Septoria and Stagonospora Diseases of Cereals - CIMMYT ...

disease severity in the biparental
population. Adult and juvenile
plant incubation period and lesion
expansion rate measured in the
detached leaf test were highly
correlated with field disease
severity measured at Kinston in
1998 in the breeding population.
Similar results were obtained
for disease measured at Laurel
Springs in 1997. Components of
resistance were not highly
correlated with field disease
measured at Laurel Springs in 1998.
Comparison of Methods of Screening for Stagonospora nodorum Resistance in Winter Wheat 165
Resistant genotypes
A comparison of genotype
rankings measured in the field with
those measured in controlled
environments indicate that for the
biparental population at Kinston in
1998, five of the ten most resistant
genotypes in the field were also
identified by the measurements of
the incubation period and % LAD
on the flag leaf in the adult plant
tests. Similarly, rankings based on
% LAD measured in the adult plant
spray test ranked five of the same
ten most resistant genotypes
identified by the field disease
severity values at Laurel Springs in
1998. The numbers were slightly
lower for the breeding population.
At Kinston in 1998, four of the ten
most resistant genotypes in the
field were also identified as
resistant by measurements of %
LAD for adult plant spray
inoculation. Combining adult plant
greenhouse tests and juvenile
detached leaf tests could increase
this number to seven or eight of the
top ten resistant genotypes
identified in controlled
Table 2. Components of resistance to Stagonospora nodorum measured on F 3:5 lines of NKC 8433 x Caldwell cross in controlled environments.
Dlt a Juvenile Dlt Adult Phytotron(Juvenile) Greenhouse
Isolate Incubation # of Incubation Lesion Incubation # of Droplet Spray
treatments b (days) lesions (days) expansion ( days) lesions incubation %LAD
A (most) 7.9 a 2.4 b 12.7 c 0.14 b 12.9 a 2.4 bc 3.8 a 5.5 ab
D (least) 8.1 b 2.3 b 10.4 b 0.13 a 13.1 a 1.7 a 4.3 a 3.9 a
AD (both) 7.6 a 2.7 c 9.4 a 0.20 c 12.9 a 1.8 b 5.4 b 4.8 a
NI(control) 20.0 c 0.0 a - - 17.1 b 1.2 a 20.0 c -
a Detached leaf test.
‘b ‘Most’ and ‘least’ aggressive refer to isolate reaction measured in the isolate screening assay done on seedlings in controlled conditions.
Table 3. Components of resistance to Stagonospora nodorum measured on random F 3 , F 4 , F 5 and F 6 lines from a southern US winter wheat nursery
in controlled environments.
Dlt a Juvenile Dlt Adult Phytotron(Juvenile) Greenhouse
Isolate Incubation # of Incubation Lesion Incubation # of Droplet Spray
treatments b (days) lesions (days) expansion ( days) lesions incubation %LAD
A (most) 8.4 a 2.5 b 12.7 b 0.11 a 13.5 a 2.1 c 5.1 b 3.7 a
D (least) 9.0 b 2.4 b 10.8 a 0.12 b 12.8 a 1.6 b 3.4 a 2.8 a
AD (both) 8.3 a 2.4 b 11.0 a 0.19 c 13.7 a 2.2 c 4.9 b 4.1 ab
NI (control) 20.0 c 0.0 a - - 17.5 b 0.9 a 20.0 c -
a Detached leaf test.
b ‘ Most’ and ‘least’ aggressive refer to isolate reaction measured in the isolate screening assay done on seedlings in controlled conditions.
Table 4. Correlations among resistance components measured in controlled environments and in field tests.
Treatment A (most) a Treatment AD(most/least) Treatment D(least)
Resistance component Biparental Breeding Biparental Breeding Biparental Breeding
Adult dlt – incubation 0.23 * 0.30 * NS NS NS 0.25 *
Adult dlt- lesion expansion NS -0.34 ** NS NS 0.2 0* 0.20 *
Juvenile dlt – incubation NS -0.40 ** NS NS NS NS
Juvenile dlt – lesion size NS NS 0.20 * 0.20* 0.27 * NS
Adult spray test - %LAD NS NS 0.23 * NS 0.33** 0.14
a ‘Most’ and ‘least’ aggressive refer to isolate reaction measured in the isolate screening assay done on seedlings in controlled conditions.