Sweet Corn Kernels Research Articles

Genome-wide association study suggests an independent genetic basis of zinc and cadmium concentrations in fresh sweet corn kernels.

Despite being one of the most consumed vegetables in the United States, the elemental profile of sweet corn (Zea mays L.) is limited in its dietary contributions. To address this through genetic improvement, a genome-wide association study was conducted for the concentrations of 15 elements in fresh kernels of a sweet corn association panel. In concordance with mapping results from mature maize kernels, we detected a probable pleiotropic association of zinc and iron concentrations with nicotianamine synthase5 (nas5), which purportedly encodes an enzyme involved in synthesis of the metal chelator nicotianamine. In addition, a pervasive association signal was identified for cadmium concentration within a recombination suppressed region on chromosome 2. The likely causal gene underlying this signal was heavy metal ATPase3 (hma3), whose counterpart in rice, OsHMA3, mediates vacuolar sequestration of cadmium and zinc in roots, whereby regulating zinc homeostasis and cadmium accumulation in grains. In our association panel, hma3 associated with cadmium but not zinc accumulation in fresh kernels. This finding implies that selection for low cadmium will not affect zinc levels in fresh kernels. Although less resolved association signals were detected for boron, nickel, and calcium, all 15 elements were shown to have moderate predictive abilities via whole-genome prediction. Collectively, these results help enhance our genomics-assisted breeding efforts centered on improving the elemental profile of fresh sweet corn kernels.

Co-Inoculation of Aflatoxigenic and Non-Aflatoxigenic Strains of Aspergillus flavus to Assess the Efficacy of Non-Aflatoxigenic Strains in Growth Inhibition and Aflatoxin B1 Reduction

The pre-harvest biocontrol approach currently used includes laboratory inoculations using non-aflatoxigenic strains of Aspergillus flavus. This strategy effectively suppresses the indigenous aflatoxigenic strains and reduces aflatoxin accumulation in sweetcorn. The current in vitro study’s main objective is to determine the diametric growth rates of both Aflatoxin (AF)+ and AF− strains and improve the understanding of competitive relationships among these strains in sweetcorn (Zea mays). Sweetcorn kernels inoculated with AF+ strains only, AF− strains only, and co-inoculated with AF+ + AF− strains were investigated for aflatoxin concentrations. The diametric growth results revealed that growth rates of AF− strains at 25 and 30 °C were much greater than AF+ strains, which was in line with previous studies. The in vitro findings showed that the AKR5− and AKL34− biocontrol strains effectively inhibited the colony propagation and subsequent AFB1 contamination (up to 79%) of AF+ strains. On the other hand, the AKR1− and AKL35− were least effective in reducing AFB1 contents only by 58% and 60%, respectively. There was a significant difference (p < 0.05) in the reduction of AFB1 contents achieved by AF− strains of A. flavus. The findings of the present study indicated the reduction in AFB1 with population expressions of AF+ strains by the AF− strains and supports the notion of competitive exclusion through vigorous development and propagation of the non-aflatoxigenic fungi.

Impact of osmotic dehydration and different drying methods on the texture and sensory characteristic of sweet corn kernels

The main aim of the study was to examine the quality and properties of sweet corn kernels treated by osmotic dehydration (OD) and different drying methods. Drying kinetics, texture profile analysis (TPA), color, and a descriptive sensory analysis were performed in the study. The study found that the use of vacuum–microwave drying (VMD) as a part of the drying process had a significant impact on the formation of crispy characteristic of the sample. Also, application of OD performed in concentrated apple juice followed by drying resulted in a fruitier, not that crispy, but juicier material when compared with non-OD samples. At the end, VMD was selected as optimal for production of crunchy sweet corn kernels, whereas OD/VMD was recommended for obtaining juicier, less crunchy material with improved taste as a result of OD. Practical applications Corn is one of the most popular crops in the world and is commonly used in the production of snacks. However, traditional snacks are often unhealthy due to the increased amount of fat. Drying can be used to obtain healthy, crispy products. Moreover, osmotic dehydration can be used to modify the sensory characteristic of the dried product. This study analyzes different drying methods with their impact on the texture of the sweet corn kernels as well as sensory analysis. Assessed process conditions can be helpful in designing and obtaining corn snacks that are not only healthy but also acceptable by consumers.

