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First Report of the Parasitic Plant Phelipanche aegyptiaca Infecting Kenaf in Israel

Kenaf (Hibiscus cannabinus L.; Malvaceae) is an annual fiber crop that has recently been introduced as a niche crop in Israel, and grown mainly at areas with high summer temperatures. It is advantageous in crop rotation in these areas since it can rapidly accumulate biomass under high temperatures when other crops (e.g., tomato, sunflower, corn, and sorghum) cannot be cultivated. Additionally, the fact that it can be irrigated with waste water makes it attractive under these climatic conditions. Broomrapes (Phelipanche and Orobanche spp.) are chlorophyll-lacking obligatory root-parasitic plants that parasitize the root system of many field crops and vegetables (1). Parasitism by P. aegyptiaca has economic impacts on various crops belonging to several botanical families (e.g., Solanaceae, Apiaceae, Fabaceae, and Asteraceae). This parasitic weed is common in most agricultural areas in Israel including the coastal plain, Yisre'el Valley, the Jordan Valley, and the Negev Desert. High infection levels by P. aegyptiaca have result in a severe yield losses and quality reduction in these crops. Parasitism of P. aegyptiaca on kenaf was observed in September 2012 in a field located in Bet-Shean Valley (Latitude 32° 30' N; Longitude 35° 30' E; 105 m), with an average density of 0.7 plant/m², in a total area of 0.3 ha. This crop was planted on May 2012 in plots that were previously affected. Infection did not lead to visible symptoms or damage to kenaf, but allowed seed production by the parasite. In order to verify that kenaf was a host of P. aegyptiaca, 10 samples of kenaf plants infected with P. aegyptiaca were taken to the lab and the root systems of the plant and the parasite were carefully washed. Cross-sections of the connection between kenaf and the parasite were taken and inspected for xylem connections under a compound microscope (BX61, Olympus) equipped with high-resolution digital camera (DP-70, Olympus), under 40× magnification. A clear xylem connection between the weed's tubercles and kenaf roots was observed, confirming the development of functional Phelipanche haustoria. To our knowledge, this is the first report of kenaf as a host for P. aegyptiaca. Kenaf has been reported to induce the germination of O. cernua in India (3). Cotton, another member of the Malvaceae, has also been reported to stimulate seed germination of O. minor (4) and P. aegyptiaca (2). However, to the best of our knowledge, this finding reports the first occurrence of a Malvaceae crop as a host for P. aegyptiaca.

References: (1) H. Eizenberg et al. Weed Sci. 55:152, 2007. (2) M. Ghotbi et al. Int. J. Agri. Sci. 2:62, 2012. (3) G. V. G. Krishnamurthy et al. Indian J. Weed Sci. 9:95, 1977. (4) Y. Ma et al. Agron. J. 104:569, 2012.