Corn Inbred Lines Research Articles

Availability and Analysis of Proprietary Dent Corn Inbred Lines with Expired U.S. Plant Variety Protection

Current U.S. commercial hybrid corn (Zea mays L.) is produced using proprietary inbred corn lines as parents. Most proprietary corn inbred lines have been protected by the U.S. Patent and/or U.S. Plant Variety Protection Act (PVPA) since approximately 1980. Currently there are 89 dent inbred corn lines (with more each year) whose intellectual proprietary protection has expired. These inbred lines are now available from the U.S. National Plant Germplasm System with freedom to operate for applications in research, plant breeding, and direct commercial use. This study facilitates an understanding of this germplasm by utilizing detailed pedigree and phenotypic information available from U.S. Patent and PVPA records to enhance their application to research and product development. This germplasm is mostly yellow dent and ranges in maturity from early (1000 heat units to mid‐silk) to full (1708 heat units to mid‐silk) season. These proprietary lines are from diverse backgrounds that include Iowa Stiff Stalk Synthetic, Argentine Maiz Amargo, Oh43, Minnesota 13, Iodent, Lancaster, Oh07Midland, Commercial Hybrid derived, and uncharacterized broad base sources from exotic, synthetic, and open pollinated populations.

CO443 corn inbred line

CO443 is a short season corn (Zea mays L.) inbred line with excellent combining ability and average to superior lodging resistance in hybrids. This stiff stalk type inbred performed best as a parent with non-stiff stalk inbreds. Excellent yields were achieved with the commercial inbred LH176. Key words: Corn, maize, Zea mays, cultivar description

Variation of sugary1 and shrunken2 gene frequency in different maize genetic backgrounds

AbstractGenotypes affect the survival of mutant genes in segregating populations. This study elucidates the effect of different maize genetic backgrounds on variation in gene frequency in sweet corn, sugary1 (su1) and sugary enhancer1 (se1), and supersweet corn, shrunken2 (sh2). Four sweet corn inbred lines and a supersweet synthetic were crossed to six field corn inbreds from diverse heterotic groups. The crosses were self‐pollinated and the F2 population was recombined twice. Gene frequencies were calculated from grain frequencies. Variation of su1 frequency differed significantly from random drift and a significant linear reduction was observed for half of the su1su1Se1Se1Sh2Sh2 × Su1Su1Se1Se1Sh2Sh2 crosses. The su1 and sh2 frequencies suffered a significant linear reduction for most su1su1se1se1Sh2Sh2 × Su1Su1Se1Se1Sh2Sh2 and Su1Su1Se1Se1sh2sh2 × Su1Su1Se1Se1Sh2Sh2 crosses, respectively. Also, the residual sums of squares, due to deviations from the linear trend, were significant for some crosses due to frequency‐dependent selection and genotypic interactions. Viability of su1 and sh2 depended on the specific sweet × field corn genotype combination but was not related to field corn heterotic groups. The se1 gene could have a detrimental effect on su1 viability.

Evolution of North American Dent Corn from Public to Proprietary Germplasm

ABSTRACTCurrent corn (Zea mays L.) hybrids are produced using proprietary inbred lines as parents. These proprietary lines are protected by U.S. Patent and/or the U.S. Plant Variety Protection Act (PVPA) and their use is restricted, but as protection expires these lines become available to the entire corn breeding industry. Our objectives were to gain understanding of this protected germplasm by utilizing pedigree information available in the U.S. Patent and PVPA records to enhance the use of this germplasm in new line development as the lines become publicly available. Ownership, derivation, and lineage of corn inbred lines protected by U.S. Patent or PVPA from 1980 to 2004 were surveyed. Thirty‐three companies have protected 908 corn inbred lines and four of these companies: Dekalb Genetics (DK), Holden's Foundation Seeds (LH), Pioneer Hi‐Bred (PH), and Syngenta (SG) originated 685 of them. We identified the most significant lines by their cumulative use as parents in the development of new lines. Much of today's germplasm originates from seven progenitor lines: B73, LH82, LH123, PH207, PH595, PHG39, and Mo17. The germplasm surveyed is grouped by pedigree lineage into Oh43, Lancaster, Oh07‐Midland, Iodent, Stiff Stalk, Commercial hybrid derived, and Argentine Maiz Amargo backgrounds, with new diversity emerging from the two latter groups. Recycling elite inbred lines using two‐parent crosses followed by pedigree breeding was the most prevalent method of new line development.

