Archivio Journal of Plant Pathology

Abstract:

Aloe vera (Aloe barbadensis Miller) is a drought-resistant perennial succulent plant of the family Liliaceae. In September 2013, plants exhibiting severe leaf blight symptoms were observed in the Experimental Farm of the Indian Agricultural Research Institute (IARI), New Delhi. The disease appeared as small circular brown lesions on the leaves which soon developed into dark-brown diffuse spots that turned grey at the centre. The spots frequently coalesced into extended patches, blightening the leaves and, gradually, the entire foliage. Isolation on potato dextrose agar (PDA) (Rao et al., 1991) yielded colonies that were initially white, but later turned grey to greyish black and produced dark-brown pycnidia. Pycniospores were brown, clavate, straight, aseptate, thick-walled, apex-obtuse, tapered to a truncate base and measured 30-45x10- 16 μm. Based on morphology, the fungus was identified as Sphaeropsis sapinea. To confirm the identification, internal transcribed spacer (ITS) region of rDNA was amplified using primers ITS1 and ITS4 (White et al., 1990), sequenced and submitted in GenBank (accession No. KM114902). The highest similarity was found with Sphaeropsis sapinea sequences. For pathogenicity tests, fives 6-month-old healthy plants of A. barbadensis were sprayed with spore suspension (5×105 spore/ml) of the pathogen whereas five control plants were sprayed with sterilized water. Leaf symptoms like those seen on naturally infected were observed only in inoculated aloe vera plants from which a fungus identical to that used for inoculation was re- isolated and deposited at the Indian Type Culture Collection (ITCC 7390), Division of Plant Pathology, New Delhi, India. This is the first report of leaf blight caused by Sphaeropsis sapinea on aloe vera in India.