Concentration of Beneficial Phytochemicals in Harvested Grain of U.S.

Subscriber access provided by GRIFFITH UNIVERSITY

Article

CONCENTRATION OF BENEFICIAL PHYTOCHEMICALS IN HARVESTED GRAIN OF US YELLOW DENT MAIZE (Zea mays L.) GERMPLASM Carrie J. Butts-Wilmsmeyer, Rita H. Mumm, and Martin O. Bohn J. Agric. Food Chem., Just Accepted Manuscript • DOI: 10.1021/acs.jafc.7b02034 • Publication Date (Web): 05 Sep 2017 Downloaded from http://pubs.acs.org on September 9, 2017

Just Accepted “Just Accepted” manuscripts have been peer-reviewed and accepted for publication. They are posted online prior to technical editing, formatting for publication and author proofing. The American Chemical Society provides “Just Accepted” as a free service to the research community to expedite the dissemination of scientific material as soon as possible after acceptance. “Just Accepted” manuscripts appear in full in PDF format accompanied by an HTML abstract. “Just Accepted” manuscripts have been fully peer reviewed, but should not be considered the official version of record. They are accessible to all readers and citable by the Digital Object Identifier (DOI®). “Just Accepted” is an optional service offered to authors. Therefore, the “Just Accepted” Web site may not include all articles that will be published in the journal. After a manuscript is technically edited and formatted, it will be removed from the “Just Accepted” Web site and published as an ASAP article. Note that technical editing may introduce minor changes to the manuscript text and/or graphics which could affect content, and all legal disclaimers and ethical guidelines that apply to the journal pertain. ACS cannot be held responsible for errors or consequences arising from the use of information contained in these “Just Accepted” manuscripts.

Journal of Agricultural and Food Chemistry is published by the American Chemical Society. 1155 Sixteenth Street N.W., Washington, DC 20036 Published by American Chemical Society. Copyright © American Chemical Society. However, no copyright claim is made to original U.S. Government works, or works produced by employees of any Commonwealth realm Crown government in the course of their duties.

Page 1 of 35

Journal of Agricultural and Food Chemistry

CONCENTRATION OF BENEFICIAL PHYTOCHEMICALS IN HARVESTED GRAIN OF US YELLOW DENT MAIZE (Zea mays L.) GERMPLASM

Carrie J. Butts-Wilmsmeyer, Rita H. Mumm, and Martin O. Bohn* Department of Crop Sciences, the University of Illinois at Urbana-Champaign, 1102 S. Goodwin Avenue, Urbana, IL 61801 *

Corresponding author: [email protected] Phone: (217) 244 2536

Keywords: Maize, Phenolics, Tocopherols, Protein, Plant Breeding

1 ACS Paragon Plus Environment


1

ABSTRACT

2

Although previous studies have examined the concentration of various nutritional

3

compounds in maize, little focus has been devoted to the study of commercial maize hybrids or

4

their inbred parents. In this study, a genetically and phenotypically diverse set of maize hybrids

5

and inbreds relevant to U.S. commercial maize germplasm was evaluated for its variability in

6

phytochemical content. Total protein, unsaturated fatty acids, tocopherols, soluble phenolics, and

7

insoluble-bound phenolics were evaluated in this study. Of these compounds, only soluble and

8

insoluble-bound phenolic acids exhibited means and variances that were at least as large as the

9

means and variances reported for other sets of germplasm. This suggests that selection for high

10

phenolic acid content is possible in current U.S. commercial germplasm. In contrast, while the

11

total protein, unsaturated fatty acid, or tocopherol content could possibly be improved using

12

current U.S. commercial germplasm, the results of this study indicate that the incorporation of

13

more diverse sources of germplasm would most likely result in quicker genetic gains.


Page 2 of 35

Page 3 of 35


INTRODUCTION

14 15

Over the last decade, consumers have become increasingly interested in the natural

16

nutritional value of their food products.1 This increased interest is not surprising. High obesity

17

rates are common in affluent nations. The incidence of aging-related diseases in developed

18

countries is rising.2 Furthermore, there is greater public concern that processed foods are less

19

nutritious.3 Therefore, food companies must consider not only the calorie and vitamin content of

20

their food products, but also the content of beneficial phytochemicals which occur naturally in

21

their food products.

22

In 2016, 2.8 billion bushels (71.12 billion kg) of maize were devoted to human food

23

consumption,4 thereby highlighting the importance of maize in the American diet. For this

24

study, the variability in the concentration of total protein content, fatty acids, tocopherols, and

25

phenolics was examined in a set of maize lines which are representative of the commercial maize

26

germplasm grown in the U.S. Corn Belt.5-6 All these phytochemicals are beneficial to human

27

health. Diets higher in total protein result in satiety and weight maintenance. Since satiety is

28

maintained for longer periods of time, people tend to eat less frequently.7 This reduced food

29

consumption contributes to a lower overall caloric intake and a decreased chance of developing

30

an obesity-related disease. Unsaturated fatty acids play important roles in blood pressure

31

regulation, cell membrane integrity, and improving cholesterol levels.8-9 Oleic acid and linoleic

32

acid are fatty acids important in the human diet and are found in maize.

33

In contrast to the health benefits of protein and unsaturated fatty acids, tocopherols and

34

phenolics exhibit antioxidant activity, prebiotic activity, and other chemopreventive properties.10-

35

13

36

Most studies have focused on α-tocopherol because it is the most efficient antioxidant of the

α-, γ-, and δ-Tocopherol are typically found in maize, whereas β-tocopherol is rarely present.14



37

three tocopherols present in maize.13 Like the tocopherols, many of the soluble phenolics exhibit

38

antioxidant activity in vitro, but, in vivo, they are more likely to activate gene cascades involved

39

in immunoprotection and chemoprevention.11-12,

40

ferulic acid and p-coumaric acid, both of which are hydroxycinnamic acids.16-17 In cereals, these

41

are mainly bound to the cell wall via ester bonds. Thus, insoluble-bound phenolics are not

42

readily available for the activation of gene cascades. However, in conjunction with the

43

arabinoxylan fibers to which they are bound, the insoluble-bound phenolics act as prebiotics by

44

creating an environment beneficial for gut bacteria, including Lactobacillus and Bifidobacterium

45

species.18

15

The predominant phenolics in maize are

46

A precursor to the phenolics in maize is the carboxylic acid cinnamic acid. Cinnamic acid

47

is stored in the vacuoles of plants19 prior to being modified in, most likely, the Golgi bodies.

48

Cinnamic acid-4 hydroxylase acts on cinnamic acid, producing p-coumaric acid. p-Coumaric

49

acid is acted upon by p-coumaric hydroxylase and then o-methyltransferase to produce ferulic

50

acid. p-Coumaric acid and ferulic acid most likely are synthesized before esterification to

51

arabinoxylans.20 It also appears that hydroxycinnamic acids are esterified to arabinoxylans in the

52

Golgi bodies.21 Therefore, to understand the variability in the composition of the phenolics in

53

maize, an understanding of cinnamic acid is useful.

