Identification of the Causal Agent of Alternaria Leaf Spot of Cabbage in Côte d›Ivoire

Identificação do agente causador da mancha foliar de Alternaria do repolho na Costa do Marfim

Cabbage (Brassica oleracea L.) is a plant of vital importance. However, its cultivation is subject to several diseases, including Alternaria leaf spot, which causes huge losses in most production areas. Thus, the present study aimed to identify the Alternaria species responsible for Alternaria leaf spot of cabbage in Côte d’Ivoire. To this end, a phytosanitary survey was carried out in three cabbage growing areas in Côte d’Ivoire (Yamoussoukro, Tiassalé and Abengourou), and symptomatic leaves were sampled. The fungi associated with the symptoms were then isolated and morphologically identified. Pathogenicity tests were also carried out with Alternaria isolates by inoculating cabbage plants in a greenhouse. Finally, pathogenic Alternaria isolates were molecularly identified using the universal primers ITS1 and ITS4. Alternaria leaf spot symptoms were found in all three locations surveyed. Disease prevalence ranged from 63.33% to 78.33%. As for symptom severity index, it was highest in Abengourou: 43.61%. Five Alternaria morphotypes were isolated from the collected samples. These isolates were all pathogenic to cabbage, and molecular tests revealed that they belonged to the species Alternaria brassicicola. This first identification of Alternaria brassicicola as a cabbage pathogen in Côte d’Ivoire will thus contribute to the implementation of an effective control strategy against Alternaria leaf spot of cabbage.

Keywords
Brassica oleracea L.; fungal disease; severity; molecular; Alternaria brassicicola