S70 Many modern cultivars, in wheat and in other crops as well, are often genetically similar, with a rather narrow genetic base. Therefore, in breeding we need to also utilize sources of new diversity. Landraces, which have arisen through a combination of natural selection and the selection performed by farmers (Belay et al. 1995), usually have a broader genetic base and can therefore provide valuable characteristics important for breeding (Keller et al. 1991; Tesemma et al. 1998). Tolerance to lo- cal stresses (Li et al. 1997) and the resulting good yield stability are also often referred to in landraces (Tesemma et al. 1998). Landraces and obsolete cultivars can be considered as a valuable portion of the gene pool (Vojdani & Meybodi 1993; Zou & Yang 1995), because they represent the broad intra-specific genetic diversity of crops, from which new cultivars have arisen. Due to those valuable characteristics, the direct practical utilization of some landraces by farmers is also discussed (Brush & Meng 1998). Protein content and some other grain quality traits of wheat belong to the features in which landraces usually provide a much broader diversity than do current cultivars. Keller et al. (1991), Wang and Guo (1992), Rodriguez-Quijano et al. (1994), and Yang and Liang (1995) refer to the high protein content in some landraces of common wheat (Triti- cum aestivum L.). In our previous experiments, the selected landraces not only showed a high protein content, but also desirable values of some other quality characteristics (Michalová & Dotlačil 1992). MATERIALS AND METHODS Two sets of winter wheat landraces and obsolete cultivars (122 accessions in Set I and 101 in Set II, How Can Wheat Landraces Contribute to Present Breeding? L. DOTLAčIL, J. HERMUTH, Z. STEHNO, V. DVOřáčEK, J. BRADOVá and L. LEIšOVá Crop Research Institute, 161 06 Prague-Ruzyně, Czech Republic, e-mail: dotlacil@vurv.cz Abstract: Two sets of winter wheat landraces and obsolete cultivars were studied in three-year field experiments, and compared with 3 modern control cultivars. The higher spike productivity in modern cultivars could mainly be attributed to an increased number of grains in a spikelet and harvest index (HI), whereas thousand grain weight (TGW) has only a slight effect. Landraces and old cultivars proved to have a higher content of crude protein. Spike productivity characteristics, except for TGW, showed a negative correlation with the crude protein content in the grain. The number of kernels in a spikelet strongly affected the spike’s productivity, whereas the TGW has only half the effect. The mean yield of four modern cultivars was 51% higher than the mean yield of 31 landraces and obsolete cultivars. Regression analysis proved the much stronger response of modern cultivars to environment ( b = 1.63), then was the response of old cultivars ( b = 0.87). Different responses to environ- ments were found within the set of 31 landraces, as well. We could also identify potentially valuable donors of earliness and winter hardiness among the old cultivars. High crude protein content (up to 18%), and other valuable quality characteristics, were rather frequent. In both sets, HMW Glu-subunits were described, and we have additionally studied 67 selected lines. Among them, 10 lines showed the crude protein content of 17.5% to 18.3% (where the gluten index and Zeleny test varied from 28.5 to 54.0 and 36.8 to 61.7, respectively). High values of all quality characteristics showed lines gained from the cultivars Mindeszentpusztai (HUN), Szekacz 19 (HUN), Bartweizen linie a (AUT), Viglašská červenoklasá (CZE), as well as some others. Keywords: donors of traits; genetic diversity; grain quality; landraces; stress tolerance; yield stability Czech J. Genet. Plant Breed., 46, 2010 (Special Issue): S70–S74