Kema, G.H.J.

Lee, T.A.J., van der

Schouten, H.J.

Wittenberg, A.H.J.

English

Wageningen Yield 

Pagina 124 Gewasbescherming  jaargang 40, nummer 3, mei 2009
Mededelingenblad van de Koninklijke Nederlandse Plantenziektekundige Vereniging
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Pagina 125Gewasbescherming  jaargang 40, nummer 3, mei 2009
Mededelingenblad van de Koninklijke Nederlandse Plantenziektekundige Vereniging
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Nowadays there is a tendency to implement 
the Lemmerzahl-test more and more in non-
official testing (screening new breeding lines) 
in the Netherlands. As Germany and Poland 
also use the Lemmerzahl-test, implementing 
this test in the Netherlands will most prob-
ably fasten up harmonisation and mutual 
acceptance of test results. 
In the Netherlands four pathotypes occur: 
pathotypes 1(D1), 2(G1), 6(O1) and 18(T1) 
(Baayen et al., 2006). These pathotypes are 
distinguished by differential reactions on a 
set of potato cultivars (bio-assay). Currently, 
six differential cultivars are used in our labo-
ratory. Disadvantages of the bio-assay are: 1) 
long period of incubation, 2) availability of 
differential cultivars sometimes problematic, 
3) purity of tubers. A new issue nowadays is 
the development of a molecular test to dis-
tinguish pathotypes. This project is called 
“Ontwikkeling van moleculaire toetsen om 
fysio’s van obligate quarantaineschimmels te 
onderscheiden”, and led by Bonants and Van 
der Lee (PRI, Wageningen). 
References
Baayen RP, Cochius G, Hendriks H, Meffert JP, Bakker J, Bekker M, van 
den Boogert PHJF, Stachewicz H & van Leeuwen GCM (2006). His-
tory of potato wart disease in Europe- a proposal for harmonisa-
tion in defining pathotypes. European Journal of Plant Pathology 
116: 21-31
Lemmerzahl J (1930) [A new simplified method for inoculation of 
potato cultivars to test for wart resistance]. Züchter 2: 288-297 (in 
German).
Spieckermann A & Kothoff P (1924) [Testing potatoes for wart resi-
stance.]. Deutsche Landwirtschaftliche Presse 51: 114-115 (in 
German)
Analysis of two genetic linkage maps of the 
wheat pathogen Mycosphaerella graminicola 
identified dispensable chromosomes that were 
present in both parents but absent in 15-20 % 
of the progeny. These Copy Number Polymor-
phisms (CNPs) were confirmed with a Compara-
tive Genomic Hybridization whole-genome array 
based on the finished genome of M. graminicola 
(http://genome.jgi-psf.org). Chromosomes 
14- 21 were frequently absent among isolates, 
without visible effect on viability or virulence, 
whereas chromosomes 1-13 were invariably pre-
sent. Genetic analyses showed that CNPs arise 
during meiosis, usually from nondisjunction 
at anaphase II. Overall, M. graminicola has the 
highest number of dispensable chromosomes 
reported. Varying from 0.41 to 0.77 Mbp, they 
comprise 38% of the chromosome number and 
11.6% of the genome. 
The dispensable chromosomes are smaller and 
have significantly lower gene densities. Most 
of their genes are duplicated on the essential 
chromosomes and show a different codon usage. 
Dispensable chromosomes also contained a 
higher density of transposons, pseudogenes, and 
unclassified genes, which could encode novel 
proteins. Moreover, the dispensable chromo-
somes show extremely low synteny with other 
Dothideomycete genomes. We hypothesize that 
the dispensable chromosomes of M. graminicola 
are adaptive in some yet unknown way.
Over the last few years many latent infections 
by Potato spindle tuber viroid (PSTVd) have 
been detected in various crops, mainly vegeta-
tively-propagated ornamentals. In a survey in 
the Netherlands in 2006, infections were found 
in 42% and 72% of the professionally grown 
lots of Brugmansia spp. and Solanum jasmi-
noides, respectively. The infected lots con-
tained 73,985 and 448,474 plants, respectively. 
Sequence analysis showed that most genoty-
pes of PSTVd isolates from Brugmansia spp. 
clearly differed from S. jasminoides isolates. 