54

Our overall objective was to determine the potential for improving the nutritional content

55

of maize hybrids that are representative of U.S. Corn Belt germplasm. In this study, we

56

determined the average content and variability of total protein, unsaturated fatty acids, α-, γ-, and

57

δ-tocopherol, and phenolics in U.S. Corn Belt maize inbred parents (i.e., inbreds) and a subset of

58

their hybrids. Using the estimated means and variability in the phytochemicals of interest, we

59

determined if this germplasm is well suited for improving the nutritional quality of yellow dent


Page 4 of 35

Page 5 of 35


60

maize hybrids or if the other germplasm sources must be tapped to access favorable alleles.

61

Using the literature base, we also discuss the potential fate of these phytochemicals during maize

62

food product processing and consider which phytochemicals may be the most feasible to

63

improve using plant breeding techniques.



MATERIALS AND METHODS

64

65

Plant Materials

66

The hybrids evaluated in this study were created from a genetically diverse set of inbreds

67

that represent important heterotic subgroups in the current U.S. maize commercial germplasm

68

base.5-6 A heterotic group is a group of parental genotypes whose observed combining ability and

69

heterosis are similar when crossed with parental genotypes from other groups.22 Heterotic

70

groups can be broken into smaller sets called subgroups. Five of the inbreds (B73, LH1, PHG39,

71

PHJ40, and 4676A) were derived from the Iowa Stiff Stalk Synthetic (SSS), which represents the

72

female side of the heterotic pattern used in the U.S. Seven other inbreds (LH123HT, LH82,

73

Mo17, PH207, PHG47, PHG84, and PHZ51) are of Non-Stiff Stalk (NSS) origin and are

74

composed largely of Iodent, Minnesota 13, Oh07, Midland yellow Dent, Oh43, Lancaster, and

75

broad-based subgroups which generally represent the male side of the heterotic pattern used in

76

the U.S.6 Using a diallel mating design, 66 hybrids were created from the 12 inbreds used in this

77

study. All inbreds and hybrids (NTotal = 78 entries) were grown at the University of Illinois Crop

78

Sciences Research and Education Center in Urbana, IL in the summer seasons of 2009, 2010,

79

and 2011.6 Plots were comprised of four rows with length of 5.3m and which were 0.76 m apart

80

at a plant density of approximately 74,000 plants ha-1; only the center 2 rows were harvested for

81

grain. Plots were managed in accordance with regional agronomic production practices (i.e. no

82

irrigation, minimum tillage, and standard fertilizer regime). Three replications of the 78 entries

83

were grown in each of the three years. Of the 78 entries, 25 of those entries were chosen for use

84

in this study. Exactly 454 g of harvested grain from each plot was dried to a moisture content of

85

approximately 8%, bagged, and placed in cold storage prior to nutritional analyses. From each


Page 6 of 35

Page 7 of 35


86

bag, a 100 g grain sample was ground to a fine powder using a Foss Cyclone Mill (1 mm mesh

87

screen). We used this powder in all wet-lab chemistry.

88 89

Subset Determination

90

The available resources allowed us to analyze 25 entries, which amounted to nine

91

samples per entry and a total number of 225 samples. For this study, we used all 12 parental

92

inbreds and 13 hybrids. The set of 13 hybrids was composed of the five highest and the five

93

lowest performing SSS×NSS hybrids in relation to their dry milling efficiency and three hybrids

94

which have Iodent parent PH207 in common. Dry milling efficiency is the proportion by weight,

95

on a dry basis, of flaking grits obtained from one kg of dry milled grain (for more information

96

see Macke et al.6). Three hybrids with PH207 parentage were included because preliminary

97

analyses (data not shown) indicated that the inbred PH207 displayed considerably high content

98

of some of the phytochemicals of interest, yet none of the ten hybrids selected based on dry

99

milling efficiency alone had PH207 as a parent. Considering that the content of many nutritional

100

compounds in the maize grain, like starch, protein, and oil, is largely influenced by additive gene

101

action,23 it was important that hybrids with PH207 as a parent were included as part of this study

102

and that inferences were made on as diverse of a subset as possible. In addition, PH207

103

represents an important heterotic subgroup in commercial maize breeding germplasm.

104 105

Reagents

106

Ethyl acetate, α-amylase, and methanol were purchased from Sigma-Aldrich (St. Louis,

107

MO). Sodium hydroxide, sodim choloride, hydrochloric acid, and pyridine were purchased from

108

Fisher Scientific (Pittsburgh, PA). N,O-Bis(tremethylsilyl)trifluoroacetamide (BSTFA) was



109

obtained from Thermo Scientific (Waltham, MA). Ferulic acid, p-coumaric acid, sinapic acid,

110

and cinnamic acid was purchased from both Sigma-Aldrich (St. Louis, MO) and Fisher Scientific

111

(Pittsburgh, PA).

112 113

Determination of Protein Content

114

Whole grain samples (8% moisture) were measured using non-destructive NIR

115

techniques. Calibration curves were built based on known standards. The remainder of the

116

procedure was conducted following the direction of the DA 7200 Diode Array Analyzer

117

Operation Manual24 and Bubert.25

118 119

Determination of Fatty Acid Content

120

The total oil content of ten random kernel maize samples and their corresponding ground

121

samples was measured and these data were used for calibration of the Nuclear Magnetic

122

Resonance (NMR) equipment.26 Ground samples underwent a hexane wash. The hexane layer

123

was removed, placed in a separate vial, and evaporated, leaving only the oil extracted from a

124

particular sample in the bottom of the vial. All vials were weighed before extraction and after

125

evaporation. The difference in the mass is equal to the mass of oil extracted for that particular

126

sample. Dividing this mass by the mass of ground maize used in the extraction gives the total oil

127

content in g oil g-1 maize sample. Three technical replicates were used for each of the ten training

128

samples, and the average content was calculated for the sample using these technical replicates.

129

These values and their corresponding whole kernel samples were used to calibrate a prediction

130

curve using the NMR. The calibration was performed by Dow AgroSciences. The total oil

131

concentration of the 225 samples was estimated using NMR.


Page 8 of 35

Page 9 of 35


132

Approximately 0.5 g of each sample was used for fatty acid quantification. The sample

133

was placed in a vial, and 3 mL of hexane was added. The vials were capped, placed in a

134

sonicator at 75°C for 10 min, and then put on a horizontal shaker for 10 min. Each vial was then

135

vortexed before being centrifuged at 465 g for 5 min. The top hexane layer was removed and

136

placed in a clean vial. The hexane wash was repeated two more times. The hexane extract was

137

dried using a centrifugal evaporator. The oil remaining in the vial was reconstituted in 1 mL of

138

heptane, and 300 L of the heptane/oil mixture was placed in a gas chromatography vial and

139

derivitized using 20 L of sodium methoxide. Subsequently, the samples underwent a Fatty Acid

140

Methyl Ester (FAME) analysis.

