In vitro and in vivo antifungal activity of microalgal treatments against Alternaria brassicicola

Résumé

Commercial preparations of three algal species (Arthrospira platensis, Chlorella vulgaris, and C. pyrenoidosa) were evaluated according to in vitro (paper disc method), and in vivo (seed, foliar, seed+foliar treatments) assays to determine the antifungal activity against Alternia brassicicola. For in vitro assays, the extracts of A. platensis, C. pyrenoidosa, and C. vulgaris showed the highest antifungal activity, inhibiting the growth of A. brassicicola at a concentration of 50 mg/ml with inhibition zones of 4.9, 4.2, and 3.9 cm, respectively. For in vivo assays, the microalgal suspensions were observed to have remarkable antifungal activity at increasing concentrations against A. brassicicola compared with control treatments. Particularly, the seed+foliar treatment of a mixture of the microalgal suspension (A. platensis+ C.vulgaris+ C. pyrenoidosa) at a concentration of 15 g/l demonstrated the highest antifungal activity with an inhibition rate above 98% in cabbage (Brassica oleracea) and mustard (Brassica juncea). The present study confirmed that the microalgae treatments had a significant potential, as an applicable and eco-friendly tool against A. brassicicola, to reduce exposure and risks of chemical pesticides.