Characterization of Alternaria brassicicola isolated from tomato in Burkina Faso, and use of two essential oils for its control in vitro

Alternaria brassicicola is considered a weak pathogen of tomato in the field, but with a high potential for mycotoxin production in fruit. However, this species belongs to a diverse and closely related group of species (Alternaria with small spores), which often makes their morphological identification and control difficult. In the present research, a molecular identification of tomato Alternaria isolates was made using sequence data of the internal transcribed spacer (ITS) region and the 5.8S ribosomal DNA (rDNA) gene of the isolates. Isolates were identified as Alternaria brassicicola. They were obtained from samples collected from symptomatic tomato leaves in Loumbila, a locality in the Central Plateau region of Burkina Faso. In vitro antifungal tests with essential oils of Cymbopogon nardus and Eucalyptus camaldulensis showed an inhibitory effect of these oils on A. brassicicola. The inhibition rates recorded by the two essential oils at appropriate doses (1, 5, 10, 50 and 100%) are higher than those obtained with the chemical fungicides Azoxystrobin and Mancozeb. The use of formulations based on these essential oils could be an alternative to hazardous pesticide treatments, thus allowing a safer and more ecological management of field diseases and toxins of Alternaria sp. in tomato fruits. Key words: Alternaria brassicicola, molecular identification, biological fungicide.