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Journal of Plant Physiology and Breeding
2023, 13(2): 113-130
ISSN: 2008-5168
Research paper
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)
in the winter wheat genotypes
Armin Vahed Rezaei1, Ali Asghari1*, Majid Norouzi2, Saied Aharizad2,
Ramin Roohparvar3,4, and Ashkboos Amini3
Received: May 7, 2022 Accepted: November 29, 2022
1Department of Agronomy and Plant Breeding, University of Mohaghegh Ardabili, Ardabil, Iran
2Department of Plant Breeding and Biotechnology, University of Tabriz, Tabriz, Iran
3Department of Cereal Research, Seed and Plant Improvement Institute, Agricultural Research, Education and
Extension Organization (AREEO), Karaj, Iran
4Crop and Horticultural Science Research Department, East Azarbaijan Agricultural and Natural Resources
Research and Education Center, Agricultural Research, Education and Extension Organization (AREEO),
Tabriz, Iran
*Correspondence author; Email: a_asghari@uma.ac.ir
Abstract
Stem rust or black rust is one of the most important fungal diseases that widely affect wheat yield and quality
in the world. Therefore, the selection of genetic materials resistant to stem rust in the breeding programs is
necessary. In this study, 24 winter wheat genotypes including eight varieties and 16 elite lines were evaluated
at the adult plant and seedling stages using a randomized complete block design under the influence of local
stem rust race TKTTF. Disease indices including the type of infection, the severity of infection, the coefficient
of infection, the area under the disease progress curve (AUDPC), the relative area under the disease progress
curve (rAUDPC), and genotype reaction were recorded. Significant differences were observed among the
genotypes for all disease indices. Based on all indices, MV-17 and C-98-17 were resistant and C-98-14, C-98-
9, Bolany, and Morocco were susceptible. Pearson’s correlation coefficients revealed a significant positive
correlation between field type of infection, the severity of infection, the coefficient of infection, AUDPC, and
rAUDPC at the field, and between greenhouse type of infection and genotype reaction at the greenhouse. Based
on cluster analysis by Ward’s method, all the genotypes were classified into four groups (R, MR, MS, and S)
in the adult plant stage and into two groups (R and S) at the seedling stage. The resistant genotypes can be
used in the breeding programs for improvement of the stem-rust-resistant genotypes.
Keywords: cluster analysis, diversity, resistance, rust, wheat
How to cite: Vahed Rezaei A, Asghari A, Norouzi M, Aharizad S, Roohparvar R, Amini A. 2023. Biometrical
analysis of resistance to stem rust (Puccinia graminis f. sp. tritici) in the winter wheat genotypes. J Plant
Physiol Breed. 13(2): 113-130.
Introduction
Rusts are the most important pathogens of the
wheat crop (Knott 2012). The main rusts are
stem rust (Puccinia graminis f. sp. tritici)(Pgt),
yellow/stripe rust (Puccinia striiformis f. sp.
tritici), and leaf/brown rust (Puccinia triticina)
(Poland and Rutkoski 2016), however, stem
rust is more dangerous to wheat than the other
two rusts (Park 2016). Stem rust is seen mainly
in warm and moist conditions. Its typical
symptoms are red-brick urediniospores on the
114 Vahed Rezaei et al. 2023, 13(2): 113-130
leaf sheaths, glumes, awns, and stems (Kolmer
2005). This pathogen reduces the
photosynthetic area, disrupts water and
nutrient transport, and causes lodging, kernel
shriveling, and yield loss in wheat plants
(Knott 2012). This pathogen has several
physiologic races (Roelfs 1985) such as
TTKSK, TKTTF, TRTTF, JRCQC, TTTTF
(Newcomb et al. 2016), and Ug99 (a virulent
race detected in Uganda and Kenya (Wanyera
et al. 2006). Since then, seven other races have
been reported: PTKST, TTKSF, TTKSP,
TTKST, TTTSK, TTKSF+, and PTKSK
(Pretorius et al. 2012).
Rusts have been controlled efficiently by
the use of genetic resistance (Olivera et al.
