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Fusarium oxysporum identification and its effect on the control of Fusarum of Vanilla

 

Dr. Roni Cohen

Agricultural Research Organization, Newe Ya'ar Research Center

Ramat Yishay, Israel

ronico@volcani.agri.gov.il

Most plant pathologists, at some time in their career, must identify a culture of a Fusarium species. The identification is based on symptoms and the host from which the pathogen was isolated, the microscopic morphology and on specific use of primers enabling molecular identification. Fusarium species cause a huge range of diseases on an extraordinary range of host plants usually involving a vascular wilt syndrome. The majority of the isolates causing vascular wilts are specific strains that infect only a small number of host plants and have been differentiated from each other using the subspecific term formae speciales (f. sp.). For example, the strains commonly attacking banana are F. oxysporum f. sp. cubense; cotton, F. oxysporum f. sp. vasinfectum; and tomato, F. oxysporum f. sp. lycopersici. Morphologically these strains are identical, and they also cannot be differentiated from nonpathogenic or saprophytic strains, of which there is a huge diversity, especially in soil.

Root and stem rot is a very detrimental disease of vanilla worldwide. Fusarium oxysporum is frequently associated with the disease but other Fusarium species are also reported.  To distinguish root rot producing strains from those produces only wilt symptoms, the addition of word radices was proposed. Since fusarium in Vanilla can cause both wilting and stem lesions the current name used for the pathogen is Fusarium oxysporum f. sp. radices vanilla (Forv). The radices fusarium types are less specific from the wilt types, thus the potential risk of other fusarium to vanilla should be studied. 

The environmental conditions in which plants are maintain such as irrigation type and regime, growing media and nutritional needs of the plants, the possibility to apply pesticides and light and humidity in the greenhouse are critical to disease development. However, those conditions may often oppose the agronomic needs. The contavers  between  the agronomical and the pathological requirements will be discussed.

Dr. Roni Cohen is a senior researcher in the division of cucurbit research and breeding in the Agriculture Research Organization (ARO), Newe Ya'ar Research Center, Israel. He received his Ph.D. in 1987 from the Hebrew University of Jerusalem, Israel.. His research interests are soil borne fungal diseases and powdery mildew of cucurbits. Roni is involved in introducing grafted plants to the Israeli agriculture as one of the alternatives of methyl bromide soil fumigation.