|131-1||Additional species of Aspergillus causing red rot disease in Agave sisalana|
|Autores:||Patricia Oliveira dos Santos (UFRB - Universidade Federal do Recôncavo da Bahia) ; Augusto César Moura da Silva (EMBRAPA - Embrapa Mandioca e Fruticultura) ; Élida Barbosa Corrêa (UEPB - Universidade Estadual da Paraíba) ; Jorge Teodoro de Souza (UFRB - Universidade Federal do Recôncavo da Bahia) |
Sisal (Agave sisalana) production has been declining due to a disease known as sisal red rot. The fungus Aspergillus niger, was identified by morphological characters as the agent of the disease. The objective of this study was to isolate, identify and test the pathogenicity of Aspergilli isolated from sisal-growing region of Bahia.
Aspergillus isolates were obtained from soil and diseased plants. The DNA of 28 isolates was obtained and Random Amplified Polymorphic DNA (RAPD) analysis was done. Six groups were selected from the RAPD analysis for molecular identification by sequencing a fragment of the β-tubulin gene. Pathogenicity tests were done by inoculating each of the six isolates studied in sisal plantlets grown under greenhouse conditions. Controls were treated with sterile distilled water and the experiment installed in randomized design with five replicates per treatment. Thirty days later, plantlets were split open to observe the incidence of the disease. This experiment was repeated at least three times for each isolate. When symptoms were present, fragments of the diseased plantlet were surface-sterilized and plated on PDA to confirm the identity of the isolates. Furthermore, DNA of the isolates were re-sequenced to compare with the sequences obtained for the isolates originally inoculated.
RAPD analysis showed that the isolates were grouped into six different genetic groups. Sequence analysis revealed that A. niger, A. aculeatus, A. alabamensis, A. tubingensis, and A. brasiliensis were found in association with sisal. Pathogenicity tests, the re-isolation and sequencing of the aspergilli from lesions of diseased plants showed A. niger, A. tubingensis and A. brasiliensis as etiologic agents of red rot disease of sisal.
Little scientific information is available on sisal in general and specifically on the diseases that affect this plant. We show here for the first time that A. niger, A. tubingensis and A. brasiliensis are able to cause the disease in sisal. Although species of Aspergillus are known as saprobes or weak pathogens, they cause a devastating disease in sisal. The species A. tubingensis and A. brasiliensis were isolated from soil and the real significance of these isolates for the epidemiology of the disease remain unclear. This report adds two new potential agents of sisal red rot disease in the sisal-growing region of Bahia State.
Palavras-chave: Sisal, pathogenicity, β-tubulin, Molecular identification