and reproductive organs. Young tomato leaves and flowers possess the most abundant PPO transcripts. PPO B is the most abundant in young leaves, whereas in the inflorescence PPO B and E/F transcripts are dominant. Differential expression of PPOs is also observed in various trichome types. PPO A/C are specifically expressed in type I and type IV trichomes. In contrast, PPO D is only expressed in type VI trichomes. Type I, IV, and VI trichomes possess PPO E/F transcripts. Immunolocalization verified the translational activity of PPOs identified by in situ hybridization and suggested cell-type-specific, developmentally programmed PPO turnover. In addition, immunolocalization demonstrated the accumulation of PPO in specific idioblast cells of stems, leaves, and fruits.

Use of random amplified polymorphic DNA (RAPD) markers in the study of the parasitic weed Orobanche.

Despite the tremendous economic impact of broomrapes (Orobanche spp.) on agriculture in many countries little is known of the pattern of genetic variation within this group of parasitic weeds. The present paper describes the use of RAPD markers for the study of five Orobanche species in agricultural fields in Israel. Pronounced genetic differentiation was found between the species, and RAPD markers were raised for the identification of each of them. Southern-hybridization patterns of RAPD products of the various species were used to confirm the interpretation. The same markers were valid both for broomrapes collected in agricultural fields and for those collected in natural habitats. The validity of the markers found for O. cumana and O. crenata was confirmed on plants of the same species that were collected in Spain. Parsimony analysis of 86 RAPD characters produced a tree that clearly distinguishes between the five studied Orobanche species, separates the two Orobanche species belonging to sect. Trionychon from those belonging to sect. Osproleon, and supports the separation of O. cumana from O. cernua and of O. aegyptiaca from O. ramosa.