Peronophythora litchii associated with root rot of litchi
1995
Chaiwatana Kraturisha | Manoch Tospol | Vichai Rukvidhyasatra | Kachornsak Bhavakul(Department of Agriculture, Bangkok (Thailand). Plant Pathology and Microbiology Div. Fruit Tree-Industrial Horticulture Crops and Herbs Pathology Group)
Root rot disease of litchi (Litchi chinensis) has occurred sporadically in certain growing areas of Pong Nam Ron district, Chanthaburi since January, 1995. The host cultivars affected were Kom and Songkanan of about 5-20 years old, resulted in a serious decline and death of trees. Infected large and branching roots developed extensive rot symptoms with brown discoloration of cortical tissue. By using tissue transplant method, Peronophythora litchii was isolated to pure culture from decayed roots on a BNPRAH-PDA medium. When 1-year-old marcottings and 1-month-old seedlings of Kom cultivar were inoculated with the fungus, rot symptoms developed on the roots followed by the death of plants. Reisolation trial with a BNPRAH-PDA medium recovered P. lichii from infected root tissues. Since P. litchii has been reported previously as the causal organism of litchi fruit rot in Taiwan, pathogenicity tests were conducted to both green and mature, wounded and nonwounded litchi fruits of Hohng-hooway and Chakraphat cultivars. The results indicated severe rot of all test fruits, and P. litchii could also be recovered from the decayed fruits. Peronophythora litchii produced excellent growth on V-8 juice agar whereas on PDA its growth rate was relatively slow. On V-8 juice agar colonies were whitish cream forming sporangia abundantly. Sporangia were lemon-shaped, 20.0-42.50*15.0-25.0 micro m, averaging about 28.2*18.6 micro m, with apical papillae similar to those of Phytophthora. They were borne on dichotomously branched sporangiophores resembling the genus Peronospora. The fungus was classified to the family Peronophythoraceae of the order Peronosporales. This is the first report implicating P. litchii in root rot and death of orchard litchi trees.
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