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.
