Unforbidden Fruits: Preventing Citrus Smuggling by Introducing Varieties Culturally Significant to Ethnic Communities

Citrus and citrus relatives are often hosts of pests and pathogens of quarantine significance. Their fruits, leaves and propagative materials are also commonly smuggled into the United States, and this has caused grave economic harm to growers. As a complement to efforts to interdict smuggling, it can be useful to recognize when smuggling results from the unfilled demand for genotypes that are not readily available through conventional nurseries and clean plant programs. The Unforbidden Fruits project has identified several such species and varieties, and is seeking to ensure that safe pathogen-tested material is available to meet demand in California. The project’s initial focus has been on curry leaf (Bergera koenigii), used in South Asian cooking, and bael (Aegle marmelos), used for Hindu ritual purposes. In both cases the leaves are the primary plant part in demand; this makes them particularly dangerous because the leaves can host the Asian citrus psyllid (Diaphorina citri), the vector of Candidatus Liberibacter asiaticus, the bacterium associated with Huanglongbing (HLB), a devastating citrus disease. No established procedures exist for the grafting and indexing of such citrus relatives, so the project is first testing seed trees for seed-transmissible diseases, and then distributing seeds to cooperating licensed California citrus nurseries. In addition, the project has acquired germplasm of citron (C. medica) suitable for Jewish ritual purposes, which according to religious requirements must be derived from never-grafted stock; this poses challenges to conventional germplasm methods, which rely on collection of budwood and micro-shoot-tip grafting. The project has started distributing seeds of ‘Assads,’ a rare, prized citron of Moroccan origin, to interested nurseries.