Table Of ContentADVANCES IN DOWNY MILDEW RESEARCH – VOLUME 2
Developments in Plant Pathology
VOLUME 16
The titles published in this series are listed at the end of this volume.
Advances in Downy Mildew
Research – Volume 2
Edited by
PETER SPENCER-PHILLIPS
University of the West of England,
Bristol, U.K.
and
MICHAEL JEGER
Imperial College London,
Kent, U.K.
SPRINGER SCIENCE+BUSINESS MEDIA, B.V.
A C.I.P. Catalogue record for this book is available from the Library of Congress.
ISBN 978-90-481-6697-8 ISBN 978-1-4020-2658-4 (eBook)
DOI 10.1007/978-1-4020-2658-4
Printed on acid-free paper
All Rights Reserved
©2004 Springe r Science+ Business Media Dordrecht
Originally published by Kluwer Academic Publishers in 2004
Softcover reprint of the hardcover 1st edition 2004
No part of this work may be reproduced, stored in a retrieval system, or transmitted
in any form or by any means, electronic, mechanical, photocopying, microfilming, recording
or otherwise, without written permission from the Publisher, with the exception
of any material supplied specifically for the purpose of being entered
and executed on a computer system, for exclusive use by the purchaser of the work.
TABLE OF CONTENTS
Preface
P. T. N. Spencer-Phillips and M. J. Jeger…........………....................vii
The compatible interaction in downy mildew infections
J. S. C. Clark and P. T. N. Spencer-Phillips..........................................1
Forecasting downy mildew diseases
T. Gilles................................................................................................35
Cucurbit downy mildew: a unique pathosystem for disease
forecasting
G. J. Holmes, C. E. Main and Z. T. Keever III….........................…...69
Evaluation of MILIONCAST, a forecaster for onion downy
mildew, with historical data
T. Gilles and R. Kennedy.....................................................................81
Use of disease forecasting models for control of onion downy
mildew in New Zealand
R. W. Chynoweth, R. M. Beresford, W. R. Henshall and
P. J. Wright...........................................................................................91
Overwintering of rose downy mildew (Peronospora sparsa)
X. Xu and T. Pettitt..............................................................................99
Influence of environmental factors on the disease cycle of
white rust, caused by Albugo candida
E. Gilijamse, J. M. Raaijmakers, C. F. Geerds and M. J. Jeger.........107
Host specialisation of the oomycete Albugo candida
E. T. M. Meekes, M. J. Jeger and J. M. Raaijmakers.........................119
Temporal and spatial variation in virulence of natural
populations of Bremia lactucae occurring on Lactuca serriola
I. Petrželová and A. Lebeda……………………………….………..141
Downy mildew of pearl millet: present scenario in India
J. K. Dang and M. S. Panwar……………..………………………...165
vi
Genetic and pathogenic variability among isolates of
Sclerospora graminicola, the downy mildew pathogen
of pearl millet
R. P. Thakur, S. Sivaramakrishnan, S. Kannan, V. P. Rao,
D. E. Hess and C. W. Magill..............................................................179
Genetic and molecular characterisation of Plasmopara
halstedii isolates from Hungary
H. Komjáti, C. Fekete and F. Virányi................................................193
Response of wild and weedy Cucurbita L. to pathotypes of
Pseudoperonospora cubensis (Berk. & Curt.) Rostov.
