The thirteen wheat cultivars differed significantly in their responses to yellow, leaf, and stem rust disease, as shown by the phenotypic expression of disease parameters during the 2019/2020 growing season (Table 3 and Supplementary TableS1).
The wheat cultivars Gem-12, Sids-14, Giza-171, and Sakha-95 displayed high APR to yellow rust, showing ITs of MR or MS. These cultivars also showed the lowest values of final rust severity (FRS), AUDPC, and r-value. Conversely, Giza-168 had a low IT, r-value, and AUDPC, which indicates that this cultivar had partial resistance to yellow rust. The remaining eight cultivars showed the lowest levels of field resistance to yellow rust infection; these had the highest recorded FRS, as well as relatively high AUDPC and high r-values (Table 3 and Supplementary Table S1).
The wheat cultivars Gem-12, Sids-14, Giza-171, Misr-1, and Sakha-95 had partial resistance to leaf rust (IT of MR to MS), AUDPC of less than 150, and the lowest r-values. The other wheat cultivars presented as susceptible to leaf rust symptoms, with reactions of 10 S to 80 S, AUDPC greater than 170, and the highest r-values (Table 3 and Supplementary Table S1).
Stem rust disease severity could be ranked into three main groups. The first group included the seven wheat cultivars Gem-12, Sids-1, Sakha-95, Gemmeiza-11, Sids-13, Giza-168, and Giza-171 (resistant cultivars), which exhibited the highest levels of resistance or partial resistance. This group had the lowest AUDPC estimates (less than 300.00), and were designated as partially resistant and slow-rusting cultivars. However, this group displayed the highest level of APR and field resistance to stem rust infection throughout the study, indicating that these cultivars may have durable resistance to stem rust. The second group included three wheat cultivars (Gem-9, Gem-10, and Sids-12), which showed intermediate stem rust resistance. These cultivars had FRS values of 20 S, 10 S, and 20 S, respectively, with intermediate AUDPC values and low r-values. This group had the lowest levels of APR to stem rust infection under field conditions. The third group included the wheat cultivars Misr-1 and Misr-2, which showed high FRS of 70 S and 60 S, respectively. These two cultivars had the highest AUDPC and highest r-values, and could therefore be classified as highly susceptible or fast-rusting cultivars (Table 3 and Supplementary Table S1).
Table 3
Final rust severity (FRS), area under disease progress curve (AUDPC), and rate of rust disease increase (r-value) of yellow, leaf, and stem rust evaluated for thirteen Egyptian wheat cultivars grown under field conditions at Sids Research Station during the 2019/2020 growing season
Genotypes
|
Yellow Rust
|
Leaf Rust
|
Stem Rust
|
FRS
|
AUDPC
|
r-value
|
FRS
|
AUDPC
|
r-value
|
FRS
|
AUDPC
|
r-value
|
|
Value
|
Type*
|
Value
|
Type
|
Value
|
Type
|
Gem-9
|
50 S
|
423.50
|
Sus.
|
0.219
|
40 S
|
315.00
|
Sus
|
0.200
|
20 S
|
178.50
|
P.R
|
0.153
|
Gem-10
|
50 S
|
388.50
|
Sus.
|
0.219
|
30 S
|
175.00
|
P.R
|
0.178
|
10 S
|
80.50
|
P.R
|
0.114
|
Gem-11
|
80 S
|
577.50
|
Sus.
|
0.206
|
20 S
|
175.00
|
P.R
|
0.153
|
5 MS
|
28.00
|
P.R
|
0.053
|
Gem-12
|
20 MS
|
129.50
|
P.R
|
0.147
|
20 MS
|
84.00
|
P.R
|
0.140
|
0
|
0.00
|
R
|
0.00
|
Sids-1
|
30 S
|
213.50
|
P.R
|
0.178
|
80 S
|
650.00
|
Sus
|
0.285
|
Tr MR
|
24.50
|
R
|
0.033
|
Sids-12
|
70 S
|
700.00
|
Sus.
|
0.145
|
30 S
|
175.00
|
P.R
|
0.178
|
20 S
|
178.50
|
P.R
|
0.153
|
Sids-13
|
60 S
|
388.50
|
Sus.
