ARS | Publication request: First Report of Macrophomina phaseolina Causing Leaf and Stem Blight of Tropical Soda Apple in Florida.

Submitted to: Plant Health Progress
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: October 11, 2011
Publication Date: October 1, 2007
Citation: Iriarte, F.B., Rosskopf, E.N., Hilf, M.E., Mccollum, T.G., Albano, J.P., Adkins, S.T. 2007. First Report of Macrophomina phaseolina Causing Leaf and Stem Blight of Tropical Soda Apple in Florida.. Plant Health Progress. doi:10.1094/PHP-2007-1115-01-BR.

Technical Abstract: In August 2006 progressive leaf necrosis was observed in tropical soda apple (SOLVI ) plants in Fort Pierce, FL. Leaves of the five month old plants presented progressive necrosis, then dried out and dropped. Necrosis progressed quickly from petioles through the stems and caused entire stems to die. A single fungus was consistently isolated from symptomatic stem tissue and from numerous pycnidia excised from infected stems. The fungus was tentatively identified as Macrophomina. Identity was confirmed by analysis of the sequence of the internal transcribed spacer (ITS) region. Koch’s postulates were completed on four month old SOLVI plants grown in soiless potting medium in the greenhouse. Disease symptoms on plants inoculated with M. phaseolina resembled those first observed in the field, whereas control plants remained healthy during the observation period. To the best of our knowledge this is the first report of M. phaseolina as a pathogen of SOLVI. The high level of virulence of M. phaseolina observed in this study suggests that it has the potential to become a limiting factor for the persistence and/or spread of this weed in Florida. However, since M. phaseolina is a plant pathogen with a wide host range, it is important to consider the potential for inoculum from this host to spread to nearby crops and cause yield losses due to disease. This report provides further evidence of this noxious weed serving as a reservoir for potential pathogens of vegetable crops.