In addition, phylogenetic studies showed that 
PSTVd genotypes from Brugmansia spp. and 
S. jasminoides cluster apart from each other 
and from PSTVd isolates from the vegetative-
ly-propagated crops of Solanum tuberosum 
(potato) and Physalis peruviana (Cape goo-
seberry). The studied PSTVd genotypes from 
the generatively-propagated crop tomato did 
not form a separate group but clustered in the 
groups of P. peruviana, S. jasminoides and S. 
tuberosum. Furthermore, repeated mechanical 
inoculations of several of these genotypes to 
tomato appeared successful without resulting 
in substantial genome mutations. Therefore, 
latently-infected plants of the vegetatively-
propagated solanaceous crops may have been 
sources of infection for tomato.
Outstanding: the dispensable chromosomes of Mycosphaerella 
graminicola
Sarrah Ben M’Barek 1,2, Theo A.J. Van der Lee1, Alexander H.J. Wittenberg1,2, Sarah B. Ware1,2, C. 
Maliepaard3, Charles F. Crane4, Braham Dhillon4, Stephen B. Goodwin4, Henk J. Schouten2, Gert H.J. 
Kema2 
1 Graduate School Experimental Plant Sciences;
2 Plant Research International B.V., Wageningen;
3 Plant Breeding, The Netherlands;
4 USDA-ARS, Crop Production and Pest Control Research Unit, and Department of Botany and Plant Pathology, Purdue University, USA. 
Corresponding author: Sarrah M’Barek; e-mail: Sarrah.benmbarek@wur.nl
The world’s most important food and feed crops 
wheat, maize, and barley are hosts for a complex 
of Fusarium species causing Fusarium Head 
Blight (FHB) in wheat and barley and stalk rot in 
maize. The disease pressure in several regions in 
China is among the highest in the world. Con-
sumption of food and feed contaminated with 
the mycotoxins produced by Fusarium species 
poses a great threat as they can cause serious ill-
nesses and immune-suppression in humans and 
animals. Fusarium asiaticum is the predominant 
causal agent of Fusarium head blight (FHB) in 
southern China. The genetic diversity was asses-
sed by analyzing 448 single-spore F. asiaticum 
isolates from 18 sampling sites that were 10 km 
to 2000 km apart. This analysis showed a signifi-
cant (P < 0.001) degree of population subdivision 
among populations from upper, middle and 
A selective sweep in Fusarium asiaticum populations in 
southern China.
Hao Zhang,1 Zheng Zhang1, Theo van der Lee2, Jin Xu1, Jing Sheng Xu1, Li-Jun Yang3, Da-Zhao Yu3, Cees 
Waalwijk2, and Jie Feng1
1 State Key Laboratory for Biology of Plant Diseases and Insect Pests, Institute of Plant Protection, Chinese Academy of 
Agriculture Sciences, Beijing 100093, China
2 Plant Research International BV, P.O. Box 16 6700 AA, The Netherlands
3 Institute for Plant Protection and Soil Sciences, Hubei Academy of Agricultural Sciences, 430064, Wuhan, China.
Corresponding author: Theo van der Lee; e-mail address: theo.vanderlee@wur.nl
Session Pathogen biology
Epidemiological evidence that vegetatively-propagated 
solanaceous plant species act as sources of Potato spindle 
tuber viroid inoculum for tomato
Ko Verhoeven, Marleen Botermans, Claudia Jansen and Annelien Roenhorst
Plant Protection Service, 
PO Box 9102, 6700 HC Wageningen, 
the Netherlands; 
e-mail: j.th.j.verhoeven@minlnv.nl
Pagina 126 Gewasbescherming  jaargang 40, nummer 3, mei 2009
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lower valleys of the Yangtze River, with little gene 
flow. We observed a strong association between 
this genetic population subdivision and the 
mycotoxin produced. Our results show that the 
dramatic decline in trichothecene chemotypes 
may be explained by a recent and significant 
sweep of 3ADON producers in FHB pathogen 
composition in the middle valley. Using Bayes-
ian statistics we found a biased gene flow from 
3ADON to NIV populations. 
In addition, we observed significant genetic dif-
ferentiation and linkage disequilibrium between 
NIV and 3ADON producing isolates at the same 
sampling sites. We discuss the impact of this shift 
on the increase of FHB in Southern China.
