Fast Analysis of Maize Kernel Plumpness Characteristics Through Micro-CT Technology

Received: 2018-06-07 | Accepted: 2018-06-19 | Available online: 2018-06-30 https://doi.org/10.15414/afz.2018.21.02.77-83 The aim of this study was to distinguishing between kernels of maize hybrids by the use of image analysis tools. We analyzed 10 registered Zea mays L. hybrids (5 – dent, 2 – semi-flint to flint, and 3 – semi-flint to dent type). Different parameters on ventral, dorsal, corolla side, and lateral side cross section of kernel were measured. Sample per each hybrid comprised 50 maize kernels. Acquired bio-images were processed by software Zeiss AxioVision Rel. 4.8. We analyzed the segmented regions of interest on the kernels. The data for area (mm 2 ), height and width (mm) were gathered from these regions. The hybrid ZE EDOX significantly differed (p < 0.05) from all other hybrids almost in all traits. It is the hybrid with the smallest area of the whole kernel, floury endosperm proportion, and depressed part on corolla. The new trait the area of the depressed part on the kernel corolla was measured. The hybrids with smaller proportion of floury endosperm had smaller area of depressed part, and vice versa. The image analysis methods can usefully contribute to selection of proper hybrids for different types of use. Keywords: maize, Zea mays L., kernel, image analysis References BLASCHKE, T. et al. (2014) Geographic Object-Based Image Analysis – Towards a new paradigm. In ISPRS Journal of Photogrammetry and Remote Sensing, vol. 87, pp. 180–191. https://doi.org/10.1016/j.isprsjprs.2013.09.014 DE CARVALHO, M. L. M., VAN AELST, A. C., VAN ECK, J. W., HOEKSTRA, F. A. (1999) Pre-harvest stress cracks in maize (Zea mays L.) kernels as characterized by visual, X-ray and low temperature scanning electron microscopical analysis: effect on kernel quality. In Seed Science Research, vol. 9, pp. 227–236. DELL´AQUILA, A. (2006) Computerised seed imaging: a new tool to evaluate germination quality. In Communications in Biometry and Crop Science, vol. 1, no. 1, pp. 20–31. ERASMUS, C. (2003) Maize kernel translucency measurement by Image Analysis and its relationship to vitreousness and dry milling performance. PhD thesis. Pretoria: University of Pretoria. FOX, G. and MANLEY, M. (2009) Hardness methods for testing maize kernels. In Journal of Agricultural and Food Chemistry, vol. 57, no. 13, pp. 5647–5657. doi: https://doi.org/10.1021/jf900623w GLASBEY, C. A. and HORGAN, G. W. (2001) Image analysis in agriculture research. In Quantitative Approaches in System Analysis, special issue, vol. 23, pp. 43–54. GUELPA, A., DU PLESIS, A., KIDD, M., MANLEY, M. (2015) Nondestructive estimation of maize (Zea mays L.) kernel hardness by means of an X-ray micro-computed tomography (μCT) density calibration. In Food and Bioprocess Technology, vol. 8, no. 6, pp. 1419–1429. JANDA, J. and MICHALEC, V. (1982) Mayze. Bratislava: Priroda. 408 p. MUTTERER, J. and ZINCK, E. (2013) Quick‐and‐clean article figures with FigureJ. In Journal of Microscopy, vol. 252, pp. 89– 91. doi: https://doi.org/10.1111/jmi.12069 ROBUTTI, J. L., HOSENEY, R. C. and WASSOM, C. E. (1974). Modified opaque-2 corn endosperms. ll. Structure viewed with a scanning electron microscope. In American Association of Cereal Chemists, vol. 51, pp. 173–180. RODRIGUEZ-PULIDO, F. J. et al. (2012) Ripeness estimation of grape berries and seeds by image analysis. In Computers and Electronics in Agriculture, vol. 82, pp. 128–133. SCHINDELIN, J., RUEDEN, C. T., HINER, M. C., ELICEIRI, K. W. (2015) The ImageJ ecosystem: An open platform for biomedical image analysis. In Mol. Reprod. Dev., vol. 82, pp. 518–529. doi: https://doi.org/10.1002/mrd.22489 UCHIDA, S. (2013) Image processing and recognition for biological images. In Development, growth and differentiation, vol. 55, pp. 523–549. doi: https://doi.org/10.1111/dgd.12054 WATSON, S. A. (1987) Structure and composition. In WATSON, S. A. and RAMSTAD, P. E. (Eds.). Corn chemistry and technology. St. Paul: American Association of Cereal Chemists. WIWART M. et al. (2012) Identification of hybrids of spelt and wheat and their parental forms using shape and color descriptors. In Computers and Electronics in Agriculture, vol. 83, pp. 68–76. https://doi.org/10.1016/j.compag.2012.01.015

