Team:Bordeaux/Template:OverviewTheProblem
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In winter, Plasmopara viticola is present on death leaves on the ground as oospores. They are inactive and do not produce any symptoms. When rain falls a lot during spring, these eggs grows and release zoospores when the temperature exceeds 11 degrees. The zoopores will be able to spread and infect the plant's upper tissues through rainwater's splashes.
Since repairing damaged tissues infected by downy mildew is impossible, the main solutions available to vinyards are preventive solutions, mainly through preventing primary infections. This is mainly done by spraying fungicides on the organs that are most infected: leaves and stems. The most efficient preventive treatment was discovered at the end of the 19th century: a solution made of copper sulfate also known as "Bouillie Bordelaise", the only treatment used until the end of the 20th century. Recently, synthetic fungicides have replaced this chemical treatment and more and more research is being done on alternative eco-friendly preventive treatments Different models (Caffi model, Potential systems model) take into account pluviometry, temperature, relative humidity and plant morphology to decide when are the best moments to apply the fungicides. However, even if these models have allowed vinyards to drastically reduce the quantities of fungicides used, they still cause environmental and sanitary problems in the surrounding regions. In 2010, each hectar or grapevine had received around 16 chemical treatments (this number was 15 in 2006) and varies greatly between regions. Amongst the biological threats on grapevine, mushroom parasites are far ahead of insects and fungi (12 fungicides are used against 2 insecticides and 2 weedkillers). Over 95% of the fongicide treatments in 2010 were due to mildew and oidium, sicknesses that are favorized by rain, humidity and heat. They bring the global quality of the wine down by reducing it's composition in phenols and sugars The risc of contamination on the leaves begin during the period where the floral buds and futur grapes are growing and lasts until the moment when the grapes touch each other. The sensibility period between oidium and mildew have common momments and vinyards don't heasitate to mix anti-mildew and anti-oidium solutions making the concentrations of these chemicals twice more concentrated in the grounds. What are the problems with these treatments? Are they really efficient? To have a really efficient treatment what would you need? The Problem
This year, iGEM Bordeaux’s project focuses on the Downy Mildew case.
It is an endemic species of North America that was only brought to Europe in the late 19th century. Even if some North american species have become resistant to this parasite through evolution, European species such as Vitis vinifera (the cultivated grapevine used for wine) are extreamly sensitive and this has lead vinyards to use whatever effective measures they can find to protect their vines.
Infection Mode of Downy Mildew
The primary contamination begins by the emission of a filament through the stomatal area where the parasite begins to develop sinkers from which is formed the mycelial network. These sinkers help to feed Plasmopara viticola by stealing the nutrient substrate of the plant. That’s create discolored and yellowish areas on leaves called “oil stain” on the upperside of the leaf. After, on the underside, conidiophores and conidia are formed. These symptoms cause damages to the leaves’ tissues and affect the plant’s photosynthetic ability, that slows down the maturity of the plant.
During the secondary contamination, conidia are transformed in zoospores that contaminate the surrounding tissues, weakening the plant even more and creating unreparable lesions.
A bit of History
little comics ?