Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

Isolate variances
Isolate variances
4.6
4.0
3.4
2.8
2.2
1.6
3.2 3.6 4.0 4.4 4.8 5.2 5.6
Mean cultivars reactions on leaves (0-9 scale)
Figure 5. Relationship between the mean reactions of 11 winter triticale (t) and 4 winter wheat
(w) cultivars and variances of SNB induction on leaves of the cultivars by 15 Stagonospora
nodorum isolates and their mixture (3 years’ data).
5.5
5.0
4.5
4.0
3.5
3.0
2.5
2.0
1.5
r = 0.044, n.s.
Lasko (t)
Bolero (t)
Presto (t)
Largo (t)
Bolero (t)
Ugo (t)
Almo (t)
Presto (t)
Liwilla (w)
Alba (w)
Lasko (t)
Malno (t)
DAD-187 (t)
Malno (t)
Almo (t)
Largo (t)
Grado (t)
Ugo (t)
DAD-187 (t)
Dagro (t)
LAD-285 (t)
Alba (w)
Liwilla (t)
LAD-285 (t)
Dagro (t)
Jawa (w)
Grado (t)
Begra (w)
Begra (w)
Jawa (w)
Isolate variance = 0.285 + 11.022
(mean cultivar reaction)
r = 0.624, p < 0.03
1.0
0.8 1.4 2.0 2.6 3.2 3.8
Mean cultivars reaction on heads (0-9 scale)
Figure 6. Relationship between the mean reactions of 11 winter triticale (t) and 4 winter wheat
(w) cultivars and variances of SNB induction on heads of the cultivars by 15 Stagonospora
nodorum isolates and their mixture (3 years’ data).
Cultivar variances
7.0
6.5
6.0
5.5
r = 0.577, n.s.
Sigma (w)
5.0
Henika (w)
4.5
4.0
Gabo (t)
Eta (w)
3.5
Jago (t) Maja (t)
3.0 Grego (t)
Migo (t)
2.5
2.0 2.4 2.8 3.2 3.6 4.0 4.4 4.8
Mean cultivar reaction on leaves (0-9 scale)
Figure 7. Relationship between mean reactions of 5 spring triticale (t) and 3 spring wheat (w)
cultivars and variances of SNB induction on leaves of the cultivars by 15 Stagonospora nodorum
isolates and their mixture (3 years’ data).
Host – Parasite Interactions: Stagonospora nodorum 69
showed two distinct resistance
groups (Figures 7 and 8).
Correlations between mean host
reactions on leaves and heads and
the variances in SNB induction
among isolates were significant
only for heads (Figures 5 and 7) and
not for leaves (Figures 6 and 8). It
was found that a highly susceptible
genotype is not necessarily efficient
in differentiating virulence among
isolates (Figures 5, 4, 7, 8).
Conclusions
The results produced in the
study do not seem to support that
using a mixture of S. nodorum
isolates is the most efficient way to
differentiate cereal breeding
materials on their SNB resistance.
The finding for S. nodorum is in
accordance with results obtained by
Zelikovitch and Eyal (1991) that
inoculation of wheat seedlings and
adult plants with a mixture of S.
tritici isolates resulted in significant
suppression of symptoms (necrosis
and pycnidial coverage) compared
to the most virulent single isolate in
the mixture.
1. Screening for SNB resistance
with a few virulent isolates that
also show good differential
capacity seems most appropriate.
Screening breeding materials
with a single highly virulent
isolate may provide reliable
information on their SNB
resistance.
2. Sets of selected isolates and
cultivars differentiated each
other sufficiently well, but
according to cluster analyses
similar results could have been
obtained with a lower number of
both isolates and germplasm
lines.