141 142

The

proportion

of

total

oil

content

was

recorded

for

each

fatty

acid.

The following equation was used to calculate the concentration of each fatty acid: =

× 1000 × 1

143

where is the concentration of the ith fatty acid and the jth observation in mg per g of maize

144

sample, is the proportion of total oil content for the ith fatty acid and the jth observation,

145

is the total oil content, in g, for the jth observation, and is the recorded mass of the jth

146

observation in grams.

147 148

Determination of Tocopherol Content

149

Following the removal of 300 L from the heptane aliquot for the FAME analysis, the

150

heptane/oil mixture was evaporated to dryness. Gas chromatography was used for quantification

151

of tocopherols in the oil extracts. The total mass of tocopherols (g) remaining was reported by

152

the gas chromatography system. In order to calculate the concentration in the original sample, the

153

following equation was used: 9 ACS Paragon Plus Environment


Page 10 of 35

1 × 10

= × 0.7 × 154

where is the actual tocopherol content of the ith tocopherol and the jth sample and

155

is the reported content of the ith tocopherol in the jth sample before the correction. We applied

156

a correction factor of 0.7, assuming that approximately 70% of the originally extracted

157

tocopherols remained in the oil extract.

158 159

Determination of Soluble Phenolics Content

160

Following the hexane wash, the maize pellet was dried using a centrifugal evaporator.

161

Then, 3 mL of 70% acetone was added to each vial. Vials were placed in a sonicator for 10 min

162

at 75°C and then placed on a horizontal shaker for 10 min. Vials were then vortexed and

163

centrifuged at 465 g for 5 min. The top acetone layer was removed and put in a separate vial. The

164

acetone wash was completed two more times for a total of three acetone washes. The extracted

165

acetone aliquot was then evaporated to dryness using a centrifugal evaporator. Soluble extracts

166

were reconstituted in 2 mL of methanol, vortexted, and filtered using syringe filters. One mL of

167

the filtered solution was then placed in an Ultra Performance Liquid Chromatography (UPLC)

168

for analysis.

169

A Waters Acquity UPLC H-Class with an Acquity BEH Shield RP18 (2.1×150 mm, 1.7

170

m) column was used for the quantification of the soluble phenolics content. The column

171

temperature was maintained at 25ºC. For the first 1.5 minutes, 60% acetonitrile with 0.1%

172

formic acid and 40% methanol was used for the elution at a flow rate of 0.2 mL / min. For the

173

time interval between 1.5 and 11 minutes, 50% acetonitrile with 0.1% formic acid and 50%

174

methanol was used for the elution at a flow rate of 0.2 mL / min. For the time interval between

175

11 and 12 minutes, 60% acetonitrile with 0.1% formic acid and 40% methanol was used for the 10 ACS Paragon Plus Environment

Page 11 of 35


176

elution at a flow rate of 0.2 mL / min. An Acquity UPLC LG 500 nm photodiode array detector

177

was used for UV detection of analytes at 300 nm, 270 nm, and 245 nm. Data signals were

178

recorded and processed using Empower 3 Software (Build 3471) (Waters Corp.).

179

Standards of the typical hydroxycinnamic acids in grains, i.e., ferulic acid, p-coumaric

180

acid, sinapic acid, and cinnamic acid were first analyzed using UPLC to record the retention time

181

of each of these compounds and to build a standard curve for the calculation of concentrations in

182

the maize samples. Our maize samples were then analyzed using UPLC using the protocol as

183

described, and the standard curve was used to calculate the concentration of the

184

hydroxycinnamic acids in each sample using the equation 2 × =

185

where is the content of the ith soluble phenolic in the jth observation and is the recorded

186

mass of the ith soluble phenolic in the jth observation as calculated from the standard curve, and

187

is the recorded mass of the jth observation. was multiplied by a factor of 2 to account for

188

the reconstitution of the soluble phenolics in 2 mL of methanol.

189 190

Determination of Insoluble-Bound Phenolics Content

191

The measurement of the insoluble-bound phenolics content took place using the protocol,

192

including -amylase digestion, as described by Butts-Wilmsmeyer and Bohn27 with the

193

exception that standards of p-coumaric acid, cinnamic acid, and sinapic acid were also used in

194

creating the standard curve. Samples were analyzed using a gas chromatograph with a flame

195

ionization detector (Agilent 6890). A DB-200 megabore column (ID = 0.53 mm, length = 30 m)

196

was used. Hydrogen gas was used as the carrier gas with a split inlet and a split ratio of 1:10

197

(split vent flow = 10 mL / min, column flow = 1 mL / min). 11 ACS Paragon Plus Environment


Page 12 of 35

198 199

Statistical Analyses An Analysis of Variance (ANOVA) was performed based on the following linear mixed

200 201

model: = + + + + +

202

where is the observed phenotypic value corresponding to the ith year, the jth replication

203

within the ith year, and the kth genotype, is the grand population mean, is the random effect

204

of the ith year, is the random effect of the jth field replication nested within the ith year, is

205

the fixed effect of the kth genotype, is the random interaction between the ith year and the kth

206

genotype, and

207

the ith year, and the kth genotype. The random error effects

208

independently distributed with mean 0 and variance !"# .

is the random error term associated with the ith year, the jth replication within are

assumed to be normally and

209

Inbreds and hybrids were analyzed separately using this statistical model in SAS PROC

210

MIXED (version 9.3). Due to adverse field conditions in 2010 and 2011, a balanced set of inbred

211

samples was not available for analysis. Therefore, the REML method was used to conduct the

212

ANOVA and calculate p-values associated with the genotypic effect as well as the standard error

213

of the differences between inbred means. The REML method was also used to conduct the

214

ANOVA for the tocopherols because several samples had tocopherol contents below the GC

215

detection level, leading to an unbalanced data set for the tocopherol analyses.

216

The assumptions of normality and homogenous variances were validated by conducting

217

Shapiro-Wilk’s test of normality on the residuals in PROC UNIVARIATE and by using the

218

Brown-Forsythe modification of the Levene test in the MEANS option of PROC GLM. If a

219

highly significant year-by-genotype interaction existed and the average concentration was high 12 ACS Paragon Plus Environment

Page 13 of 35


220

enough to warrant further investigation of the compound, multi-degree of freedom contrast

221

statements were used to examine the genotype effect in each year. If phytochemicals displayed

222

either a mean or a variance that was at least as large as what is found in other germplasm sources

223

reported in the literature, the relationship between years was measured using Pearson correlation

224

coefficients, which were calculated in PROC CORR.



