| dc.description.abstract | Aggressiveness of fifteen isolates of Phaeoisariopsis griseola and variations in angular leaf spot symptom
development in common bean were studied. The isolates were selected based on their virulence and genetic
differences and represented Andean, Afro-Andean and Mesoamerican groups of P. griseola. Aggressiveness was
determined based on length of incubation period, rate of lesion expansion, lesion size and density, rate of
sporulation, disease severity and area under disease progress curve (AUDPC). There was a wide variation in
aggressiveness and the type of symptoms induced by the different isolates of the pathogen. Incubation period
varied significantly (P < 0.05) among isolates and ranged from six to 15 days. Mesoamerican isolates had
significantly shorter incubation period than Andean and Afro-Andean isolates. Disease severity, AUDPC and rate
of sporulation differed significantly (P < 0.05) among the isolates. Lesions induced by the different isolates varied
significantly in size, density and rate of expansion. Mesoamerican isolates induced significantly more lesions than
Andean and Afro-Andean isolates. Disease severity was negatively correlated to incubation period and positively
correlated to lesion density, lesion size and rate of sporulation. The significant correlations between disease
severity, AUDPC, incubation period, lesion density and rate of sporulation indicate that all these parameters are
important measures of aggressiveness in P. griseola. The significant variations in aggressiveness between isolates,
virulence and genetically defined groups of P. griseola indicate that this parameter can be used to characterise
isolates of the pathogen. Symptoms induced by isolates of P. griseola in different bean cultivars varied extensively
in size, shape and time of appearance. These variations could, however, not be attributed to any particular
cultivar or isolate and can, therefore, not be used to characterise the pathogen. | en |
