Real-time monitoring of crop responses to environmental deviations represents a new avenue for applications of remote and proximal sensing. Combining the high-throughput devices with novel machine ...learning (ML) approaches shows promise in the monitoring of agricultural production. The 3 × 2 multispectral arrays with responses at 610 and 680 nm (red), 730 and 760 nm (red-edge) and 810 and 860 nm (infrared) spectra were used to assess the occurrence of leaf rolling (LR) in 545 experimental maize plots measured four times for calibration dataset (n = 2180) and 145 plots measured once for external validation. Multispectral reads were used to calculate 15 simple normalized vegetation indices. Four ML algorithms were assessed: single and multilayer perceptron (SLP and MLP), convolutional neural network (CNN) and support vector machines (SVM) in three validation procedures, which were stratified cross-validation, random subset validation and validation with external dataset. Leaf rolling occurrence caused visible changes in spectral responses and calculated vegetation indexes. All algorithms showed good performance metrics in stratified cross-validation (accuracy >80%). SLP was the least efficient in predictions with external datasets, while MLP, CNN and SVM showed comparable performance. Combining ML with multispectral sensing shows promise in transition towards agriculture based on data-driven decisions especially considering the novel Internet of Things (IoT) avenues.
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.
This study aimed to investigate the impact of cold stress and priming on photosynthesis in the early development of maize and soybean, crops with diverse photosynthetic pathways. The main objectives ...were to determine the effect of cold stress on chlorophyll
fluorescence parameters and spectral reflectance indices, to determine the effect of cold stress priming and possible stress memory and to determine the relationship between different parameters used in determining the stress response. Fourteen maize inbred lines and twelve soybean cultivars were subjected to control, cold stress, and priming followed by cold stress in a walk-in growth chamber. Measurements were conducted using a portable fluorometer and a handheld reflectance instrument. Cold stress induced an overall downregulation of PSII-related specific energy fluxes and efficiencies, the inactivation of RCs resulting in higher energy dissipation, and electron transport chain impairment in both crops. Spectral reflectance indices suggested cold stress resulted in pigment differences between crops. The effect of priming was more pronounced in maize than in soybean with mostly a cumulatively negative effect. However, priming stabilized the electron trapping efficiency and upregulated the electron transfer system in maize, indicating an adaptive response. Overall, this comprehensive analysis provides insights into the complex physiological responses of maize and soybean to cold stress, emphasizing the need for further genotype-specific cold stress response and priming effect research.
In order to achieve a high-quality product, sweet corn should be harvested at the optimal stage of maturity. The taste of sweet corn depends largely on the kernel moisture (KM) and total sugars (TS) ...content while its health properties are attributed to the content of total phenols (TPH) and antioxidant activity (AO). This study aimed to estimate quality in sugary (su1) sweet corn hybrids based on the maximum content of kernel chemical compounds and the content change during maturation. During two growing seasons, five harvests by year were made at 2-day intervals from 17 to 25 days after pollination (DAP). KM decreased among hybrids from 6.6% to 14% over an eight-day period, or 0.8% to 1.8% per day. TS content was the highest at 17 DAP (16.5–28.7 mg/g DW) and decreased during maturation from 27% to 67%. Hybrids differed significantly in TPH at 17 DAP (204.4–357.1 mg GAE/100 g DW). TPH change during maturation ranged from the no significant differences up to a 29.3% decrease. DPPH- radical scavenging activity ranged among genotypes from 52.5% to 74.9% inhibition at 17 DAP and significantly increased during maturation. A well-defined hybrid-specific harvest window is necessary to maintain kernel quality in su1 sweet corn.
