© 2008 Plant Management Network.
First Report of Colletotrichum dematium on Pongamia pinnata in India
B. R. Vinay, J. Sudisha, N. Sunayana, and S. Lokesh, Department of Studies in Applied Botany, Seed Pathology and Biotechnology, University of Mysore, Manasagangothri, Mysore 570 006, Karnataka, India; M. Govindappa, Institute of Plant Genomics and Biotechnology, Borlaug Center for Southern Crop Improvement, Texas A & M University, College Station 77843, USA; and T. Vasanth Kumar, Green Life Science Technologies Pvt. Ltd., Mysore 570016, India
Corresponding author: Dr. S. Lokesh. firstname.lastname@example.org
Vinay, B. R., Sudisha, J., Sunayana, N., Lokesh, S., Govindappa, M., and Kumar, T. V. 2008. First report of Colletotrichum dematium on Pongamia pinnata in India. Online. Plant Health Progress doi:10.1094/PHP-2008-0902-01-BR.
Karanj or Indian beech (Pongamia pinnata) is a commonly planted urban tree in India, which is useful for many purposes. For example, its leaves can be used as a green manure in wetlands. Additionally, the oil from its seeds can be used to produce an effective biofuel (2) or for medicinal use (3). Chlorotic leaf spots were detected on P. pinnata seedlings during surveys of forest nurseries at Ramanathapur (12.47°N, 73.12°E) Hassan district of Karnataka, India in 2006. (Figs. 1 and 2). Chlorotic leaf spots were 1 to 3 mm in diameter with minute raised black acervuli on the adaxial surface (Figs. 3 and 4). In severe cases, infected leaves withered and plants died. In order to complete Koch’s postulates, infected leaves with black dots were harvested, washed, surface sterilized with 2% sodium hypochlorite for 2 min followed by three washes with sterile distilled water and dried, cut into pieces of 2 to 3 cm² and placed equidistantly on three layers of moistened blotter discs in sterile petriplates, and incubated at 22 ± 2°C in the dark for 7 days. White to dull-white acervuli developed on the leaves following incubation (Fig. 5). Conidia from the acervuli were transferred to sterilized glass Petri plates containing potato dextrose agar (PDA) and incubated for 7 days in the dark at 22 ± 2°C. Resulting cultures produced cottony white mycelial growth and slimy, dull-white acervuli that producing 15-27 × 2-5 μm falcate conidia with slightly tapered ends. Brown setae within the acervuli were aseptate and measured 50-468 × 2-7 μm (Fig. 6). Based on the symptoms and morphological characteristics, the fungus was identified as Colletotrichum dematium (1,4). To confirm pathogenicity of C. dematium, 25 two-month-old healthy P. pinnata were mist sprayed till runoff with suspension of 2 × 105 conidia/ml sterile distilled water. Plants sprayed with sterile distilled water served as controls. The inoculated plants were covered with plastic bags for 10 days and kept at 23°C and 90% humidity, with a 12 h photoperiod. Inoculated plants were assessed 15 days after infection. Inoculated plants produced chlorotic leaf spots measuring 1 to 3 mm in diameter with minute raised black acervuli on the adaxial surface. C. dematium was consistently re-isolated from infected leaves. In contrast, the control plants did not show symptoms. This is the first confirmed report of anthracnose caused by C. dematium on P. pinnata in this country. The disease incidence has increased from 9% in 2006 to 17% in 2007 in forest nurseries at Ramanathapur. Consequently, disease monitoring and management measures need to be taken.
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