RESULTS

225 226

Page 14 of 35

Total Protein Content

227

The mean total protein content of hybrids and inbreds was found to be 9.12% and

228

11.51%, respectively (Table 2). The protein content observed in this study ranged between

229

8.34% and 10.22% in the hybrids and between 9.86% and 13.24% in the inbreds.

230 231

Unsaturated Fatty Acid Content

232

In the hybrid group, oleic acid varied between 7.21 and 12.22 mg g-1, whereas linoleic

233

acid ranged from 17.38 to 21.71 mg g-1. In the inbred group, oleic acid ranged between 4.77 and

234

9.51 mg g-1, whereas linoleic acid ranged between 15.92 and 22.90 mg g-1. The hybrids

235

examined in this study varied between 21.2% and 33.4% for oleic acid and between 50.4% and

236

62.7% for linoleic acid content in the oil (Table 2).

237 238

Tocopherols The mean content of α-, γ-, and δ-tocopherol in the hybrids were 5.42 g g-1, 21.74 g g-

239 240

1

, and 1.47 g g-1, respectively (Table 2). The mean content of α-, γ-, and δ-tocopherol in the

241

parental inbreds was 5.70 g g-1, 18.68 g g-1, and 1.16 g g-1, respectively (Table 2). The

242

tocopherol values observed in the hybrids differed very little from the values observed in the

243

inbreds.

244 245

Soluble and Insoluble-Bound Phenolics

246

Soluble ferulic acid and p-coumaric acid were consistently detected at low concentration

247

levels using UPLC. The average concentrations of these two compounds in hybrids were 1.44 g


Page 15 of 35


248

g-1 and 1.65 g g-1, respectively. In addition to the low mean concentration of both soluble

249

ferulic acid and soluble p-coumaric acid, these compounds exhibited a small range in

250

concentrations among both inbreds and hybrids (Table 2). Conversely, soluble cinnamic acid, a

251

carboxylic acid, was consistently more prevalent than either of the detected phenolic acids (Table

252

2). The average soluble cinnamic acid concentration was 67.09 g g-1 in the hybrids and 78.89

253

g g-1 in the inbreds. Additionally, the range in soluble cinnamic acid content was relatively

254

large in comparison to the soluble phenolics (Table 2).

255

Insoluble-bound ferulic acid and p-coumaric acid were consistently detected using gas

256

chromatography. Insoluble-bound ferulic acid was the most prevalent of all the phenolics. The

257

average concentration of insoluble-bound ferulic acid in hybrids and inbreds was 1,950.29 g g-1

258

and 1,952.49 g g-1, respectively. The average concentration of insoluble-bound p-coumaric acid

259

was 176.19 g g-1 in the hybrids and 222.94 g g-1 in the inbreds. The range observed in the

260

insoluble-bound phenolics content was the highest of all compounds examined in this research

261

(Table 2).

262 263

Year×Genotype Interactions

264

The three growing seasons used in this experiment were widely different with regard to

265

their temperature and rainfall totals.28 In general, 2009 was a very mild year. The year 2010 was

266

mild but wet during the first half of the growing season and hot and somewhat dry during the

267

second half of the growing season. Lastly, the year 2011 was very hot and dry during flowering,

268

pollination, and seed set. Not surprisingly, the Year and Year×Genotype interaction terms in the

269

model were often significant. However, while the mean concentration of a genotype for a

270

particular phytochemical may have changed depending on the specific environment, the relative



Page 16 of 35

271

ranking of the hybrid and inbred means for each specific beneficial phytochemical changed very

272

little. Interestingly, the beneficial phytochemicals which displayed relatively large means or

273

variances in this study, in comparison to the means and variances reported for other sets of

274

germplasm, were largely controlled by genotypic effects rather than by environmental effects

275

(Table 3). Furthermore, the correlation between the mean insoluble-bound ferulic acid content

276

for each hybrid across all three years ranged between 76% and 83%. The correlation between the

277

mean insoluble-bound p-coumaric acid content for each hybrid across all three years ranged

278

between 84% and 92%. Lastly, the correlation between the mean soluble cinnamic acid content

279

for each hybrid across all three years ranged between 73% and 87%.


Page 17 of 35

280


DISCUSSION

281

The ultimate goal of this research was to examine the potential for improving the

282

nutritional content and grain composition of maize hybrids adapted to the U.S. Corn Belt. As a

283

first step toward this goal, we determined the average content and variability of total protein,

284

unsaturated fatty acids, tocopherols, and phenolics in elite U.S. maize germplasm. This

285

information could prove beneficial to plant breeders, food scientists, and animal scientists who

286

have either an interest in improving the nutritional quality of maize grain for animal feed or an

287

interest in improving the nutritional quality of processed maize food products for human

288

consumption. If the research focus is to increase the quality of processed maize food products for

289

human consumption, then both breeding and processing considerations must be examined in

290

future studies. Here, we address the initial question of whether the U.S. maize germplasm alone

291

is well-suited for use in improving the nutritional quality of the whole grain.

292 293

Precision of Analytical Chemistry Analyses

294

The standard errors of all compounds analyzed were very small in comparison to the

295

averages of the respective traits (Table 2). This is indicative of very precise analytical chemistry

296

techniques, which is unquestionably favorable because it shows the high quality of the analyses

297

in this study. However, this also shows that even the slightest differences among hybrid or inbred

298

means could result in a significant P-value. Even if significant differences between hybrid means

299

or inbred means exist, as indicated by a significant P-value, the range in those differences might

300

be much smaller than what is already present in other germplasm collections. Additionally, as in

301

this study, the mean concentrations of certain phytochemicals were small in comparison to those

302

reported in other studies, even though significant P-values were detected for the differences in



Page 18 of 35

303

mean content. Thus, while plant improvement, as measured by the selection response, can be

304

accomplished if significant differences exist between genotypes, the rate and magnitude of the

305

selection response will be greater if plant breeders work with germplasm that already exhibits a

306

large mean and variance for the trait(s) of interest. Therefore, while significance levels for all

307

phytochemicals examined are reported, the magnitude of the mean and range of each beneficial

308

phytochemical should also be considered and compared to other sets of germplasm.

309 310

Protein

311

The protein content measured in our study corresponds closely to the typical average of

312

8-11% in commercial maize germplasm.29 Also, the range in the average protein content in this

313

study is small in comparison to other studies, particularly the Illinois Long-Term Selection

314

Experiments. For instance, Goldman, et al.30 evaluated germplasm that ranged between 4% and

315

25% protein content, and Dudley and Lambert31 reported protein contents that ranged between

316

5.2% and 25.2%.