2015). However, the R-gene-type resistance
has not been stable (Johnson 1983) because of
the development of new races mainly due to
sexual and para-sexual recombination (Burdon
1993), migration of the virulent variants into
new areas (Singh et al. 2011), and climatic
changes (Semenov and Halford 2009). Minor-
genes-controlled partial resistance is viewed as
durable compared to the resistance governed
by the R-genes. However, both resistance
types are complementary to each other in
developing durable resistance (Hundie et al.
2018). Breeding for genetic resistance is
considered the most economical and
environmentally friendly method to combat
the rust pathogen (Zhang et al. 2017). Many
attempts have been made to achieve rust
resistance in wheat and other cereals since
genetic resistance can provide effective and
chemical-free disease control (Mapuranga et
al. 2022). Achieving this goal is possible only
by having sufficient knowledge about the
genetics of pathogen populations and
identifying effective resistance genes in wheat
genotypes (Roelfs et al. 1992).
Stem rust resistance can be found in the
seedling and adult plant stages of wheat (Ellis
et al. 2014). The number of stem-rust-
resistance Sr genes has been cataloged and
lines with unique Sr genes are available in
several wheat backgrounds (Rouse et al.
2011). The results of recent research about the
identification of new resistance sources in
response to new races have shown that only
Sr2, Sr13, Sr14, Sr22, Sr26, Sr28, Sr33, Sr35,
Sr42, and Sr45 genes had effective resistance
to stem rust races. Also, 12 new genes (Sr46 to
Sr57) and several other genes have been
identified as new sources of resistance (Jin et
al. 2007; Hiebert et al. 2010; Singh et al.
2011; Ghazvini et al. 2012). Hiebert et al.
(2016) indicated that the resistance in adapted
germplasm is governed by relatively few
resistance genes such as Sr2, Sr25, Sr26,
SrCad, SrTmp, and Sr1A.1R. Also, Ug99
variants of the stem rust races such as PTKST,
TTKSF, TTKSK, TTKSP, TTKST, and
TTTSK with virulence to Sr21, Sr24, and Sr36
genes indicate that the race Ug99 is evolving
on wheat (Jin et al. 2008; Jin et al. 2009).
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)… 115
This study aimed to evaluate the resistance
of the 24 winter wheat genotypes to the stem
rust pathogen in the field (adult plants) and
greenhouse (seedlings) conditions and identify
possible stem-rust-resistant genotypes in the
East Azarbaijan Province, Iran.
Materials and Methods
Plant material
The seeds of the studied genotypes were
provided by the Department of Cereal
Research, Seed and Plant Improvement
Institute, Karaj, Iran. The genotypes included
eight cultivars from the Iran and Hungary
winter wheat collection and 16 elite lines. The
characteristics, origin, released year, and
pedigree of the genotypes are presented in
Table 1. Two cultivars, MV-17 and Morocco,
were selected based on their distinctiveness in
responses to stem rust. MV-17 was resistant
(Dadrezaei et al. 2015) and Morocco was
susceptible to stem rust (Denbel et al. 2013;
Salcedo et al. 2017).
Pathogen, collection, and reproduction
An isolate of Pgt, identified as the race
TKTTF, was used for evaluating the winter
wheat genotypes. The isolate of TKTTF was
collocated according to Woldeab et al. (2017).
The infected stems and leaves were cut and
labeled from wheat fields of Tabriz (37º 56′
59.57′′ N, 46º 03′ 49.10′′ E), East Azarbaijan,
Iran, in 2020 (Figure 1). The collected
urediniospores after recovery in the
Department of Cereal Pathology Lab, Seed and
Plant Improvement Institute, were suspended
Figure 1. Pathogen collection area and adult plant evaluation site.
116 Vahed Rezaei et al. 2023, 13(2): 113-130
Table 1. Characteristics and pedigree of 24 wheat genotypes that was used in this study.
No.
