Agriculture Reference
In-Depth Information
be affected by leaf rust in winter wheat compared
with spring wheat.
Leaf rust infection generally reduces the protein
content in harvested grain (Caldwell et al., 1934;
Peturson et al., 1945, 1948; Dyck and Lukow
1988), although in some tests protein content was
unaffected or increased. In spring wheat heavy
leaf rust infection generally resulted in fl our with
increased loaf volume (Peturson et al., 1945) and
farinograph absorption (Dyck and Lukow 1988).
Color of harvested grain and fl our was also affected
by leaf rust. In spring wheat yellow pigmentation
of the fl our was increased (Peturson et al., 1945);
in winter wheat, increased yellow pigmentation
of the grain was noted (Caldwell et al., 1934).
Everts et al. (2001) determined that leaf rust
affected the softness equivalent parameter and
may reduce fl our yield of soft red winter wheat.
Reduced fl our yield due to leaf rust was also
determined in some tests with spring wheat
(Peturson et al., 1945).
D' Oliveira and Samborski (1966) conducted
infection experiments of telial grass hosts with
aeciospores derived from naturally infected plants
of
Thalictrum speciosissimum
and
Anchusa
spp. and
other genera in the Boraginacea in Portugal. They
showed that the leaf rusts that differed for infec-
tion on
Thalictrum
speciosissimum
, and hosts in the
Boraginacea, also differed for telial hosts. Anikster
et al. (1997) showed that the leaf rust from
common wheat (
T. aestivum
ssp.
aestivum
), wild
emmer wheat (
T. turgidum
ssp.
dicoccoides
), and
durum wheat belonged to a distinct group with
the alternate host
Thalictrum speciosissimum
. A
second distinct group of leaf rusts with alternate
hosts in the Boraginacea and telial hosts of wild
wheats and rye was also described. The two
groups could not be successfully crossed using
either
Thalictrum speciosissimum
or alternate hosts
in the Boraginacea. Based on these results, it was
apparent that the leaf rust on wheat is a distinct
species from the other leaf rusts on wild wheats
and rye.
Puccinia triticina
Eriks. has since been
used by most workers to describe leaf rust on
wheat.
Puccinia triticina
is a macrocyclic rust (Webster
1980) with fi ve distinct spore stages on two taxo-
nomically distinct hosts. The teliospores on wheat
leaf tissue germinate to produce haploid basidio-
spores that are clear and hyaline. The basidio-
spores infect the alternate host, producing haploid
pycnia that appear as circular yellow pustules
on the upper leaf surface. The pycnia produce
haploid pycniospores, which are carried by insects
or rain to other pycnia. Fertilization in the pycnial
structures occurs with the transfer of nuclei from
pycniospores to fl exuous hyphae in compatible
combinations of opposite mating types. After fer-
tilization dikaryotic aecia develop on the under-
side of the leaf beneath the pycnial infections.
Aecial cups are produced in the aecia, from which
dikaryotic aeciospores are released and wind-
disseminated to infect wheat or other telial hosts.
Infections from aeciospores result in production
of urediniospores. Sexual reproduction in
P. tri-
ticina
has been observed in Portugal (d' Oliveira
and Samborski 1966), where one of the alternate
hosts,
Thalictrum speciosissimum
is commonly
found. However, throughout most of the world
Taxonomy, life cycle, and host range
Leaf rust on wheat was originally placed in the
highly complex species of
P. rubigo-vera
by Winter
(1884). Leaf rusts with telial hosts on grasses and
alternate hosts in the Boraginacea were placed
into this single species. Eriksson (1899) described
the leaf rust on wheat as a single species,
P. tri-
ticina
. Jackson and Mains (1921) determined that
the most compatible alternate host for leaf rust on
wheat was
Thalictrum fl avuum
(=
Thalictrum spe-
ciosissimum
), which is in the Ranunculaceae.
Mains (1932) preferred to group leaf rust of wheat
within the complex group of
P. rubigo-vera
. Based
on nondiscrete spore morphology and host range,
Cummins and Caldwell (1956) also chose to place
leaf rust of wheat within a complex species,
P.
recondita
, with alternate hosts in Boraginacea and
also Ranunculacea. In North America most rust
workers referred to leaf rust on wheat as
P. recon-
dita
f. sp.
tritici
, while in Europe leaf rust on
wheat was placed in the more narrowly defi ned
species of
P. triticina
Eriks. (Savile 1984) based
on small and consistent differences in spore
morphology.
