Significant genotype x environment interaction for quantitative traits, such is grain yield, reduces the usefulness of genotype means, over all environments, for selecting superior genotypes. AMMI model is a valuable statistical tool in identifying systemic variation contained in the interaction effect. Obtained data could be applied in maximizing yield potential in every environment based on both narrow and wide genotype adaptability, without the necessity of developing breeding programs for smaller targeted environments. Precise assortment of superior genotypes, with the assistance of AMMI model, leads to the better recommendation of newly bred hybrids, and thus increasing maize grain yield in a targeted environment. In this research genotype x environment interaction and yield stability of 36 maize hybrids of FAO 300-700 maturity group was investigating. The trial was set according to Randomized Complete Block Design (RCBD). Data were processed in order to obtain average estimates of grain yield, and yield stability was assessed by the method of AMMI analysis. The highest average grain yield was achieved in 2011 (11.62 t/ha), and the lowest in the most stressful and dry 2012 (6.90 t/ha). In the region Loznica L2 the highest average yield was noticed (13.81 t/ha), while at L7 (Sremska Mitrovica) average grain yield was the lowest (6.97 t/ha). Results of AMMI analysis gave precise recommendation for production of maize hybrids in certain environments, by determining winning areas of hybrids H20, H11 and H36. Medium early maturing and high yielding hybrids (H11 and H20) are therefore considered more favorable for production in environments with lower precipitation, while high yielding and more stable hybrids H21 and H35 are suitable for a wider range of environments. Hybrid H36 (FAO 700) showed its full potential at L2, and L3 which did not suffer from a lack of moisture. This hybrid also expressed its best potential in environments with favorable conditions.

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Genetic potential of maize hybrids grown in Serbia is 10-15 t ha-1 , while the average yields are considerably lower. There are many reasons for this. At first, it is well known that drought is present often in some parts of country. Some soils are not suitable in the same degree for intensive maize production, application of mineral fertilizers is insufficient, mechanization is outdated and arable farms are small and fragmented. During the period 19652012 high variations in precipitation were present during the maize vegetation. The yearly average precipitation sum was 688.9 mm, with 397.5 mm during vegetation. According to precipitation amount, years were divided into groups: I 200-300 mm 7, (15%); II 301-400 mm 21, (44%) and III 401-500 mm 14, (30%), and IV in 5 years (11%) more than 500 mm of precipitation was present. The highest average yield in Serbia was achieved in 1991 (5.95 t ha-1) and the lowest in 2000 (2.44 t ha-1). The average yield increase was 114 kg ha-1 per year from 1965 to 1985, and it was 22 kg ha-1 per year from 1986 to 2012. In experiments during the period 1998-2012, when the standard cropping technology (MSY) was applied, the average grain yield was10.46 t ha-1 for hybrids of FAO 300-400, 10.39 t ha-1 for hybrids from FAO 500 and 11.38 for FAO 600-700. There were no significant differences in yield between hybrids from examined FAO groups. According to this, average maize yield includes only 44.2% for FAO 300-400, 44.5% for FAO 500 and 40.6% for FAO 600700 utilized maize genetic potential. The significant improvement of maize production demand the strategic long-term program, where it will be elaborated: merging of land properties, increasing of the areas with irrigation and increasing of the technology level in maize cropping.

The breeding programme on speciality maize with specific traits was established at the Maize Research Institute, Zemun Polje, several decades ago. The initial material was collected, new methods applying to breeding of speciality maize, i.e. popping maize, sweet maize and white-seeded maize, were introduced. The aim was to enhance and improve variability of the initial material for breeding these three types of maize. Then, inbred lines of good combining abilities were developed and used as components for deriving new superior popping maize hybrids, sweet maize hybrids and white-seeded maize hybrids. Breeding was aimed at the increase of the popping volume of new inbred lines and hybrids of popping maize, then at the improvement of quality of popped kernels - flakes, and at yield increasing. Furthermore, the aim was to improve quality of sweet maize for different purposes, industrial processing and consumption as fresh food and also to improve yield and quality of white-seeded maize. As a result of such breeding, 28, 11 and 9 sweet maize, popping maize and white-seeded maize hybrids were released, respectively.

Sweet corn is mutation of field corn in which greater accumulation of sugars and water soluble polysaccharides provide specific taste and texture. It is consumed in the milky stage of the endosperm, so the product?s quality and its appearance are important as well as ear yield. That is why breeders pay the same attention to these traits in breeding process. In this paper we analyzed combining ability and mode of inheritance of ear yield and yield components in sweet corn, such as kernel-row number, and ear length, by the use of diallel crosses of six sweet corn inbred lines. ANOVA showed that estimates of general (GCA) and specific (SCA) combining abilities were highly significant (p<0.01) for all observed traits. Nonaditive gene effects were more significant in the expression of ear yield and ear length, while additive gene effects were more important for kernel-row number. Analysis of components of genetic variance was in agreement with the results of ANOVA of combining ability. The mode of inheritance of kernel-row number was partial dominance, while overdominance was of greater importance for ear yield, and ear length. Inbred line L4 was indicted as the most desirable, among the examined set of inbreds, in the further sweet corn breeding programs, due to its significant GCA effects concerning ear yield and number of kernels per ear, and ear yield performances of the hybrids in which one of the components was this inbred, according to SCA and hetrosis estimates.