(cucurbit downy mildew)
A. Lebeda and M. P. Widrlechner......................................................203
Potential and limits for the use of new characters in the
systematics of biotrophic oomycetes
O. Spring............................................................................................211
A seedling bioassay to detect the presence of Plasmopara
halstedii in soil
T. J. Gulya..........................................................................................233
Eicosapentaenoic acid, a possible marker for downy mildew
contamination in sunflower seeds
O. Spring and K. Haas........................................................................241
Isolation of viable Peronospora viciae hyphae from infected
Pisum sativum leaves and accumulation of nutrients in vitro
N. K. El-Gariani and P. T. N. Spencer-Phillips..................................249
Benzothiadiazole-induced resistance to Plasmopara halstedii
(Farl.) Berl. et de Toni in sunflower
R. Bán, F. Virányi and H. Komjáti.....................................................265
Index..........................................................................................................275
PREFACE
P.T.N. Spencer-Phillips1and M.J. Jeger2
1Centre for Research in Plant Science, University of the West of England, Coldharbour
Lane, Bristol BS16 1QY, UK
2Department of Agricultural Sciences, Imperial College London, Wye Campus, Wye,
Ashford, Kent TN25 5AH, UK
This second volume of Advances in Downy Mildew Research has
arisen from novel data presented at the Downy Mildews Workshop at the 8th
International Congress of Plant Pathology (ICPP) held in Christchurch,
New Zealand in February 2003, together with more general overview
contributions.
Emphasis in this volume is on the biology of compatible
interactions, forecasting and epidemiology, host specialisation, genetic
variability amongst pathogen populations, novel methods for detection and
systematics, and induced resistance. Two chapters focus on the related
oomycete Albugo candida, which shares many pathogenic characteristics
with the downy mildews. Much can be learnt by comparing different
pathosystems, and it is important to maintain this breadth when a small
number of model systems, such as downy mildew on Arabidopsis thaliana,
are commanding the most research attention. Contributions on specific
downy mildews focus on Bremia lactucae, Peronospora destructor,
Peronospora sparsa, Peronospora viciae, Plasmopara halstedii,
Plasmopara viticola, Pseudoperonospora cubensis and Sclerospora
graminicola. Review chapters on compatibility, forecasting and systematics
consider a broader range of downy mildew fungi, and compare them with
other oomycete and biotrophic pathogens.
As with the previous volume, the aim has been to address a variety
of aspects rather than encompass all downy mildew research. It is envisaged
that other topics and pathogens will be included in future volumes linked to
the five year ICPP cycle. Areas based on molecular technology are
undergoing the greatest change due to a very substantial investment of
resources. Thus the genetics of virulence, avirulence and host resistance,
phylogeny and nomenclature, rapid in-field diagnostics, cell signalling and
molecular mechanisms of compatibility are where many significant
vii
viii P.T.N. SPENCER-PHILLIPS AND M.J. JEGER
advances are occurring. These advances have the potential to underpin
improved control measures, which are more durable, sustainable and safer
for both consumers and the environment. They also promise to help provide
the increased crop yields required to feed hungry people in the developing
nations. With some 17% of the world fungicide market directed towards
controlling downy mildew diseases (Gisi, 2002), let alone other oomycetes,
significant progress is essential.
It is important that advances in knowledge and technology are
integrated and applied in disease control. For the latter to be successful,
there is a continued need for parallel research and practical expertise at the
basic biology, disease control and epidemiological levels. We look forward
to learning what has been achieved in the next volume of this series and at
the 2008 ICPP in Torino, Italy.
Gisi U. (2002) Chemical control of downy mildews. In Advances in Downy Mildew
Research, P.T.N. Spencer-Phillips, U. Gisi, A. Lebeda, eds. Kluwer Academic Publishers,
Dordrecht, The Netherlands, pp. 119-159.
TH E COMPATIB LE INTERACTIO N IN DOWNY
MILDEW INFECTIONS
J.S.C. Clark1and P.T.N. Spencer-Phillips2
1Max-Planck-Institute of Molecular Plant Physiology, Am Mühlenberg 1, 14476 Golm,
Germany
2Centre for Research in Plant Science, University of the West of England, Coldharbour
Lane, Bristol BS16 1QY, UK
1. INTRODUCTION
Downy mildews are oomycetes belonging to the orders
Peronosporales and Sclerosporales in the class Peronosporomycetes, within
the kingdom Straminipila, according to Dick (2002a, 2002b). The taxonomy
of this group of organisms, however, is under continuous revision. For
example, Peronospora parasitica causing downy mildew of brassicas is
now known correctly as Hyaloperonospora parasitica (Constantinescu and
Fatehi, 2002), and will be referred to as such throughout this review.
