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RHIZOCTONIA NEWSLETTER

Published by the Rhizoctonia Subject-Matter Committee (IRC)
of the International Society for Plant Pathology (ISPP)

Volume 1, Number 1, June, 1996

Editor: Martin M. Kulik, USDA-ARS, Room 101, Building 008, BARC-West,
Beltsville, MD 20705, U.S.A. e-mail: mkulik@asrr.arsusda.gov

A MESSAGE FROM THE EDITOR

This first issue of the Rhizoctonia Newsletter is being distributed
gratis by e-mail and air mail to approximately 400 colleagues, many of
whom had responded to the first announcement of ISR'95. The
distribution of subsequent issues may be limited to colleagues who
have either already asked to be put on the distribution list or who,
upon receipt of this first issue, will have notified the editor by e-mail
or air mail and indicated their desire to receive this publication.

I would like to thank Harry Adding of the IPO-DLO, Wageningen, for
providing me with the list of the names and addresses of the
respondents to the first announcement of ISR'95.

The Rhizoctonia Committee is able to publish and distribute the
Rhizoctonia Newsletter gratis because of a generous grant from the
Dutch National Organizing Committee for ISR'95 plus additional funding
from the International Society for Plant Pathology. We intend to
continue to provide this publication free-of-charge, as long as we have
the necessary funds. We will explore other sources of funding,
including soliciting agricultural chemical companies and similar
organizations. We welcome your suggestions and help in attaining
funding for the Rhizoctonia Newsletter.

One priority that has to be met in order for subsequent issues of
this newsletter to be published, is that I need to receive material from
its readers. Therefore, I am soliciting articles on subjects that would
be of value to our colleagues who are either working on or simply
interested in Rhizoctonia. These articles could include descriptions of
current research projects, results of research studies, news of
colleagues (transfers, awards, retirements, etc.), names and addresses
of graduate students and the titles of their thesis and dissertation
research projects, your thoughts on any subject related to Rhizoctonia,
etc. I hope to publish these contributions in the order that they are
received, but especially newsworthy items may be included in the next
newsletter to be published. Contributions may be reduced in length
by the editor.

MEMBERS OF THE ISPP SUBJECT-MATTER
COMMITTEE ON RHIZOCTONIA (IRC)

Baruch Sneh, Tel Aviv University, Ramat Aviv, Israel (Chairman)
Don Carling, University of Alaska, Fairbanks, Alaska, U.S.A.
Gerda Dijst, IPO-DLO, Wageningen, The Netherlands
Mitsuro Hyakumachi, Gifu University, Gifu, Japan
Suha Jibaji-Hare, McGill University, Quebec, Canada
Martin Kulik, USDA-ARS, Beltsville, MD, U.S.A.
Stephen Neate, CSIRO, Glen Osmond, SA, Australia

A LETTER FROM BARUCH SNEH, CHAIRMAN, IRC

I am pleased to write this letter for the first issue of the
Rhizoctonia Newsletter. I hope that this new publication will serve as
a catalyst for the fruitful exchange of information among colleagues
interested in or working on the various aspects of Rhizoctonia
research.

Although a considerable amount of research has been and is being
carried out worldwide on various aspects of Rhizoctonia, it seems that
this research has not generated any interest in workshops, scientific
meetings or other forums. Other genera such as Phytophthora,
Fusarium, Verticillium, and Trichoderma, have been appropriately
treated for many years. Researchers working on species in these
genera have had many opportunities to exchange their ideas and new
findings through the media of periodic workshops, symposia,
newsletters, etc. Unfortunately, for quite a long time, Rhizoctonia
researchers have not been able to benefit from these activities due to
a lack of organization, that is to say, the framework which is essential
for the efficient exchange of ideas and international collaboration did
not exist. Several colleagues with whom I had previously talked about
this situation were of the same opinion.

The ICPP held in Montreal in 1993 provided a good opportunity to
gather people who were determined to do something to correct the
situation. We had an informal meeting at which we elected seven
colleagues to serve on a proposed International Society for Plant
Pathology (ISPP) subject-matter committee on Rhizoctonia (IRC). After
several months, the IRC was officially accepted by the ISPP, which had
also sponsored our first symposium, ISR'95.