Maize kernel density affects milling quality of the grain. Kernel density of bulk samples can be predicted by near-infrared reflectance (NIR) spectroscopy, but no accurate method to measure individual kernel density has been reported. This study demonstrates that individual kernel density and volume are accurately measured using X-ray microcomputed tomography (μCT). Kernel density was significantly correlated with kernel volume, air space within the kernel, and protein content. Embryo density and volume did not influence overall kernel density. Partial least-squares (PLS) regression of μCT traits with single-kernel NIR spectra gave stable predictive models for kernel density (R(2) = 0.78, SEP = 0.034 g/cm(3)) and volume (R(2) = 0.86, SEP = 2.88 cm(3)). Density and volume predictions were accurate for data collected over 10 months based on kernel weights calculated from predicted density and volume (R(2) = 0.83, SEP = 24.78 mg). Kernel density was significantly correlated with bulk test weight (r = 0.80), suggesting that selection of dense kernels can translate to improved agronomic performance.

A high-throughput X-ray micro-computed tomography (μCT) approach for measuring single kernel maize (Zea mays L.) volumes and densities

Maize (Zea mays L.) kernel infection by Aspergillus flavus is a chronic problem in the southern USA. Genetic resistance to A. flavus is needed to solve this problem. To ascertain and understand the inheritance of resistance to field kernel infection by A. flavus, a five-parent diallel analysis and a half-sib family analysis of 35 maize crosses were conducted during 2003 and 2004 for percent kernel infection (PKI) rates. All parents contained the leafy gene (Lfy). From the combining ability analysis of the five maize parents and their 20 F1s, highly significant general combining ability (GCA), specific combining ability (SCA), and reciprocal effects were found. The analysis of genetic effects showed that the parents 914 and A619 had desirable GCA effects to enhance the average performance of A. flavus resistance in hybrid progeny. The crosses 914 �� A632, 914 �� WF9, and HY �� WF9 had consistently negative SCA effects across the two years. These results suggested that resistance to kernel infection by A. flavus existed among the parents and some of their crosses. Their potential performance with desired GCAs and SCAs could be exploited to develop resistant lines in breeding programs and to produce resistant hybrids. The reciprocal effects in the crosses across years reflected the presence of maternal effects in the maize kernel. These effects were partly responsible for resistance to A. flavus and should be considered in making crosses. The cross A632 �� HY had the highest negative significant reciprocal effect, indicating that it should promote resistance to A. flavus. Analyses of the 35 half-sib crosses derived from seven maize breeding lines indicated that both the genotype and genotype-by-year effects were highly significant. Broad-sense heritability for PKI estimated from variance components was 73.8%. A North Carolina Design-II analysis of 12 crosses was used to estimate additive and dominance genetic variances. Narrow-sense heritability and the average degree of dominance for PKI were 37.6% and 1.67, respectively. A comparison of a laboratory-based infection resistance screening (LIRS) with field-based PKI demonstrated that LIRS was effective and could be used to improve maize germplasm screening and to expedite A. flavus resistance breeding.