Widely Targeted Metabolomics Analysis Reveals Key Quality-Related Metabolites in Kernels of Sweet Corn.

Sweet corn (Zea mays convar. saccharata var. rugosa) is a major economic vegetable crop. Different sweet corn cultivars vary largely in flavor, texture, and nutrition. The present study performed widely targeted metabolomics analysis based on the HPLC-MS/MS technology to analyze the metabolic profiles in three sweet corn cultivars widely grown in China. A total of 568 metabolites in the three sweet corn cultivars were detected, of which 262 differential metabolites significantly changed among cultivars. Carbohydrates, organic acids, and amino acids were the majority detected primary metabolites. Organic acids were mainly concentrated on shikimate, benzoic acids, and quinic acid with aromatic groups. And the essential amino acids for the human body, methionine and threonine, were highly accumulated in the high-quality cultivar. In addition, phenylpropanoids and alkaloids were the most enriched secondary metabolites while terpenes were low-detected in sweet corn kernels. We found that the flavonoids exist in both free form and glycosylated form in sweet corn kernels. PCA and HCA revealed clear separations among the three sweet corn cultivars, suggesting distinctive metabolome profiles among three cultivars. The differential metabolites were mapped into flavonoid biosynthesis, phenylpropanoid biosynthesis, biosynthesis of amino acids, and other pathways according to the KEGG classification. Furthermore, we identified skimmin, N′,N″-diferuloylspermidine, and 3-hydroxyanthranilic acid as the key quality-related metabolites related to grain quality traits in sweet corn. The results suggested variations of metabolic composition among the three cultivars, providing the reference quality-related metabolites for sweet corn breeding.

Effect of Temperature and Processing Time on Physico-Chemical Characteristics in Hot Water Blanching of Sweet Corn Kernels

Sweet corn is popular due to its distinct taste. It remains extremely perishable due to high moisture content. For inactivation of enzymes, hot water blanching method was used to inactivate the enzyme at temperature differences of 60–100 °C for 30–150 s for sweet corn kernels and effect on various properties of sweet corn was studied. The increase in temperature and duration of treatment reduced residual peroxidase activity in samples. The increase in blanching temperature and increase in time increases length, width, thickness, true density, porosity, colour a*, colour b*, chroma, browning index, total colour difference, pH, moisture content in sweet corn kernels. The bulk density, colour L*, ascorbic acid and total sugar of samples also decreased with increase in blanching temperature and increase in processing time. The minimum time for achieving 95% reduction in peroxidase activity was 90 s at 90 °C, and was therefore recommended for hot water blanching of sweet corn kernels.

Morphological Characterization and Determination of Aflatoxigenic and Non-Aflatoxigenic Aspergillus flavus Isolated from Sweet Corn Kernels and Soil in Malaysia

This study aimed to morphologically characterize and determine the aflatoxigenic and non-aflatoxigenic Aspergillus flavus isolates. Forty isolates of A. flavus were obtained from sweet corn kernels and soil samples collected from Kampong Raja, Rose Valley, Kea, and Klebang farms in Malaysia. They were cultured on potato dextrose agar (PDA), dichloran rose-bengal chloramphenicol (DRBC), Aspergillusflavus and Aspergillus parasiticus agar (AFPA), and coconut cream agar (CCA). Macromorphological characteristics were determined by observing the colony color and texture, while the micromorphological characteristics were determined by examining the spore color, size, structure, conidiophore structure, and vesicle shape. The production of aflatoxin was determined by direct visualization of the UV fluorescence of A. flavus colonies on CCA. Aflatoxin was qualitatively detected in 18 (45%) isolates of A. flavus using UV fluorescence screening while the remaining 22 (55%) isolates did not exhibit any aflatoxin production. The highest incidence of A. flavus (30%) and aflatoxin production (15%) was recorded in samples from Kampong Raja. On the other hand, isolates from Rose Valley (17%) and Kea (12%) were non-aflatoxigenic. Klebang recorded a 25% incidence of A. flavus in which 15% were aflatoxigenic while 10% were non-aflatoxigenic. The occurrence of aflatoxin-producing A. flavus emphasizes the need for the measure to eradicate their presence in food crops. A biological control treatment utilizing the non-aflatoxigenic strains to compete with the aflatoxigenic ones is underway. Validation of aflatoxin production through high performance liquid chromatography is also ongoing.