The aim of the IRC is to promote international collaboration among
colleagues working on the various aspects of Rhizoctonia research. To
achieve this goal, we need to have a strong subject matter working
group composed of serious and active members, hold periodic meetings
and workshops that are focused on various aspects of Rhizoctonia
research, distribute the Rhizoctonia Newsletter, and encourage
collaborative international research projects. We welcome suggestions,
initiatives, and the active participation of enthusiastic colleagues, from
which all Rhizoctonia researchers will benefit, and call upon our
colleagues to collaborate in creating sub-committees and act on
important issues such as Rhizoctonia taxonomy.
During the ICPP in Montreal, the newly formed IRC decided to
organize the Second International Symposium on Rhizoctonia (the first
one was held in 1965!) and to publish a comprehensive book on the
subject. This symposium, ISR-95, was held in Noordwijkerhout, The
Netherlands from 27-30 June, 1995, and was a great success. All of the
review papers presented by the invited speakers during this
symposium have been expanded to provide comprehensive reviews for
inclusion in the book. In addition, chapters on additional subjects
have been written by invited authors, in order to cover all aspects of
Rhizoctonia research. A total of 50 chapters have been included in a
book entitled: "Rhizoctonia species: Taxonomy, Molecular Biology,
Ecology, Pathology and Disease Control." This book has been edited by
Baruch Sneh, Suha Jabaji-Hare, Stephen Neate and Gerda Dijst. The
book summarizes years of research on the various aspects of the
ubiquitous complex of soil-borne fungi belonging to the anamorphic
genus Rhizoctonia. The reviews of the various subject areas covered
in this book include classical as well as modern molecular approaches
to Rhizoctonia research in taxonomy and evolution, genetics and
pathogenicity, plant-Rhizoctonia interactions, ecology, population and
disease dynamics, disease occurrence and management in various crops,
cultural control, biological control, germplasm for resistance, use of
molecular biological techniques in breeding strategies for resistance,
and chemical and integrated control. This publication will be an
important source book on Rhizoctonia, not only for plant pathologists,
but also for other researchers, students, extension specialists, crop
producers and companies interested in plant disease control. The
complete manuscript of the book has already been submitted to Kluwer
Academic Publishers, and should be published sometime around the fall
of 1996.

The IRC has been asked by the programme committee of the ICPP to
be held in 1998 in Edinburgh, to participate in the planning of the
programme for the topics dealing with Rhizoctonia, which will be
presented at the 1998 ICPP. We will plan to have a business meeting
during this congress in which we would like to discuss issues
regarding the continued activities of the IRC, including the exchange
of ideas among committee members, future workshops and symposia, etc.
We welcome the active participation of colleagues to promote the
international exchange of ideas and collaboration among Rhizoctonia
researchers. We hope that the Rhizoctonia Newsletter will be an
effective medium to spread this information among all of our colleagues.

Baruch Sneh, Department of Botany, Tel Aviv University, Ramat Aviv,
Israel 69978; e-mail: snehb@vm.tau.ac.il

REDUCING SOIL INOCULUM POTENTIAL TO PREVENT
DISEASES CAUSED BY RHIZOCTONIA SOLANI

Gerda Dijst, DLO-Research Institute for Plant Protection (IPO-DLO) P.O.
Box 9060, 6700 GW Wageningen, The Netherlands. Fax: +31 317 476082.
E-mail: DIJST@IPO.DLO.NL

The objectives of this research are to identify and understand the
factors that affect the inoculum potential of soils and determine the
severity of diseases caused by Rhizoctonia solani AGs. Ecological and
(soil) environmental factors are included as well as those related to the
cropping system. Attainment of these objectives will facilitate the
development of new approaches to risk assessment, disease prevention
and integrated control.

From 1990 through 1995, a research project was carried out with
the financial support of the "Urgency Program for Research on
Diseases and Breeding of Flower Bulbs." The objectives were to
characterize the major pathogens and some of the factors that may
determine the severity of Rhizoctonia-incited disease in tulip and iris.
This disease can be incited by several AGs of R. solani which differ in
their pathogenicity and in their temperature requirements to cause
(severe) disease. Investigations carried out under standardized
conditions revealed that for AG-2-t (at 12 C) and AG-4 (at 18 C), the
spread of the disease and its severity depended on the natural

suppressiveness of the soil. Soil samples from commercial fields
differed significantly in their degree of disease suppression. Microbial
activity appeared to mediate this general soil antagonism because
sterilization of the soil eliminated any natural suppression. Conversely,
amendment with straw increased the level of soil suppression. These
results may imply that measures like soil disinfestation could be risky.
We also found that under our experimental conditions, the severity of
disease appeared to be more affected by the food base of the inoculum
than by the inoculum density, especially at unfavorable temperatures.

For the period of 1996 through 1999, a new research project is
being supported by the Dutch Product Board for Ornamental
Horticulture (PVS). This new investigation is concerned with biocontrol
to reduce soil infestation caused by infested crop residues.
Furthermore, it aims to identify the role of different plant parts and
crop residues as: (1) a site for inoculum survival, (2) an opportunity
for inoculum spread through the soil, (3) a stimulatory food base for
inoculum potential, or (4) a stimulus for soil suppressiveness. Both
susceptible and non-susceptible plants used by growers in rotation
with tulip and iris, are included in this investigation of the factors
affecting the inoculum potential of soils.

