Abstract:The antifungal effect of rhamnolipids (RLS) on the vegetative growth of Alternaria alternata and on the black spot control were studied, and the possible mechanism of its antifungal activity was evaluated. The results showed that RLS significantly inhibited the growth of A. alternata, and the inhibition effect was significantly increased with the increase of RLS concentration. The mycelium diameters of A. alternata treated with 30 mg/mL RLS was only 19.22% of the control group after 7 days' incubation, and mycelium was white and ball in shape. The development of black spot in pear fruit treated with RLS was also inhibited, lesion diameter of 50 mg/mL RLS treatment group was only 21.42% of that in the control group. Further research showed that the RLS treatment severely damaged the integrity of A. alternata cell membranes and mitochondria, increased membrane conductivity, and promoted the generation and accumulation of reactive oxygen species. Ultramicroscopic observation showed that the hyphae morphology and cellular structure of A. alternata were significantly destroyed by RLS treatment.
