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There is a lack of information about the level of resistance of cotton genotypes to a wider range of Ramularia areola isolates occurring across the cotton growing areas of Brazil. For this purpose, firstly it is necessary to know the existence or not of genotypic and phenotypic variability among the R. areola isolates from different geographical origins. The objective of the present investigation was to verify the existence of phenotypic variability among 23 R. areola isolates collected from six cotton growing states of Brazil. Two resistant genotypes, FMT 02102996 and CNPA BA 2003-2059, and the susceptible genotype FMT 701 were individually inoculated with 23 R. areola isolates under glasshouse conditions and the severity of infection was evaluated 30 days after inoculation. Genotypes CNPA BA 2003-2059 and FMT 02102996 were susceptible to three isolates and resistant to the rest of the isolates. Genotype FMT 701 was susceptible to all the isolates except the isolates 22.3 and 42.7. Results indicate the existence of variability among R. areola isolates and that the three genotypes are useful in distinguishing phenotypic variability within isolates of this pathogen.

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