QTL Analysis of Starch Content in Maize Kernels using the Trisomic Inheritance of the Endosperm Model

Two hundred and fifty-nine F2:3 families, developed from the cross between a dent corn inbred line Dan232 and a popcorn inbred line N04, were evaluated for its starch content in the replicated experiments under two environments. One hundred and eighty three pairs of SSR markers were selected to construct a genetic linkage map, covering 1,762.2 cM (centiMorgan) and on the average distance of 9.63 cM between the markers. Quantative trait loci (QTL) were identified and its effects were analyzed, using the triploid endosperm genetic model and the interval mapping method. Ten QTL, detected on chromosome 1, 3, 4, 5 and 7 respectively, were mapped in spring and in summer. All detected QTL in spring were also identified in summer. The phenotypic variation of a single QTL varied from 4.74% to 11.26%, and the total contributions of all QTL under two environments were 36.84% and 72.65%, respectively. Two QTL of all identified QTL in spring showed over-dominant effects, but additive and partially dominant in summer respectively, the amounts of other QTL showing Additive, partially dominant and over-dominant effects were 2, 1, 5 respectively. The positive alleles of three QTL were contributed by the normal corn parent Dan232, and the other positive alleles were contributed by the popcorn parent N04.

Thermal Properties of Starch from Exotic‐by‐Adapted Corn (Zea mays L.) Lines Grown in Four Environments

ABSTRACTThe effect of four growing environments (two at Ames, IA; one at Clinton, IL; and one at Columbia, MO) on the thermal properties of starch from five exotic‐by‐adapted corn inbred lines (Chis37, Cuba34, Cuba38, Dk8, Dk10) and two control lines (B73 and Mo17) were studied using differential scanning calorimetry (DSC). The variations in thermal properties within environments were similar for the exotic‐by‐adapted lines and control lines. Missouri was the warmest environment and generally produced starch with the greatest gelatinization onset temperature (ToG), the narrowest range of gelatinization (RG), and the greatest enthalpy of gelatinization (ΔHG). Illinois was the coolest environment and generally resulted in starch with the lowest ToG, widest RG, and lowest ΔHG. These differences were attributed to higher temperatures in Missouri during grain‐filling months either increasing the amount of longer branches of amylopectin or perfecting amylopectin crystalline structure. The Ames 1 environment produced starch with thermal properties most similar to those of Illinois, whereas the Ames 2 environment produced starch with thermal properties most similar to those of Missouri. Ames 2, located near a river bottom where temperatures tend to be warmer, likely had temperatures most similar to those found in Missouri during grain filling.

Manganese peroxidase from the white‐rot fungus Phanerochaete chrysosporium is enzymatically active and accumulates to high levels in transgenic maize seed

Manganese peroxidase (MnP) has been implicated in lignin degradation and thus has potential applications in pulp and paper bleaching, enzymatic remediation and the textile industry. Transgenic plants are an emerging protein expression platform that offer many advantages over traditional systems, in particular their potential for large-scale industrial enzyme production. Several plant expression vectors were created to evaluate the accumulation of MnP from the wood-rot fungus Phanerochaete chrysosporium in maize seed. We showed that cell wall targeting yielded full-length MnP, whereas cytoplasmic localization resulted in multiple truncated peroxidase polypeptides as detected by immunoblot analysis. In addition, the use of a seed-preferred promoter dramatically increased the expression levels and reduced the negative effects on plant health. Multiple independent transgenic lines were backcrossed with elite inbred corn lines for several generations with the maintenance of high-level expression, indicating genetic stability of the transgene.

Genetic variation between Spanish and American versions of sweet corn inbred lines

AbstractConservation of maize inbred lines in different stations causes variability among strains. The objective of this research was to determine agronomic and molecular differences in American sweet corn inbreds maintained in Spain. American and Spanish strains of five sweet corn inbred lines were characterized by using 34 RAPD primers that produced 168 consistent bands. Strains of four of these inbreds were crossed in a diallel design, and hybrids were evaluated in four environments in northwestern Spain. The RAPD characterization showed no differences between strains for two inbreds, while divergence between strains was largest for the inbred 15125. Most primers did not reveal any variability between pairs of strains, while some primers produced variations at high rates. Differences in agronomic performance among Spanish and American strains were most important for P51, followed by P39, while strains 1453 or 15125 were not significantly different. Molecular differences between strains were not related to agronomic performance. Residual heterozygosity or outcrossing cannot explain these results. Lack of adaptation could have caused stress‐induced mutagenesis. Natural selection could have eliminated unfavourable selective mutations, but neutral mutations can be found at the molecular level and favourable mutations could have been selected at the agronomic level.

