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Abstract

A new disease of acid lime was observed during surveys conducted in the citrus growing tracts of India. Symptoms of the disease include appearance of small chlorotic leaves, highly proliferating shoots and shortened internodes. Leaves drop prematurely and infected branches have distorted twigs characteristic of witches’ broom symptoms. In advanced stages, infected branches show die-back symptoms. Electron microscopy revealed the presence of phytoplasmas (non-culturable plant mycoplasma) in the sieve tubes of leaf midribs. The disease was successfully transmitted from infected acid lime to periwinkle plants and vice-versa by dodder. A bright yellowish-green fluorescence was observed in the phloem sieve elements of diseased periwinkle stem tissue 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 first report of natural occurrence of phytoplasma-induced witches’ broom disease of acid lime in India.