Anthocyanins in maize (Zea mays L.) kernels determine the plant's color and can enhance its resistance. Selenium (Se) significantly impacts plant growth, development, and secondary metabolic regulation. However, the molecular mechanisms by which Se regulates anthocyanin synthesis in waxy corn remain unclear. This study employed integrated transcriptomic and metabolomic analyses to investigate the mechanisms through which selenium influences anthocyanin synthesis in yellow and purple waxy corn. The results showed that maize varieties with higher anthocyanin content had higher selenium enrichment capacity in their kernels. Under selenium stress, HN2025 exhibited 1,904 more differentially expressed genes (DEGs) and 140 more differential metabolites compared to HN5. The expression levels of anthocyanin synthesis-related genes and transcription factors such as phenylalanine ammonia-lyase, flavonoid 3-hydroxylase (F3H), dihydroflavonol reductase (DFR), chalcone synthase (CHS), cinnamate-4-hydroxylase (C4H), anthocyanin 5,3-O-glucosyltransferases, and anthocyanidin reductase, MYB, and bHLH were strongly induced in HN2025. Metabolomic analysis revealed significant enrichment in anthocyanin biosynthesis, flavonoid and flavonol biosynthesis, glutathione metabolism, phenylalanine biosynthesis, and phenylalanine metabolism under selenium treatment. Three up-regulated PAL genes and one C4H gene were significantly enriched with DAMs in phenylalanine metabolism, phenylpropanoid biosynthesis, flavonoid biosynthesis, and anthocyanin biosynthesis, resulting in significant differences between HN5 and HN2025 in selenium-induced anthocyanin metabolism-related pathways. These findings provide a theoretical basis for understanding the effects of selenium on the molecular regulatory mechanisms of anthocyanin biosynthesis in maize kernels.

The distribution of abscisic acid (ABA) within maize (Zea mays L.) kernels was studied in kernels from nontreated plants, from plants in which assimilate supply had been altered by source/sink manipulations, and in kernels cultured in vitro on ABA-free media. Prior to growth of the embryo, both the pedicel/placento-chalazal complex and the endosperm contained high concentration of ABA; however, the quantity of ABA in these tissues declined as the concentration in the embryo increased during the early stages of embryo growth. Peaks in the levels of ABA appeared to occur prior to and not concurrent with physiological events during grain filling. During most of the grain filling period, ABA concentration in the embryo was higher than that found in other kernel components. Altering assimilate supply by partial defoliation at two stages of development resulted in variable and transient effects on the relative distribution and concentration of ABA in kernel components. The concentration and distribution of ABA among components of kernels grown in vitro was similar to that observed for field-grown kernels. On the basis of these findings, in situ synthesis of ABA by kernel components is implicated and the putative role of ABA in the regulation of kernel development is discussed.

To study the influence of PINFORMED1 (PIN1)-mediated auxin transport during embryogenesis and endosperm development in monocots, the expression pattern of the three identified ZmPIN1 genes was determined at the transcript level. Localization of the corresponding proteins was also analyzed during maize (Zea mays) kernel development. An anti-indole-3-acetic acid (IAA) monoclonal antibody was used to visualize IAA distribution and correlate the direction of auxin active transport, mediated by ZmPIN1 proteins, with the actual amount of auxin present in maize kernels at different developmental stages. ZmPIN1 genes are expressed in the endosperm soon after double fertilization occurs; however, unlike other tissues, the ZmPIN1 proteins were never polarly localized in the plasma membrane of endosperm cells. ZmPIN1 transcripts and proteins also colocalize in developing embryos, and the ZmPIN1 proteins are polarly localized in the embryo cell plasma membrane from the first developmental stages, indicating the existence of ZmPIN1-mediated auxin fluxes. Auxin distribution visualization indicates that the aleurone, the basal endosperm transfer layer, and the embryo-surrounding region accumulate free auxin, which also has a maximum in the kernel maternal chalaza. During embryogenesis, polar auxin transport always correlates with the differentiation of embryo tissues and the definition of the embryo organs. On the basis of these reports and of the observations on tissue differentiation and IAA distribution in defective endosperm-B18 mutant and in N-1-naphthylphthalamic acid-treated kernels, a model for ZmPIN1-mediated transport of auxin and the related auxin fluxes during maize kernel development is proposed. Common features between this model and the model previously proposed for Arabidopsis (Arabidopsis thaliana) are discussed.

