ABSTRACT Quality protein maize (QPM) (Zea mays L.) is primarily used for food in countries of tropical and sub-tropical regions where maize is the main source of protein. Although its cultivation in temperate regions is hampered by residues of exotic germplasm, it could be beneficial for use in livestock feeds as it was shown that substitution of standard maize with QPM can improve livestock characteristics and decrease dietary lysine supplementation. The aim of this study was to test 11 QPM hybrids obtained by crossing adapted QPM inbred lines for their performance in field trials in 2 yr at four locations, as well as to determine their relevant biochemical components. The main reason for rejecting nine QPM hybrids was low grain yield, standard hybrids had higher yields on average for 37.8%. Hybrid ZPQPM6 had good agronomic characteristics, but its biochemical components were nonsignificantly different from the standard hybrid. Only hybrid ZPQPM13 met necessary criteria, grain yield comparable with standard hybrids, high tryptophan content in different environments (average 0.083%) and hard endosperm (average score 1.87). Lysine content, measured after mercantile production, was 0.44%. Quality index, although below the QPM threshold (which is 0.80%) was significantly higher (p < 0.05) in ZPQPM13 in comparison with standard hybrid, indicating improved nutritional quality of the protein. The results indicated that presence of exotic germplasm in these QPM hybrids is a consequential difficulty and that in their parental inbred lines at least one more backcross with temperate germplasm should be done to select better adapted QPM.

ABSTRACT A pilot experiment was undertaken in order to examine high oil populations of maize (Zea mays L.) to be used as pollinators in TopCross blends with commercial ZP341 standard hybrid. Five high oil populations (HOPs) from the Maize Research Institute (MRI) gene bank were chosen for this research, according to their high grain oil content, synchrony between silking of ZP341 and anthesis of the populations and good agronomic performances in 2012. Selfing of ZP341 and HOPs, as well as crosses of ZP341 cmsS sterile × HOPs were carried out in 2013. Oil content, fatty acid composition, protein and tryptophan content, and physical characteristics of the obtained kernels were measured. Four HOPs showed significant positive influence on the oil content in the TopCrosses (TC), 16.85 g kg−1 on average. Oleic acid, which is the principal monounsaturated fatty acid, was significantly lower in all HOPs and all TCs, while selfed ZP341 had almost twice the average value typical for standard maize. However, this decrease in TCs was in a narrow range from 1 % (in TC-3) to 5 % (in TC-4) and the oleic content of TCs was on average higher by 60 % compared to the typical standard maize. Different favorable and unfavorable significant changes were detected in fatty acid compositions, protein and tryptophan contents and physical kernel properties for each potential TC combination. Results indicate differences in gene effects present in different TC combinations and underscore the need to examine each potential TC blend by conducting similar simple experiments.

Plus-hybrid effect refere to a combined effect of cytoplasmic male sterility (CMS) and xenia in maize (Zea mays L.) It could be used in commercial production by growing a mixture of 80% CMS hybrid and 20% of another fertile hybrid. The aim of this research was to examine individual and combined CMS and xenia effects on two hybrids widely grown in Serbia. Sterile and fertile versions of ZP 1 and ZP 2 hybrids (three-way; Iodent x Lancaster dents) were used as females, while ZP 1, ZP 2, ZP 3, ZP 4, and ZP 5 (three-way or single cross; Iodent (BSSS) x Lancaster dents) were used as pollinators. All of them belong to medium maturity group. The trial was set up at one location in Serbia (Zemun Polje) in 2009, 2010, and 2011. Molecular analysis of the five genotypes was done using simple sequence repeat (SSR) primers. Plus-hybrid effect on grain yield ranged from -6.2% to 6.2%; on thousand kernel weight from -1.7% to 5.2%; on number of kernels per area from -1.0% to 8.0%. The poor response could be due to a use of three-way instead of single cross hybrids in S type of sterility. Modified Rogers’ distance between hybrids was in the range 0.211 to 0.378 and was not relevant for the effect, which depended mostly on the sterile hybrid genotype and the fertile hybrid pollinator ability. This approach should be more suitable for female hybrids with slightly poorer performance, already being produced on a sterile base.

Maize (Zea mays L.) landraces are an important source of genes for improving commercial germplasm. Today, drought tolerance and grain quality are major challenges in maize cultivation due to climatic changes and population growth. The Maize Research Institute genebank has a drought tolerant collection, which includes 13 landraces (from the former Yugoslavia) and 12 introduced populations (from different countries). These accessions were analyzed for protein, oil, starch and tryptophan contents, in order to identify drought tolerant accessions with high grain quality. Also, simple sequence repeat (SSR) analysis with specific primers for opaque2 recessive allele (o2) was carried out. All analyzed accessions showed high levels of protein. Oil content ranged from 3.75 % to 5.40 % and starch content from 67.5 % to 71.30 %. Average protein content was not different (p < 0.01) between landraces and introduced populations. Starch and oil contents were higher in introduced populations at 0.84 % and 0.39 %, respectively (p < 0.01). Twenty-three accessions had high levels of tryptophan content. A high percentage of kernel type 1 and 2 indicated the presence of endosperm hardness modifier genes. Recessive o2 allele was found in most of the accessions. Absence of o2 in some high tryptophan accessions indicated action of another mutation. In two high tryptophan accessions an unknown band was detected. Absence of negative correlations between proteins, tryptophan and oil makes certain accessions suitable for use in the simultaneous improvement of target genotypes for these traits. Identified drought tolerant, high quality accessions can be used in breeding programs aimed at nutritional improvement of maize grown under drought conditions.