The genetic parameters associated with resistance to the carrot leaf blight disease complex were evaluated using half-sib families derived from the varietal group 'Brasília'. We also evaluated which populations would provide larger gains for this character. Field assay was carried out in Brasília during the summer season (from November 2006 to February 2007). Five advanced breeding populations (processing 1 (P1), processing 2 (P2), table 3 (M3), table 4 (M4) and table 5 (M5), were evaluated using an experimental design of completely randomized block with two replicates. The total area per plot was of 2 m². Evaluation for leaf blight symptom severity was done 90 days after sowing. ANOVA was used to estimate genetic parameters and the genetic gain from selection. Leaf blight resistance levels were significant and allowed the discrimination of the populations under evaluation. According to the genetic parameters and the expected gains with selection, the population P1 was the most and M3 was the less promising genetic material aiming to improve leaf blight resistance levels in Brasília-type carrots. The values of the relationship among the genetic and environmental variation coefficients and heritability were low. Apparently, genetic variability for leaf blight resistance in the populations under study is already depleted. On the other hand, it might also indicate the need for refinement in both the evaluation system as well as in the inoculation technique, which are crucial to allow uniform epidemics of the leaf blight complex across field plots.
Daucus carota L; Alternaria dauci; Cercospora carotae; Xanthomonas campestris pv. carotae