BackgroundMaize (Zea mays ssp. mays) is the most abundantly cultivated and highly valued food commodity in the world. Oil from maize kernels is highly nutritious and important for the diet and health of humans, and it can be used as a source of bioenergy. A better understanding of genetic basis for maize kernel oil can help improve the oil content and quality when applied in breeding.ResultsIn this study, a KUI3/SC55 recombinant inbred line (RIL) population, consisting of 180 individuals was constructed from a cross between inbred lines KUI3 and SC55. We phenotyped 19 oil-related traits and subsequently dissected the genetic architecture of oil-related traits in maize kernels based on a high-density genetic map. In total, 62 quantitative trait loci (QTLs), with 2 to 5 QTLs per trait, were detected in the KUI3/SC55 RIL population. Each QTL accounted for 6.7% (qSTOL1) to 31.02% (qBELI6) of phenotypic variation and the total phenotypic variation explained (PVE) of all detected QTLs for each trait ranged from 12.5% (OIL) to 52.5% (C16:0/C16:1). Of all these identified QTLs, only 5 were major QTLs located in three genomic regions on chromosome 6 and 9. In addition, two pairs of epistatic QTLs with additive effects were detected and they explained 3.3 and 2.4% of the phenotypic variation, respectively. Colocalization with a previous GWAS on oil-related traits, identified 19 genes. Of these genes, two important candidate genes, GRMZM2G101515 and GRMZM2G022558, were further verified to be associated with C20:0/C22:0 and C18:0/C20:0, respectively, according to a gene-based association analysis. The first gene encodes a kinase-related protein with unknown function, while the second gene encodes fatty acid elongase 2 (fae2) and directly participates in the biosynthesis of very long chain fatty acids in Arabidopsis.ConclusionsOur results provide insights on the genetic basis of oil-related traits and a theoretical basis for improving maize quality by marker-assisted selection.

We isolated two nitrilase genes, ZmNIT1 and ZmNIT2, from maize (Zea mays) that share 75% sequence identity on the amino acid level. Despite the relatively high homology to Arabidopsis NIT4, ZmNIT2 shows no activity toward beta-cyano-alanine, the substrate of Arabidopsis NIT4, but instead hydrolyzes indole-3-acetonitrile (IAN) to indole-3-acetic acid (IAA). ZmNIT2 converts IAN to IAA at least seven to 20 times more efficiently than AtNIT1/2/3. Quantitative real-time polymerase chain reaction revealed the gene expression of both nitrilases in maize kernels where high concentrations of IAA are synthesized tryptophan dependently. Nitrilase protein and endogenous nitrilase activity are present in maize kernels together with the substrate IAN. These results suggest a role for ZmNIT2 in auxin biosynthesis.

Chitosan nanoparticles loaded with Lactobacillus rhamnosus bioactive metabolites: Preparation, characterization, and antifungal activity.

Carotenoids perform a broad range of important functions in humans; therefore, carotenoid biofortification of maize (Zea mays L.), one of the most highly produced cereal crops worldwide, would have a global impact on human health. PLASTID TERMINAL OXIDASE (PTOX) genes play an important role in carotenoid metabolism; however, the possible function of PTOX in carotenoid biosynthesis in maize has not yet been explored. In this study, we characterized the maize PTOX locus by forward- and reverse-genetic analyses. While most higher plant species possess a single copy of the PTOX gene, maize carries two tandemly duplicated copies. Characterization of mutants revealed that disruption of either copy resulted in a carotenoid-deficient phenotype. We identified mutations in the PTOX genes as being causal of the classic maize mutant, albescent1. Remarkably, overexpression of ZmPTOX1 significantly improved the content of carotenoids, especially β-carotene (provitamin A), which was increased by ~threefold, in maize kernels. Overall, our study shows that maize PTOX locus plays an important role in carotenoid biosynthesis in maize kernels and suggests that fine-tuning the expression of this gene could improve the nutritional value of cereal grains.

Fumonisin B 1 (FB 1 ) is among the most common mycotoxins found in maize kernels and maize products worldwide. The microbiological process of detoxification and transformation of toxic organic pollutants is a promising method for foodstuffs decontamination. Some basidiomycetes, such as the Pleurotus eryngii species complex, include several important commercial edible varieties that can detoxify polycyclic organic compounds and a range of wastes and pollutants. We investigated the potential role of P. eryngii , one of the most consumed mushrooms, in the decontamination of FB 1 in maize. In addition, selected antioxidant enzymes, (soluble peroxidase (POD), catalase (CAT) and ascorbate peroxidase), primarily involved in control of cell hydrogen peroxide levels, and lignin degradation, were analyzed, to evaluate their contributions to the molecular mechanisms of FB 1 by P. eryngii . FB 1 decontamination by P. eryngii and involvement of CAT and POD enzymes in the control of toxic decontamination levels of H 2 O 2 were demonstrated. A consistent reduction of FB 1 was observed at different incubation times. The average decrease levels of FB 1 , with respect to the control cultures, ranged from 45 to 61% (RSD < 15%). This study is a possible eco-friendly approach to reducing this mycotoxin in the feed supply chains.