that traps the compounds of interest. The second 
method is based on the static pre-concentration of 
VOCs.  In this case, a material is exposed to the air, 
in which the trapping of VOCs mainly depends on 
mass diffusion processes. In both cases, the selec-
tion of the material is crucial in order to trap the 
VOCs of interest. 
Before identification and/or quantification of the 
plant-emitted volatiles, the mixture of compounds 
is often separated, mostly by gas chromatography. 
This method is a type of chromatography in which 
the mobile phase is a carrier gas, usually an inert gas 
such as helium, and the stationary phase is a layer of 
a polymer on an inert solid support, inside a glass or 
metal column. The properties of this column should 
be selected with care since they have a large effect 
on the ability to separate plant-emitted volatiles. 
There are various types of detectors available on 
the market to identify and quantify plant-emitted 
VOCs. The most popular detectors in use are the 
flame ionization detector and the mass spectrom-
eter. Electronic noses are also widely used to detect 
plant-emitted VOCs in air. More recently, biosen-
sors have emerged as promising tool to identify and 
quantify low levels of VOCs in ambient air.
At this moment, we consider gas chromatography 
coupled to mass spectrometry (GC-MS) as the best 
method for monitoring the health status of crops 
on the basis of plant-emitted VOCs at high-input 
greenhouse facilities. This preference is based on 
its favourable combination of high selectivity and 
resolution, good accuracy and precision, wide 
dynamic concentration range, high sensitivity, and 
the current commercialization of robust GC-MS sys-
tems. Only due to the high costs, we are years away 
from having this kind of instruments in horticultural 
practice. But, the ongoing expansion and intensifi-
cation of greenhouse production and the concern 
among consumers about the potential intake of 
pesticide residues on fruits and vegetables will 
support the prospected application of plant health 
monitoring in a commercial setting.
References
Jansen R.M.C., Miebach M., Kleist E., van Henten E.J. & Wildt J. (2009a) 
Release of lipoxygenase products and monoterpenes by tomato 
plants as an indicator of Botrytis cinerea-induced stress. Plant Biology, 
(in press).
Jansen R.M.C., Hofstee J.W., Wildt J., Verstappen F.W.A., Bouwmeester 
H.J., Posthumus M.A. & van Henten E.J. (2009b) Health monitoring 
of plants by their emitted volatiles: trichome damage and cell-mem-
brane damage are detectable at greenhouse scale. Annals of Applied 
Biology, (in press).
Jansen R.M.C., Hofstee J.W., Vestappen F.W.A., Bouwmeester H.J., Post-
humus M.A. & van Henten E.J. (2009a) Health monitoring of plants 
by their emitted volatiles: a temporary increase in the concentration 
of methyl salicylate after pathogen inoculation of tomato plants 
(Lycopersicum esculentum) at greenhouse scale. Paper presented at 
the Greensys2009, Quebec, Canada.
Traditional inspections of greenhouse crops are 
done by greenhouse personnel and rely on the pres-
ence of visual symptoms on the crop. This method 
has its limitations. Namely, visual symptoms are 
often difficult to observe, or when seen, it may be 
too late to remedy the problem. For example, early 
signs of pathogen infections and herbivore infesta-
tions often appear on the abaxial side of leaves or 
on stem parts that are hidden by the foliage. When 
these symptoms remain unnoticed, such infections 
or infestations may disperse rapidly and result in 
irretrievable crop damage.
These limitations have led to the emergence of a 
wide range of methods to improve the inspection 
of greenhouse crops. Ideally, such methods would 
enable continuous monitoring of individual plants 
in order to reveal health problems at an early stage. 
This would enable a grower to take early action, 
and prevent further crop damage. One approach to 
monitor the health status of plants is based on the 
volatile organic compounds (VOCs) emitted from 
