In the process of plant breeding the application of relevant breeding criteria is very important. The Path analysis is broadly applied with the aim to define yield components that mostly determine the yield and that can be used as quality breeding criteria. However, the significance of revealed relationships between yield and yield components can be affected by various factors, such as diverse genetic material that is observed, traits included into analysis, environments in which the material is observed, as well as, the applied statistic approach to determine the nature of the relationships itself. The interrelationships of yield and yield components of 15 commercial maize hybrids were observed using the Path and factor analyses. According to results of Path analysis, plant height, ear diameter and grain moisture had highly significant genetic and phenotypic direct effects on grain yield. At the same time, factor analysis points out significant effects of two factors on grain yield. Factor 1 was mostly determined by ear length and number of kernels per row, while grain moisture content, ear and cob diameter mostly determined Factor 2.

Six inbred lines were crossed according to incomplete diallel method. In this way fifteen hybrid combinations were obtained. Hybrid combinations derived from these parental components were used in this work. The objective of study was to estimate direct and indirect effects of five morphological traits on grain yield by the application of the simple coefficient correlation and path coefficient analysis. The trait number of leaves above the top ear with the value of 0.736 has the strongest direct positive effect on grain yield. Positive direct effects on grain yield were also observed for height to tassel base and plant height, while negative direct effects were observed for ear height and total number of leaves. As far as indirect effects were considered, a positive effect of the ear position height on yield over the total plant height stands out. The evaluation of the proportion of mutual effects of five observed morphological traits on grain yield, expressed by the coefficient of multiple determination (R2y12345) amounted to 0.7881.

Analysis of 60 maize populations was conducted to identify genotypes that had either low or high concentration of phytate. Genetic variability in seed phytate content was observed, with values ranging from 1,147 to 4, 13 g kg-1. Inorganic phosphorus (Pi) concentrations were between 0, 35 and 1, 29 and averaged 0, 65 g kg-1. Three groups of populations were identified as having low, intermediate and high phytate content. The low phytate concentration was measured in eight, intermediate in 25 and high in 27 populations. Positive correlation was found between phytate and protein. Population 216 had the lowest phytate concentration of 1, 14 gkg-1, and a Pi concentration 40% greater than Pi mean but lower than average protein content. This population will be used for further breeding genotypes with low phytate content and good agronomic traits.

The combined effect of cytoplasmic male sterility and xenia on maize hybrid traits is referred to as the plus-hybrid effect. Two studied ZP hybrids differently responded to this effect for grain yield. All plus-hybrid combinations of the firstly observed hybrid had a higher yield than their fertile counterparts, but not significantly, while only one combination of the second hybrid positively responded, also without statistical significance. It seems that the observed effect mostly depended on the genotype of the female component.

The contemporary trends in maize breeding are directed at identification of genotypes with improved grain quality for human consumption, industrial processing, and their incorporation into breeding programmes. In this study, three maize hybrids and three open-pollinated varieties (OPVs), differing in grain colour and type, were used to examine the differences in the total carotenoid content, the phenolic compounds profile and total antioxidant capacity (TAC). In addition, physical parameters, basic chemical composition, as well as the content of protein fractions in grain, were analysed. The multivariate approach through Principal Component Analysis (PCA) application contributed to better understanding of the complexity of the interdependence for maize grain quality parameters tested. From the aspect of different end use, better technological quality desirable for dry milling and snack food processing found in OPVs Osmak and Bosanac, as well as high content of bioactive compounds (i.e. TAC) exhibited by OPV Rumenka, make these genotypes superior compared to hybrids' varieties evaluated.

The initial idea of this study was a hypothesis that erect leaf maize inbred lines were characterized by properties of an efficient photo-model and that as such were very desirable in increasing the number of plants per area unit (plant density) in the process of contemporary selection and seed production. The application of a non-invasive bioluminescence-photosynthetic method, suitable for the efficiency estimation of the photo-model, verified the hypothesis. Obtained photosynthetic properties of observed erect leaf maize inbred lines were based on the effects and characteristics of thermal processes of delayed chlorophyll fluorescence occurring in their thylakoid membranes. The temperature dependence of the delayed chlorophyll fluorescence intensity phase transitions (critical temperatures) in the thylakoid membranes and activation energy are the principal parameters of the thermal processes. Based on obtained photosynthetic properties it is possible to select erect leaf maize inbred lines that are resistant and tolerant to high and very high temperatures, as well as, to drought. They could be good and efficient photo-models wherewith.