Name
Cultivar
Origin
Release
year
Pedigree
1
C-98-1
Mihan
Iran
2010
Bkt/90-Zhong 87
2
C-98-2
Haydari
Iran
2015
Ghk"s"/Bow"s"//90Zhong87/3/Shiroodi
3
C-98-3
Zarrineh
Iran
2017
Omid/4/Bb/Kal//Ald/3/Y50E/Kal*3//Emu"s"/5/Zrn/6/Zrn/Shiroodi
4
C-98-4
Zareh
Iran
2010
130L1,11//F35,70/Mo73/4/Ymh/Tob//Mcd/3/Lira
5
C-98-5
-
-
-
Alvd/4/Ghk"s"/Bow"s"//90Zhong87/3/Shiroodi
6
C-98-6
-
-
-
Alvd/4/Ghk"s"/Bow"s"//90Zhong87/3/Shiroodi
7
C-98-7
-
-
-
Charger//CMH80A.768/3*Cno79/3/Zrn
8
C-98-8
-
-
-
Charger//CMH80A.768/3*Cno79/3/Zrn
9
C-98-9
-
-
-
Spb"s"//K1349/Go/3/Vee"s"/4/Bkt/90-Zhong 87
10
C-98-10
-
-
-
Shahpasand/Norman
11
C-98-11
-
-
-
Alvd/4/Ghk"s"/Bow"s"//90Zhong87/3/Shiroodi
12
C-98-12
-
-
-
Alvd/4/Ghk"s"/Bow"s"//90Zhong87/3/Shiroodi
13
C-98-13
-
-
-
Alvd/4/Ghk"s"/Bow"s"//90Zhong87/3/Shiroodi
14
C-98-14
-
-
-
Spb"s"//K1349/Go/3/Vee"s"/4/Pishgam
15
C-98-15
-
-
-
AU/3/MINN//HK/38MA/4/YMH/ERA/5/PMF//CNO/GLL/6/KAUZ//ALTAR
84/AOS/7/TAM105/3/NE70654/BBY//BOW"S"/4/Century*3/TA2450
16
C-98-16
-
-
-
GRK79/TUKURU
17
C-98-17
-
-
-
MV NEMERE
18
C-98-18
-
-
-
ARS97135-9/O3A-B4//KS06O3A~49
19
CD-94-9
-
-
-
Zarrin/Shiroodi/6/Zarrin/5/Omid/4/Bb/Kal//Ald/3/Y50E/Kal*3//Emu
20
CD-94-5
-
-
-
Ga961565-27-6/La95283Ca-78-1-2
21
MV-17
MV-17
Hungar
y
1993
SLAVIA/MV-FT//BARANJK
22
CD-92-6
Heyran
Iran
2019
Lufer-1/Kinaci97
23
Morocco
Morocco
-
-
Susceptible check
24
Bolany
Bolany
-
-
Susceptible check
in lightweight mineral oil (Soltrol 170) and
inoculated onto the fully expanded primary
leaves of the seedling of McNair wheat
cultivars. The inoculated seedlings were
incubated in a dew chamber for 16 hours in the
dark, and four hours under light. The
inoculated seedlings were placed in a growth
chamber at 7-12 ºC for three days and in the
greenhouse at 18-25 ºC for two weeks. After
infection of the seedlings, the race was
multiplied and stored in the refrigerator at -80
ºC to use for screening of the genotypes at
seedling and adult plant stages.
Adult plant evaluation
Twenty-four winter wheat genotypes were
screened and evaluated for their level of
infection to the stem rust pathogen in the field.
The experiment was arranged as a randomized
complete block design with three replications
in the research field (37º 58′ 40.56′′ N, 46º 02′
39.42′′ E; 1385m above sea level) of the East
Azarbaijan Research Center for Agriculture
and Natural Resources, East Azarbaijan, Iran,
during 2019-2020 cropping season. Each
experimental plot was 7.5 m2 (5 m long and 1.5
m wide), with six rows, spaced 20 cm apart.
The space between plots and blocks was 0.5
and 1.5 m, respectively. The information about
the climate and temperature of the
experimental site are presented in Figures 2
and 3. In general, the experimental site is
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)… 117
Figure 2. Monthly weather graph of the experimental site.