Agronomic practices affect corn (Zea mays L.) grain yield and may affect physical and chemical characteristics of corn kernels. These characteristics affect feed, food, and industrial uses of corn grain. Four field experiments consisting of planting date and population combinations were conducted to determine the effect of these agronomic practices on grain yield, kernel N concentration, and kernel hardness. Kernel hardness was estimated by kernel weight, kernel density, and grinding resistance. A fixed ear hybrid, B73 × LH38, was used in all four experiments. Two of the four experiments also included LH119 × LH51, a flexible ear hybrid. Planting date affected yield in only one experiment. In this instance, delaying planting 4 wk decreased yield 55%. Yield reduction from planting delay was greater for B73 × LH38 than for LH119 × LH51. In two experiments, increasing population increased yield quadratrically; whereas, in the other two experiments the effect of population on yield was linear. No interaction between hybrid and population occurred. Delayed planting increased kernel N concentration in one experiment. In all four experiments, increasing population resulted in a linear decrease in kernel N concentration. Few effects from either planting date or population on kernel weight and density were found. Grinding resistance was increased by delayed planting in one experiment but was not affected by plant population in any of the four experiments. Inverse relationships between yield and important kernel physical and chemical characteristics were found. Emphasis on high yield may result in less desirable grain. End‐users that require high grain quality may need to provide incentives to growers.

Breeding to increase beta-carotene levels in cereal grains, termed provitamin A biofortification, is an economical approach to address dietary vitamin A deficiency in the developing world. Experimental evidence from association and linkage populations in maize (Zea mays L.) demonstrate that the gene encoding beta-carotene hydroxylase 1 (crtRB1) underlies a principal quantitative trait locus associated with beta-carotene concentration and conversion in maize kernels. crtRB1 alleles associated with reduced transcript expression correlate with higher beta-carotene concentrations. Genetic variation at crtRB1 also affects hydroxylation efficiency among encoded allozymes, as observed by resultant carotenoid profiles in recombinant expression assays. The most favorable crtRB1 alleles, rare in frequency and unique to temperate germplasm, are being introgressed via inexpensive PCR marker-assisted selection into tropical maize germplasm adapted to developing countries, where it is most needed for human health.

Grain quality specifications for maize (Zea mays L.) have been established for several processing industries. Our objective was to investigate the effects of planting date and moisture level on grain yield, physical grain quality, and alkaline‐processing characteristics of food‐grade maize. Field experiments were conducted in 1998 and 1989 at the Texas A&amp;M University Farm, Burleson County, Texas. Seven food‐grade maize hybrids and one nonprocessing hybrid were grown with two planting dates (normal and delayed) and two moisture levels (irrigated and dryland). Delayed planting, averaged across years, decreased grain yield 15.2%, kernel weight 6.8%, kernel density 1.8%, and kernel hardness 4.4%. In 1988, the dryland treatment decreased grain yield 30.0%, kernel weight 15.2%, and kernel density 1.8%, and increased kernel protein 5%, but had no effect in 1989. Kernel hardness decreased 2.8% in 1988 with dryland treatment, but increased 4.5% in 1989. Hybrid effects varied with year for kernel weight, density, hardness, and protein. The nonprocessing hybrid (B73 × Mo17) produced high grain yield (7911 kg ha−1) and average kernel protein (109 g kg−1 but relatively low kernel weight (270 mg), density (1.06 g cm−3), and hardness (45.4%). Of the food‐quality hybrids, none consistently outperformed the others in all categories. Alkaline‐processing characteristics of the grain were affected by agronomic inputs. In general, nixtamal (i.e., cooked grain after alkaline processing) moisture increased due to delayed plantings and reduced soil water availability. Dry‐matter loss exhibited no discernible trends. Pericarp removal (qualitatively scored) was greatly affected by hybrid; RX404 consistently outperformed all other hybrids.