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Eur J Plant Pathol (2015) 141:779787 DOI 10.1007/s10658-014-0578-3
ORIGINAL RESEARCH
Airborne inoculum of Fusarium oxysporum f. sp. cucumerinum
K. Scarlett & L. Tesoriero & R. Daniel & D. Maffi &
F. Faoro & D. I. Guest
Accepted: 11 December 2014 /Published online: 7 January 2015 # Koninklijke Nederlandse Planteziektenkundige Vereniging 2015
Abstract Fusarium oxysporum f. sp. cucumerinum is the fungal pathogen responsible for Fusarium vascular wilt of cucumber. In Australia, disease management in soilless greenhouse cucumbers is limited by the understanding of the disease cycle, in particular the risk associated with infection of pruning wounds by airborne propagules. Aerial dissemination of the pathogen in response to temperature and relative humidity was investigated using a specific and sensitive quantitative real-time PCR assay. Both macroconidia and microconidia were identified as airborne propagules and a potential relationship between fluctuation in relative humidity and spore release was found, however, it appears that crop disturbance may also influence conidia liberation. Experimental inoculation of stem wounds with conidia however, failed to establish infections. These results suggest that aerial inoculum propagates
and disseminates the pathogen, however airborne spores are deposited on the substrate surface and infection occurs primarily through the root. We conclude that while airborne conidia are a risk to infection of cucumber plants in soilless greenhouse crops, resistant root-stocks are likely to provide good protection against this pathogen.
Keywords Epidemiology. Disease cycle . Fusarium wilt . Aerial conidia
Introduction
Fusarium oxysporum f. sp. cucumerinum is responsible for a vascular wilt disease in Australian commercial cucumber greenhouses (Tesoriero 2011), for which there are few effective control measures. While the use of soilless media in greenhouse cropping aims to reduce disease incidence by excluding soil borne pathogens from the system (Jarvis 1989), Fusarium wilt remains an important disease. Developing management strategies to prevent pathogen entry and survival in soilless greenhouse production systems is limited by our understanding of its disease cycle and epidemiology.
It has been shown that poor crop hygiene practices, including inadequate cleaning and disinfestation of irrigation lines in recycled water-nutrient systems (Jarvis 1989), infrequent removal of organic crop waste and use of infected growth substrates, particularly by reusing media, has led to the introduction, survival and
K. Scarlett : D. I. GuestFaculty of Agriculture and Environment, The University of...