INSTITUTE OF EXPERIMENTAL BIOLOGY AT THE ESTONIAN AGRICULTURAL UNIVERSITY
Department of Plant Genetics, 76902, Harku, Harjumaa, Estonia.
T. Enno, H. Peusha, and O. Priilinn.
Knowledge of the interactions between the genetic systems of host plants and pathogens is very important for successful breeding programs and the development of resistant cultivars. Powdery mildew is one of the most destructive diseases of common wheat and, 28 genes for resistance against this disease have been described to date (McIntosh et al. 1998; Järve et al. 2000; Peusha et al. 2000). Some wheat cultivars contain only one gene for powdery mildew resistance, but others have two or three, and combinations of two or more effective genes may afford better genetic control (Szunics and Szunics 1999).
The common spring-wheat cultivar Sunnan was bred in Sweden (Weibullsholm Breeding Station) and has the pedigree 'Pompe B2//Sappo/Drabent'.
We attempted to locate the resistance genes for powdery mildew in Sunnan by monosomic analysis and determined if they were new resistance genes. The monosomic plants of Chinese Spring were identified cytologically and crossed as females with disomic plants of Sunnan. All F1 hybrids were screened cytologically and monosomic lines were grown in the greenhouse to obtain an F2 population. Powdery mildew isolate No. 6, known to be avirulent on Sunnan, was used to test the segregating F2 population. The detailed methods for inoculation of leaf segments and disease assessments were described in Hsam and Zeller (1997).
Segregation for resistant and susceptible plants in the F2 populations fit the ratio of 243:13, except for chromosomes 2A, 7A, 6B, and 5D, which were clearly different, indicating that resistance in Sunnan is controlled by four duplicate complementary genes located on these chromosomes (Table 1). Assessment of resistance in the F3 families demonstrated that all plants in the progenies of two crosses, 'CS-M 2A/Sunnan' (244 plants) and 'CS-M5D/Sunnan' (492 plants), were resistant to the pathogen.
| Monosomic line | No. of plants | Powdery mildew isolate N6 | X2 | |
|---|---|---|---|---|
| Resistant | Susceptible | 243:13 | ||
| 1A | 125 | 119 | 6 | 0.019 |
| 2A | 92 | 91 | 1 | 3.039* |
| 3A | 148 | 143 | 5 | 0.883 |
| 4A | 121 | 115 | 6 | 0.003 |
| 5A | 257 | 244 | 13 | 0.000 |
| 6A | 63 | 60 | 3 | 0.012 |
| 7A | 92 | 91 | 1 | 3.039* |
| 1B | 89 | 85 | 4 | 0.060 |
| 2B | 81 | 77 | 4 | 0.003 |
| 3B | 29 | 28 | 1 | 0.158 |
| 4B | 125 | 120 | 5 | 0.327 |
| 5B | 55 | 52 | 3 | 0.014 |
| 6B | 127 | 125 | 2 | 3.234* |
| 7B | 147 | 140 | 7 | 0.029 |
| 1D | 111 | 106 | 5 | 0.073 |
| 2D | 13 | 12 | 1 | 0.184 |
| 3D | 113 | 108 | 5 | 0.098 |
| 4D | 130 | 123 | 7 | 0.025 |
| 5D | 66 | 66 | 0 | --- |
| 6D | 89 | 83 | 6 | 0.517 |
| 7D | 112 | 107 | 5 | 0.085 |
| CSdisomic/Sunnan | 316 | 304 | 12 | 1.071 |
Powdery mildew genes Pm4b, Pm1 + Pm9, and Pm2 are located on the chromosomes 2A, 7AL, and 5DS, respectively (Briggle 1969; Sears and Briggle 1969; McIntosh and Baker 1970). Transfers of resistance genes from cultivated and wild relatives of Triticum to commercial common wheat cultivars have been successful. For example, Pm4b was transferred from the tetraploid T. carthlicum to hexaploid wheat (The et al. 1979), and Pm2 was transferred from Ae. tauschii to common wheat (McIntosh and Baker 1970; Tosa and Sakai 1991; Lutz et al. 1995). The resistance genes located on the 2A and 5D chromosomes in Sunnan are the effective genes Pm4b and Pm2, inherited from tetraploid wheat. In future experiments, we intend to test allelism to verify our suspicions. The source and origin of genes located on chromosomes 7A and 6B could not be deduced now.