317

Furthermore, the mean protein content observed in this study is lower than what is

318

recorded for other germplasm sets. As another example, Singh et al.32 evaluated a set of 49

319

accessions used in the Germplasm Enhancement of Maize (GEM) project. These accessions had

320

protein contents ranging between 12 and 14%. However, most breeding efforts for commercial

321

germplasm have focused primarily on the improvement of grain yield. Grain yield is chiefly

322

governed by the starch content, and the starch content and grain yield significantly decrease if

323

protein content is increased beyond 11 to 12%.29 It also appears that as breeders have selected for

324

higher yield (and an inherently higher starch content), indirect selection has caused protein

325

contents to decrease in commercial maize germplasm in the U.S. The DuPont Pioneer Hi-Bred


Page 19 of 35


326

Era study found that generations of plant breeding and selection caused protein content to

327

decrease from approximately 13.4% in 1920 to the lower percentages seen in the adapted

328

germplasm grown today.33 Therefore, the relatively low protein content and the small range in

329

protein content observed in this study are not surprising. Thus, while it is possible to improve

330

protein content using typical commercial maize germplasm, it appears that the rate of

331

improvement would be greater if other germplasm sources, such as those found in the Illinois

332

High Protein experiments or the accessions used in the GEM project, were used in addition to

333

commercial maize germplasm. It should be noted that this statement is in reference to the

334

improvement of total protein, not the protein quality. Other studies, such as those making use of

335

the Opaque-2 gene in maize, have had considerable success in improving the quality of maize

336

protein. However, that is not the focus of this research.

337 338

Unsaturated Fatty Acids and Tocopherols

339

In this study, neither the oleic acid content nor the linoleic acid content displayed a large

340

mean or a wide range, particularly in comparison to studies such as the Illinois Long-Term

341

Selection experiments. This is true of both the inbreds and the hybrids (Table 2). In comparison

342

to the results presented here, a study conducted by Poneleit and Davis34 reported that oleic acid

343

accounts for approximately 17% to 39% of the total extracted oil, whereas linoleic acid

344

constituted approximately 44% to 69%. Another study which used lines derived from Cycle 90

345

of the Illinois High Oil population and Cycle 19 of the Illinois Low Oil population (Early

346

Maturity) as well as other maize lines with slightly less extreme phenotypes showed that the

347

oleic acid content of the oil ranged between approximately 14% and 38% and that the linoleic

348

acid content ranged between approximately 47% and 72%.35 This suggests that other germplasm



Page 20 of 35

349

resources show more diversity not only for the total amount of unsaturated fatty acids but also

350

for the overall composition of these fatty acids in the oil. Given that corn yield is correlated with

351

starch content in the grain, it is not surprising that there is little variability in the unsaturated fatty

352

acid content and composition among the elite hybrids and inbreds used in this study. Breeders

353

have traditionally prioritized yield, and the grain yield of high oil lines tends to be reduced.29

354

As expected, γ-tocopherol was the most prevalent tocopherol, followed by α-tocopherol

355

and then δ-tocopherol (Table 2). The small ranges observed for both α- and δ-tocopherol (Table

356

2) and the fact that the concentrations of these two phytochemicals were so small that they were

357

barely detectable using gas chromatography make these two phytochemicals unlikely candidates

358

for future maize improvements studies using our germplasm alone without tapping other sources.

359

However, γ-tocopherol did exhibit some variability, which might present potential for continued

360

study and selection.

361

Interestingly, the tocopherol concentration found in our study and those reported by

362

Egesel et al.36 and Lipka et al.37 were considerably different. These discrepancies can be

363

explained by the different germplasm sets used in each study. Egesel et al.36 chose high-oil lines,

364

high tocopherol-containing lines, and inbreds which were known to have either a high or low

365

ratio of α- to γ-tocopherol. As a result, Egesel et al.36 reported ranges of 11.3 to 66.3 µg g-1 for α-

366

tocopherol and 22.8 to 238.7 µg g-1 for γ-tocopherol. They also reported means of 32.9 µg g-1

367

and 120.5 µg g-1 for α-tocopherol and γ-tocopherol, respectively. The concentration of δ-

368

tocopherol was not explicitly reported in that study. In Lipka et al,37 281 maize lines which

369

collectively represent a significant portion of the variation in both temperate and tropical maize

370

breeding programs were used, but these did not include as extreme phenotypes as those

371

evaluated in Egesel, et al.36 Lipka et al.37 reported ranges of 0.70 to 31.35 µg g-1, 5.04 to 85.94


Page 21 of 35


372

µg g-1, and 0.22 to 3.32 µg g-1 for α-, γ-, and δ-tocopherol, respectively. Our results more closely

373

resembled those of Lipka, et al.37 because, like Lipka et al,37 we did not use as extreme

374

phenotypes as Egesel, et al.36 However, the range observed in our study is less than that observed

375

in Lipka, et al.37 because we did not measure as diverse of a germplasm set. Additionally, our

376

results indicate that for all three tocopherols, the environmental factor was the greatest source of

377

variability, whereas genotype×environment interactions were not significant. This could explain

378

why the means and ranges observed in our study differ from those reported in other studies, but it

379

is still apparent that the means and ranges of the materials used in our study would most likely

380

not be as extreme even under different environmental conditions.

381

The location of the fatty acids and tocopherols in maize kernels makes the improvement

382

of their concentrations in maize-based food products challenging. Fatty acids and tocopherols are

383

almost exclusively found in the germ.36 The germ is typically removed during food product

384

processing and used in the production of corn oil. However, oil-containing foods tend to have

385

relatively short shelf lives because oils can become rancid.36, 38 Therefore, many other maize-

386

based processed food products, including breakfast cereals and snack products, are often derived

387

from the endosperm. Thus, the small amount of oleic acid, linoleic acid, and tocopherols present

388

in the whole kernel will not be present in many maize-based processed food products.

389

γ- and δ-Tocopherol have much lower antioxidant activity than α-tocopherol. Since γ-

390

tocopherol is by far the most prevalent of the tocopherols and α-tocopherol was only found in

391

small quantities in the materials examined, this set of germplasm is not well suited for

392

improvement of tocopherol concentration if improved antioxidant activity is the main objective.

393

It should be noted, however, that the results of Egesel et al.36 and Lipka et al.37 indicate that other

394

germplasm resources have considerably higher mean tocopherol contents and more variable



Page 22 of 35

395

tocopherol contents than the germplasm examined in our study. These studies suggest that it may

396

be possible to improve the tocopherol content of whole maize kernels. However, the yellow dent

397

maize genotypes adapted and commercialized in the U.S. Corn Belt do not appear to be well

398

suited for use in such a breeding program without the incorporation of other germplasm sources

399

into this collection of genotypes.