Figure 3. Average temperature of the experimental site.
characterized by local steppe climate,
corresponding to BSk in the Köppen and
Geiger classification, with two distinct
seasons: a hot season from March to
September and a cold season from November
to February. The mean annual temperature is
11.5 ºC. The warmest month of the year is July
with an average temperature of 24.2 ºC and
January has the lowest average temperature of
-1.3 ºC. The annual rainfall is 329 mm
(Schwarz 2020). The physicochemical
properties of the soil of the experiment are
presented in Table 2. The site represents a
proper condition for the stem-rust disease
development. To inoculate the genotypes, all
plots were inoculated with the Pgt race TKTTF
118 Vahed Rezaei et al. 2023, 13(2): 113-130
between the late booting and early heading
stages. Plot surfaces were first sprayed with the
deionized water and lightweight mineral oil
(Soltrol 170) by 1 drop per liter after sunset,
and then the stored spores at -80 ºC were mixed
with talc powder (5:1 ratio) and sprayed onto
the plants by a spore gun. The disease was
scored on 10 plants from each plot. Disease
scoring started a week after the spraying and
continued three times at 5-day intervals
(Roelfs et al. 1992) (Figure 4, Table 3). Also,
the stem rust infection severity was estimated
based on Peterson et al. (1948) shown in
Figure 5. The coefficient of infection was
calculated by multiplying the disease severity
by the field infection scores (Table 3). In the
adult plant stage, area under the disease
progress curve (AUDPC) and relative area
under the disease progress curve (rAUDPC)
were calculated by using the following formula
(Wilcoxson et al. 1975), where xi = injury
intensity in the ith observation, and t = time at
the ith observation:
Table 2. Physico-chemical properties of the soil in the experiment.
Index
Unit
Value
Index
Unit
Value
Sand (> 0.02 mm)
%
60
pH
-
7.7
Silt (0.02-0.002 mm)
%
20
Total nitrogen
%
0.079
Clay (<0.002 mm)
%
20
Available
phosphorous
mg.kg-1
19
Depth
cm
0-30
Available
potassium
mg.kg-1
310
TNV+
%
11
Fe
mg.kg-1
8.6
Soil texture
-
Loamy sand
Zn
mg.kg-1
0.86
Organic matter
g kg-1
0.86
Cu
mg.kg-1
1.1
+Total neutralizing value
Table 3. Description of the stem rust infection types and symptoms at the adult plant stage of wheat.
Infection types
Symptoms
Value
O
No visible infection on the plant.
0
R (Resistant)
Visible chlorosis or necrosis, no uredia are present.
0.2
MR (Moderately resistant)
Small uredia are present and surrounded by either chlorates or necrotic areas.
0.4
M (Intermediate)
Variable-sized uredia are present, some with chlorosis, necrosis, or both.
0.6
MS (Moderately susceptible)
Medium-sized uredia are present and possibly, surrounded by chlorotic areas.
0.8
S (Susceptible)
Large uredia are present, generally with little or no chlorosis and no necrosis.
1
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)… 119
Figure 4. Adult plant infection type scoring scale recommended by Roelfs et al. (1992).
Figure 5. The adult plant infection severity scoring scale recommended by Peterson et al. (1948)
Seedling evaluation
For the seedling assessment, a randomized
complete block design with four replications
was conducted in a greenhouse in the
Department of Cereal Research, Seed and
Plant Improvement Institute, Karaj, Iran.
Twenty seeds from each genotype were
planted in a separate sterilized plastic pot with
a diameter of 6 cm and a depth of 8 cm, filled
with sterilized soil and peat moss with 1 to 1
ratio at 18 ºC. Seven days after germination,
for infection of the seedlings, all pots were
inoculated with the Pgt race TKTTF
uredospores which were suspended with the
light-weight mineral oil (Soltrol 170) by 50:50
% ratio and placed in a dew chamber for 24
120 Vahed Rezaei et al. 2023, 13(2): 113-130
hours of dark at 18 to 22 ºC. Then, the
seedlings were returned to the greenhouse and
kept at 21-24 ºC for 14 days (Woldeab et al.
2017). The infection type was assessed 14 days
after inoculation using a modified 0-4 scale
(Figure 6) according to Stakman et al. (1962).
Observations recorded in the field and
greenhouse experiments were as follows: field
type of infection (FTI), severity of infection
(SI), coefficient of infection (CI), AUDPC,
rAUDPC, genotype reaction at field (FGR),
greenhouse type of infection (GTI), and
genotype reaction at greenhouse (GGR).
Statistical analysis
All statistical analyses including analysis of
variance, comparison of means, calculating of
correlation coefficients, cluster analysis, and
discriminant function analysis were run using
SPSS 23 and STATISTICA 12 software.
