ITEMS FROM ESTONIA
INSTITUTE OF EXPERIMENTAL BIOLOGY
EE 3051 Harku, Estonia.
K. Jarve, H. Peusha, M. Tohver, S. Tamm, L. Timofejeva, E. Tsimbalova, O. Priilinn, and T. Enno.
To improve disease resistance and increase the number
of alien genes available for wheat breeding, the tetraploid wheat
species T. timopheevii, T. militinae, and the F1
hybrid (T. militinae/T. timopheevii) were used in
crosses with common wheat cultivars. Plants of the pentaploid,
interspecific F1 hybrids were backcrossed to their common wheat
parents for three generations to restore fertility. Backcross
and advanced generations were screened for powdery mildew, E.
graminis f. sp. tritici, resistance in the artificial
provocative background. A number of derived lines with a resistant
reaction to powdery mildew were identified and stabilized (Enno
et al. 1995).
A genetic monosomic analysis of the introgressed
line SMT 34, selected in the progeny of crosses between common
wheat cultivar Saratovskaya 29 with the `T. militinae/T.
timopheevii' F1, was used to locate the powdery mildew-resistance
gene. On the basis of monosomic segregation, the lack of susceptible
seedlings in the progeny of cross combination between Chinese
Spring monosomic 4A and SMT 34 was highly significant (P <
0.01). The resistance gene located on chromosome 4A shows a dominant
inheritance.
The dominant, powdery mildew-resistance gene Pml6
is reported to be located on chromosome 4A. This gene was introduced
into hexaploid wheat from the wild emmer, T. dicoccoides
(Reader and Miller 1991, Euphytica 53:57-60). Currently,
the F1 hybrids between SMT 34 and the common wheat line with the
Pml6 gene are growing, and further allelism tests on the
progenies will be made.
Powdery mildew is a widespread disease of common
wheat in Europe and in other regions where wheat is grown under
cool temperate conditions. The use of resistance genes is the
most effective way to combat the spread of this disease. The Italian
common wheat cultivar `Virest' has mildew resistance
that is different from the resistance reaction expressed by currently
documented mildew resistance genes, which are detected by response
to 11 differential wheat powdery mildew isolates. F2 populations
from crosses between the Chinese Spring monosomic lines and Virest
revealed one major, dominant gene located on wheat chromosome
lD. The new gene is designated as Pm22 (Peusha et al. in
press).
The study was made to characterize and identify the
mildew resistance-genes in common wheat cultivars grown in Finland.
Among the cultivars tested, seven showed susceptible response
(Aura, HJA22/92, NGB212, NGB231, NGB341, Pitko, and Vakka) and
eight cultivars (Apu, Hjan Ilves, Ilves, Luja, NGB347, Otso, Ruso,
and Taava) had a susceptible and/or intermediate reaction or were
heterogeneic, after inoculation with the 11 differential powdery
mildew isolates. Seven cultivars (Tapio, Hjan Tapio, Manu, Runar,
NGB43, Heta, and Hjan Ulla) were resistant to one or more isolates
(Peusha et al. in press). This work with Italian and Finnish wheat
cultivars is supported by Deutsche Forschungsgemeinschaft, Bonn,
Germany.
An introgressed line, resistant to leaf rust and
powdery mildew and a derivative of `T. timopheevii
(146-155)/T. timopheevii', and its parents
were analyzed in order to isolate markers of T. timopheevii-genome
origin in the resistant introgressed lines. Genomic probing, with
blocking of the common sequences, discriminated between T.
aestivum (line 146-155) and T. timopheevii genome-specific
repetitive DNA sequences. The repetitive genome-specific
markers were used further to isolate 100-1,000 kb PFGE-separated
fragments of T. timopheevii origin in this hybrid line.
Two repetitive DNA sequences, specific to T. timopheevii
DNA, were cloned from the genome of the hybrid line `146-155/T.
timopheevii'. We are looking for markers physically
linked to the resistance genes using large restriction fragments
of T. timopheevii origin from the hybrid DNA (separated
by PAGE).
The synthesis of the wheat storage protein gliadin
is known to be controlled by genes located on the chromosomes
of homoeologous groups 1 and 6. We suggest that these may be suitable
for identifying the location of disease resistance genes closely
linked with genes controlling gliadin synthesis. Previous work
based on C-banded chromosome analysis (Priilinn et al. 1994)
concluded that resistance to the pathogen is conditioned by the
presence of chromosome 6G(or a segment) of T. timopheevii
in the 146-155 genome. The analysis of the gliadin fractions
of 146-155, T. timopheevii, and `146-155/T.
timopheevii' confirmed that the translocation on the
lB chromosome does not include the Gli-B1 locus. Protein
fractions, coded by the Gli-B2 locus on the short
arm of chromosome 6B, revealed a substitution by T. timopheevii-gliadin
alleles in the hybrid line.
Publications.
Enno T, Peusha H, Jarve K, Timofejeva L, Tsimbalova
E, and Priilinn O. 1995. Introduction of alien genetic variation
by means of interspecific hybridization. Proc 9th EWAC Conf Cereal
aneuploids for genetical analysis and molecular techniques. Euphytica
65-67.
Peusha H, Hsam SLK, and Zeller FJ. 1996. Chromosomal
location of powdery mildew resistance genes in common wheat (Triticum
aestivum L. em. Thell.) 3. Gene Pm22 in cultivar
Virest. Euphytica (In press).
Peusha H, Hsam SLK, Enno T, and Zeller FJ. 1996.
Identification of powdery mildew resistance genes in common wheat
(Triticum aestivum L. em. Thell.). VIII. Cultivars grown
in Finland. Hereditas (In press).
Priilinn O, Enno T, Kuuts H, and Peusha H. 1996.
Genetic resources for the adaptive breeding of wheat. J Agr Sci
Estonia (In press).
Priilinn O, Peusha H, Jarve K, Timofeyeva L, Tsimbalova
E, and Enno T. 1994. Use of alien genetic variation for wheat
improvement. Ann Wheat Newslet 40:101-102.