Abstract
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.
Highlights
Like animals, plants are exposed to a wide variety of enemy organisms, which can damage their tissues
Examining the effect of the obtained aqueous and ethanolic extracts from all collected algae on the growth of P. cinnamomi or B. cinerea by using the agar-diffusion assay technique demonstrated that most of them do not alter the development of either fungi, suggesting either that they are not able to diffuse across the agar or that the extracting condition does not allow the isolation of compounds with properties to alter fungal growth under these conditions
Durvillaea antarctica (DA), Gracilaria chilensis (GC), Gigartina skottsbergii (GS), Lessonia nigrescens (LN), Lessonia trabeculata (LT), Macrocystis integrifolia (MI), Macrocystis pyrifera (MP), Porphyra columbina (PC), and Ulva costata (UC) were collected from the Chilean coast during four different periods distributed in summer, autumn, spring and spring-summer (Season 4, November–December 2009)
Summary
Plants are exposed to a wide variety of enemy organisms, which can damage their tissues. Other pathogens are more opportunistic, infecting a broad range of susceptible hosts [19,20,21] Gram negative bacteria such as Pseudomonas syringae and Erwinia carotovora use a large and well-defined repertoire of effector proteins to cause disease in tomato, Arabidopsis and potato plants among others [22,23,24]. Fungal plant pathogens such as Botrytis cinerea and Phytophthora cinnamomi attack a wide range of agriculturally and ornamentally important plants [25,26]. We evaluate the effects of aqueous and ethanolic crude extracts from nine different seaweeds collected on the coastline of Chile in different seasons on plants pathogens such as the bacteria Pseudomonas syringae, Erwinia carotovora, the fungal pathogens Phythophthora cinnamomi and Botrytis cinerea, and on the tobacco mosaic virus (TMV)
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