400 401

Soluble and Insoluble-Bound Phenolics

402

The concentrations reported in this study correspond closely to those reported in other

403

studies.17, 39 All phenolics detected were phenolic acids; furthermore, all of the phenolic acids

404

were hydroxycinnamic acids. Of these, ferulic acid was the most prevalent, followed by p-

405

coumaric acid. Most of the hydroxycinnamic acids were in the insoluble-bound state, which is in

406

agreement with Adom and Liu.17 In contrast to the hydroxycinnamic acids, cinnamic acid was

407

found primarily in the soluble state.

408

In comparison to other studies which examined the concentration of ferulic acid in

409

different maize genotypes, the amount of insoluble-bound ferulic acid extracted from maize

410

germplasm typical of the U.S. Corn Belt is moderate to high and variable between genotypes.

411

For instance, Lopez-Martinez et al.40 studied the amount and range of insoluble-bound ferulic

412

acid in 18 maize lines from Mexico, yellow dent maize, and more darkly pigmented maize

413

varieties. In that study, the extractable insoluble-bound ferulic acid content ranged between

414

1,380 g g-1 and 1,610 g g-1. In our study, the insoluble-bound ferulic acid content ranged from

415

1,567 g g-1 to 2,375 g g-1. Furthermore, Garcia-Lara and Bergvinson41 reported that P84, a

416

maize line bred specifically for resistance to insect feeding, largely due to an increased

417

concentration of insoluble-bound hydroxycinnamic acids, had an average ferulic acid


Page 23 of 35


418

concentration of 2,200 g g-1. This is comparable to some of the hybrids and inbreds used in our

419

study.

420

The finding that maize germplasm from the U.S. Corn Belt contains relatively high levels

421

of insoluble-bound hydroxycinnamic acids, particularly ferulic acid, is not surprising. Insoluble-

422

bound hydroxycinnamic acid content is positively correlated with insect and pathogen resistance

423

in maize.42-47 Therefore, while plant breeders have not been directly selecting for higher

424

insoluble-bound hydroxycinnamic acid content, they have been selecting for improved resistance

425

to insect pests and diseases. However, insect and pathogen resistance are not solely influenced by

426

the insoluble-bound hydroxycinnamic acid content. Therefore, the observed variability in the

427

insoluble-bound hydroxycinnamic acid concentrations in our germplasm is not unexpected. It

428

should also be noted that Garcia-Lara and Bergvinson41 further increased P84’s insoluble-bound

429

phenolic acid content by incorporating new germplasm in their breeding program. Therefore,

430

while the adapted germplasm typical of the U.S. Corn Belt appears to be useful in improving the

431

phenolic acid content in maize, the gradual incorporation of other germplasm sources into the

432

plant breeding scheme may help improve the phenolic acid content in maize more rapidly.

433

Due to their high concentrations and variability, the insoluble-bound hydroxycinnamic

434

acids present opportunity for further study and possible improvement in maize. Furthermore, the

435

lack of a change of rank in the hybrids and the inbreds, even when the Year and Year×Genotype

436

terms were significant, suggests that selection implemented in a breeding program would result

437

in genetic gain for these traits. Collectively, these observations suggest that breeding maize for

438

improved insoluble-bound hydroxycinnamic acid content in the whole grain is feasible.

439

However, because maize-based food products must be processed before human

440

consumption, special care should be taken to monitor the fate of the insoluble-bound



Page 24 of 35

441

hydroxycinnamic acids during food product processing. There is some evidence that thermal

442

stresses encountered in processing may free insoluble-bound hydroxycinnamic acids from the

443

arabinoxylans of the cell wall.48 If this observation holds true during maize food product

444

processing, it is possible that the concentration of the soluble ferulic acid and p-coumaric acid

445

may increase while the concentration of the insoluble-bound hydroxycinnamic acids decreases. It

446

is also possible that processing and thermal stresses may degrade the hydroxycinnamic acids,

447

leading to higher concentrations of cinnamic acid. Due to the fact that most phenolic acids in

448

maize are located in the bran, it is also possible that many of the phenolic acids may be “lost” if

449

the bran is removed during food product processing. Future studies may examine the fate of both

450

soluble and insoluble-bound hydroxycinnamic acids as well as cinnamic acid throughout food

451

product processing. Such studies may prove beneficial in increasing the concentrations of these

452

phytochemicals in processed maize-based food products and point the way for new uses of

453

maize.


Page 25 of 35


ABBREVIATIONS USED

454 455

FAME – Fatty Acid Methyl Ester

456

NIR – Near-Infrared Spectroscopy

457

NMR – Nuclear Magnetic Resonance

458

NSS – Non-Stiff Stalk

459

SSS – Stiff Stalk Synthetic

460

UPLC – Ultra Performance Liquid Chromatography

461 462

ACKNOWLEDGEMENTS

463

The authors would like to thank Tom Patterson and the Analytical Technologies Team at Dow

464

AgroSciences for their assistance in developing these protocols and for their mentorship. We

465

would also like to thank Nicole Yana for her invaluable help in coordinating research logistics.

466

FUNDING SOURCES

467 468

This work was funded in part through gifts from the Kellogg Company and Dow AgroSciences

469

and through USDA Hatch Grant, award ILLU-802-354. Student support was provided by the

470

Illinois Distinguished Fellowship and the William B. and Nancy L. Ambrose Fellowship in Crop

471

Sciences.

472 473 474 475

CONFLICT OF INTEREST The authors declare no competing financial interest.



REFERENCES

476 477

1.

Lähteenmäki, L., Claiming Health in Food Products. Food Quality and Preference 2013,

478

27 (2), 196-201.

479

2.

World Health Organization, Global Health and Aging. World Health Organization: 2011.

480

3.

Mendis, S., Global Status Report on Noncommunicable Diseases. World Health

481

Organization: Geneva Switzerland, 2014.

482

4.

ERS, Feed Grains: Yearbook Tables. USDA, Ed. 2017.

483

5.

Hauck, A. L.; Johnson, G. R.; Mikel, M. A.; Mahone, G. S.; Morales, A. J.; Rocheford,

484

T. R.; Bohn, M. O., Generation Means Analysis of Elite Ex-Plant Variety Protection Commercial

485

Inbreds: A New Public Maize Genetics Resource. Crop Sci. 2014, 54 (1), 174-189.

486

6.

487

Dry-Milling Efficiency and Flaking-Grit Yield Examined in US Maize Germplasm. Crop Sci.

488

2016, 56 (5), 2516-2526.

489

7.

490

R., Dietary Protein, Weight Loss, and Weight Maintenance. Annual Review of Nutrition 2009,

491

29, 21-41.

492

8.

493

Journal of Clinical Nutrition 1999, 70 (3), 560S-569S.

494

9.

495

Escriba, P. V., Oleic Acid Content is Responsible for the Reduction in Blood Pressure Induced

496

by Olive Oil. Proceedings of the National Academy of Sciences of the United States of America

497

2008, 105 (37), 13811-13816.

