Recent Approaches to Orobanche Management

Abstract

Parasitic plants account for approximately 1% of angiosperm species and are present in 22 botanical families. Several of the parasitic species are important agricultural weeds, infest a wide range of crops around the globe, and pose a major threat to the food security of numerous communities. The agriculturally important parasitic weeds fall into four main groups: 1. Viscaceae and Loranthaceae (mistletoes): green hemiparasites that parasitize aerial parts of shrubs and trees. 2. Cuscutaceae (dodders): holoparasitic twining stem parasites that attack dicot plants. 3. Scrophulariaceae (figworts and witchweeds): contains hemi-parasitic root parasites that invade roots of host plants. 4. Orobanchaceae (broomrapes): holoparasitic root parasites that invade dicot plants. The Orobanchaceae consists of 14 genera of chlorophyll-lacking root holoparasites of which the genus Orobanche (common name broomrape), includes more than 100 species that subsist on broad-leaf plants, depleting them of nutrients, minerals and water. Several review papers and books on Orobanche have been published (Kasasian, 1973a; Pieterse, 1979; Musselman, 1980; Ramaiah, 1987; Foy et al., 1989; Parker and Riches, 1993; Press and Graves, 1995; Dhanapal et al., 1996; Alonso, 1998). The start of the new millennium is an appropriate time to summarize the past and update methods for Orobanche control, and point out the prospects for new tools to combat the devastating effects of this parasitic plant in the future. Even though significant advances have been made in the study of parasitic plant biology and control measures, most of this information has not percolated to the farmers, especially in developing countries because of setbacks in technology transfer and lack of resources.Numerous worldwide surveys, evaluations and studies describing the parasitic plant problem have been conducted, but research on practical and feasible control measures has been minimal. Most of the devastating cases of parasitic weeds occur in developing countries of Africa and Asia, thus the big seed and chemical companies show little interest in this market and have failed to develop and register resistant crop varieties and specific herbicides for combating parasitic plants. Furthermore, ongoing inadvertent introduction of Orobanche species to the USA, South America, Australia and Germany have not to date stimulated research on control. The number of these introduced infestations will increase in future years due to increasing global travel and trade. More emphasis should be given to the development of tools for parasitic plant control and to ensure the utilization of these tools by farmers. Potential control tools exist (resistant varieties, selective herbicides, and herbicide resistant crop plants) but lack of funds and interest impede fighting the plague and insuring the food stability of millions of people. This review summarizes research regarding the actual and potential control of Orobanche in the field. Most of the data presented in this chapter is based on research conducted by the authors in Israel.