Involvement of antifungal compounds from rockmelon fruit rind (Cucumis melo L.) in resistance against the fruit rot pathogen Fusarium oxysporum f. sp. melonis.
- 278 Downloads
Fusarium rot caused by Fusarium oxysporum f. sp. melonis, causes significant postharvest losses in rockmelon crops. Although latent infection is often present in the field, symptoms of the disease may not appear until fruit maturity. The susceptibility of different-aged rockmelon fruit cv. “Colorado” was determined by inoculating fruit at different stages of development with a spore suspension of F. oxysporum f. sp. melonis. Disease symptoms appeared first and were more severe in older fruit compared to younger fruit. Disease symptoms on fruit 35 DAA (Days After Anthesis) and 42 DAA appeared within 3 days of inoculation and rapidly covered the fruit within 5 days. In contrast, disease symptoms on fruit 7 DAA appeared 6 days after inoculation and grew slowly. Extraction of antifungal compounds without involving acid hydrolysis from 7 DAA fruit rind did not show antifungal activity on TLC plates. However, hydrolysis of the ethyl acetate fraction resulted in a strong fungal inhibitory zone on agar plates against colonies of F. oxysporum f. sp. melonis. Separation of the hydrolysed crude extracts on TLC plates indicated the presence of two distinct antifungal zones with Rf 0.36 and 0.13 in young fruit 7, 14 and 21 DAA. The area of fungal inhibition of compound Rf 0.36 was greater than that of Rf 0.13 on the TLC plate. Extracts from mature fruit of 35 and 42 DAA did not have detectable levels of antifungal compounds. The decrease in the susceptibility of rockmelon fruit during maturity may be correlated to a decrease in the antifungal compounds in the fruit with maturity.
KeywordsInduced resistance Latent infection Phytoalexin Phytoanticipin Systemic acquired resistance Thin layer chromatography
- Bokshi, A. I., Morris, S. C., & McConchie, R. (2007). Environmentally safe control of postharvest disease of melon (Cucumis melo) by integrating heat treatment, safe chemicals and systemic acquired resistance. New Zealand Journal of Crop and Horticultural Science, 35, 179–186.Google Scholar
- Burgess, L. W., Liddell, C. M., & Summerell, B. A. (1988). Laboratory manual for Fusarium research (2nd ed.). Department of Plant Pathology and Agricultural Entomology, University of Sydney.Google Scholar
- Daayf, F., Schmitt, A., & Belanger, R. R. (1997a). Evidence of phytoalexins in cucumber leaves infected with powdery mildew following treatment with leaf extracts of Reynoutria sachalinensis. Plant Physiology, 113, 719–727.Google Scholar
- Daayf, F., Ongena, M., Boulanger, R., El Hadrami, I., & Belanger, R. R. (2000). Induction of phenolic compounds in two cultivars of cucumber by treatment of healthy and powdery mildew infected plants with extracts of Reynoutria sachalinensis. Journal of Chemical Ecology, 26, 1579–1593.CrossRefGoogle Scholar
- Droby, S., Prusky, D., Jacoby, B., & Goldman, A. (1986). Presence of antifungal compounds in peel of mango fruits and their relation to latent infection of Alternaria alternata. Physiological and Molecular Plant Pathology, 29, 173–183.Google Scholar
- Joyce, D. C., & Johnson, G. I. (1999). Prospects for exploitation of natural disease resistance in harvested horticultural crops. Postharvest News and Information, 10, 45–48.Google Scholar
- Markham, K. R. (1982). Techniques of flavonoid identification. London: Academic.Google Scholar
- McConchie, R., McDonald, K., Anowarul, B., & Morris, S. C. (2007). Systemic acquired resistance as a strategy for disease management in rockmelon (Cucumis melo var.reticulatus). Acta Horticulture, 731, 205–210.Google Scholar
- Morrissey, J. P., & Osbourn, A. E. (1999). Fungal resistance to plant antibiotics as a mechanism of pathogenesis. Microbiology and Molecular Biology Research, 63, 708–724.Google Scholar
- Prusky, D., & Keen, N. T. (1993). Involvement of preformed antifungal compounds in the resistance of subtropical fruits to fungal decay. Plant Diseases, 77, 114–119.Google Scholar
- Randerath, K. (1966). Thin layer chromatography. New York: Verlag Chemie Academic.Google Scholar
- StatSoft Inc. (2005). STATISTICA (data analysis software system) version 7th ed. StatSoft Inc. OK. USA; www.statsoft.com.