Means were compared by Duncan’s multiple
range tests at the 0.01 significance level.
Relationships between field and greenhouse
traits were determined by Pearson’s
correlation coefficients (Benesty et al. 2009).
Cluster analysis for grouping of the genotypes
was carried out using Ward’s method with
squared Euclidian distance. The cutting point
in the dendrogram was determined by the
discriminant analysis.
Results
Adult plant stage Results of the analysis of
variance for different disease indices at the
adult plant and seedling stages are presented in
Tables 4 and 5. Significant differences (p ≤
0.01) were observed among the studied
genotypes for all indices under the stem rust
infection conditions at the adult plant stage.
Figure 6. Seedling infection type scoring scale recommended by Stakman et al. (1962).
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)… 121
Table 4. Analysis of variance for different disease indices obtained from reaction to stem rust
in the studied wheat genotypes at the field experiment.
SOV
df
Mean squares
FTI
SI
CI
AUDPC
rAUDPC
FGR
Replication
2
0.042
173.39*
137.81*
525.56*
286.54*
0.10
Genotype
23
0.210**
1707.48**
1718.08**
2626.91**
1432.26**
0.57**
Error
46
0.018
50.20
35.69
123.76
67.48
0.10
CV (%)
20.55
30.76
31.70
25.40
25.40
20.02
FTI: Field type of infection, SI: Severity of infection, CI: Coefficient of infection, AUDPC: Area
under the disease progress curve, rAUDPC: Relative area under the disease progress curve, FGR:
Genotype reaction at field.
*, **: Significant at 5% and 1% levels of probability, respectively.
Table 5. Analysis of variance for the greenhouse type of
infection (GTI) and genotype reaction at the greenhouse (GGR)
obtained from the reaction to stem rust in the studied wheat
genotypes at the greenhouse experiment.
SOV
df
Mean squares
GTI
GGR
Replication
3
0.028
0.066
Genotype
23
14.080**
0.739**
Error
69
0.521
0.044
CV (%)
8.70
12.35
**: Significant at 1% level of probability.
The disease indices of the 24 winter
wheat genotypes at the adult plant stages are
shown in Table 6. Based on the FTI index, two
cultivars and 10 lines showed adult plant
resistance, and six cultivars and six lines were
susceptible. At the adult plant stage, 20% of
the genotypes were susceptible, 30% were
moderately susceptible, 16% were
intermediate, 25% were moderately resistant,
and 8% were resistant. MV-17 and C-98-17
were resistant, C-98-11, C-98-12, C-98-13, C-
98-15, C-98-16, and C-98-18 were moderately
resistant, C-98-5, C-98-7, and C-98-10 were
intermediate, Haydari, Zareh, Heyran, C-98-6,
C-98-8, CD-94-5, and CD-94-9 were
moderately susceptible, and Mihan, Morocco,
Bolany, C-98-9, and C-98-14 were susceptible
genotypes. Among the 24 genotypes,
Morocco, Bolany, Heyran, Haydari, Mihan,
CD-94-5, CD-94-9, and showed the highest
severity of infection (SI > 30), while MV-17
and C-98-17 showed the lowest disease
severity (SI < 5) at the adult plant stage. MV-
17 and C-98-17 also had the lowest CI,
AUDPC, and rAUDPC while Morocco,
Bolany, Heyran, Mihan showed the
highest values of CI, AUDPC, and rAUDPC.
In total, MV-17 and C-98-17 had a better
resistance based on all disease indices as
compared to other genotypes. On the other
122 Vahed Rezaei et al. 2023, 13(2): 113-130
hand, Morocco, Bolany, Heyran, Haydari,
Mihan, CD-94-5, and CD-94-9 were
susceptible to stem rust at the adult plant stage.
Pearson’s correlation coefficients (Table
7) indicated a significant positive correlation
among FTI, SI, CI, AUDPC, and rAUDPC.
FTI and CI were highly correlated with
AUDPC and rAUDPC. The correlations of CI
with SI, AUDPC, and rAUDPC were higher
than the correlation between FTI and CI.
