Aqueous and ethanolic extracts obtained from nine Chilean marine macro-algae collected at different seasons were examined in vitro
and in vivo
for properties that reduce the growth of plant pathogens or decrease the injury severity of plant foliar tissues following pathogen infection. Particular crude aqueous or organic extracts showed effects on the growth of pathogenic bacteria whereas others displayed important effects against pathogenic fungi or viruses, either by inhibiting fungal mycelia growth or by reducing the disease symptoms in leaves caused by pathogen challenge. Organic extracts obtained from the brown-alga Lessonia trabeculata
inhibited bacterial growth and reduced both the number and size of the necrotic lesion in tomato leaves following infection with Botrytis cinerea
Aqueous and ethanolic extracts from the red-alga Gracillaria chilensis
prevent the growth of Phytophthora cinnamomi
, showing a response which depends on doses and collecting-time. Similarly, aqueous and ethanolic extracts from the brown-alga Durvillaea antarctica
were able to diminish the damage caused by tobacco mosaic virus (TMV) in tobacco leaves, and the aqueous procedure is, in addition, more effective and seasonally independent. These results suggest that macro-algae contain compounds with different chemical properties which could be considered for controlling specific plant pathogens.