Nicoletta Contaldo, Maria Grazia Bellardi, Lisa Cavicchi, Francesco Epifano et al., Phytochemical effects of phytoplasma infections on essential oil of Monarda fistulosa L. Bulletin of Insectology 64 (Supplement): S177-S178, 2011

Two essential oils hydrodistilled from the aerial parts of phytoplasma-infected plants of Monarda fistulosa L. (wild bergamot) growing at the Herb Garden of Casola Valsenio (Emilia Romagna Region; Italy), have been analyzed and compared by GC and GC/MS. The first oil was extracted from wild bergamot plants showing phytoplasma symptoms (virescence, yellows and stunting) and infected by aster yellows and stolbur phytoplasmas; the second oil was distilled from asymptomatic plants in which stolbur phytoplasmas were identified. These two oils were similar in composition to a third oil, of Italian origin, from M. fistulosa cultivated in Trentino Region. The oil from plants infected with aster yellows plus stolbur infected plants showed an increase in the quantity of some monoterpenes, as well as in the content of -caryophyllene and a marked decrease in the content of thymol; the oil from symptomless material (in which stolbur phytoplasmas were detected) yielded a significant increase in thymol concentration and a marked decrease in monoterpene compounds.