First report of Alternaria alternata causing leaf spot on Aloe barbadensis in India A. Kamalakannan A , C. Gopalakrishnan A,B , R. Renuka A , K. Kalpana A , D. Ladha Lakshmi A and V. Valluvaparidasan A A Department of Plant Pathology, Tamil Nadu Agricultural University, Coimbatore 641 003, Tamil Nadu, India. B Corresponding author. Email: pc_gopal@yahoo.co.in Abstract. Aloe (Aloe barbadensis), an important medicinal plant grown in the state of Tamil Nadu, India has suffered heavy losses due to a leaf disease in 2006. The symptoms observed were small, circular to oval dark brown necrotic sunken spots located mostly on the leaf tip, with average diameter of 1.0 mm and reaching 3.0 mm. The pathogen was isolated and identified as Alternaria alternata and the pathogenicity was established. The conidiophores were branched, straight, golden brown in colour, measuring 15 mm long and 2--6 mm thick. The conidia were golden brown in colour, produced in long branched chains, obclavate in shape, with short conical flask. The literature indicates that this is the first report of a leaf spot disease of aloe in India. Aloe barbadensis (syn. Aloe vera) popularly known as Indian Aloe or Barbados Aloe is a perennial herb with fleshy leaves, which have great medicinal value. In June and July 2006, aloe grown in Coimbatore, Erode and Madurai districts of Tamil Nadu, India, suffered heavy losses due to a disease (Fig. 1). The symptoms observed were small circular to oval dark brown necrotic sunken spots located mostly on the leaf tip with an average diameter of 1.0 mm, reaching 3.0 mm (Fig. 2). The spots were characterised by having grey centres with brown margins. Black sporulation appeared in the centre of the spots. In a later stage of infection, the affected leaves dried from the tip downwards and lost the mucilaginous jelly (Fig. 3). The causal agent of this disease was successfully isolated on potato dextrose agar (PDA) from the diseased leaves. In total, 16 samples of infected leaves were collected from different parts of Tamil Nadu state and these infected leaves were used for isolations. The target pathogen was isolated from 11 samples. No other pathogenic fungus was Fig. 1. Aloe field infected with leaf spot disease. Fig. 2. Necrotic spots on the leaf tip. CSIRO PUBLISHING www.publish.csiro.au/journals/apdn Australasian Plant Disease Notes, 2008, 3, 110--111 Ó Australasian Plant Pathology Society 2008 10.1071/DN08044 1833-928X/08/010110