Elevated zinc concentration in zeaxanthin-biofortified sweetcorn kernels compared with a commercial hybrid

A glasshouse experiment was conducted to assess the potential for increasing sweetcorn (Zea mays L. var. rugosa) kernel zinc (Zn) concentration. Uptake of Zn was compared between a standard commercial supersweet variety ‘Hybrix 5’ and a zeaxanthin-biofortified variety ‘High zeaxanthin 103146’. The plants were grown in potted soil culture using a Vertisol soil, and five rates of Zn (0, 0.75, 1.5, 3 and 6 kg Zn ha‑1) applied as ZnSO4.7H2O. Cobs were harvested at the appropriate maturity for sweetcorn eating, three weeks after pollination. On a fresh weight (FW) basis, the kernel Zn concentration in ‘High zeaxanthin 103146’ (7.11±0.21 mg Zn kg‑1) was ca. three times that of ‘Hybrix 5’ (2.57±0.20 mg Zn kg‑1) (p<0.001). The higher Zn concentration of ‘High zeaxanthin 103146’ was also significant in other plants parts, although not to the same extent as in kernel concentration. There was no effect of soil Zn fertilisation within the range of concentrations tested on increasing tissue Zn concentration of any plant part. Interestingly, the pollination of ‘High zeaxanthin 103146’ was generally poorer than ‘Hybrix 5’, resulting in lower kernel numbers per cob. Pollination differences may have contributed to the higher Zn concentration in ’High zeaxanthin 103146’ by reducing inter-kernel competition for Zn transported into the cob. The results show that sweetcorn kernels can potentially accumulate higher Zn concentrations and sweetcorn may be a useful target crop for Zn biofortification, while the lack of a soil Zn fertilisation effect suggests that genetic biofortification may be more effective in achieving elevated Zn concentrations in sweetcorn kernels.

Anthocyanin accumulation, biosynthesis and antioxidant capacity of black sweet corn (Zea mays L.) during kernel development over two growing seasons

In this study, the content changes of anthocyanins levels, antioxidant activities as well as related genes in their biosynthesis pathways of two seasons black sweet corn kernels were determined. Generally, three anthocyanins contents showed similar trend with peak at 10 days after pollination (DAP) in both seasons existing as free forms, and they gradually grew afterwards as kernel matured. Pelargonidin as the leading component was decreased significantly in autumn comparing to contents in summer which may be affected by lower photosynthetically active radiation (PAR) and distinct gene expression levels. CF1, F3H and LAD as the essential genes in flavonoid and anthocyanin biosynthesis had high expression levels indicating higher production of flavonoid and anthocyanin. Black sweet corn (BSC) exhibited good in vitro and cellular antioxidant abilities compared to many fruits and vegetables indicating that BSC could be developed as a substitute food with high anthocyanin profiles and antioxidant capacity.

