Morphological changes in Nordic spring wheat (Triticum aestivum L.) landraces and cultivars released from 1892 to 1994

A descriptor list of 34 phenological and morphological characters was applied to assess the changes of diversity in 57 Nordic spring wheat (Triticum aestivum L.) cultivars released between 1892 and 1994 and to compare their diversity to 22 Nordic landraces. The field observations were conducted at the Nordic Genetic Resource Centre at Alnarp, Sweden, in 2010. Over time the cultivars became shorter, less inclined to lodging, earlier in heading and maturity. The spikes became shorter and denser with more grains per spikelet, and seed shattering of mature spikes decreased. The morphological type of Nordic spring wheat cultivars did not change after the 1960s, although improvements in disease resistances, yield and quality characters still occurred. All recent cultivars represented T. aestivum L. var. lutescens (Alef.) Mansf., characterised by awnless spikes with white glabrous glumes and red grains. Compared to the cultivars, the landraces were generally earlier in heading and maturity, much taller, inclined to lodging and they had looser spikes with less grains per spikelet than cultivars. In some characters such as glume colour and awnedness the landraces showed more diversity within and among the accessions than the cultivars and hence represented more infraspeficic taxa than the cultivars. Nordic landraces seemed adapted to low-input growing conditions. However, for the use in ecological agriculture, they would need improvements, e.g. in reducing seed shattering, lodging and enhancing disease resistances. The role of plant breeding in preserving and developing genetic diversity in Nordic spring wheat with emphasis on Sweden is discussed.