EPIDEMIOLOGICAL ASPECTS OF LEAF BLIGHT OF CARROT (Daucus carota L.) CAUSED BY Alternaria dauci (KÜHN) GROVES & SKOLKO: EFFECT OF INOCULUN CONCENTRATION AND DETERMINATION OF THE GENERATION TIME OF Alternaria dauci

Abstract

The effect of the concentration of conidial inoculum of Alternaria dauci (Kühn) Groves & Skolko in relation to the degree of severity of occurrence of leaf blight on carrot (Daucus carota L.) cultivar Nantes Half Long at 67 - 70 days of age, was studied. The plants were cultivated under green-house conditions innoculated by atomizing with spore suspension, and afterwards, maintained for 72 hours in an incubation chamber with temperature controlled at 18 – 24°C and relative humidity of 100% (foggy). The spore concentrations tests were 0, 10², 10³, 5x10³ and 2x10^4 spores/ml. There were significant differences in the treatments at the 5% level in relation to severity of the leaf blight, the total weight of the plants, and the weight of the roots. The generation period of the fungus was 6-7, 5, 6 and 6 days, respectively, at 16, 20, 24°C and room temperature. Detached leaflets were innoculated individually, by using a small brush to spread the spores. After innoculation, the leaflets were maintained in a moisture chamber. The vitality of the inoculum, seems to be a highly important factor in the determination of the generation time of the of fungus.