Additives affect the distribution of metabolic profile, microbial communities and antibiotic resistance genes in high-moisture sweet corn kernel silage

This work investigated the effects of chemical additive vanillin (V), homofermentative Lactobacillus plantarum (LP), and heterofermentative Lactobacillus brevis (LB) on the distribution of the metabolome, microbial communities, viruses, and antibiotic-resistance genes in high-moisture corn kernel silage. LP and LB improved lactic acid production, whereas V and LB inhibited protein degradation. A significant difference was observed between the metabolite profiles of silage treated with additives and a control. In silage, the Proteobacteria and Ascomycota were the main hosts of antibiotic-resistance genes, primarily antibiotic efflux. The additives significantly affected the virus content in silage, and LB-treated silage featured the lowest virus content. Overall, these findings suggest that the application of the additive LB to high-moisture corn kernel silage impacts antibiotic-resistance gene reduction and virus distribution within the silage.

Zinc biofortification of immature maize and sweetcorn (Zea mays L.) kernels for human health

This study explores the potential for genetic biofortification of sweetcorn (Zea mays L.) by quantifying immature kernel zinc (Zn) concentrations across a broad range of Zea mays L. germplasm. Varieties examined included commercial sweetcorn cultivars, high zeaxanthin sweetcorns, purple sweetcorns, blue maize, quality protein maize and popcorns. Though all kernel samples were harvested at a physiologically immature stage typical of sweetcorn harvest and consumption (21 days after pollination, DAP), the varieties accumulated distinctly different kernel dry matter concentrations depending on whether they were classified as sugary or starchy varieties. The difference in dry matter concentration between types confounded comparisons of kernel Zn concentration when assessed on a fresh mass basis, which is typically used to quantify dietary intake. Kernel mass (indicative of kernel size) and the ratio of embryo-to-kernel mass also contributed to variation in kernel Zn concentration. Analysis of a broader range of nutrient concentrations suggested that variation in kernel Zn concentration was more closely associated with variations in S concentration than P concentration in the sugary varieties. This suggested the possibility of biofortifying sweetcorn kernel Zn without necessarily increasing kernel P and associated anti-nutrient compounds like phytate.

Quantifying soluble sugar in super sweet corn using near-infrared spectroscopy combined with chemometrics

Soluble sugar content is a key factor affecting super sweet corn quality, making the development of a rapid, simple, and environmentally friendly method for measuring soluble sugar content significant for successful breeding. The near-infrared (NIR) spectra of 131 sets of super sweet corn kernels with different soluble sugar contents (5.57–45.35 mg/g) were collected and preprocessed using multiple scattering correction (MSC), standard normal variate (SNV) transformation, and first and second derivatives. The first derivative spectrum, which gave the best preprocessing result, was used to construct the synergy interval partial least squares (Si-PLS) model. The PLS model developed using the 1349−1513 nm, 1842−2005 nm, 2005−2168 nm, and 2337−2500 nm wavebands gave the best result: root mean square error of the prediction set (RMSEP) =6.9199 mg/g and correlation coefficient of the prediction set (RP) = 0.7695. A competitive adaptive reweighted sampling (CARS)-Si-PLS wavelength screening algorithm was used to improve the predictive accuracy of the model further (RMSEP =5.8292 mg/g and RP = 0.8431). Compared to the original spectrum, the optimized model using CARS-SI-PLS is more concise and robust, confirming the ability of NIR spectroscopy to accurately measure soluble sugar content in super sweet corn.

Variation in zinc concentration of sweetcorn kernels reflects source-sink dynamics influenced by kernel number.

Grain yield and mineral nutrient concentration in cereal crops are usually inversely correlated, undermining biofortification efforts. Here, sink size, expressed as kernel number per cob, was manipulated by controlling the time when the silks of sweetcorn (Zea mays) cv. Hybrix 5 and var. HiZeax 103146 were exposed to pollen. Twelve other varieties were manually pollinated to achieve the maximum potential kernel number per cob, and kernel Zn concentration was correlated with kernel number and kernel mass. As kernel number increased, kernel Zn concentration decreased, with the decrease occurring to similar extents in the embryo tissue and the rest of the kernel. However, total kernel Zn accumulated per cob increased with increasing kernel number, as the small decreases in individual kernel Zn concentration were more than offset by increases in kernel number. When both kernel number and mass were considered, 90% of the variation in kernel Zn concentration was accounted for. Differential distribution of assimilates and Zn to sweetcorn cobs led to significant decreases in kernel Zn concentration with increasing kernel number. This suggests there will be challenges to achieving high kernel Zn concentrations in modern high-yielding sweetcorn varieties unless genotypes with higher Zn translocation rates into kernels can be identified.

