Abstract
The antifungal activity of volatile compounds from the fruit, leaf, rhizome and root of 109 plant species was evaluated against Fusarium oxysporum f. sp. lycopersici (FOL) race 1—the tomato wilt pathogen—by using the modified dish pack method. Eighty-eight plant samples inhibited mycelial growth, including volatiles from fruits of Heracleum sosnowskyi, which exhibited the strongest antifungal activity, showing 67% inhibition. Two volatile compounds from the fruits of H. sosnowskyi (octanol and octanal) and trans-2-hexenal as a control were tested for their antifungal activities against FOL race 1 and race 2. In terms of half-maximal effective concentration (EC50) values, octanol was found to be the most inhibitory compound for both pathogenic races, with the smallest EC50 values of 8.1 and 9.3 ng/mL for race 1 and race 2, respectively. In the biofumigation experiment, the lowest disease severity of tomato plants and smallest conidial population of race 1 and race 2 were found in trans-2-hexenal and octanol treated soil, while octanal had an inhibitory effect only on race 2. Therefore, our study demonstrated the effectiveness of volatile octanol and trans-2-hexenal on the control of the mycelial growth of two races of Fusarium oxysporum f. sp. lycopersici and may have potential for the future development of novel biofumigants.
Highlights
Plants produce a variety of secondary metabolites which act as a direct or indirect defense against fungal, microbial or insect attack [1,2,3]
Our study demonstrated the effectiveness of volatile octanol and trans-2-hexenal on the control of the mycelial growth of two races of Fusarium oxysporum f. sp. lycopersici and may have potential for the future development of novel biofumigants
Essential oils of Origanum heracleoticum, which are rich in phenols, are able to inhibit the growth of some post-harvest phytopathogenic fungi (Botrytis cinerea, Penicillium expansum, Aspergillus niger and Monilinia fructicola) [7]
Summary
Plants produce a variety of secondary metabolites which act as a direct or indirect defense against fungal, microbial or insect attack [1,2,3]. Laurel oil can completely stop the growth of Monilinia laxa at a concentration of 200 μg/mL and B. cinerea at 1000 μg/mL [9]. The antifungal effects of volatile compounds from black zira and other herbs were investigated against F. oxysporum. Neri et al (2006) demonstrated in vitro and in vivo activities of nine plant volatiles against P. expansum, the cause of blue mold in pear, while trans-2-hexenal and carvacrol were the best inhibitors of conidial germination (ED50 (half maximal (50%) effective concentration) = 10·2 μL/L) and mycelial growth (ED50 = 9 μL/L) [11]. Volatile 2E-hexenal completely inhibited the growth of the potato blemish pathogens Pectobacterium atrosepticum (bacterial soft rot), Colletotrichum coccodes (black dot) and Helminthosporium solani (silver scurf) in an in vitro test [12]
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