Maize is affected by drought and heat, abiotic stress factors that have been encountered more often in recent years in various parts of Europe. In the area of Turda, Romania, extreme temperatures and heat waves combined with an uneven distribution of precipitation have been recorded that had an unfavorable influence on the maize crop. In this study, the ASI (anthesis-to-silking interval), yield, and stability of 35 old and new maize hybrids created at the Agricultural Research and Development Station Turda were studied under drought and heat conditions. An increase in temperature was observed during vegetative growth and grain filling, and rainfall was deficient during and after flowering. These conditions had a negative influence on ASI, grain filling, and, indirectly, yield, which varied significantly during the seven experimental years. The five newest hybrids (Turda335, Turda2020, Turda380, Sur18/399, and HST148) stood out, with average yields of over 8400 kg ha⁻¹ in unfavorable years and over 15–16,000 kg ha⁻¹ under favorable conditions. They generally outperformed the mean by 29–33%. In contrast, the old hybrids achieved yields up to 22% lower than the experimental mean. Yield was 43.1% lower in 2022 and 31.8% lower in 2023 compared to the best year (2021).

Carotenoids are important biologically active compounds in the human diet due to their role in maintaining a proper health status. Maize (Zea mays L.) is one of the main crops worldwide, in terms of production quantity, yield and harvested area, as it is also an important source of carotenoids in human nutrition worldwide. Increasing the carotenoid content of maize grains is one of the major targets of the research into maize breeding; in this context, the aim of this study was to establish the influence of some fertile cytoplasm on the carotenoid content in inbred lines and hybrids. Twenty-five isonuclear lines and 100 hybrids were studied for the genetic determinism involved in the transmission of four target carotenoids: lutein, zeaxanthin, β-cryptoxanthin and β-carotene. The analysis of carotenoids was carried out using high performance liquid chromatography using a Flexar system with UV-VIS detection. The obtained data revealed that the cytoplasms did not have a significant influence on the carotenoid content of the inbred lines; larger differences were attributed to the cytoplasm × nucleus interaction. For hybrids, the cytoplasmic nuclear interactions have a significant influence on the content of lutein, zeaxanthin and β-cryptoxanthin. For the cytoplasm × nucleus × tester interactions, significant differences were identified for all traits.

Maize is one of the most important crops, both worldwide and in Romania, and preserving the diversity of the biological material used in the breeding of this plant is of particular importance. The Agricultural Research and Development Station (ARDS) Turda, Romania, inbred lines collection includes both its own genotypes and some obtained as a result of germplasm exchanges with other institutions in the country or abroad. In the present study, 575 lines created at Turda were analysed regarding some traits of the plant (plant height, ear height, total number of leaves, number of tassel branches) and the ear (ear length and weight, number of kernel rows and number of kernels/row). The biological material used in this study shows a great diversity: a medium or high variability coefficient was identified for several of the traits analysed (number of tassel branches, ear height, ear height). Frequency histograms were made for the studied lines, for plant and ear traits. A great variability also was observed in the colours of the anther and silk, but also for kernel type and colour and cob colour.

Maize, one of the most cultivated crops worldwide, has multiple uses, one of which is human food. Maize flour intended for human consumption is preferably produced from var. indurata. This maize variety, although it has some desirable traits, generally has a lower yield capacity. In order to obtain high-yielding hybrids that would have some traits necessary to obtain flour for human consumption, fourteen lines with dent or semi-dent grains were crossed with four inbred lines with flint grain in a cyclic system. The 56 resulting hybrids were tested in two experimental years for yield, the percentage of unlodged plants, grain dry matter at harvest, as well as other traits, such as ASI (anthesis-to-silking interval), the interval from sowing to the appearance of stigmas and to physiological maturity, and plant senescence. The maternal lines A478 and A480 were noted for transmitting higher yields. Three hybrids were identified with higher yields, good silking–flowering coincidence, stay-green, and a high unlodged plants percentage: A478 × D328, A480 × B330, and A480 × D328.

Climate change effects on maize performance have been already detectable during the last twenty years in many parts of the world. This study aims to assess the relationship between climatic factors and maize yield, grain moisture at harvest and resistance of plants to broken and stalk lodging, with reference to maize hybrids created at the Agricultural Research and Development Station Turda (ARDS), in the centre area of Romania. The purpose of this study was to detect trends in the yield ability of 35 maize hybrids (18 historical and 17 recently released) and the possible association with weather trends. A significant increase in temperature both during vegetative growth and grain filling was observed, while rainfall presented a decrease in the critical period of flowering and grain-filling, during the last two decades (2000-2020), with large year to year variations. During the analyzed period, yields of the historical hybrids showed a reduction trend from -72 kg/ha/year for FAO groups 210-300, to -272 kg/ha/year for FAO groups over 300. The average yield of recently released hybrids showed an increasing trend from +91 kg/ha/year for FAO 300-hybrids, to +215 kg/ha/year for FAO groups 210-300. This suggests that genetic progress reflected in the release of new maize hybrids was able to counteract the negative effect of climate change seen on the yield of the historical hybrids. The yield difference between recently released hybrids and the historical ones showed the rate of genetic progress of +171 kg/ha/year for very early hybrids, +116 kg/ha/year for early hybrids, and +275 kg/ha/year for semi-early hybrids.

Knowledge of relatedness among maize elite breeding genotypes is useful in planning crosses for hybrid and inbred line improvement and assigning them into heterotic groups. This study investigated phenotypic and genetic similarities or diversities between 7 flint inbred lines (of common origin) adapted to the early maize growing regions created at ARDS Turda-Romania. They were studied for per se traits and in two crossing systems: a diallel crossing system, resulting in 21 hybrids and a cyclic system using four testers, thus resulting in 28 maize hybrids. Both parental inbred lines and hybrids were evaluated for several traits over three years. The level of relatedness/diversity was determined by various methods, grouped into: phenotypic methods and genetic methods. Similarities were identified between certain lines and a degree of differentiation between others. The analysis of the hybrid combinations from the diallel crossings between the seven sister lines highlighted the TD236 inbred line as the only one that differs genetically from the other. Following the analysis of the data obtained in the cyclic system, some inbred lines can be sources of favorable traits: TD236 and TD233 for yield, ear weight, grain/ear weight; TD233 and TD234 for the number of kernels/row, TD237 for plant breaking resistance.