Storage stability and characterization of biochemical, rehydration and colour characteristics of dehydrated sweet corn kernels

The degradation kinetics of dehydrated sweet corn for total sugar, ascorbic acid, TSS, pH, rehydration parameters, colour and moisture content using low density polyethylene pouches (LDPE) and laminated aluminium foil pouches (LAFP) with or without vacuum were studied. The samples were kept for 3 months and were analysed at every 15 days. During the storage, total sugar, ascorbic acid and total soluble solids reduced from 10.50 to 9.73 g/100 g, 9.36 to 8.86 mg/100 g, 83 to 51°Brix respectively. Rehydration coefficient and rehydration ratio reduced from 90.28 to 75.27, 2.64 to 1.56. Colour L∗ value, a∗ value. b∗ value changed from 61.00 to 70.13, 42.93 to 53.27, 55.58 to 64.24 respectively resulting in increase in ΔE value and chroma value up to 16.29, 70.23 to 83.45 respectively. The moisture content increased from 2.12 to 3.92% in packages. The average sensory score of 7.86 even after 90 days of storage in laminated aluminium foil pouch with vacuum indicates that the product may be stored for 90 days satisfactorily. Zero and first order models fitted well and can be used for predicting various properties of dehydrated sweet corn during storage.

Dynamic effects of post‐harvest preservation on phytochemical profiles and antioxidant activities in sweet corn kernels

SummaryIn order to investigate the effects of thermal processing and preservation on phytochemicals and antioxidant activity of sweet corn kernels, 100 °C, 115 °C and 121 °C were operated as processed conditions and‐20 °C was provided for 6 months storage in this study. Results showed that phenolics, vitamin E content and antioxidant activity in sweet corn kernels raised after thermal processing. Three months preservation slightly declined phenolics and vitamin E content. Thermal processing in favor of the retentions of vitamin E and carotenoids. Principle component analyses and correlation analyses were operated to identify the roles of detected compounds. The study figured out the phytochemical profiles of sweet corn kernels during preservation and elaborated the effect of thermal processing, which could be a guidance for the procession and preservation of post‐harvest fresh kernels.

The Effect of Temperature on the Development of Spodoptera frugiperda (Lepidoptera: Noctuidae).

The fall armyworm (Spodoptera frugiperda) is a pest of tropical origin which recently invaded Africa, the Far East and Australia. Temperature, therefore, plays an important role in its invasion biology, since this pest does not go into diapause. The aim of this study was to determine the development rate of S. frugiperda at different temperatures and to calculate the number of degree-days (°D) required for each stage to complete its development. This study was conducted at five different temperatures—18, 22, 26, 30 and 32 ± 1 °C. Larvae were reared individually in Petri dishes with sweetcorn kernels provided as food. The development rate of S. frugiperda increased linearly with increasing temperatures between 18 and 30 °C and larval survival was the highest between 26 and 30 °C. The optimal range for egg, larval and egg-to-adult development was between 26 and 30 °C. The optimum temperature with the fastest larval development rate and lowest mortality was at 30 °C. The pupal development period ranged between 7.82 and 30.68 days (32–18 °C). The minimum temperature threshold for egg and larva development was 13.01 and 12.12 °C, respectively, 13.06 °C for pupae and 12.57 °C for egg-to-adult development. Degree-day requirements for the development of the respective life cycle stages of S. frugiperda were 35.68 ± 0.22 for eggs, 204.60 ± 1.23 °D for larvae, 150.54 ± 0.93 °D for pupae and 391.61 ± 1.42 °D for egg-to-adult development.

