Evaluation of stress metabolites in coffee leaves by a non-pathogen :
Detached coffee leaves (Coffea arabica cv. "Mundo Novo") inoculated with a spore suspension of Heminthosporium carbonum, non-pathogenic to coffee plants, showed accumulation of fungitoxic compounds which diffused into the infection-droplets on the leaf surface. The fungitoxic activity of crude diffusates was tested towards the germination of urediniospores of Hemileia vastatrix, "in vitro". This fungitoxic activity is dependent upon the diffusate concentration used, as well as the leaf age, time period and incubation temperature of inoculated leaves. Crude diffusates from both inoculated and control leaves submitted to partition with ethyl acetate showed antifungal activity against the development of Cladosporium cucumerinum in bioassays done on TLC plates. The analysis of the inhibitory zones of the growth of C. cucumerinum showed that both inoculated an control leaves diffused caffeine (Compound II) among other fungitoxic compounds into the infection droplets. Results suggest the presence of a higher amount of caffeine in samples from inoculated leaves than in those from controls. On the other hand, other fungitoxic compounds (Compounds I, IV) were detected only in the samples from inoculated leaves, suggesting that their synthesis is a consequence of the interaction between the host and the non-pathogenic parasite as a plant defense response. It was also observed that a pre-formed fungitoxic compound present in the control leaves disappeared after inoculation (Compound III). The chemical nature and structure of the fungitoxic compounds are still unknown
| Main Authors: | , , |
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| Format: | biblioteca |
| Language: | eng |
| Published: |
Oct
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| Subjects: | COFFEA ARABICA, HELMINTHOSPORIUM, HEMILEIA, ROYA, INOCULACION, ENFERMEDADES FUNGOSAS, MUNDO NOVO, ESPORULACION, UREDOSPORAS, |
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