Monosomic and disomic hybrids F1 'CS/Sunnan' were analyzed cytologically for chromosome behavior at metaphase of the first meiotic division. Cytogenetical analysis of meiotic associations revealed two reciprocal translocations involving chromosomes 1A/1D and 7B/6D (Table 2). We found that the genes that cause a decrease in chromosome pairing in F1 hybrids between the CS monosomics and Sunnan were on chromosomes 3A, 6A, 2D, and 4D, and genes that enhance pairing are on chromosomes 5A, 7A, 5B, and 7D.
| Monosomic line | No. of PMCs | Mean number per cell X2 | No. of PMCs with trivalents but no univalents | No. of PMCs with multivalents | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Bivalents | Univalents | Chiasmata | Multivalents | 1^III^ | 1^IV^ | |||||
| Ring | Rod | Total | ||||||||
| 1A | 137 | 15.74 | 3.39 | 19.13 | 2.51 | 35.03 | 0.06 | 1.46 | 3 | 5 |
| 2A | 109 | 16.67 | 2,76 | 19.43 | 2.08 | 36.24 | 0.05 | --- | --- | 5 |
| 3A | 143 | 15.38 | 3.99 | 19.37 | 2.09 | 34.86 | 0.04 | --- | 3 | 3 |
| 4A | 73 | 16.26 | 3.44 | 19.69 | 1.55 | 36.00 | 0.01 | --- | --- | 1 |
| 5A | 51 | 16.76 | 2.98 | 19.74 | 1.43 | 36.56 | 0.02 | --- | --- | 1 |
| 6A | 102 | 14.53 | 4.74 | 19.27 | 2.26 | 33.95 | 0.05 | --- | 1 | 4 |
| 7A | 118 | 16.92 | 3.17 | 20.09 | 1.41 | 37.05 | 0.02 | --- | 1 | 1 |
| 1B | 79 | 16.76 | 2.94 | 19.72 | 1.47 | 36.55 | 0.02 | --- | 1 | 1 |
| 2B | 58 | 16.60 | 2.86 | 19.46 | 1.93 | 36.17 | 0.03 | --- | --- | 2 |
| 3B | 82 | 15.90 | 3.50 | 19.40 | 2.12 | 35.35 | 0.02 | --- | 2 | --- |
| 4B | 96 | 15.68 | 3.93 | 19.61 | 1.69 | 35.35 | 0.02 | --- | 1 | 1 |
| 5B | 92 | 17.25 | 2.51 | 19.76 | 1.34 | 37.11 | 0.03 | --- | --- | 3 |
| 6B | 157 | 15.94 | 3.48 | 19.42 | 2.01 | 35.48 | 0.04 | --- | 1 | 5 |
| 7B | 99 | 16.79 | 2.89 | 19.68 | 1.51 | 36.57 | 0.03 | 1.01 | --- | 2 |
| 1D | 65 | 16.20 | 3.09 | 19.29 | 2.09 | 35.63 | 0.08 | 1.54 | 3 | 1 |
| 2D | 136 | 15.01 | 4.33 | 19.34 | 2.22 | 34.41 | 0.02 | --- | 1 | 2 |
| 3D | 94 | 16.54 | 3.06 | 19.60 | 1.71 | 36.20 | 0.02 | --- | 1 | 1 |
| 4D | 97 | 14.60 | 4.29 | 18.89 | 1.94 | 33.62 | 0.04 | --- | --- | 4 |
| 5D | 127 | 16.57 | 3.08 | 19.65 | 1.55 | 35.32 | 0.04 | --- | 2 | 3 |
| 6D | 98 | 16.64 | 3.04 | 19.68 | 1.60 | 36.34 | 0.01 | 1.02 | 1 | --- |
| 7D | 136 | 17.74 | 2.09 | 19.83 | 1.30 | 37.59 | 0.01 | --- | --- | 1 |
| CSdisomic/Sunnan | 140 | 16.76 | 3.67 | 20.43 | 1.08 | 37.24 | 0.01 | --- | 1 | 1 |
This work was supported by the Estonian Science Foundation (Grant N 4720).
References.
M. Tohver and R. Koppel (Jögeva Plant Breeding Institute, EE 48309 Jögeva, Estonia) and A. Kann, A. Mihhalevski, I. Rahnu, and R. Täht (Tallinn Technical University, Ehitajate tee 5, EE 19086 Tallinn, Estonia).
In 2000-01, the polymorphism of gliadin and HMW-glutenin subunits of wheat, triticale, and rye cultivars and breeding lines was examined with the aid of one-dimensional A- and SDS-PAGE. Our aim was to identify new breeding lines, test the authenticity of cultivars, and study the influence of the Glu-1 loci on bread-making quality.
Plant stocks were obtained from comparative variety trials, the Estonian Control Center of Plant Production, and the Jögeva Plant Breeding Institute, and comprise of cultivars from Estonia, Finland, Norway, Sweden, Lithuania, Poland, and Germany.