The result of the cluster analysis for the
wheat genotypes, based on different disease
indices at the adult plant stage, is demonstrated
in Figure 7. The genotypes were grouped into
four major clusters, each comprising 10, 7, 5,
and 2 genotypes, respectively. Group means
and their percentage deviation from the grand
mean for disease indices are shown in Figure
8. The genotypes with minimum values of FTI,
SI, CI, AUDPC, and rAUDPC were grouped in
Clusters 4 and 3, and the genotypes with
maximum values were grouped in the
Table 6. Scores of reaction to stem rust for the studied wheat genotypes at the field and greenhouse conditions.
Genotype
Field exp.
Greenhouse exp.
FTI
SI
CI
AUDPC
rAUDPC
FGR
GTI
GGR
Mihan
S
30.00ef
30.00d-f
63.51h
46.89h
L
4
L
Haydari
MS
40.00gh
27.33de
60.60gh
44.74gh
L
3
L
Zarrineh
M
8.67a-d
4.13a
27.90a-d
20.60a-d
L
4
L
Zareh
MS
21.67de
19.67cd
51.00e-h
37.66e-h
H
4
L
C-98-5
M
13.33a-d
10.00a-c
27.23a-d
20.11a-d
L
2-
H
C-98-6
MS
6.67a-c
5.00a
28.27a-d
20.88a-d
L
4
L
C-98-7
M
11.67a-d
8.67a-c
24.00a-d
17.72a-d
H
3+
L
C-98-8
MS
11.67a-d
9.33a-c
38.19c-f
28.2c-f
H
3+
L
C-98-9
S
10.00a-d
10.00a-c
43.66d-h
32.24d-h
L
4
L
C-98-10
M
16.67cd
10.67a-c
40.12c-g
29.62c-g
L
2-
H
C-98-11
MR
7.00a-c
2.73a
15.34ab
11.33ab
L
2
H
C-98-12
MR
6.67a-c
2.67a
20.88a-c
15.42a-c
H
3
H
C-98-13
MR
16.67cd
6.67ab
32.51a-e
24.01a-e
L
2
H
C-98-14
S
16.67cd
16.67bc
50.15e-h
37.03e-h
L
3
L
C-98-15
MR
15.00b-d
6.00ab
35.83b-e
26.45b-e
H
2C
H
C-98-16
MR
8.33a-d
3.33a
20.72a-c
15.3a-c
H
3+
L
C-98-17
R
2.33ab
0.47a
11.94a
8.81a
H
1+
H
C-98-18
MR
5.33a-c
2.07a
20.68a-c
15.27a-c
L
4
L
CD-94-9
MS
50.00h
40.00f
60.35gh
44.56gh
L
4
L
CD-94-5
MS
36.67fg
29.33de
58.39f-h
43.11f-h
L
4
L
MV-17
R
1.00a
0.20a
12.13a
8.96a
H
2-
H
Heyran
MS
46.67gh
37.33ef
62.33ef
46.02ef
L
3+
L
Morocco
S
100.00j
100.00h
135.43j
100.00j
L
4
L
Bolany
S
70.00i
70.00g
109.63i
80.95i
L
4
L
FTI, SI, CI, AUDPC, rAUDPC, FGR, GTI, GGR, L and H is: field type of infection, severity of infection, coefficient of
infection, area under the disease progress curve, relative area under the disease progress curve, field genotype reaction,
greenhouse type of infection, greenhouse genotype reaction, low and high, respectively.
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)… 123
Table 7. Pearson’s correlation coefficients of different disease indices obtained from reaction to stem
rust in the studied wheat genotypes at the field and greenhouse experiments.
FTI
SI
CI
AUDPC
rAUDPC
GIT
FGR
GGR
FTI
1
SI
0.62**
1
CI
0.65**
0.99**
1
AUDPC
0.75**
0.96**
0.98**
1
rAUDPC
0.75**
0.96**
0.98**
1**
1
GTI
0.65**
0.43**
0.45**
0.50**
0.50**
1
FGR
0.32ns
0.33ns
0.32ns
0.33ns
0.32ns
0.11ns
1
GGR
0.63**
0.36ns
0.39ns
0.44**
0.44**
0.95**
0.08ns
1
FTI, SI, CI, AUDPC, rAUDPC, FGR, GTI, GGR, L, and H are field type of infection, the severity of infection, coefficient of
infection, the area under the disease progress curve, the relative area under the disease progress curve, field genotype reaction,
greenhouse type of infection, greenhouse genotype reaction, low and high, respectively.
