Changes in requirements on vernalization of winter wheat varieties in the Czech Republic in 1950-2000

The need for vernalization of winter wheat varieties cultivated in the CzechRepublic in 2000 was studied in comparison with the need for vernalization in the past decades since 1950. In 2000, many foreign varieties were cultivated in the Czech Republic, mostly West European. Varieties with a vernalization of 40-50 days and 50-60 days show the highest representation in the assortment (47.3% and 31.6%, resp.). The share of varieties with a long vernalization over 60 days is 15.8%. In around 1990, when varieties of domestic breeding were mostly grown, there were, next to the largest group with a vernalization of 40-50 days, 21.7% of varieties with a vernalization of 30-40 days and the same amount with a vernalization of 50-60 days. During the last ten years, the share of varieties with a longer vernalization has risen, not only due to foreign varieties, but also due to new domestic varieties. It is apparent from a 50-year overview that what has predominated are varieties with a vernalization of 40-50 or 40-60 days, which is a range usual for winter varieties of wheat in Middle and West Europe. After 1950, a departure from original domestic varieties appeared; those were represented by original alternative varieties (in Czech přesívky, in German Wechselweizen, in Russian dvuručki) and half-winter varieties with a shorter vernalization, strictly speaking with a vernalization fixed to a short day, and a strong photoperiodic reaction. Representation of varieties as related to their length of vernalization has changed in the course of the decades following utilization of foreign varieties; this was affected above all by varieties from Russia (the former USSR), Germany, but also Yugoslavia. Varieties from these countries were utilized also as parent components in domestic breeding.