Physiological, genetic, and pathogenetic variability in Macrophomina phaseolina, the causal agent of charcoal rot

Abstract

Motivation: Macrophomina phaseolina (Tassi) Goidanich is a primarily soilborne pathogen with a wide distribution, variedhost range, great longevity and high competitive saprophytic ability (Babu et al., 2010). About 500 plant diseases are causedby this fungus (Su et al., 2001), and it is often termed ‘charcoal rot’. Charcoal rot has emerged as an important disease instrawberry production systems that have abandoned soil fumigation with methyl bromide (Mertely et al., 2005; Zveibil andFreeman, 2005; Aviles et al., 2008). Although, only one species (M. phaseolina) is recognized within the genus Macrophomina(Sutton, 1980), the high levels of morphological variability of M. phaseolina across different hosts and geographical regionssuggest that this species may be divided into subgroups (Aboshosha et al., 2007; Beas-Fernández et al., 2006; Hawatema yHameed, 2006; Karunanithi et al., 1999; Mayek-Pérez et al., 1997; Mihail y Taylor, 1995; Omar et al., 2007). This work aimedto study the population structure of M. phaseolina associated with strawberry crop in Huelva, and to characterize the isolateswith respect to in vitro growth rate, genotypic variability, and pathogenicity to strawberry plants.Methods and results: Twenty two isolates of M. phaseolina from strawberry, blueberry, watermelon and rice are tested in thiswork. The morphological characteristics of the isolates are investigated, including colony phenotype on medium containing 120mM potassium chlorate (Pearson et al., 1986), and relative growth rate at different temperatures and pH (Beas-Fernandez etal., 2006; Mayek-Perez et al., 1997). Pathogenicity test are carried out under controlled conditions. Mono-sclerotic cultures ofthe fungus were obtained for molecular characterization