Clusters 1 and 2. Cluster 1 had susceptible
genotypes and Cluster 4 had resistant
genotypes, while Clusters 2 and 3 had
moderate susceptible and moderate resistant
reactions in response to the stem rust.
Seedling stage
The results of the analysis of variance for
different disease indices are presented in Table
5 for the greenhouse experiment. Significant
differences (p ≤ 0.01) were observed among
the genotypes for both GTI and GGR at the
seedling stage.
The disease indices of 24 winter wheat
genotypes at the seedling stage are presented
in Table 6. Based on the GTI index, one
cultivar and six lines showed seedling
resistance and seven cultivars and 10 lines
were susceptible at the seedling stage. In terms
of the seedling reaction, 66% of the genotypes
were susceptible and 34% were resistant. At
the seedling stage, MV-17 and C-98-17 were
resistant, C-98-11, C-98-13, and C-98-15 were
moderately resistant, C-98-5 and C-98-10 were
intermediate, C-98-8, Haydari, and Heyran
were moderately susceptible, and Mihan,
Morocco, Bolany, C-98-9, and C-98-14 were
susceptible. C-98-12, C-98-16, C-98-18, CD-
94-9, and CD-98-5 didn’t show similar
reactions at the adult plant and seedling stages.
Pearson’s correlation coefficients
indicated a strong positive correlation between
GTI and GGR (Table 7). There was no
significant correlation between FGR and GGR
at the seedling stage. Also, FGR at the seedling
stage was not significantly correlated with any
of the disease indices at the adult plant stage.
However, GGR at the seedling stage was
moderately and significantly correlated with
FTI, AUDPC, and rAUDPC, and highly and
significantly correlated with GIT at the adult
plant stage.
124 Vahed Rezaei et al. 2023, 13(2): 113-130
Figure 7. Dendogram of cluster analysis based on disease indices obtained from reaction to stem rust in the studied wheat
genotypes by Ward’s method at the field experiment. Orange = Cluster 4, Yellow = Cluster 3, Blue = Cluster 2, and
Green = Cluster 1.
The result of the cluster analysis for the
wheat genotypes based on different disease
indices is shown in Figure 9 at the seedling
stage. The genotypes were grouped into two
clusters, which comprised 17 and 7 genotypes,
respectively. Also, based on the mean of
groups and their percentage deviation from the
grand mean (Figure 10) at the seedling stage,
genotypes with minimum and maximum
values of GTI were grouped in Clusters 2 and
Cluster 1, respectively. In other words, at the
seedling stage, Cluster 1 had susceptible
genotypes and Cluster 2 had resistant
genotypes.
Discussion
Stem rust races are responsible for up to 100%
yield loss of wheat. Therefore, breeders
evaluate the resistance and genetic diversity of
wheat genotypes to control this disease (Knott
2012). The existence of significant variability
among the genotypes provides an opportunity
for improving stem rust resistance in breeding
programs. In this respect, our results were
similar to the reports of Degete and Chala
(2019), Taye et al. (2013), Hundie et al.
(2018), and Soresa (2018). In this study,
AUDPC was between 8.81 to 135.43 which
was due to the expression of different
resistance genes at the adult plant stage. The
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)… 125
Figure 8. Group means (A) and their percentage deviation from the grand mean (B) based on the disease indices obtained
from reactions to stem rust in the studied wheat genotypes at the adult plant stage.
1
0.8267
0.7238
0.4467
0.6528
85
40.66
15.47
7.1
23.02
85
32.8
11.28
3.92
18.84
122.52
61.03
41.63
20.9
43.78
90.47
45.06
30.74
15.43
32.32
0
10
20
30
40
50
60
70
80
90
100
110
120
Cluster 1 Cluster 2 Cluster 3 Cluster 4 Grand mean
Mean
Group
A
FTI
SI
CI
AUDPC
rAUDPC
53.18
26.63
10.87
-31.57
269.24
76.62
-32.79
-69.15
351.16
74.09
-40.12
-79.19
179.85
39.4
-4.91
-52.26
179.91
39.41
-4.88
-52.25
-150 -100 -50 0 50 100 150 200 250 300 350 400
Cluster 1
Cluster 2
Cluster 3
Cluster 4
Deviation from the grand mean (%)
Group
B
rAUDPC
AUDPC
CI
SI
FTI
126 Vahed Rezaei et al. 2023, 13(2): 113-130
Figure 9. Dendogram of the cluster analysis based on disease indices obtained from reactions to stem rust in the
studied wheat genotypes at the seedling stage (Green = Cluster 1) and (Red = Cluster 2).