|
0.238
|
30 S
|
175.00
|
P.R
|
0.178
|
TrMS
|
28.00
|
R
|
0.053
|
Sids-14
|
20 MS
|
122.50
|
P.R
|
0.140
|
30 MS
|
126.00
|
P.R
|
0.164
|
TrMR
|
24.50
|
R
|
0.033
|
Giza-168
|
10 S
|
80.50
|
P.R
|
0.114
|
20 S
|
210.00
|
P.R
|
0.178
|
10 MS
|
52.50
|
P.R
|
0.088
|
Giza-171
|
10 MR
|
52.50
|
R
|
0.088
|
30 MS
|
140.00
|
P.R
|
0.164
|
5 MS
|
28.00
|
P.R
|
0.053
|
Misr-1
|
40 S
|
437.50
|
Sus
|
0.121
|
20 MS
|
112.00
|
PR
|
0.140
|
70 S
|
570.50
|
Sus
|
0.160
|
Misr-2
|
50 S
|
472.50
|
Sus.
|
0.140
|
10 S
|
70.00
|
P.R
|
0.114
|
50 S
|
353.50
|
P.R
|
0.219
|
Sakha-95
|
10 MS
|
59.50
|
P.R
|
0.103
|
Tr MR
|
17.50
|
R
|
0.053
|
Tr MR
|
28.00
|
R
|
0.053
|
Mean
|
-
|
578
|
-
|
0.294
|
-
|
346.35
|
-
|
0.303
|
--
|
134.14
|
-
|
0.166
|
LSD 0.05
|
1.79
|
1.85
|
1.67
|
*AUDPC type: Susceptible (Sus.) = AUDPC value greater than 300; Partial resistance (PR) = AUDPC value less than 300; Resistance (R) = AUDPC value less than 300 and infection type (IT) of 0, MR, Tr-MR, and Tr-MS. |
Validation of resistance genes (yellow, leaf, and stem rust) in wheat cultivars
Simple sequence repeat molecular markers were amplified to validate the resistance genes Yr, Sr, and Lr in all thirteen Egyptian wheat cultivars (Table 4).
Validation of markers linked to yellow rust resistance genes
The SSR marker barc147-3B was linked to the Yr resistance gene. The marker’s bands showed amplification in the range of 115-150bp. The 150bp band was present only in Sids-12, which was a susceptible cultivar, whereas the 115bp band was present in eight cultivars (Gem-9, Gemmeiza-10, Gem-11, Gem-12, Sids-1, Sids-14, Giza-171, and Misr-1). These cultivars had AUDPC types of partial resistance (PR: Gem-12, Sids-1, and Sids-14), resistance (R: Giza 171), and susceptible (Sus: Gem-9, Gem-10, and Gem-11) (Table 4, Fig. 1a). The SSR marker barc180-3B was linked with Yr78. Four genotypes (Gm-12, Sids-1, Sids-13, and Giza-168) showed the presence of Yr78 with a band size of 150bp. Three of these cultivars had an AUDPC type of PR, whereas Sids 13 was of the type Sus. Nine cultivars (Gm-9, Gm-10, Gm-11, Sids-12, Sids-14, Giza-171, Misr-1, Misr-2, and Sakha-95) did not contain Yr78 (Table 4, Fig. 1b).
Validation of markers linked to leaf rust resistance genes
The marker barc64-7A amplified a 200bp fragment for the leaf rust resistance gene. This marker was present in eight genotypes (Gm-9, Gm-10, Gm-11, Gm-12,-Sids-13, Sids-14, Giza-171, and Misr-2); all eight of these cultivars were of the AUDPC type PR, except for Gm 9, which was AUDPC type Sus. Eight genotypes indicated the presence of the leaf rust resistance gene with a band size of 200bp, whereas five genotypes did not contain this gene (Table 4, Fig. 2a). The SSR molecular marker barc130-5D exhibited linkage with the Lr70 leaf rust resistance gene present on chromosomal locus 5D. This marker showed amplified bands of 285bp, which were present in all thirteen genotypes. Of these, ten were AUDPC type PR (Gm-10, Gm-11, Gm-12, Sids-12, Sids-13, Sids-14, Giza-168, Giza-171, Misr-1, and Misr-2); one AUDPC type R (Sakha-95); and two type Sus. (Gm-9 and Sids-1) (Table 4, Fig. 2b). The marker barc167-2B amplified a 255bp fragment for leaf rust resistance. This marker was present in three genotypes (Gm-11, Sids-14, and Sakha-95), of which two were AUDPC type PR (Gm-11 and Sids-14), and one was type R (Sakha-95) (Table 4, Fig. 2c).