NEWS FROM THE UNIVERSITY OF ADELAIDE

Several graduate students at the University of Adelaide, Australia,
who recently obtained their PhD degrees, had done their research on
Rhizoctonia:

Dr. Reza Balali
Address: Department of Biology, Faculty of Sciences, University of
Isfehan, Isfehan 81744, Iran
PhD Title: Genetic variation of Rhizoctonia solani AG-3 in South
Australia.
Major professors: Dr. Eileen Scott, Dr. Stephen Neate, Dr. Dara
Whisson


Dr. Abdol Taheri
Address: Department of Crop Protection, Faculty of Agriculture, P.O.
Box 538, Zabol, Iran
PhD Title: Interaction between the root lesion nematode, Pratylenchus
neglectus and root-rotting fungi of wheat.
Major professors: Dr. Gil Hollamby, Dr Vivien Vanstone, Dr. Stephen
Neate


Dr. Bronwyn Wiseman
Address: Agriculture Victoria, Institute for Horticultural Development,
P.B. No 15, S.E. Mail Centre, Victoria 3176, Australia
PhD Title: Characterisation of Rhizoctonia barepatch decline.
Major Professors: Dr. Sally Smith, Dr. S. Neate, Dr. Kathy Ophel-Keller

THREE IRC MEMBERS ATTEND MEETING IN BEIJING

IRC members Mitsuro Hyakumachi, Suha Jibaji-Hare, and Stephen
Neate, recently attended the International Workshop on Biological
Control of Plant Diseases held in Beijing, China from 22-27 May 1996.
There were 122 participants from 16 countries, of which approximately
half were Chinese. There was strong interest in the biological control
of diseases caused by Rhizoctonia, with more than 16 papers devoted to
that topic. The book containing the full papers can be obtained for a
small fee from Prof. Tang Wenhua, Department of Plant Pathology,
Beijing Agricultural University, Beijing 100094, PRC.

(Submitted by Stephen Neate, CSIRO, Glen Osmond, SA, Australia; e-mail
address: stephen.neate@adl.soils.csiro.au)

GRACIELA GODOY-LUTZ TO SPEND THE SUMMER AT THE
UNIVERSITY OF NEBRASKA

Graciela Godoy-Lutz of the Dominican Republic, is spending four
months in the laboratory of J. R. Steadman in the Department of Plant
Pathology, University of Nebraska, where she is conducting a follow-up
study of the variability of isolates of Thanatephorus cucumeris from
countries in Central America and the Caribbean area. This pathogen
causes a disease known as web blight that affects the aerial parts of
the common bean, leading to severe defoliation and reduction in seed
yield. An initial survey led to the collection of 122 isolates of this
fungus. These isolates were found to belong to AG 1-IA, AG 1-IB
(microsclerotial type), AG 1-IB (macrosclerotial type), and AG 2. They
caused similar symptoms of web blight on beans growing in 11
counties. This study was done in collaboration with Don Carling of the
University of Alaska. The emphasis during this summer will be the
extent of variation of within-field populations of the web blight
pathogen. She can be contacted at the following e-mail address:
ggodoy@unlinfo.unl.edu

POTENTIAL USE OF ACTINOMYCETES AND THEIR PRODUCTS
FOR CONTROL OF RHIZOCTONIA SOLANI

Martin M. Kulik, USDA-ARS, Room 101, Building 008, BARC-West,
Beltsville, MD 20705, U. S. A.

Actinomycetes or "ray fungi" are fungal-like eubacteria that are
widespread and common. They have long been known to be able to
produce antibacterial and antifungal compounds in culture, although it

has not yet been conclusively shown that these materials are actually
elaborated in nature.

Rhizoctonia solani can be controlled with fungicides or methyl
bromide but these materials are expensive and can harm the
environment. These considerations have led to renewed interest in the
use of microorganisms to control plant diseases. I undertook a study
to evaluate actinomycetes and their products for their potential use in
controlling R. solani.

One-hundred and fifteen isolates of various actinomycetes were
obtained from a sample of soil in which damping-off of alfalfa (lucerne;
Medicago sativa L.). attributed to R. solani had occurred. When
biomass of these isolates was evaluated in an agar test, 48 of them
significantly reduced the lateral growth of an AG 4 isolate of this
fungus. When cell-free culture filtrates of these 48 isolates were
evaluated in the same manner, only 11 of them significantly inhibited
the growth of R. solani.

These results should encourage researchers to evaluate
actinomycetes and their products for controlling isolates of R. solani
that incite damping-off. Filtrates from cultures of suppressive
actinomycetes could be applied to seeds by pelleting them or using the
new thin-film technology. In addition, culture filtrates could be
absorbed on materials such as clay and placed in the seed furrow. To
be effective, the suppressive material would have to remain in place
and active during the period when the seed is susceptible to R. solani.
(From a manuscript accepted for publication in the Journal of Plant
Diseases and Protection)