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

Resumen

Motivation: Macrophomina phaseolina (Tassi) Goidanich is a primarily soilborne pathogen with a wide distribution, varied
host range, great longevity and high competitive saprophytic ability (Babu et al., 2010). About 500 plant diseases are caused
by this fungus (Su et al., 2001), and it is often termed ‘charcoal rot’. Charcoal rot has emerged as an important disease in
strawberry production systems that have abandoned soil fumigation with methyl bromide (Mertely et al., 2005; Zveibil and
Freeman, 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 regions
suggest that this species may be divided into subgroups (Aboshosha et al., 2007; Beas-Fernández et al., 2006; Hawatema y
Hameed, 2006; Karunanithi et al., 1999; Mayek-Pérez et al., 1997; Mihail y Taylor, 1995; Omar et al., 2007). This work aimed
to study the population structure of M. phaseolina associated with strawberry crop in Huelva, and to characterize the isolates
with 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 this
work. The morphological characteristics of the isolates are investigated, including colony phenotype on medium containing 120
mM potassium chlorate (Pearson et al., 1986), and relative growth rate at different temperatures and pH (Beas-Fernandez et
al., 2006; Mayek-Perez et al., 1997). Pathogenicity test are carried out under controlled conditions. Mono-sclerotic cultures of
the fungus were obtained for molecular characterization.