Validation of markers linked to stem rust resistance genes
The SSR marker barc104-6A was linked to the gene Sr13. This marker had an amplified band size of 250bp in seven genotypes (Gm-9, Gm-10, Gm-11, Sids-13, Sids-14, Giza-171, and Misr-2), of which five were AUDPC type PR (Gm-9, Gm-10, Gm-11, Giza-171, and Misr-2), and two were type R (Sids-13 and Sids-14). This resistance gene was absent in the genotypes Gm-12, Sids-1, Sids-12, Giza-168, Misr-1, and Sakha-95. The gene Sr13 is the only known gene to be operative against the TTKS complex of P. graminis f. sp. tritici; this includes the TTKSK (Ug99) race and its variants, TTKST and TTTSK (Table 4, Fig. 3a). The PCR-based diagnostic marker barc152-1B was linked to Sr33, which is found on chromosomal locus 1BS. All genotypes indicated the presence of this gene with a band size of 130bp. Of these, seven were AUDPC type PR (Gm-9, Gm-10, Gm-11, Sids-12, Giza-168, Giza-171, and Misr-2); five were type R (Gm-12, Sids-1, Sids-13, Sids-14, and Sakha-95); and one was Sus. (Misr-1) (Table 4, Fig. 3b). The marker barc173-6D was linked with the stem rust resistance gene SrTA10187, with a band size of 240bp. This gene was found in ten cultivars (Gm-9, Gm-10, Gm-11, Gm-12, Sids-12, Sids-13, Sids-14, Giza-171, Misr-1, and Misr-2), of which seven were AUDPC type PR (Gm-9, Gm-10, Gm-11, Sids-12, Giza-171, Misr-1, and Misr-2) and three were type R (Gm-12, Sids-13, and Sids-14). This marker was absent in the remaining four cultivars (Sids-1, Giza-168, Giza-171, and Sakha-95) (Table 4, Fig. 3c). The marker barc200-2B was amplified as a 150bp fragment for the stem rust resistance gene. This marker was present in two genotypes (Giza-171 and Sakha-95), which were AUDPC types PR and R, respectively (Table 4, Fig. 3e). The SSR marker wmc169 was linked with the stem rust resistance gene Sr35. This marker was amplified to a band size of 120bp and was found to be present in seven cultivars (Sids-1, Sids-12, Sids-13, Sids-14, Gm-168, Misr-2, and Sakha-95), and absent in the remaining six cultivars (Table 4, Fig. 3d).
Validation of markers linked to leaf/yellow rust resistance genes
The SSR marker barc352-4D was linked with the leaf/yellow rust resistance gene Lr34/Yr18. Eight cultivars (Gm-10, Gm-12, Sids-1, Sids-12, Sids-14, Giza-168, Misr-2, and Sakha-95) indicated the presence of these genes with an amplified band size of 255bp. Of these, four cultivars (Gem-12, Sids-14, Giza-168, and Sakha-95) were AUDPC type PR or R. The remaining five cultivars showed no introgression for these markers (Table 4, Fig. 4a). The SSR marker wmc44-1B, mapped on the long arm of chromosome 1B and linked to the leaf/yellow rust resistance gene Lr49/Yr29, was amplified to a band size of 242bp. Out of the thirteen cultivars, six were positive for this marker (Gm-9, Gm-10, Gm-11, Sids-1, Sids-13, and Sids-14) and seven were negative (Table 4, Fig. 4b).
Validation of markers linked to stem/yellow rust resistance genes
The SSR marker wmc175-3A, mapped on the long arm of chromosome 3A and linked to the stem/yellow rust resistance genes Sr9 and Yr5, was used to identify the presence of Sr9 and Yr5 with an amplified band size of 260bp. Out of the thirteen cultivars, seven (Gm-9, Gm-10, Sids-12, Sids-14, Giza-168, Giza-171, and Sakha-95) were positive for this marker. Of these, three cultivars (Sids-14, Giza-168, and Sakha-95) were AUDPC type PR, and one (Giza-171) was type R (Table 4, Fig. 4c).
Identification of wheat cultivars containing more than one rust resistance dieses
The results of molecular marker detection indicated that Yr (yellow rust); Lr (leaf rust); Sr (stem rust); and Lr/Yr (leaf/yellow rusts), were present alone or in different gene combinations among the wheat cultivars. The cultivar Sakha-95 was AUDPC type R for leaf and stem rusts, and PR for yellow rust dieses. However, Sakha-95 contained several other rust resistance genes (Lr, Sr and Lr/Yr) (Table 5). The AUDPC types for cultivars Gm-12, Sids-14, Giza-171, and Giza-168 were PR and R (Table 5). The cultivar Sids-1 was recorded as PR, Sus, and R for Yr, Lr, and Sr respectively, whereas Sids-13 had respective AUDPC types of Sus, PR, and R for dieses (Yr, Lr, and Sr) respectively. Seven cultivars (Sakha-95, Gm-12, Sids-14, Giza-171, Giza-168, Sids-1, and Sids-13) contained more than one rust resistance gene (Table 5). The phenotypic responses to infection by different rusts indicated the presence of additional slow-rusting resistance genes.