Influence of corn (Zea mays L.) inbred lines seed processing on their damage

Manipulation of corn seed from harvest throughout processing to disinfections is associated with seed damage. Such damage causes lower germination and germination energy. Seed damage, especially in the embryo and crown, are factors that decrease germination, especially under low temperatures. Also, damaged seed is inclined to infections by soil pathogens (Aspergillus, Pythium, Penicillium), causing seed and germ rotting. In some cases, plant density is seriously reduced by infestations so that resowing is required. Seed of five corn-inbred lines differing in form and type (A: shallow and round form of the dent type MO-17, Os6-2; B: deep and uniform of the semi-flint type B-73, Os84-28 and Os87-24) were tested for their quantity and damaged spots (crown, germ, back side and belly side). Seed damage following the manipulations ranged as follows: from 3.8 to 7.2% (harvest), from 36.2 to 52.8% (husking) and from 38.4 to 54.0% (the end of processing). Also, damage of different parts of seed following their processing was as follows: from 17.8 to 29.2% (crown), from 4.1 to 6.7% (germ), from 6.3 to 9.8% (back side) and from 5.7 to 8.3% (belly side). High negative correlation (from r = –0.620 to r = –0.960) between damage of seed and seed quality (germination energy, germination) and high positive correlation between germination energy and germination were found over the investigated years and for both lines.

Matrix-assisted laser desorption ionization time-of-flight mass spectrometry analysis of zeins in mature maize kernels.

A high-throughput method has been developed to allow rapid analysis of maize seed storage proteins by matrix-assisted laser desorption time-of-flight mass spectrometry. The extraction solution containing an organic solvent, a reducing agent, and a volatile base has been optimized to enable extraction of all classes of zein proteins (alpha-, beta-, gamma-, and delta-). A near-saturating concentration of matrix, 2-(4-hydroxyphenylazo)benzoic acid, was necessary to obtain strong peaks for the most lipophilic zeins, the alpha-zeins. Zein proteins with small mass differences, difficult to separate by sodium dodecyl sulfate polyacrylamide gel electrophoresis, were resolved through this analysis. Mass signals corresponding to the 10-kDa delta-, 15-kDa beta-, 16-kDa gamma-, 27-kDa gamma-, and several 19 and 22-kDa alpha-zeins were detected. The zein identities were further confirmed by the association of the number of cysteine residues in each zein MS peak, as determined by iodoacetamide derivatization, with the number predicted from its coding sequence. The relative zein abundance in the zein MS peaks was also correlated with the relative zein EST abundance among endosperm EST libraries. This method was utilized to examine the zein composition of a number of corn inbred lines and opaque mutants.

CO441 corn inbred line

CO441 is a short-season corn inbred line with improved resistance to silk infection by Fusarium graminearum. Resistance to infection via wounded kernels is also high in CO441. This inbred exhibits excellent combining ability and average to superior lodging resistance in hybrids. Key words: Corn, maize, Zea mays, cultivar description, ear rot, Fusarium

Combining ability in baby corn inbred lines (Zea mays L.)

Seven baby corn inbreds were crossed in a complete diallel scheme. The single-cross hybrids obtained were assessed at the Sao Manuel Experimental Station, in Sao Paulo State, Brazil. The experiment was set up in a randomized complete block design with three replications, including one commercial control. The experimental plots consisted of a single row, 5 m long, with 25 plants. The traits assessed were: number of ears/plot, weight, length and diameter of husked and dehusked ears, plant height and ear height. General and specific combining ability effects (GCA and SCA) were determined. There was genetic variability among hybrids and the best hybrid (27Ax31B) was superior to the control for number of ears/plot and weight of ears dehusked. Inbreds 27 and 29 showed the best GCA effects for number of ears/plot, weight of husked and dehusked ears. The magnitude of GCA showed that the additive effects were dominant in most traits evaluated. The existence of dominance effects was also found.