Macke, J. A.; Bohn, M. O.; Rausch, K. D.; Mumm, R. H., Genetic Factors Underlying

Westerterp-Plantenga, M. S.; Nieuwenhuizen, A.; Tome, D.; Soenen, S.; Westerterp, K.

Simopoulos, A. P., Essential Fatty Acids in Health and Chronic Disease. American

Teres, S.; Barcelo-Coblijn, G.; Benet, M.; Alvarez, R.; Bressani, R.; Halver, J. E.;


Page 26 of 35

Page 27 of 35


498

10.

Christen, S.; Woodall, A. A.; Shigenaga, M. K.; SouthwellKeely, P. T.; Duncan, M. W.;

499

Ames, B. N., γ-Tocopherol Traps Mutagenic Electrophiles Such as NOx and Complements α-

500

Tocopherol: Physiological Implications. Proceedings of the National Academy of Sciences of the

501

United States of America 1997, 94 (7), 3217-3222.

502

11.

503

Properties of Dietary Polyphenols. Medicinal Research Reviews 2006, 26 (6), 747-766.

504

12.

505

Modulation of Nrf2/ARE Pathway by Food Polyphenols: A Nutritional Neuroprotective Strategy

506

for Cognitive and Neurodegenerative Disorders. Molecular Neurobiology 2011, 44 (2), 192-201.

507

13.

508

American Journal of Clinical Nutrition 1995, 62 (6), 1315-1321.

509

14.

510

American Oil Chemists Society 1987, 64 (8), 1129-1134.

511

15.

512

Protection Against Hydroxyl and Peroxyl Radical Oxidation in Synaptosomal and Neuronal Cell

513

Culture Systems in vitro: Structure-Activity Studies. Journal of Nutritional Biochemistry 2002,

514

13 (5), 273-281.

515

16.

516

Remesy, C., The Bioavailability of Ferulic Acid is Governed Primarily by the Food Matrix

517

Rather than its Metabolism in Intestine and Liver in Rats. Journal of Nutrition 2002, 132 (7),

518

1962-1968.

519

17.

520

Food Chemistry 2002, 50 (21), 6182-6187.

Fresco, P.; Borges, F.; Diniz, C.; Marques, M. P. M., New Insights on the Anticancer

Scapagnini, G.; Vasto, S.; Abraham, N. G.; Calogero, C.; Zella, D.; Galvano, F.,

Sies, H.; Stahl, W., Vitamin E and C, β-Carotene, and Other Carotenoids as Antioxidants.

Weber, E. J., Carotenoids and Tocols of Corn Grain Determined by HPLC. Journal of the

Kanski, J.; Aksenova, M.; Stoyanova, A.; Butterfield, D. A., Ferulic Acid Antioxidant

Adam, A.; Crespy, V.; Levrat-Verny, M. A.; Leenhardt, F.; Leuillet, M.; Demigne, C.;

Adom, K. K.; Liu, R. H., Antioxidant Activity of Grains. Journal of Agricultural and



521

18.

Rumpagapom, P. Structural Features of Cereal Bran Arabinoxylans Related to Colon

522

Fermentation Rate. Purdue University, West Lafayette, IN, 2011.

523

19.

524

and Disease. Oxidative Medicine and Cellular Longevity 2009, 2 (5), 270-278.

525

20.

526

Resistance. Annual Review of Phytopathology 1980, 18, 259-288.

527

21.

528

Formation of Arabinoxylan-Bound Diferulates and Larger Ferulate Coupling-Products in Maize

529

Cell-Suspension Cultures. Planta 2000, 211 (5), 679-692.

530

22.

531

agronomic crops. Concepts and Breeding of Heterosis in Crop Plants 1998, (25), 29-44.

532

23.

533

Buckler, E. S.; Flint-Garcia, S. A., Genetic Architecture of Maize Kernel Composition in the

534

Nested Association Mapping and Inbred Association Panels. Plant Physiology 2012, 158 (2),

535

824-834.

536

24.

537

http://wenku.baidu.com/view/29483f7e27284b73f2425061.

538

25.

539

Urbana-Champaign, Urbana, IL, 2014.

540

26.

541

Crop Sci. 1968, 8 (3), 273-274.

Pandey, K. B.; Rizvi, S. I., Plant Polyphenols as Dietary Antioxidants in Human Health

Vance, C. P.; Kirk, T. K.; Sherwood, R. T., Lignification as a Mechanism of Disease

Fry, S. C.; Willis, S. C.; Paterson, A. E. J., Intraprotoplasmic and Wall-Localised

Melchinger, A. E.; Gumber, R. K., Overview of heterosis and heterotic groups in

Cook, J. P.; McMullen, M. D.; Holland, J. B.; Tian, F.; Bradbury, P.; Ross-Ibarra, J.;

Baidu, DA 7200 Diode Array Analyzer Operation Manual. 2007.

Bubert, J. Genetic Improvement of Nitrogen Utilization in Maize. University of Illinois at

Alexander, D. E.; Lambert, R. J., Relationship of Kernel Oil Content to Yield in Maize.


Page 28 of 35

Page 29 of 35


542

27.

Butts-Wilmsmeyer, C. J.; Bohn, M. O., High-Throughput Extraction of Insoluble-Bound

543

Ferulic Acid In Maize. Crop Sci. 2016, 56 (6), 3152-3159.

544

28.

545

http://www.isws.illinois.edu/atmos/statecli/cuweather/.

546

29.

547

Sprague, G.; Dudley, J., Eds. ASA-CSSA-SSSA: Madison, WI, 1988.

548

30.

549

Starch Concentration in the Illinois Long Term Selection Maize Strains. Theoretical and Applied

550

Genetics 1993, 87 (1-2), 217-224.

551

31.

552

Illinois High Oil, Low Oil, High Protein, and Low Protein Strains of Zea mays L. Crop Sci.

553

1969, 9 (2), 179-&.

554

32.

555

and wet-milling properties of accessions used in Germplasm Enhancement of Maize project.

556

Cereal Chemistry 2001, 78 (3), 330-335.

557

33.

558

Composition and Amino Acid Content in Maize Cultivars Representing 80 Years of Commercial

559

Maize Varieties. Maydica 2006, 51 (2), 417-423.

560

34.

561

Development. Phytochemistry (Oxford) 1972, 11 (12), 3421-3426.

562

35.

563

Acid Concentrations in Maize. Genome 1995, 38 (5), 894-901.

Angel, J. Climate Observations for Champaign-Urbana, IL.

