The past Finnish slash-and-burn or kaski turnip (Brassica rapa) as an ignored resource for selecting of the oil turnip rape, and about the mutants of the kaski turnip

In 1845, the wild turnip (Brassica rapa ssp. campestris) was presented as the worst weed species in barley fields in Finland in a text-book for the Mustiala Institute written by S. Gripenberg. Since then, the growing of turnip (B. rapa) in fire lands, i.e. kaski and kytö, declined, and wild turnip became rare. The now extinct wild turnip formed a genetic continuum together with the cultured form. Wood as charcoal was dated with 95.4% probability 24 ... 226 AD with radiocarbon in the studied Saarela Site (Kouvola, SE Finland) where and when growing of turnip was shown to have occurred. The Saarela Site has a megalith gnomon which could be used to determine the summer solstice, which defines the sowing time of turnip. An oven between boulders covered with a megalith had been used to bake turnips in the Saarela Site, which has depressions of ancient turnip pits, and altogether 129 ancient turnip pits occur within 1-km radius around. The indicator of using fire, Geranium bohemicum appeared in the Saarela Site after two soil digging events, and in a nearby site, after prescribed forest land burning. Historical remarks and remains of past pantio towers in the village are shown. The pantios were used to make souerkraut for food and feed from heat treated turnip tops and other vegetables. My crosses within the kaski turnip landrace ‘Liperi’ resulted in the segregation of spring habit, which could also have a hypocotyl-tuber. Mutations from slender base to the hypocotyl-tuber are not rare and demonstrate a single-step evolution of the kaski turnip from the wild turnip. Liperi also segregated a novel stem mutant, named varsinauris, ‘stem-turnip’. This recessive mutant has a 2 á 3 cm thick and 0.5–1.3 m high stem as its storage tissue. Back-mutation from spring habit to winter habit was observed. The ‘Enon kanta’ landrace of kaski turnip was very variable. A single turnip plant wintered in my cocultivation trial of winter rye sown on the first of July as juuriruis (‘root-rye’) together with Enon kanta turnip as the first-season crop. The base of the wintered turnip was slender, representing a spontaneous segregant of the turnip rape type. Enon kanta produced i.a. riplikas segregants with red-and-whitish variegating cortex of the hypocotyl-tuber. To produce a true-breeding, homozygous riplikas variegating strain failed; a low, non-Mendelian proportion of plants with all-whitish cortex repeatedly occurred in progenies from crossing or self-pollinating. This suggests that the riplikas variegation is caused by an unstable gene. The weedy turnip was not exploited to develop an adapted seed oil crop. On the contrary, learned people warned of spontaneous outcrossing of flowering Brassica seed stocks with weedy turnip causing harmful progenies. Since 1757 until 1945, the few trials done in Finland with imported oil seed B. rapa strains resulted in failure due to lack of wintering, lateness when sown in the spring, and damage by insects in the small trials.