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The objective of this study was to evaluate the yield and yield components of wheat cultivars, and compare the productivity obtained in the field and estimated with Jensen model, at different sowing dates, in Cascavel and Palotina cities, Parana state, Brazil. The experiments were carried out in the field at the COODETEC Research Center, located in Cascavel and Palotina. The experiment was conducted in a randomized blocks design in a 7 × 3 factorial, with plots consisting of six lines spaced at 5 × 0.17 meters, with seven wheat cultivars and three sowing dates, with three repetitions. The pluvial precipitation higher than crop evapotranspiration in all cultivation cycles analyzed did not prevent water deficiencies, which occurred predominantly in the heading and physiological maturation stages. The smallest water deficiencies in Cascavel (31.2 mm; April 22) and Palotina (7.2 mm; March 31), from sowing to heading, reduced grain yield by 41.7% and 42.8%, respectively, in relation to the higher productivity of each location. Small differences in yield components (NEM, NGE and MMG) provide differences in grain yield between the cultivars tested. The sowing carried out at the end of April and in May tended to have a higher yield. The best performances with Jensen model to estimate wheat grains yield were obtained for CD 1440 and QUARTZO cultivars. The Jensen model overestimated the grain yield of the CD 108, CD 1104, CD 150 and CD 154 cultivars, since the model do not consider losses due to excessive rainfall and/or pests and diseases.

The wheat Triticum aestivum L. is one of the most important foods in the human diet due to its high nutritional value. The grains can be eaten as bread, noodles, pasta, cookies, among others. The cultivation of wheat in Brazil has high production potential; the southern is region responsible for the largest acreage in the country, due to its soil and climate more favorable for crop development. The objective of this study was to determine the growing degree-days sum and the relationship between the period length from sowing to physiological maturity and sowing dates of thirteen wheat cultivars. The data on wheat crop correspond to the harvests of 2007 to 2011. The treatments consisted of 13 wheat cultivars and 3 sowing dates. The data used for the analysis were: Total elapsed days from sowing to silking, to physiological maturity, and of the silking to physiological maturity, along with the growing degree-days sum for these periods, beyond grains yield and hectoliter weight. The results indicate that the average length of sowing to the silking was 71 days. For the period from silking to physiological maturity the average length was 54 days. The increase in length of time from sowing to the silking in cultivars sown in May 25 th was due to the decrease in air temperature. The average of growing degreedays sum between the period from sowing to physiological maturity was 1487. The cultivars that stood out presenting a shorter period of silking to physiological maturity and high productivity were the cultivars CD 114, CD 120, CD 121, CD 122, CD 124 and Onix.

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