Ear Damage of Sweet Corn Inbreds and Their Hybrids under Multiple Corn Borer Infestation

In Mediterranean countries, the principal corn (Zea mays L.) pest is the pink stem borer (PSB) (Sesamia nonagrioides Lef.), followed in importance by the European corn borer (ECB) [Ostrinia nubilalis (Hübner)]. Our objective was to quantify injury by these pests in a set of inbreds that showed different levels of ear damage by the PSB in a previous study and in their hybrids. A diallel among seven sweet corn inbreds that varied for ear damage by PSB was evaluated in three environments under PSB and ECB infestations. The importance of general combining ability (GCA) and specific combining ability (SCA) for ear damage by corn borer was determined. Inbred parents were also tested under manual infestation conditions with both borers. There was variability for ear damage traits among sweet corn inbred lines, but none of them were completely resistant. General combining ability effects were significant for the general appearance of the ear, ears with damaged grain, and ears with damaged shanks under PSB infestation. Under PSB infestation, SCA was not significant for any trait. Most traits showed significant GCA effects under ECB infestation, although SCA effects were also important for some damage traits. The inbred EP61 could supply some favorable alleles because it showed negative and significant GCA effects for ear damage under infestation by both species. Inbreds EP59 and V7726 showed negative and significant GCA effects for ear damage by ECB. These inbreds could be included in a sweet corn synthetic population that would be improved to decrease ear damage by corn borers.

Evaluation of Corn Inbreds and Advanced Breeding Lines for Resistance to Aflatoxin Contamination in the Field.

Eighteen corn inbred lines and advanced breeding lines were evaluated for resistance to aflatoxin contamination when artificially inoculated with Aspergillus flavus in 1998, 1999 (two tests), and 2000 at Mississippi State, MS, in field studies. The top ear of each plant was inoculated with the A. flavus isolate NRRL 3357 seven days after midsilk (50% of the plants in a plot had silks emerged) using the side-needle technique. Ears were harvested at kernel maturity approximately 63 days after midsilk and aflatoxin levels were measured using the Vicam AflaTest. Aflatoxin contamination in the inbreds was extremely high in 1998. Levels ranged from 139 to 21,090 ng/g. In 1999, aflatoxin contamination ranged from 17 to 1,070 ng/g in one test and 14 to 1,278 ng/g in another test. In 2000, aflatoxin levels ranged from 237 to 7,503 ng/g. Lines that supported lowest levels of aflatoxin contamination included Mp81:112, Mp92:673, Mp92:679, and Mp494. These lines provide potential new sources of resistance that can be used to move aflatoxin resistance into commercial corn hybrids.

CO388 and CO389 corn inbred lines

CO388 and CO389 are short-season corn inbred lines with improved resistance to silk infection by Fusarium graminearum. These inbreds are the first to be released from a public breeding program with improved resistance to ear rot; they can be used by maize breeders as a source of resistance. Both inbreds exhibit good combining ability and average to superior lodging resistance in hybrids. Key words: Corn, maize, Zea mays, cultivar description, ear rot, Fusarium

Corn Inbred Lines CG60 and CG62

CG60 and CG62 are short seasoned corn (Zea mays L.) inbred lines. Key words: Corn, Zea mays L., cultivar description

Corn Inbred Line CG102

CG102 is short seasoned corn (Zea mays L.) inbred line. Key words: Corn, Zea mays L., cultivar description

CO430, CO431 and CO432 corn inbred lines

CO430, CO431 and CO432 are short-season corn inbred lines with improved resistance to silk infection by Fusarium graminearum. These inbreds exhibit average combining ability, average to superior lodging resistance in hybrids and were rated as having excellent emergence and seedling vigour. Key words: Corn, maize, Zea mays, cultivar description, ear rot, Fusarium

CO427 and CO428 corn inbred lines

CO427 and CO428 are short-season corn inbred lines with excellent combining ability, average to superior lodging resistance in hybrids and excellent emergence and early season vigour. Key words: Corn, maize, Zea mays, cultivar description

CO429 corn inbred line

CO429 is a short-season corn inbred line with good combining ability, average to superior lodging resistance in hybrids, and excellent emergence and early season vigour. Key words: Corn, maize, Zea mays, cultivar description