Genetic resources in Finnish landrace rye (Secale cereale) and experimental evolving of its spring-habit from winter rye
Rye was the most important grain crop in Finland towards the end of the 19th century. Rye was largely grown in burned lands, kaski (slash-and-burn) and kytö, in the past. In the primary form of kytö, shoveled topsoil was heated on fires slowly combusting extraneous wood, brushwood or reed, or in the secondary form, a dry upper layer of organic topsoil of field was burned in a prescribed frontal mode in situ. The kytö selected against the brittle spike type, largely eliminating the weedy seed banks in the soil. Likewise, seed handling, especially the common cleaning with a pohdin -device further eliminated partially brittle spike types and selected against weedy rye. Rye was a cash-crop for the peasants in the past and was mainly attempted to be exported as seed. The commonly used smoky riihi-drying sanitized and conserved grains, which retained germinabilty, and in part increased demand for seed abroad. The grains produced on burned lands were fortified with minerals, including the minor elements, and good winter-hardiness occurred in the Finnish rye. The immigrant Finns were probably the first since 1638 to grow rye from seeds brought along with them to New Sweden in North America, where de-domesticated or feral rye became a weed problem in the 1950s. Some genetically variable landraces could be sown during different times of the year, thanks to segregate plants adapted to different sowing-times. Sowing of a winter rye landrace in May, the season of spring grain sowing, enabled selection of spring-habit mutants or segregants, which could be used to establish a true-breeding spring stock of rye shown experimentally. In the past, mid-summer sowing could occur with co-cultivation, e.g. with the traditional slash-and-burn turnip as the first season crop, or the autumn seedling of rye could be used as pasture. The Finnish rye populations frequently had cytoplasmic male sterility (CMS) and nuclear restorer genes of anther fertility effective in the CMS. A non-leaky CMS and a leaky CMS (with male fertility in the late stems) are shown. Homozygosity obtained through forced self-pollination in a Finnish rye revealed unnoticed genes, such as dwarfs. A local rye population originating from Putkosjärvi area (64° 27’ N), in Ristijärvi Municipality, evidently devoid of the frequently contaminating weed, rye brome (Bromus secalinus), is thought to present an uncontaminated, ancient Finnish rye. The rye brome has contaminated growth in Finland at least since the Iron Age. Morphological variants, like brown spike or glume color and awnlessness were detected in the landrace. Two of 18 Finnish landraces were found to carry accessory or B chromosomes in a study in 1964. B chromosomes are known to interfere with the expression of some genes, perhaps also ensuring variation in the vernalisation needs of the plants.