Alexander, D. E., Corn and Corn Improvement. In Corn and Corn Improvement, 3rd ed.;

Goldman, I.; Rocheford, T.; Dudley, J., Quantitative Trait Loci Influencing Protein and

Dudley, J. W.; Lambert, R. J., Genetic Variability After 65 Generations of Selection in

Singh, S. K.; Johnson, L. A.; Pollak, L. M.; Hurburgh, C. R., Compositional, physical,

Scott, M. P.; Edwards, J. W.; Bell, C. P.; Schussler, J. R.; Smith, J. S., Grain

Poneleit, C. G.; Davis, D. L., Fatty-Acid Compositional of Oil During Maize Kernel

Alrefai, R.; Berke, T. G.; Rocheford, T. R., Quantitative Trait Locus Analysis of Fatty-



564

36.

Egesel, C. O.; Wong, J. C.; Lambert, R. J.; Rocheford, T. R., Combining Ability of Maize

565

Inbreds for Carotenoids and Tocopherols. Crop Sci. 2003, 43 (3), 818-823.

566

37.

567

Chen, C.; Buell, C. R.; Buckler, E. S.; Rocheford, T.; DellaPenna, D., Genome-Wide Association

568

Study and Pathway-Level Analysis of Tocochromanol Levels in Maize Grain. G3-Genes

569

Genomes Genetics 2013, 3 (8), 1287-1299.

570

38.

571

in Corn and Soybean Oils. International Journal for Vitamin and Nutrition Research 1974, 44

572

(3), 396-403.

573

39.

574

Associated with Purified Corn Fiber Arabinoxylans. Journal of Agricultural and Food Chemistry

575

2007, 55 (3), 943-947.

576

40.

577

Garcia, H. S., Antioxidant Activity, Phenolic Compounds and Anthocyanins Content of Eighteen

578

Strains of Mexican Maize. Lwt-Food Science and Technology 2009, 42 (6), 1187-1192.

579

41.

580

Recurrent Selection for Storage Pest Resistance in Tropical Maize. Crop Sci. 2014, 54 (6), 2423-

581

2432.

582

42.

583

Lambert, J. D. H.; Fulcher, R. G.; Serratos, A.; Mihm, J., Role of Phenolics in Resistance of

584

Maize Grain to the Stored Grain Insects, Prostephanus truncatus (Horn) and Sitophilus zeamais

585

(Motsch). Journal of Stored Products Research 1992, 28 (2), 119-126.

Lipka, A. E.; Gore, M. A.; Magallanes-Lundback, M.; Mesberg, A.; Lin, H. N.; Tiede, T.;

Chow, C. K.; Draper, H. H., Oxidative Stability and Antioxidant Activity of Tocopherols

Yadav, M. P.; Moreau, R. A.; Hicks, K. B., Phenolic Acids, Lipids, and Proteins

Lopez-Martinez, L. X.; Oliart-Ros, R. M.; Valerio-Alfaro, G.; Lee, C. H.; Parkin, K. L.;

Garcia-Lara, S.; Bergvinson, D. J., Phytochemical and Nutraceutical Changes During

Arnason, J. T.; Gale, J.; Debeyssac, B. C.; Sen, A.; Miller, S. S.; Philogene, B. J. R.;


Page 30 of 35

Page 31 of 35


586

43.

Assabgui, R. A.; Reid, L. M.; Hamilton, R. I.; Arnason, J. T., Correlation of Kernel (E)-

587

Ferulic Acid Content of Maize with Resistance to Fusarium graminearum. Phytopathology

588

1993, 83 (9), 949-953.

589

44.

590

Regnault-Roger, C.; Pauls, K. P.; Arnason, J. T.; Philogene, B. J. R., Dehydrodimers of Ferulic

591

Acid in Maize Grain Pericarp and Aleurone: Resistance Factors to Fusarium graminearum.

592

Phytopathology 2003, 93 (6), 712-719.

593

45.

594

B. J. R., Correlation of Phenolic Acid Content of Maize to Resistance to Sitophilus zeamais, the

595

Maize Weevil, in CIMMYT's Collections. Journal of Chemical Ecology 1990, 16 (2), 301-315.

596

46.

597

Enzymatic Oxidation Products to Maize Fungal Pathogens, Emphasizing Fusarium

598

graminearum. Natural toxins 1997, 5 (5), 180-185.

599

47.

600

Arnason, J. T., The Role of Pericarp Cell Wall Components in Maize Weevil Resistance. Crop

601

Sci. 2004, 44 (5), 1546-1552.

602

48.

603

Activity. Journal of Agricultural and Food Chemistry 2002, 50 (17), 4959-4964.

Bily, A. C.; Reid, L. M.; Taylor, J. H.; Johnston, D.; Malouin, C.; Burt, A. J.; Bakan, B.;

Classen, D.; Arnason, J. T.; Serratos, J. A.; Lambert, J. D. H.; Nozzolillo, C.; Philogene,

Dowd, P. F.; Duvick, J. P.; Rood, T., Comparative Toxicity of Allelochemicals and Their

Garcia-Lara, S.; Bergvinson, D. J.; Burt, A. J.; Ramputh, A. I.; Diaz-Pontones, D. M.;

Dewanto, V.; Wu, X. Z.; Liu, R. H., Processed Sweet Corn Has Higher Antioxidant

604



TABLES Table 1. Inbred maize parents used in this study and additional information regarding their pedigree background Line

Group

Assignee

Background

B73

SSS

None (Public)

Iowa Stiff Stalk Synthetic

LH1

SSS

Holden Foundation Seeds

Iowa Stiff Stalk Synthetic; B37 type

PHG39

SSS

Pioneer Hi-Bred International

Maiz Amargo/Iowa Stiff Stalk Synthetic; B37/B14 type

PHJ40

SSS


Iowa Stiff Stalk Synthetic

4676A

SSS

Dekalb Genetics Corporation

1067-1 / B-Line Composite; B14 type

LH123HT

NSS


Pioneer Hybrid 3535

LH82

NSS


Krug /W153

Mo17

NSS

None (Public)

Lancaster

PH207

NSS


Iodent/Long Ear OPV/Minn13

PHG47

NSS


Oh43/Iodent*Wf9/MKSDTA C10 Synthetic

PHG84

NSS


Oh07-Midland/Minn13/Iodent/Reid YD/Osterland YD/Lancaster/Pioneer Female Composite OPV

PHZ51

NSS


Minn13/Iodent/Reid YD/Osterland YD/Lancaster/South US Land Race Synthetic/Funks G4949/ Midland


Page 32 of 35

Page 33 of 35


Table 2. Summary statistics of protein, unsaturated fatty acids, tocopherols, phenolics, and cinnamic acid by generation. The minimum, maximum, and average values reported are based off of the LSMEANS of the hybrids and inbreds.

HYBRIDS Average Min Max Std. Errora P-Valueb

Protein

Unsaturated Fatty Acids

Total Protein

Oleic Acid

—%—

—— mg g-1 ——

9.12 8.34 10.22 0.26

Concentration of Beneficial Phytochemicals in Harvested Grain of U.S.

Recommend Documents