Wheat (Triticum aestivum L.)‐Rye (Secale cereale L.) T2BS.2RL translocations were shown to increase grain yield, resistance to biotic and abiotic stresses, and had minor effects on baking quality. The objective of this study was to test agronomic performance and resistance of a new wheat‐rye translocation (T2BS.2RL, SLU) to powdery mildew (Blumeria graminis f. sp. tritici (DC.) E. O. Speer), leaf rust (Puccinia triticina Eriks.), stem rust (Puccinia graminis f. sp. tritici Eriks. & Henn.), stripe rust (Puccinia striiformis f. sp. tritici Westend.) and Hessian fly [Mayetiola destructor (Say)]. F2 derived F4–F6 T2BS.2RL lines, non‐translocation lines, and the wheat cultivar Holme were compared using intact seedlings or leaf segments. T2BS.2RL conferred seedling resistance to 17 powdery mildew isolates, 14 leaf rust and one stem rust pathotype. The T2BS.2RL lines were susceptible to 3 stripe rust pathotypes as seedlings, while showing adult plant resistance under natural conditions. Agronomic characters were compared in a 2‐yr hill‐plot field trial in Sweden. T2BS.2RL lines flowered 2 to 3 d later and had an increased number of spikelets per spike. The T2BS.2RL had no significant effect on yield, straw length, lodging, volume weight, 1000‐kernel weight, fertility, α‐amylase activity, or starch or protein content. The multiple disease resistance and the minor negative effects on agronomic performance of the T2BS.2RL, SLU translocation encourage its use in wheat breeding.

Diversity of resistance to leaf rust caused by Puccinia triticina can be enhanced in wheat (Triticum aestivum) cultivars through a better knowledge of resistance genes that are present in important cultivars and germplasm. Multi-pathotype tests on 84 wheat cultivars grown in Denmark, Finland, Norway and Sweden during 1992-2002 and 39 differential testers enabled the postulation of nine known genes for seedling resistance to leaf rust. Genes Lr1, Lr2a, Lr3, Lr10, Lr13, Lr14a, Lr17, Lr23 and Lr26 were found singly or in combination in 47 of the cultivars (55.9%). The most frequently occurring genes in cultivars grown in Sweden were Lr13 (20.4%), Lr14a (14.8%) and Lr26 (14.8%). Lr14a was the most common gene in cultivars grown in Norway (18.7%), Lr13 in Denmark (35.5%) and Lr10 in Finland (20.0%). Although 28 cultivars (33.3%) exhibited a response pattern that could not be assigned to resistance genes or combinations present in the tester lines, several pathotypes carried virulence and hence these genes or combinations are of limited use. Nine cultivars (10.7%) lacked detectable seedling resistance. One cultivar was resistant to all pathotypes used in the study.

The occurrence and distribution of seedling resistance genes and the presence of adult plant resistance to powdery mildew, was investigated in a collection of 155 Nordic bread wheat landraces and cultivars by inoculation with 11 powdery mildew isolates. Eighty-nine accessions were susceptible in the seedling stage, while 66 accessions showed some resistance. Comparisons of response patterns allowed postulation of combinations of genes Pm1a, Pm2, Pm4b, Pm5, Pm6, Pm8 and Pm9 in 21 lines. Seedling resistance was three times more frequent in spring wheat than in winter wheat. The most commonly postulated genes were Pm1a+Pm2+Pm9 in Sweden, Pm5 in Denmark and Norway, and Pm4b in Finland. Forty-five accessions were postulated to carry only unidentified genes or a combination of identified and unidentified genes that could not be resolved by the 11 isolates. Complete resistance to all 11 isolates was present in 18 cultivars. Adult plant resistance was assessed for 109 accessions after natural infection with a mixture of races. In all, 92% of the accessions developed less than 3-5% pathogen coverage while nine lines showed 10-15% infected leaf surface. The characterization of powdery mildew resistance in Nordic wheat germplasm could facilitate the combination of resistance genes in plant breeding programmes to promote durability of resistance and disease management.

The sequence-specific amplified polymorphism (S-SAP) method was used to genotype 198 Nordic bread wheat landraces and cultivars from the 19th to the 21st centuries. It was shown that theSukkula-9900-LARD retrotransposon primer was highly suitable for resolving closely related wheat materials. Cluster analysis was generally consistent with pedigree information and revealed a clear separation for growth habit but not for countries. A principal coordinates analysis (PCoA) showed a separation into different time periods (before 1910, 1910–1969 and 1970–2003). These results are consistent with the breeding history and pedigree information, indicating that little hybridization has occurred between winter and spring wheat, in contrast to frequent exchange of germplasm between the Nordic countries. Estimates of gene diversity, the PCoA results, and changes in band frequencies across time indicate that plant breeding has led to substantial genetic shifts in Nordic wheat. Diversity was reduced through selections from landraces during the early 20th century, followed by a period of relatively lower genetic diversity, and a subsequent increase and net gains in diversity from the late 1960s onwards through the use of exotic germplasm. Thus, an anticipated loss of overall genetic diversity was found to be negligible, although allele losses have occurred at specific loci.

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