Influence of Blanching Time on Moisture, Sugars, Protein, and Processing Recovery of Sweet Corn Kernels

The objective of this work is to determine the influence of blanching time on moisture content, sugars, protein, and processing recovery (degree of cut corn) of sweet corn kernels. Sweetcorn cobs of the Jubilee variety were blanched in the water at the temperature 85 °C during the period of 2, 4, 6, and 8 min. Non-blanched cobs were used as control samples. Blanched cobs were made subject to a mechanical process of cutting-off the kernels. It was stated that the blanching time has significant statistical influence on the content of moisture, sugars, and protein in kernel as well as on the quantity of the cut-off kernel mass.

Natural variation for carotenoids in fresh kernels is controlled by uncommon variants in sweet corn.

Sweet corn (Zea mays L.) is highly consumed in the United States, but does not make major contributions to the daily intake of carotenoids (provitamin A carotenoids, lutein and zeaxanthin) that would help in the prevention of health complications. A genome-wide association study of seven kernel carotenoids and twelve derivative traits was conducted in a sweet corn inbred line association panel ranging from light to dark yellow in endosperm color to elucidate the genetic basis of carotenoid levels in fresh kernels. In agreement with earlier studies of maize kernels at maturity, we detected an association of β-carotene hydroxylase (crtRB1) with β-carotene concentration and lycopene epsilon cyclase (lcyE) with the ratio of flux between the α- and β-carotene branches in the carotenoid biosynthetic pathway. Additionally, we found that 5% or less of the evaluated inbred lines possessing the shrunken2 (sh2) endosperm mutation had the most favorable lycE allele or crtRB1 haplotype for elevating β-branch carotenoids (β-carotene and zeaxanthin) or β-carotene, respectively. Genomic prediction models with genome-wide markers obtained moderately high predictive abilities for the carotenoid traits, especially lutein, and outperformed models with less markers that targeted candidate genes implicated in the synthesis, retention, and/or genetic control of kernel carotenoids. Taken together, our results constitute an important step toward increasing carotenoids in fresh sweet corn kernels.

Comparison of Zn accumulation and speciation in kernels of sweetcorn and maize differing in maturity.

Understanding the speciation of Zn in edible portions of crops helps identify the most effective biofortification strategies to increase the supply of nutrients for improving the health and nutrition of consumers. Kernels of 12 sweetcorn and three maize (Zea mays) varieties were analysed for Zn concentration and content. The speciation of the Zn in the embryos, endosperms and whole kernels at 21, 28 and 56 days after pollination (DAP) was then examined for one maize and one sweetcorn variety using synchrotron-based X-ray absorption spectroscopy (XAS). Averaged across all sweetcorn and maize varieties at 21 DAP, the embryo contributed 27-29% of the whole kernel Zn whilst the endosperm contributed 71-73 %. While sweetcorn embryos contributed a lower proportion to the total kernel Zn than those of maize, the proportion of total Zn in the embryo increased as kernels aged for both varieties, reaching 33 % for sweetcorn and 49% for maize at 28 DAP. Using XAS, it was predicted that an average of 90 % of the Zn in the embryos was present as Zn-phytate, while in the endosperm the Zn was primarily complexed with an N-containing ligand such as histidine and to a lesser extent with phytate. However, in maize endosperms, it was also observed that the proportion of Zn present as Zn-phytate increased as the kernel matured, thereby also probably decreasing its bioavailability in these mature maize kernels. The apparent low bioavailability of Zn supplied in maize at its consumption stage (i.e. mature kernels) probably undermines the effectiveness of biofortification of this crop. Conversely, successful biofortification of Zn in sweetcorn and green maize consumed as immature kernels could potentially provide a good source of bioavailable Zn in human diets.

