Association of a phytoplasma with witches' broom, a new disease of acid lime (Citrus aurantifolia)

A new disease of acid lime was observed during surveys conducted in the cit rus growing tracts of India. Symptoms of the disease include appearance of small chlorotic leaves, highly proliferating shoots and shortened internode s, Leaves drop prematurely and infected branches have distorted twigs chara cteristic of witches' broom symptoms. In advanced stages, infected branches show die-back symptoms. Electron microscopy revealed the presence of phyto plasmas (non-culturable plant mycoplasma) in the sieve tubes of leaf midrib s. The disease was successfully transmitted from infected acid lime to peri winkle plants and vice-versa by dodder, A bright yellowish-green fluorescen ce was observed in the phloem sieve elements of diseased periwinkle stem ti ssue when stained with DAPI (4',6-diamidino-2-phenylindole), a DNA binding fluorochrome. The leafhopper, Hishimonus phycitis, infesting the acid lime trees failed to transmit the pathogen in glass house tests. This is the fir st report of natural occurrence of phytoplasma-induced witches' broom disea se of acid lime in India.