Abstract
Many phytopathogenic fungi are disseminated as spores via the atmosphere from short to long distances. The distance of dissemination determines the extent to which plant diseases can spread and novel genotypes of pathogens can invade new territories. Predictive tools including models that forecast the arrival of spores in areas where susceptible crops are grown can help to more efficiently manage crop health. However, such models are difficult to establish for fungi with broad host ranges because sources of inoculum cannot be readily identified. Sclerotinia sclerotiorum, the pandemic agent of white mold disease, can attack >400 plant species including economically important crops. Monitoring airborne inoculum of S. sclerotiorum in several French cropping areas has shown that viable ascospores are present in the air almost all the time, even when no susceptible crops are nearby. This raises the hypothesis of a distant origin of airborne inoculum. The objective of the present study was to determine the interconnectivity of reservoirs of S. sclerotiorum from distant regions based on networks of air mass movement. Viable airborne inoculum of S. sclerotiorum was collected in four distinct regions of France and 498 strains were genotyped with 16 specific microsatellite markers and compared among the regions. Air mass movements were inferred using the HYSPLIT model and archived meteorological data from the global data assimilation system (GDAS). The results show that up to 700 km could separate collection sites that shared the same haplotypes. There was low or no genetic differentiation between strains collected from the four sites. The rate of aerial connectivity between two sites varied according to the direction considered. The results also show that the aerial connectivity between sites is a better indicator of the probability of the incoming component (PIC) of inoculum at a given site from another one than is geographic distance. We identified the links between specific sites in the trajectories of air masses and we quantified the frequencies at which the directional links occurred as a proof-of-concept for an operational method to assess the arrival of airborne inoculum in a given area from distant origins.
Highlights
Many phytopathogenic fungi are disseminated via the atmosphere from micro- to macro-geographical scales in the form of spores (Aylor et al, 1982; Brown and Hovmoller, 2002; Prospero et al, 2005)
Samplers were placed in the North region of France (N) in a chicory witloof field (Cichorium intybus L.), in the Center-West region (CW) in a cantaloupe field (Cucumis melo L.) and in the South-West (SW) and North-West regions (NW) in carrot fields (Daucus carota L.)
Information about airborne inoculum potentially arriving in a territory is important to obtain since the traits of exogenous strains may differ from endogenous ones and sometimes may lead to more damaging epidemics
Summary
Many phytopathogenic fungi are disseminated via the atmosphere from micro- to macro-geographical scales in the form of spores (Aylor et al, 1982; Brown and Hovmoller, 2002; Prospero et al, 2005). Some pathogens make long distance jumps from one susceptible host to another throughout the growing season following prevailing winds This is, for example, the case of Oomycetes responsible for tobacco blue mold and cucurbit downy mildew. It is the case for cereal stem rust that migrates following the “Puccinia pathway” in the United States wheat belt, or for wheat yellow rust in China (Aylor et al, 1982; Hovmoller et al, 2002; Ojiambo and Holmes, 2011). Modeled wind trajectories indicate that air movements are likely responsible for the spread of Ug99 in Africa and for its predicted trajectory into Asia (Singh et al, 2011; Meyer et al, 2017)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
