Combining experimental studies on grain yield variability with crop model simulations in maize could assist in choosing the optimum maturity group for a certain location, counteracting the effect of climate change. However, studies considering specificities in Southeast Europe are lacking. The objectives were to put various environmental covariates including stress degree days (SDD) into FAO maturity settings to determine the impact of climate change on maize growing in Southeast Europe and to compare trends for grain yields over twenty years of maize experimental and simulation data grouped in five FAO maturity groups (FAO 200–FAO 600). Pre-registration yield trials of maize planted in one location in Croatia grown from 1996 to 2015 were used to determine “potential yield”. Correlation coefficients between 12 climate covariates and grain yield (GY) across the maturity groups revealed the tightest negative associations between SDD and GY that were weakened by later-maturity groups. Similar trends in GY were obtained by both experimental and simulation data, highlighting FAO 600 as a nearly no yield-reducing FAO group over the two decades. Our results indicate that choosing early maize hybrids in Southeast Europe does not seem to be an optimum option in the future, since these hybrids are more sensitive to omnipresent heat stress than late hybrids.

The evolutionary history of crop pathogens is shaped by a complex interaction of natural and anthropogenic factors. The fungus Colletotrichum graminicola causes maize anthracnose which results in significant yield losses worldwide. We conducted a comprehensive investigation into the evolutionary genomics of C. graminicola using a collection of 212 isolates from 17 countries across five continents. Genomic analyses supported the existence of three geographically isolated genetic lineages, with a significant pattern of isolation by distance. We identified two distinct gene flow patterns, driven by short- and long-distance dispersal, likely resulting from the natural spread of the pathogen and the exchange of contaminated seeds. We present evidence of genetic introgression between lineages, suggesting a long history of recombination. We identified significant recombination events coalescing at distinct points in time, with the North American lineage displaying evidence of the most ancient recombination. Demographic modelling has indicated that North America is an intermediate between Brazil, Europe and an ancestral, unsampled source population, which is hypothesised to be Mesoamerican. Our analyses revealed that the global genomic structure of C. graminicola is shaped by geographic differentiation driven by long-distance migration and a long history of recombination and introgression. We show historical relationships amongst these lineages, identifying a potential route for fungal spread, with the North American population emerging ancestrally, followed sequentially by the Brazilian and European populations. Our research indicates that the European lineage is more virulent, which has implications for the potential emergence of new outbreaks of maize anthracnose in Europe.

Carotenoids are an abundant group of lipid-soluble antioxidants in maize kernels. Maize is a key target crop for carotenoid biofortification focused on using conventional plant breeding in native germplasm of temperate areas traced back partially to traditional cultivars (landraces). In this study, the objectives were to determine the variability of lutein (LUT), zeaxanthin (ZEA), α-cryptoxanthin (αCX), β-cryptoxanthin (βCX), α-carotene (αC), and β-carotene (βC) contents in the grain of 88 accessions of temperate maize from the Croatian genebank, and to evaluate the relationships among the contents of different carotenoids as well as the relationships between kernel color and hardness and carotenoid content. Highly significant variability among the 88 accessions was detected for all carotenoids. On average, the most abundant carotenoid was LUT with 13.2 μg g⁻¹ followed by ZEA with 6.8 μg g⁻¹ dry matter. A Principal Component Analysis revealed a clear distinction between α- (LUT, αCX, and αC) and β-branch (ZEA; βCX, and βC) carotenoids. β-branch carotenoids were positively correlated with kernel color, and weakly positively associated with kernel hardness. Our results suggest that some genebank accessions with a certain percentage of native germplasm may be a good source of carotenoid biofortification in Southeast Europe. However, due to the lack of association between LUT and ZEA, the breeding process could be cumbersome.