Grain yield of maize is mostly affected by amount of available water and nitrogen and correlated to yield components. In this 2-years study the influence of different irrigation water amounts ...(a1=rainfed; a2=60-100% field water capacity (FWC); a3=80-100% FWC), nitrogen fertilizer levels (b1=0 kg*N*ha-1; b2=100 kg*N*ha-1; b3=200 kg*N*ha-1) and hybrids (c1=OSSK515; c2=OS5997; c3=OS5775; c4=OS5885) on grain yield and yield components was tested. Furthermore the correlation analysis as well as direct and indirect path coefficients were used to analyse the connection between yield and yield components (grain number/cob, grain weight, 1000 grain weight, cob length, cob weight) across tested treatments. The influence of all tested factors was significant (P<0.05) in both years of study. Specific study results were obtained in extremely wet year 2010 when irrigation water reduced grain yield and yield components (a1=9.9; a2=8.8; a3=7.8 t*ha-1). Opposite to year 2013 when irrigation water increased grain yield as well as yield components (a1=8.9; a2=9.7; a3=10.3 t*ha-1). Nitrogen fertilizer was significant to all tested variables in both years of the study (b1=5.7; b2=9.2; b3=11.7 t*ha-1 in 2010 and b1=6.3; b2=8.9; b3=10.6 t*ha-1 in 2013). Generally, the greatest amount of nitrogen fertilizer the larger yield or yield components are achieved. The influence of hybrid was significant for all tested variables with exemption to 1000 grain weight and grain weight/cob during growing season 2013. In both years of the study hybrid c2 OS5997 achieved the highest yield as well as yield components. Correlation analysis showed strong positive correlation between yield and cob weight (r=0.77 (2010); r=0.84 (2013)) what is confirmed with direct and indirect path analysis test.
Kernel water (KW) and total soluble sugars (TSS) are major components of sweet corn taste, while total carotenoids (TC), total phenols (TP) and antioxidant activity (AA) contribute to its health ...benefits. Main objective was to determine the effect of genotype, harvest date and year on chemical components of kernel quality in shrunken (sh2) sweet corn. Nine sh2 genotypes were harvested at 3-day intervals from 20 to 32 days after pollination (DAP) over two years. Growing season significantly affected TC and TP only. Significant differences among genotypes were found for KW (75.3 - 77.4%), TTS (282.4 - 343.2 mg/g), TC (9.3 - 15.7 µg/g), TP (243.6 - 289.4 mg GEA/100 g) and AA (74.6 - 83.6 % inhibition). Effect of harvest date and genotype by harvest date interaction was significant for all traits. Compared to the 20 DAP, KW and TSS decreased, while TC, TP and AA tended to increase with later harvest dates. Based on KW, genotypes OS 5Esh and Overland extended harvest window up to 29 DAP. In contrast, optimum harvest window for genotype OS 244sh finished at 20 DAP. Extended harvest window for genotype Overland resulted in significant increase of TC (62.8%), TP (12.1%) and AA (12.4%).
Genomic prediction accuracy (r_MP) is affected by many factors, such as the trait heritability, training population size and structure, and the number of markers. This study’s objective was to ...investigate the factors associated with r_MP for the ear height and the plant height in two planting densities in testcrosses of maize (Zea mays L.) IBM population. Genetic correlations between the training and validation populations were calculated. The high heritability estimates and correlations between the traits were observed. The non-zero estimates of r_MP for all trait-density combinations implied an efficiency of genomic selection. The lower than expected values of genetic correlations were observed between the training and validation populations. However, a strong correlation was observed between a genetic correlation of training and the validation population and r_MP in all three sizes of training populations assessed (20-40%, 40-60%, and 60-80%), suggesting that the size of the training population can be kept low by an appropriate selection while maintaining a high r_MP. Further studies of relationships between the training and validation populations with larger effective population sizes are suggested, as reducing the size of training population while maintaining a high r_MP can facilitate a more effective allocation of resources in a maize breeding program.
The in vivo haploid induction has been widely applied to the maize breeding in recent decades, but it has not been used in the breeding programs in the Republic of Croatia by now. This study's ...objectives were to examine the haploid induction rates in the Croatian germplasm and to evaluate the properties of the D0 haploids, which are essential for a successful implementation of this method in breeding. The in vivo haploid induction was performed on 11 single-cross hybrids using the Zarodyshevy Marker Krasnodarsky (ZMK) inducer, and colchicine was used as a chromosome doubling agent. Emergence, misclassification rate, colchicine treatment survival, chromosome doubling rate and self-pollination success were examined in the D0 generation. The haploid induction rates ranged from 6.9 to 15.8%, which is consistent with the average induction rates characteristic of the ZMK inducer and the other modern ones. Significant differences were found among the populations of D0 haploids for all tested properties, except for self-pollination success. On average, the misclassification rates were lower, and the seedling survival rates were higher than those reported in other studies, indicating a possibility of a successful application of the doubled haploid method in maize breeding.
