S14 - Session P5 - Survey of disease of amaranth (Amaranthus spp. L.) in Tanzania revealed multiple fungi and virus infections

Authors: Wubetu Bihon Legesse *, Zong-ming Sheu, Raphael Mallogo, Jaw-rong Chen, Li-mei Lee, Lawrence Kenyon, Ramasamy Srinivasan, Roland Schafleitner

Amaranth ( Amaranthus L.) is one of the traditional crops grown for its seed and as leafy vegetable in Tanzania. It is popular in Tanzania as a leafy vegetable not only because of its nutritional content, but also for its adaptability and resistance to abiotic and biotic stresses. However, in recent years diseases and pests affecting the yield and quality of amaranth leaf have been regularly observed. The objective of this study was therefore to identify the important plant diseases associated with amaranth in the major growing regions of Tanzania. Leaf samples collected from plants with virus-like symptoms were dried using anhydrous silica gel and stored in dry-cool conditions. Fungi from the stems and roots of suspected diseases plants were isolated on malt extract agar (MEA). FTA (Flinder Technology Associates) cards were used to collect and extract suspect pathogen DNA directly from infected leaves and from fungal isolates. The samples on the FTA cards and the dried leaves were shipped to the World Vegetable Center headquarters in Taiwan for identification of the pathogens using ELISA for viruses and polymerase chain reaction (PCR) for viral, fungal and bacterial pathogens. The ELISA test results showed the presence of potyviruses, cucumber mosaic virus, turnip mosaic virus and Poleroviurses infecting amaranth. In addition, Begomovirus DNA was detected by PCR using Begomovirus universal primers. Thirty two species of fungi from eight genera were detected. The genera identified comprised Fusarium , Cercospora , Colletotrichum, Alternaria , Rhizoctonia , Pythium , Cladosporium , and Arthrinium . Multiple infection of a sample by two or more fungal or viral species were commonly observed.