This study aimed to quantify the changes in grain yield and main agronomic traits in winter wheat cultivars registered during the past 90 years . A field trial with 18 winter wheat cultivars registered from 1930 to 2016 was conducted at the experimental field Rimiski šančevi during two growing seasons . The following agronomic traits were measured: grain yield, stem height, spike length, heading date, hectolitre mass, 1000 grain weight, and grain number per unit area . The results of this study showed that there was a significant genotypic effect on the studied traits . Du-ring the past 90 years, grain yield increased at rate of 50 kg ha -1 per year of cultivar release . Grain yield improvement was followed by stem height decrease (0 .4 cm per year of cultivar release) and earlier heading date in modern cultivars, which were 7 -8 days earlier than the older ones . Modern wheat cultivars were characterized by a higher grain number per unit area than the ol-der ones while during the past 90 years, the 1000 grain weight was not significantly related to the year of cultivar release . Further grain yield improvement should be related to a further increase of grain number per unit area while maintaining a higher 1000 grain weight.

During the creation of new wheat cultivars (Triticum aestivum L.), in addition to high yield potential and good technological quality, it is necessary to incorporate genes responsible for resistance to lodging, low temperatures and adaptability to different production conditions. NS Lenija, a new winter wheat cultivar developed at the Institute of Field and Vegetable Crops (National Institute of the Republic of Serbia) was created by crossing the three divergent parents: cultivar Kupava (Russia) and the cultivars Donna (Serbia) and Aria (Serbia). By crossing these parents, genes responsible for high yield potential, good technological quality, adaptability and stability were successfully combined, enabling this cultivar to be successfully cultivated in the agroecological conditions of Southeast Europe. During the two-year trials of the Commission for the registration of varieties, NS Lenija successfully passed the DUS test (distinctness, uniformity and stability), and on the 7 tested locations achieved a significantly higher average grain yield compared to the grain yield of the check cultivars. When evaluating its chemical and technological properties, it was classified in quality class II, farinograph quality group A-2, and in the technological group of improvers.

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Magnitude and type of gene actions in a specific population are the main criteria for the parents' selection that will develop the best recombinants after hybridization. Information about the genetic control of complex traits is useful for the further development of efficient breeding programs. In order to identify action of genes for grain yield plant-1 and its correlation with main yield components, incomplete diallel crossing was applied. The field trial was conducted at the experimental field of the Agricultural Advisory Service in southeastern Europe, during season 2012-2013. Mean values of F1 generation showed that crosses Apache × Prima had the highest value of grain yield plant-1 and Jackson × Balkan had the lowest. Common type of inheritance for grain yield plant-1 was over dominance. The ANOVA revealed that this trait was controlled by additive and non-additive effects. The best general combiner for grain yield plant-1 was Apache, and two crosses (Dragana × Jackson; Balaton × Nevesinjka) showed significant SCA effects. Components of genetic variance showed that dominant was more important than additive component, and the total number of dominant genes were in excess over the number of recessive genes in all parents. Furthermore, moderately low value of narrow sense heritability (h2=31.96%) was observed for grain yield plant-1 . Parent Sana contained maximum dominant genes, whereas parent Jackson had maximum recessive genes. Grain yield plant-1 was significantly correlated with tillers numbers plant-1 at genotypic level (rg=0.494). The results from this study might be helpful for creating new wheat cultivars with highyielding potential.

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