genotypes that showed some resistance at the
seedling and adult plant stages, such as MV-
17, C-98-17, C-98-11, and C-98-5, may
contain seedling resistance Sr gene that
controls resistance reaction at the seedling
stage or they may have minor genes that are
working together to reduce the disease.
However, the genotypes that showed some
resistance only at the adult plant stage, such as
C-98-12, C-98-18, C-98-16, C-98-3, C-98-6,
C-98-5, and C-98-7 may only have adult plant
resistance Sr gene expressed at this stage
(Roelfs 1992).
The results of the present study showed
that the stem rust resistance level of C-98-17
was comparable to the MV-17 check variety.
Also, the resistance of lines C-98-11, C-98-12,
C-98-18, and C-98-16 was close to MV-17.
Thus, these plant materials could have
resistance genes in their background and other
unknown resistance genes (Hundie et al.
2018) and can be used in wheat breeding
programs to produce rust-resistant varieties.
At the seedling stage, C-98-17, C-98-10, and
C-98-5 displayed almost comparable indices to
MV-17. Also, based on disease indices, C-98-
17 and C-98-9 were resistant and susceptible
elite lines at both adult plant and seedling
stages, respectively, which were derived from
MV NEMERE and
Spb"s"//K1349/Go/3/Vee"s"/4/Bkt/90-Zhong
87 pedigree. C-98-17 seems a promising
resistant line at both adult plant and seedling
stages.
Biometrical analysis of resistance to stem rust (Puccinia graminis f. sp. tritici)… 127
Figure 10. Mean of groups (A) and their percentage deviation from the grand mean (B) based on disease indices
obtained from reactions to stem rust in the studied wheat genotypes at the seedling stage.
Conclusion
This study demonstrated the infection and
pathogenicity of East Azarbaijan stem rust race
TKTTF toward the winter wheat cultivars and
elite lines at the field (adult plant stage) and
greenhouse (seedling stage) conditions. This
race was effective in both experimental
conditions. At both adult plant and seedling
stages, C-98-17 had resistance to stem rust
very similar to MV-17 check cultivar. This
line, together with several moderately resistant
lines (such as C-98-11, C-98-12, C-98-18, and
C-98-16), can be in the breeding programs to
improve stem- rust resistance. The cluster
analysis showed the existence of adequate
genetic diversity for the studied stem rust
disease indices, which will be useful in the
rust-resistance breeding of winter wheat
genotypes. However, the variability of
environmental conditions influences the
response of genotypes to pathogens.
Therefore, this study should be repeated in
12.9
-31.6
-40 -30 -20 -10 0 10 20
Cluster 1
Cluster 2
Deviation from the grand mean (%)
Group
B
GTI
9.36
5.67
8.29
0
2
4
6
8
10
Cluster 1 Cluster 2 Grand mean
Mean
Groups
A
GTI
128 Vahed Rezaei et al. 2023, 13(2): 113-130
different locations and years.
Acknowledgments
Thanks to Seed and Plant Improvement
Institute and East Azerbaijan Research Center
for Agriculture and Natural Resources that
supported this project. Sincere gratitude goes
to Seed and Plant Improvement Institute,
Cereal Research Department for providing the
wheat genotypes, trial sites, and technical
assistance. Final gratitude goes to Ms. Zohreh
Bayat for their assistance in providing
experimental sites and technical assistance to
this project.
Conflict of Interest
The authors declare that they have no conflict
of interest with any people or organization
concerning the subject of this manuscript.
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(Puccinia graminis f. sp. tritici)
AREEO
AREEO
a_asghari@uma.ac.ir: Email
TKTTF
AUDPC
rAUDPC
MV-17C-98-17C-98-14C-
98-9
AUDPC rAUDPC
Ward