them. This approach was successfully tested at both 
laboratory-scale (Jansen et al., 2009a) as well as 
greenhouse-scale (Jansen et al,. 2009b, Jansen et al., 
2009c).
In general, measurement of plant emission consists 
of three steps: (1) collection of plant-emitted VOCs, 
(2) separation of plant-emitted VOCs in the mix-
ture, and (3) identification, and/or quantification of 
separate VOCs. 
In the first step, a fraction of the compounds emit-
ted from the plants is collected. This sampling step 
is usually combined with pre-concentration of the 
VOCs in the air to achieve the detection limits of 
commonly applied analytical instruments. Two 
methods are generally applied to pre-concentrate 
VOCs present in air. The first method is based on the 
dynamic pre-concentration of VOCs. This method 
is referred to as dynamic because the air is actively 
pumped through a cartridge packed with a material 
Session Scientific tools and 
pathogen detection
Trends in plant science: detecting air-borne chemicals sent off 
by plants to monitor their state of health
Roel Jansen1, Kotaro Takayama2, Jürgen Wildt3, Jan Willem Hofstee1, Harro  Bouwmeester4,5 and Eldert 
van Henten1,6
1 Wageningen University, Farm Technology Group, P.O. Box 17, 6700 AA, Wageningen, 6708 PD, The Netherlands, Roel.Jansen@
wur.nl
2 Lab. Physiological Green Systems, Department of Biomechanical Systems, Faculty of Agriculture, Ehime University, Japan
3 Institute Phytosphere (ICG-III), Research Centre Jülich, D-52435 Jülich, Germany
4 Plant Research International, P.O. Box 14, 6700 AA, Wageningen, The Netherlands
5 Wageningen University, Laboratory of Plant Physiology, P.O. Box 14, 6700 AA, Wageningen, The Netherlands
6 Wageningen UR Greenhouse Horticulture, P.O. Box 16, Wageningen, The Netherlands
What can we learn from the Botrytis cinerea genome sequence?
Jan van Kan
Wageningen University, Laboratory of Phytopathology, PO Box 8025, 6700 EE Wageningen, the Netherlands;  
e-mail: jan.vankan@wur.nl
Botrytis cinerea (also known as grey mould) is 
a serious pre- and post-harvest pathogen in a 
wide range of fruit, vegetable and ornamental 
crops. The application of molecular genetic 
tools in the past two decades has provided 
an increased insight into the mechanisms by 
which B. cinerea infects plants. This insight may 
be useful for developing novel, rational control 
strategies to reduce pathogen damage, either 
by using novel chemicals or by enhancing plant 
resistance.
The previous molecular-genetic studies on 
B. cinerea have resulted in the cloning and 
functional analysis of many dozens of genes, 
but cloning of individual genes can be time-
consuming when the sequences are unknown. 
In the 1990’s the genome of one B. cinerea 
strain has been determined by Syngenta. More 
recently, a different strain has been sequenced 
by an international consortium, coordinated 
by French partners. The genome sequences of 
both B. cinerea strains, as well as of the closely 
related pathogen Sclerotinia sclerotiorum, are 
in the process of annotation. An important part 
of the analysis is dedicated to the comparison 
between the two fungal species and the two  
B. cinerea isolates.
I will present an overview of the current status 
of the B. cinerea genome analysis and highlight 
what we have learned thus far from the se-
quence with respect to evolution, (sexual and 
asexual) reproduction and the infection strate-
gies of B. cinerea. 


Health monitoring of plants by their emitted volatiles: trichome damage and cell-membrane damage are detectable at greenhouse scale. Annals of Applied Biology,

Release of lipoxygenase products and monoterpenes by tomato plants as an indicator of Botrytis cinerea-induced stress. Plant Biology,

Outstanding : the dispensable chromosomes of Mycosphaerella graminicola

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van der Lee, T.A.J.

NARCIS 

Outstanding : the dispensable chromosomes of Mycosphaerella graminicola

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