A total of 20 spring (including Heta, Bastian, Laari, and Tähti), 46 winter (including Portal, Otto, Residence, Bercy, Sani, Eka, Kalvi, Linna, Aura, Nisu, Pitko, Vakka, Ramiro, and Virvinta) wheat, 14 triticale (including Vision, Moreno, Tewo, Lupus, Dagro, Modus, Dato Prego, Pinokio, Lasko, Presto, SV 92280, and SW 98578), 2 rye (Sangaste and Apart) cultivars, and numerous breeding lines were investigated.
The electrophoreses were performed on the 10 % polyacrylamide gels in acid (A-PAGE) (Metakovsky, Novoselskaya 1991) for gliadin proteins and in SDS-PAGE (D'Ovidio 1996) for HMW-glutenin subunits. Gliadins were extracted from crushed kernel with 70 % ethyl alcohol at 40°C for 1 h. The electrophoresis was performed for 20 min at 200 V and 1 h at 500 V. HMW-glutenin subunits were extracted using a buffer containing 0.125 M Tris-HCl, pH 6.8, 2.75 % (w/v) SDS, 10 % (v/v) glycerol, and 1 % (w/v) ditiothreitol (DTT) for 1 h at 70°C. Electrophoresis was by SDS-PAGE (T = 10 %, C = 1.28 %). After electrophoreses, the gels were stained with Coomassie Brilliant Blue R-250, destained, and photographed. Gliadins were analyzed according to the nomenclature of Metakovsky and Novoselskaya (1991) and Jackson et al. (1996); HMW-glutenin bands were analyzed according to the nomenclature of Payne and Lawrence (1983).
The most represented Gli-1 alleles in wheat cultivars and breeding lines were Gli-A1a, Gli-B1b, and Gli-D1a. The most frequent alleles for the HMW-glutenin subunits were Glu-A1b, Glu-B1b, and Glu-D1d. In some cases, we detected secalin bands in breeding lines of winter wheat. The T1BL·1RS translocation is easily detectable in A-PAGE. Many cultivars from neighboring countries were analyzed earlier and data were published (Johansson et al. 1995; Sontag-Strohm 1997; Ruzgas and Liutkevicius 2000). These cultivars were grown in our environment, and we verified their authenticity.
The baking quality of wheat was positively influenced by HMW-glutenin subunits 1 (Glu-A1), 7+9 (Glu-B1), 14+15 (Glu-B1), and 5+10 (Glu-D1).
Recent years have seen an increased interest in growing triticale in Estonia. The most common HMW-glutenin (Glu-1) alleles in hexaploid triticale (AABBRR) were subunits 0 or 2* (Glu-A1) and 7+19 or 13+16 (Glu-B1). Some cultivars were heterogeneous, representing different alleles in kernels. We found two variations of Glu-B1 in Moreno (bands 7+26 or 6+8), Presto (bands 7+9 or 7+26), Pinokio (7+8 or 7+9), and SW 98578 (7+8 or 7+9). Some HMW-glutenin subunit patterns in the triticale cultivars (Dato) were more similar to the typical pattern of rye, whereas the glutenin-subunit patterns of most of the triticale cultivars were closer to that of wheat. As for chemical composition, triticale is more similar to wheat, whereas for free sugars, it is closer to rye, and this is the reason of the low baking quality of triticale. Considering those indices characterizing bread-making properties (falling number, protein content, Zeleny number, water absorption capacity, and bread volume), the best cultivars were Moreno, Presto, Tewo, Dato, and SV 92280, which agrees with HMW-glutenin subunit composition.
The winter rye is traditional crop in Estonia, well adapted for local soil and weather conditions. Rye is highly heterozygous crop. This species usually cross-pollinates, consequently most cultivars are the mixtures of different genotypes. We observed this on the electrophorograms. Nearly every kernel had a different protein pattern.
The protein pattern of rye (AARR) lacks many of the bands that are found in wheat (AABBDD) or triticale (AABBRR). The absence of a-gliadins is characteristic for rye.
The rye proteins do not be able to form gluten because of the structure of proteins. The suitability of rye for bread making is defined with reading the viscosity of amylograms, which cannot be less than 200 BU with Falling Numbers between 90-140. Falling Numbers of Estonian-grown rye have been in the range of 113-241 (Veskus and Kann 1997).
Two Master of Science theses, The relationship between fractional composition of proteins and bread-making quality of triticale varieties, by I. Rahnu, and The investigation of bread-making quality of triticale cultivars proposed for cultivation in Estonia, by A. Mihhalevski, were defended in 2000 and 2002, respectively.
References.