Two cycles of simultaneous selection for stalk rot resistance and grain yield have been conducted in the FAOSYNFR1B population synthesized from Eastern European maize germplasm. The objectives of this study were: 1) to compare expected genetic gain from S 1 and HSI methods of selection in the second cycle and 2) to evaluate improvement (gain) of stalk rot resistance and grain yield in the population per se associated with two cycles of selection. In the first cycle of selection, S 1 method and HSI method (using an inbred tester) were combined (S 1 -HSI) to produce C1 population. In the second cycle of selection the S 1 and HSI methods were applied separately to produce C2(S 1 ) and C2(HSI) populations, respectively. In 1996, the C0, C1, C2(S 1 ), and C2(HSI) populations per se were evaluated at four locations in natural conditions and at one under artificial stalk infection. Combined S 1 -HSI method was successful in improving both stalk rot resistance and grain yield. In the second cycle, further improvement for stalk rot resistance was observed with a more favorable response for S 1 method. Neither S 1 nor HSI method, applied separately in the second cycle, were successful in improving grain yield. Therefore, combining of S 1 and HSI methods of recurrent selection seems to be more effective way in simultaneous improvement of stalk rot resistance and grain yield in maize

Background/Objectives: A critical part of the maize life cycle takes place during the summer, and due to climate change, its growth and development are increasingly exposed to the irregular and unpredictable effects of drought stress. Developing and using new cultivars with increased drought tolerance for farmers is the easiest and cheapest solution. One of the concepts to screen for drought tolerance is to expose germplasm to various growth scenarios (environments), expecting that random drought will occur in some of them. Methods: In the present study, thirty-two maize hybrids belonging to four FAO maturity groups were tested for grain yield at six locations over two consecutive years. In parallel, data of the basic meteorological elements such as air temperature, relative humidity and precipitation were collected and used to compute two indices, scPDSI (Self-calibrating Palmer Drought Severity Index) and VPD (Vapor Pressure Deficit), that were assessed as indicators of drought (water deficit) severity during the vegetation period. Practical implementation of these indices was carried out indirectly by first analyzing yield data using a factor analytic model to detect latent environmental variables affecting yield and then correlating those latent variables with drought indices. Results: The first latent variable, which explained 47.97% of the total variability, was correlated with VPD (r = −0.58); the second latent variable explained 9.57% of the total variability and was correlated with scPDSI (r = −0.74). Furthermore, latent regression coefficients (i.e., genotypic sensitivities to latent environmental variables) were correlated with genotypic drought tolerance. Conclusions: This could be considered an indication that there were two different acting mechanisms in which drought affected yield.

Maize is considered a promising candidate for biofortification through breeding, given its widespread cultivation and significance as a food crop. This cost-effective and sustainable approach could be used to increase the content of different tocol compounds, i.e., vitamin E, in maize grain due to the well-documented genetic variability. In the present study, an evaluation of the content of nine different tocol traits was performed in a genebank collection of 88 inbred lines of temperate maize grown at two locations in Croatia in 2019. A large genotypic variability within the studied material was observed for α-tocopherol, γ-tocopherol, δ-tocopherol, total tocopherols, α-/γ-tocopherol ratio, α-tocotrienol, γ-tocotrienol, total tocotrienols and total tocols with corresponding coefficients of variation of 52, 61, 51, 45, 106, 24, 54, 33 and 38%, respectively. Heritability estimates ranged from 0.66 for α-tocotrienol to 0.95 for γ-tocopherol. The content of α-tocopherol, which has the highest vitamin E activity and is therefore most interesting for selection, was not significantly correlated with either grain color or grain type. Comparison of the effects of simulated selection with an intensity of 20% on increased α-tocopherol content using the two selection criteria, absolute α-tocopherol content and α-/γ-tocopherol ratio, showed that the highest absolute α-tocopherol content was a better selection criterion. Indeed, simulated selection based on the absolute α-tocopherol content resulted in a 64% increase in this compound without significantly affecting the total tocopherols, the total tocotrienols, and the α-/γ-tocopherol ratio.