In 1993 abnormalities observed on Poncan mandarin (Citrus reticulata Blanco), in the area of Perdões, State of Minas Gerais, were suspected to be related to "greening", a citrus disease, not yet detected in Brazil. The affected plants presented very small and hard fruits, with thick and rough peel and drop prematurely. Cutting these fruits, conspicuous formation of gum pockets was seen in the albedo and some also in the flavedo, similar to boron deficiency. The seeds were dark and aborted. The normal fruits of the same trees did not show these symptoms. Leaf and fruit material were collected, as well as soil samples, at two depths. Leaves taken from symptomatic branches, have 6 to 12 tng/kg of boron, too low in relation with normal ones of 30 to 40 mg/kg. Leaf application of 1.5 mg/L of boric acid solution have promoted normal growth, 30 days after the application. Results of electronic microscopy did not indicate the presence of greening bacteria from neither foliar midribs nor fruits columella. A brief description of greening symptoms is presented. It was concluded that the abnormalities are due to boron deficiency instead of citrus greening as previously reported.
poncan mandarin; citrus greening; boron deficiency