RESEARCH REPORTS TGC REPORT 52, 2002
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Evaluation of tomato breeding material for resistance against late blight
pathogen
1Bagirova, S.F., 2Ignatova, S.I., 2Tereshonkova, T.A., and 2Gorshkova, N.S.
1Department of Mycology and Algology, Moscow State University, Moscow
119899, Russia, e-mail: slana@sbagirova.home.bio.msu.ru
2All-Russian Research Institute for Vegetable Crops, Mitishi-18, Moscow Region
141018, Russia, e-mail: tter@msk.net.ru
Key words: disease resistance, evaluation, late blight, Phytophthora infestans,
plant breeding, population structure, tomato
Abstract
In three late blight epidemic years (1998-2000) selected tomato breeding material
were evaluated under natural conditions of a severe epiphytotic in greenhouses
in the Moscow Region. More than 1500 tomato lines or hybrids were screened for
resistance against a new more aggressive population of the tomato late blight
pathogen. Eighteen lines were created using different wild tomato species as
resistant sources and these were found to show the greatest resistance to the
late blight. Simultaneously, Phytophthora strains were collected from diseased
plants and studied. High polymorphism of the new sexual population of the late
blight pathogen that was similar to polymorphism of the Mexican populations was
revealed. Our data concerning population diversity suggests that the monitoring
of P. infestans in the Moscow Region is a good model for study of different
aspects of population biology of P. infestans (the spread of new pathotypes, role
of oospores in disease development, interrelationships between the tomato and
potato populations) and for reevaluation of plant breeding material.
Introduction
The most severe plant disease in Russia is late blight. Tomato crop losses in
epidemic years in the Moscow Region can be greater than 80%. Russian
populations of Phytophthora infestans, the causal agent of the late blight, are
characterized by high polymorphism and variability. During the last 15 years there
has been a change of population structure and increase of population size of
strains adopted to parasitize tomatoes (Dyakov Y.T., Rybakova I.N., Dolgova
A.V., Bagirova S.F., 1994). Marked differences between the populations attacking
tomatoes and potatoes were found (Bagirova S.F., An Dzan Li, Dyakov Y.T.,
1998). Until now only one clone has predominated. Tomato late blight has not
been considered such a big problem in the Moscow Region. Variability of new
populations is expressed in differences between strains in the mating types,
virulence, resistance to fungicides, isozymes, mitochondrial and nuclear DNA
(Vorobeva Y.V., Gridnev V.V., Bashaeva E.G., 1991, Gorbunova E. V., Bagirova
S.F., Dolgova A.V., Dyakov Y.T., 1989; Maleeva Yu.V., Naumoff S.P., Yatsentiuk
S.P., Dolgova A.V., Kolesnikov A.A., 1999). With the spread of new strains, the
disease epidemics appeared earlier and developed rapidly. Abundant oospores
are formed in foliage, stem and fruit tissue and are able to overcome cold
Moscow winters (Bagirova S.F., Dyakov Y.T, 1998). The tomato cultivars that
were previously characterized by moderate resistance are now very susceptible
(Ignatova S.I., Gorshkova N.S., Bagirova S.F., 1999). Registered changes of
population composition are similar to replacement of ”old” genotypes by “new”
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