Research from Holland on early identification on plant disease from odours, provides a potential disease management tool in glasshouses. Combined with precision technology could these techniques be of relevance to paddock production

Jansen, R.M.C.

NARCIS 

Sniffing out disease

Wageningen Yield 

20 Precision Ag News
Research from Holland on early identification of plant disease from odours, provides a 
potential disease management tool in 
glasshouses.  Combined with precision 
technology could these techniques be 
of relevance to paddock production?
The smells in your garden are often 
rich and differ in intensities.  Blossoms 
can smell sweet, spicy, woody or be 
strongly intoxicating.  For decades, 
floral scent was difficult to measure 
or even to describe.  Therefore, vague 
terms were often related to scents 
such as warm, fruity, fresh or even 
sensual.  We now know that a plant’s 
scent is a unique combination of 
volatile compounds, organic molecules 
that evaporate off the leaves, filling 
the air with perfume to attract 
pollinators.  However, until recently, 
no one anticipated that volatile 
compounds emitted by plants provide 
important information relating to the 
plant’s health status.
In 1984, Prof. Marcel Dicke at 
Wageningen University, The 
Netherlands, discovered that plants 
actively release volatile substances 
after insect damage.  These volatile 
substances were found to attract 
predators of the herbivorous insects, so 
they functioned as bodyguards.  This 
resulted in the concept ‘the enemy of 
your enemy is your friend’, which is 
still a hot topic in plant sciences.
Several years later, it became clearer 
that volatile compounds released by 
plants are able to transfer information 
between plants and insects.  Therefore, 
they were termed ‘infochemicals’.  
These infochemicals play an active 
role as bodyguards and in inter-plant 
and plant to plant communication.
Furthermore, these volatile chemicals 
serve as a disinfectant for bacterial 
and fungal infections and probably 
play a role in plant protection against 
harmful gases, such as high ozone 
concentrations.
So, plants release volatiles when they 
are stressed by pathogen infection, 
bacterial infection or herbivore 
attack.  Technologically, it is likely 
that commercially available sensors 
would be able to detect these 
compounds.  Applying such sensors 
in a greenhouse could lead to an 
early-warning monitoring system, in 
which greenhouse managers would 
be warned of plant stress before visual 
symptoms occurred.
Plants release 
volatile substances 
when they are 
stressed by insect 
and disease attack
To test this hypothesis we selected the 
tomato as a model.  The tomato was 
selected because it is a commercially 
important crop throughout the world 
—both for the fresh fruit market and 
the processed food industries.  In the 
Netherlands it covers about 1400 
hectares or one-third of the Dutch 
greenhouse vegetable area.  The plant 
pathogen Botrytis was selected as 
stressor because this fungal pathogen 
is among the most important and 
devastating disease problems for 
tomato growers worldwide.  This 
disease affects fruits and stems, as well 
as leaves. 
The research started in 2005, when 
detached tomato leaves were 
inoculated with Botrytis and placed in 
a Petri dish.  Identification of the air 
surrounding the leaf confirmed the 
emission altered and a clear difference 
was observed between inoculated and 
control leaves. 
In 2006, the process was scaled-up 
enabling the analysis of the emission 
from four intact tomato plants in a 
closed glass chamber.  This enclosure 
was required to prevent contamination 
of the air surrounding the plants.  In 
addition, this set-up enabled the 
identification of disease discriminatory 
compounds at an early stage, before 
visible symptoms appeared on the 
leaf surface. 
During 2007, further experiments 
will be conducted to validate our 
theories in a semi-closed greenhouse 
of 45 square meters.  This last step 
is the most exciting, as it approaches 
practical conditions similar to those 
found in Dutch greenhouses.  Initial 
results indicate that it is easy to detect 
artificial damage due to touching of 
the plants.
My challenge is to develop a 
monitoring system for greenhouse 
crops based on volatile sensing.  To do 
this I need to combine knowledge of 
chemistry, biology and engineering.  It 
is important to know how cultivation is 
arranged inside a greenhouse.  Plant-
pathogen interaction and the role 
of light, humidity and temperature 
on this interaction need to be fully 
understood.  Finally, knowledge 
of maths and sensor technology 
is required as most sensors deliver 
enormous amounts of data that need 
to be automatically processed and 
interpreted.  I hope that you can share 
this challenge with me or think about 
it while you eat your tomato.
For more information
Roel Jansen
Wageningen University
The Netherlands
Roel.Jansen@wur.nl
Roel Jensen, Wageningen University
Sniffing out disease
Dutch researchers are working on identifying disease from 
volatile substances before any plant symptoms occur.
Horticulture


Research from Holland on early identification on plant disease from odours, provides a potential disease managment tool in glasshouses. Combined with precision technology could these techniques be of relevance to paddock production

Sniffing out disease

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