Isolation, characterization, and identification of phosphate-solubilizing Burkholderia cepacia from the sweet corn cv. Golden Bantam rhizosphere soil and effect on growth-promoting activities

ABSTRACT The average growth and productivity of sweet corn (Zea mays L, cv. Golden Bantam) in India is lower than its potential, likely due to lack of proper phosphorus (P) management. Phosphorus is normally applied to soil as a synthetic P fertilizer. The industrial manufacturer of chemical P fertilizer is a highly energy-intensive process. There can be long-term environmental implications due to eutrophication, soil fertility depletion, and the size of the carbon footprint. Alternate strategies for use of P in sustainable agriculture are being developed. Phosphate-solubilizing bacteria (PSB) can make available insoluble phosphate compounds as an alternate strategy to phosphatic fertilizers. Even though PSB occur in soil, their numbers are usually not high enough in the rhizosphere, their performance in situ is not reliable, and needs to be improved. The project was undertaken to isolate, and characterize, PSB from the rhizosphere of sweet corn (Zea mays L, cv. Golden Bantam) and investigate their potential for the promotion of plant growth. Eight phosphate-solubilizing bacterial colonies were isolated on Pikovskaya’s (PKV) agar medium, containing insoluble tricalcium phosphate. Clear halo zones occurring around colonies indicated they were phosphate solubilizers. The phosphate-solubilization index (PSI) ranged from 1.77 ± 0.92 to 4.88 ± 0.69, broth medium pH ranged from 5.44 ± 0.40 to 3.08 ± 0.08 and phosphate solubilization varied from 125.33 ± 8.78 to 305.49 ± 10 μg∙mL−1. Bacterial isolates, MS1, MS2, and MS5, exhibited high PSI, low pH, and high phosphate solubilization and were further studied. There was a negative correlation (r = −0.72) between soluble P content and medium pH, and a positive correlation (r = 0.90) between soluble P content and PSI, indicating acidification of the medium can aid phosphate solubilization. Pot and field studies indicated isolate MS1 had the greatest efficiency in promoting sweet corn growth and kernel productivity over isolates MS2 and MS5 and the control. Based on the 16S rRNA gene sequence analysis isolate MS1 was closely related to Burkholderia cepacia (99%). Isolates MS2 and MS5 were related to B. contaminans (94%–99%). Isolate B. cepacia was superior over MS2 and MS5 in terms of concentration of soluble P, pH of the broth medium, pot experiment and field experiment, and selected for further study. The HPLC analysis indicated isolate MS1 produced gluconic and formic acids, and an unknown acid, in a culture which may be the principal mechanism for phosphate solubilization. Burkholderia cepacia isolates could be used as a plant growth-promoting bacterium instead of synthetic chemicals and may help to sustain sweet corn productivity.

Genome-wide association study of vitamin E in sweet corn kernels

Vitamin E, consisting of tocopherols and tocotrienols, serves as a lipid-soluble antioxidant in sweet corn kernels, providing nutrients to both plants and humans. Though the key genes involved in the vitamin E biosynthesis pathway have been identified in plants, the genetic architecture of vitamin E content in sweet corn kernels remains largely unclear. In the present study, an association panel of 204 inbred lines of sweet corn was constructed. Seven compounds of vitamin E were quantified in sweet corn kernels at 28 days after pollination. A total of 119 loci for vitamin E were identified using a genome-wide association study based on genotyping by sequencing, and a genetic network of vitamin E was constructed. Candidate genes identified were involved mainly in RNA regulation and protein metabolism. The known gene ZmVTE4, encoding γ-tocopherol methyltransferase, was significantly associated with four traits (α-tocopherol, α-tocotrienol, the α/γ-tocopherol ratio, and the α/γ-tocotrienol ratio). The effects of two causative markers on ZmVTE4 were validated by haplotype analysis. Finally, two elite cultivars (Yuetian 9 and Yuetian 22) with a 4.5-fold increase in the sum of α- and γ-tocopherols were developed by marker-assisted selection, demonstrating the successful biofortification of sweet corn. Three genes (DAHPS, ADT2, and cmu2) involved in chorismate and tyrosine synthesis were significantly associated with the α/γ-tocotrienol ratio. These results shed light on the genetic architecture of vitamin E and may accelerate the nutritional improvement of sweet corn.