DNA-BASED FUNGAL IDENTIFICATION: FIRST REPORT OF DOUBLE INFECTION OF ALTERNARIA TENUISSIMA AND AMPELOMYCES SPECIES ON MALFORMED PODS OF ACACIA KAROO IN NAMIBIAP.M. CHIMWAMUROMBE, I. MAPAURE AND M.S. HAUFIKU
Acacia karoo tree species has a wide distribution in Namibia. It is generally well adapted to the dry conditions that are present in Namibia. In addition to Acacia karoo, Acacia mellifera, Acacia hebeclada, Acacia erioloba, Acacia luderitzii and Acacia hereroense are some of the commonest species. These species have a variety of uses, from industrial, medicinal, ornamental to ecological uses. Recently pods of Acacia karoo were observed to be malformed leading to decline of seed production of the trees. In addition, the malformed pods appeared in a variety of morphologies. The objective of this investigation was to pinpoint the identity of the causal agents of pod malformation as a dedicated first step towards design of effective control mechanisms to this disease that blocks the reproduction step of Acacia karoo life cycle, In order to determine the causal agents, fresh malformed pods from Acacia karoo, were sampled and single spore cultures were made. Pure cultures of two fungi were made from single spores. DNA was extracted from these pure cultures and used in an internal transcribed spacer (ITS) PCR used ITS1 and ITS 2 primers. The PCR products were purified and sequenced. The sequences were used in BLAST searches to interrogate the Genbank for sequence similarity. High sequence similarity of 100% was obtained with Alternaria tenuissima and a similarity of 98% was observed with Ampehnnyces species. From this work we can conclude that Alternaria tenuissima and Ampolontyces sp. are associated with Acacia /woo pod malformation. A new question again arises which of the two fungi is the culprit for malformation or is there double causation or synergistic interaction of the two fungi that leads to pod malformation. This can be answered by experimentation that is guided by Koch's postulate5. Purthermore, the identity of insect vectors that carry the fungi from one flower to the other need to be determined.
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