Table 4
Response of molecular markers for the detection of rust resistance genes (yellow rust, leaf rust, stem rust, leaf/yellow rust, and stem/yellow rust) in thirteen wheat cultivars
Rust type
|
Marker
|
Expected Resistance genes
|
Cultivar
|
Band
Size (bp)
|
Gm9
|
Gm10
|
Gm11
|
Gm12
|
Sids1
|
Sids12
|
Sids13
|
Sids14
|
Giza168
|
Giza171
|
Misr1
|
Misr2
|
Sakha95
|
Yellow rust
|
Barc147
|
Yr
|
+
|
+
|
+
|
+
|
+
|
|
|
+
|
|
+
|
+
|
|
|
115
|
Barc180
|
Yr78
|
|
|
|
+
|
+
|
|
+
|
|
+
|
|
|
|
|
150
|
Leaf rust
|
Barc64
|
Lr
|
+
|
+
|
+
|
+
|
|
-
|
+
|
+
|
|
+
|
|
+
|
|
200
|
Barc130
|
Lr70
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
285
|
Barc167
|
Lr
|
|
|
+
|
|
|
|
|
+
|
|
|
|
|
+
|
255
|
Stem rust
|
Barc104
|
Sr13
|
+
|
+
|
+
|
|
|
|
+
|
+
|
|
+
|
|
+
|
|
230
|
Barc152
|
Sr33
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
+
|
130
|
Barc173
|
SrTA10187
|
+
|
+
|
+
|
+
|
|
+
|
+
|
+
|
|
+
|
+
|
+
|
|
240
|
Barc200
|
Sr
|
|
|
|
|
|
|
|
|
+
|
|
|
|
+
|
160
|
Wmc169
|
Sr35
|
|
|
|
|
|
+
|
+
|
+
|
+
|
|
|
+
|
+
|
110
|
Leaf/yellow rust
|
Barc352
|
Lr34/Yr18
|
|
+
|
|
+
|
+
|
+
|
|
+
|
+
|
|
|
+
|
+
|
255
|
Wmc44
|
Lr49/Yr29
|
+
|
+
|
+
|
|
+
|
|
+
|
+
|
|
|
|
|
|
215
|
Stem/yellow rust
|
Wmc175
|
Sr9 and Yr5
|
+
|
+
|
|
|
|
+
|
|
+
|
+
|
+
|
|
|
+
|
260
|
Table 5
Slow-rusting resistance genes (Yr, Lr, Sr and Lr/Yr) associated with molecular markers, and the corresponding phenotypic AUDPC type of seven wheat cultivars
Cultivar
|
Yellow rust
|
Leaf rust
|
Stem rust
|
Yellow, Leaf, Stem rust
|
AUDPC Type
|
Expected Resistance genes
|
AUDPC Type
|
Expected Resistance genes
|
AUDPC Type
|
Expected Resistance genes
|
Expected Resistance genes
|
Sakha-95
|
PR
|
None
|
R
|
Lr˜70
|
R
|
Sr˜33
|
Lr˜34/Yr˜18
|
Gm-12
|
PR
|
Yr˜78
|
PR
|
Lr˜70
|
R
|
Sr˜33, TA10187
|
Lr˜34/Yr˜18
|
Sids-14
|
PR
|
Yr˜
|
PR
|
Lr˜70
|
R
|
Sr˜13, 33, TA10187
|
Lr˜34/Yr˜18,
Lr˜49/Yr˜29
|
Giza-171
|
R
|
Yr˜
|
PR
|
Lr˜70
|
PR
|
Sr˜13, 33, TA10187
|
None
|
Giza-168
|
PR
|
None
|
PR
|
Lr˜70
|
PR
|
Sr˜33, TA10187
|
Lr˜34/Yr˜18
|
Sids-1
|
PR
|
Yr˜78
|
Sus
|
Lr˜70
|
R
|
Sr˜33
|
Lr˜34/Yr˜18,
Lr˜49/Yr˜29
|
Sids-13
|
S
|
None
|
PR
|
Lr˜70
|
R
|
Sr˜13, 33, 35, TA10187
|
Lr˜49/Yr˜29
|