Hidden diversity of Macrophomina associated with broadacre and horticultural crops in Australia

Abstract

Worldwide, most isolates of Macrophomina (Botryosphaeriaceae) have been attributed to the generalist phytopathogen M. phaseolina. Since 2014, three cryptic species of Macrophomina have been recognised by molecular methods. This study elucidates the taxonomy of Macrophomina species associated with broadacre and horticultural crops in Australia. A five-locus phylogenetic analysis of 80 isolates of Macrophomina from 28 plant species in Australia, combined with genealogical concordance phylogenetic species recognition and coalescent-based species delimitation approaches, found M. phaseolina, M. pseudophaseolina and supported the introduction of M. tecta sp. nov. Macrophomina phaseolina was the most frequently isolated (88%). Macrophomina pseudophaseolina is reported for the first time in Australia. Macrophomina tecta was isolated from stems of Sorghum bicolor and Vigna radiata with charcoal rot symptoms in New South Wales and Queensland. The potential for two or more Macrophomina species to co-infect the same host has implications for disease epidemiology and pathogen evolution. Future investigations into the distribution, biology, host range and population diversity of the new Macrophomina records are needed.