Further revisions will follow shortly: Choi and co-workers (2003) recently
suggested that H. parasitica should be divided into several distinct species,
based on sequence analysis of the ITS region of rDNA.
Although these oomycetes do not map phylogenetically to the
kingdom Fungi, they are considered to be fungi in the broadest sense
because they share a life-style based on a hyphal and mycelial mode of
growth, an absorptive heterotrophic nutrition and reproduction via spores
(Dick, 2002a; Diéguez-Uribeondo et al., 2004). The downy mildew fungi
are also examples of endophytic biotrophs forming an intercellular
mycelium, typically with intracellular haustoria, and gaining nutrients from
living host cells. They are obligate to this biotrophic mode of nutrition and
none have been grown in axenic culture, although hyphae of Peronospora
viciae isolated from pea leaves are able to accumulate carbon from glucose
in vitro (El-Gariani and Spencer-Phillips, this volume). They share these
characteristics with the Albuginaceae (monogeneric, ie all Albugo spp.),
another family of obligate biotrophic pathogens within the Peronosporales
1
P. Spencer-Phillips and M. Jeger (eds.), Advances in Downy Mildew Research, Vol. 2, 1-34.
© 2004 Kluwer Academic Publishers.
2 J.S.C. CLARK AND P.T.N. SPENCER-PHILLIPS
that cause white rust or white blister diseases (see Meekes et al. and
Gilijamse et al., this volume). In some respects, they also share much with
the biotrophic phase of hemi-biotrophic Phytophthora species such as
Phytophthora infestans (Hohl, 1991). Indeed it appears that the largest
downy mildew genus, Peronospora, is more closely related to
Phytophthora than it is to both the other downy mildew genera and the
Albuginaceae (Cooke et al., 2002; Voglmayr, 2003).
The fact that downy mildew fungi form intercellular hyphae and
intracellular haustoria has meant that inevitably they are compared with the
haustorial forming epiphytic and endophytic powdery mildew (ascomycete)
and the endophytic rust (basidiomycete) fungi. It should be remembered,
however, that downy mildews do not always form haustoria (Fraymouth,
1956), and their intercellular hyphae also provide an interface for nutrient
uptake and general inter-communication, as in other non-haustorial
biotrophs (Spencer-Phillips, 1997). Indeed Dick (2002a) has pointed out
that the development of haustoria may have evolved separately even within
the oomycetes, so that haustoria may have a different physiology and
function in each of the genera Albugo,Peronospora and Sclerospora.
Whilst it is tempting to assume that molecular mechanisms of
biotrophy will have evolved in parallel with morphological features (viz.
haustoria), there are many examples in the history of biology where this
approach has been misleading. In fungal systematics, similar morphological
features used previously for taxonomic and nomenclature purposes do not
fit with contemporary phylogenic concepts based on molecular data. In
relation to physiological function, the debate concerning the apoplastic
versus symplastic pathways for phloem loading provides another example
that is potentially relevant to strategies for nutrient acquisition by biotrophic
fungi (Spencer-Phillips, 1997). These alternative pathways were
championed by opposing research teams, with each group working with
their favoured model plant species. It was realised subsequently that
different plants might use different mechanisms, as exemplified by this
statement from Bourquin et al. (1990): “either one of these two concepts...
is not valid, or phloem loading occurs via the symplastic pathway in some
species and via the apoplastic pathway in other species”. The latter, with a
plethora of intermediates, is now accepted widely (Lalonde et al., 2003).
Thus it is important to retain an open mind about mechanisms of
compatibility in downy mildews, and to ensure that they are studied in
parallel with other oomycetes, as well as the rusts and powdery mildews.
An additional reason for a special focus on downy mildew diseases is that
they cause significant crop losses (Clark and Spencer-Phillips, 2000), and
account for approximately 17% of the world fungicide market (Gisi, 2002).