Indukcija haploida in vivo posljednjih se desetljeća sve više primjenjuje u oplemenjivanju kukuruza, ali se dosad nije koristila u oplemenjivačkim programima u Republici Hrvatskoj. Ciljevi ovoga istraživanja bili su utvrditi relativne frekvencije induciranih haploida kod germplazme koja se upotrebljava u domaćim oplemenjivačkim programima i ispitati svojstva haploida generacije D0 koja su važna za uspješnu primjenu ove metode u oplemenjivanju. Indukcija haploida in vivo obavljena je na 11 jednostrukih hibrida pomoću induktora ZMK, a za udvostručenje kromosoma korišten je kolhicin. U generaciji D0 ispitana su svojstva nicanja, pogrešne klasifikacije, preživljavanja tretmana kolhicinom, udvostručenja kromosoma i uspješnosti izvođenja samooplodnje. Relativna frekvencija haploida kretala se od 6,9 do 15,8%, što je usporedivo s prosječnim stopama indukcije specifičnim za induktor ZMK i druge moderne induktore. Statistički značajne razlike pronađene su između populacija haploida D0 za sva ispitana svojstva, osim za uspješnost izvođenja samooplodnje. U prosjeku, stope pogrešne klasifikacije bile su niže, a stope preživljavanja tretmana kolhicinom više u odnosu na one zabilježene u drugim istraživanjima, što ukazuje na mogućnost uspješne primjene metode udvostručenih haploida u oplemenjivanju.
Southeast Europe (SEE) is a very important maize-growing region, comparable to the Corn belt region of the United States, with similar dent germplasm (dent by dent hybrids). Historically, this region ...has undergone several genetic material swaps, following the trends in the US, with one of the most significant swaps related to US aid programs after WWII. The imported accessions used to make double-cross hybrids were also mixed with previously adapted germplasm originating from several more distant OPVs, supporting the transition to single cross-breeding. Many of these materials were deposited at the Maize Gene Bank of the Maize Research Institute Zemun Polje (MRIZP) between the 1960s and 1980s. A part of this Gene Bank (572 inbreds) was genotyped with Affymetrix Axiom Maize Genotyping Array with 616,201 polymorphic variants. Data were merged with two other genotyping datasets with mostly European flint (TUM dataset) and dent (DROPS dataset) germplasm. The final pan-European dataset consisted of 974 inbreds and 460,243 markers. Admixture analysis showed seven ancestral populations representing European flint, B73/B14, Lancaster, B37, Wf9/Oh07, A374, and Iodent pools. Subpanel of inbreds with SEE origin showed a lack of Iodent germplasm, marking its historical context. Several signatures of selection were identified at chromosomes 1, 3, 6, 7, 8, 9, and 10. The regions under selection were mined for protein-coding genes and were used for gene ontology (GO) analysis, showing a highly significant overrepresentation of genes involved in response to stress. Our results suggest the accumulation of favorable allelic diversity, especially in the context of changing climate in the genetic resources of SEE.
We performed QTL mapping in testcrosses of maize population IBMSyn4 for three grain quality traits: oil and protein contents and test weight. 191 phenotyped and genotyped lines were used as a ...training set while 85 genotyped only lines comprised a validation set used to calculate best linear unbiased predictions (BLUP), making a total of 276 phenotypes for the QTL analysis. 92000 filtered Genotyping-By-Sequencing (GBS) SNP markers were used to calculate BLUPs, while a set of 2178 genetically mapped SSRs was used in QTL analysis. By simple QTL scan, we scored several minor effect QTLs: one for oil content (chromosome 1), one for protein content (chromosome 10) and four for test weight (chromosomes 1, 3, 5 and 10). QTLs associated with test weight were found to be additive, and 18.25% of phenotypic variance was explained by their joint effect. Only one QTL for test weight was found to be significant in composite interval mapping and it was mapped on chromosome 5. This QTL accounted for 9.97% of phenotypic variance. QTLs detected in this study represent monitoring of commercially most successful elite maize germplasm for grain quality traits.
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