Chemical composition of acid lime leaves infected with Candidatus Phytoplasma aurantifolia

The production of acid lime (Citrus aurantifolia) has declined in many parts of the world due to phytoplasmal infection by "Candidatus Phytoplasma aurantifolia". The resulting Witches' Broom Disease of Lime (WBDL) causes stem and leaf proliferation and clustering that starts on a few branches and continues to spread until trees are killed within 5 - 7 years. Recent studies have shown that Phytoplasma alters the chemical composition of leaves. Leaves from WBDL-symptomatic lime trees were collected to determine their volatile compound composition. Phytoplasmal infection was confirmed by a polymerase chain reaction (PCR) assay using primers P1/P7 and R16F2n/R16R2 in direct and nested PCR, respectively. Restriction fragment length polymorphism (RFLP) profiles of acid lime Phytoplasma were identical with those of WBDL Phytoplasma. The phytochemical composition of symptomatic (infected) and asymptomatic (healthy) leaves of acid lime were determined using GC-MS analysis of steam distilled extract. The WBDL-symptomatic leaves had higher concentration in Delta -limonene, beta -ocimene and trans-caryophyllene and a reduction in other compounds (i.e. citral, citronellal, cis-verbenol, neryl acetate, and linalool). Variations in the leaf phytochemical concentration indicate a possible role in the development of the WBDL disease symptoms.