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The synthetic maize population 316PO2 was subjected to genetic correlation analyses between grain yield, yield components and morphological traits. The purpose was to enable estimates to be made of the advantage of using selection indices compared with selection based on grain yield only, and if that advantage was present, to choose enough simple selection indices for practical use. Selection indices were constructed out of four traits highly significantly correlated with grain yield, in addition to yield itself.Grain yield exhibited a highly significant additive genetic correlation with ear diameter (r a =0.588**), kernels row -1 (r a =0.643**), ears plant -1 (r a =0.871**) and ear height (r a =0.427**). The most efficient index was Index No. 14 (R.E.I 12345 = 108.83%), which included all four traits and grain yield. Index No. 3, one of the simplest forms of index, including only ears plant -1 and grain yield, showed slightly less relative efficiency (R.E.I 35 =107.24%) than Index No. 14. Using this simple form of index with two characters (Index No. 3) could improve the efficiency of selection for grain yield. The estimated advantage from its use is 179.6 kg/selection cycle for grain yield over selection based only on grain yield.

One of the objectives of this paper was to determine relationship between grain yield and yield components, in S1 and HS progenies of one early synthetic maize population. Grain yield was in high significant, medium strong and strong association with all studied yield components, in both populations. The strongest correlation was recorded between grain yield and 1000-kernel weight (S1 progenies rg = 0.684; HS progenies rg = 0.633). Between other studied traits, the highest values of genotypic coefficient of correlations were found between 1000-kernel weight and kernel depth in S1 population, and 1000-kernel weight and ear length in HS population. Also, objective of this research was founding the direct and indirect effects of yield components on grain yield. Desirable, high significant influence on grain yield, in path coefficient analysis, was found for 1000-kernel weight and kernel row number, and in S1 and HS progenies, and for ear length in population of S1 progenies. Kernel depth has undesirable direct effect on grain yield, in both populations

Studies on genetic gains in grain yield and other traits may be very useful in providing necessary information to plant breeders about the effectiveness of their breeding programs. The objective of this research was to analyze changes in grain yield, yield stability and morphological characteristics of maize hybrids released in Serbia between 1978 and 2011. Five hybrids, representatives of different breeding periods, were chosen for this study. Field trials were conducted during 2013 and 2014 at three locations in Serbia. The estimated genetic gain per breeding period was 440 kg ha -1 which corresponds to an approximate annual linear increase in yield of 63 kg ha -1 . Changes in morphological characteristics were presented graphically, compared to the reference value and defined by the third period of breeding. Plant and ear height, kernel row number, number of kernels per row and leaf number were reduced compared to the third breeding period. Kernel depth showed higher variation through periods while in other analyzed traits, major changes in value through the periods were not found. Stability analysis distinguished the hybrids from the sixth and seventh period of breeding as the most stable, whereas the most unstable were representatives of the fifth and third period. Changes in certain morphological traits and yield stability have led to an increase in the genetic potential of the hybrids most probably through the increased tolerance to biotic and abiotic stress factors.

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Genetic variation for stay green character has been exploited in maize improvement mainly in the light of selecting high yielding rather then typical stay green genotypes. Stay green is an indicator of good plant health later in the season, reduced progressive senescence, tolerance to post-flowering drought and stalk lodging, what ensure superiority of stay green genotypes in comparison to non-stay green ones, especially in drought conditions. The objective of the study was to examine relationship of stay green trait with some vegetative characters in two genetically broad based maize populations. The most consistent correlations with stay green were established for leaf and stalk water content, which has been confirmed by path-coefficient analysis