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GERMPLASMS

Registration of Maize Germplasm Line GEMS-0067

^a Dep. of Agronomy, Truman State Univ., 100 E. Normal, Kirksville, MO 63501
^b Department of Food Science and Human Nutrition, 1333 Food Sciences Bldg., Iowa State Univ., Ames, IA, 50011-0000
^c Corn Insects and Crop Genetics Research, Research Geneticist (Plants), Room 1405 Agronomy Hall, Iowa State Univ., Ames, IA, 50011
^d Corn Insects and Crop Genetics Research, Research Geneticist (Plants), Room 1405 Agronomy Hall, Iowa State Univ., Ames, IA, 50011

^* Corresponding author (campbell{at}truman.edu).

GEMS-0067 (Reg. no GP-550, PI 643420) is a partially inbred germplasm line released by Truman State University (TSU) in accordance with the Germplasm Enhancement of Maize Project (GEM) protocol (Pollak, 2003). This line is being released for use in the development of genetically diverse, elite, Amylomaize Class VII (starch amylose > 70%) parental lines. These lines possess modifier genes that, together with the recessive amylose-extender (ae) allele, elevate starch amylose content to at least 70%. The development of high-amylose maize varieties was described by Fergason (1994) where difficulties encountered during development were likely due to the lack of modifier genes needed to reach required amylose percentages in most breeding sources. To our knowledge GEMS-0067 represents the only public source of Amylomaize VII germplasm to date. Development of GEMS-0067 was achieved utilizing exotic tropical germplasm as a source of these modifiers from the cooperative USDA-ARS GEM project and is here described.

Selection for high amylose modifier genes began in 1997 at Truman State when a sister-line hybrid H99ae x OH43 ae (provided by Dr. David Glover, Purdue University) was used as a male in crosses with many sources of exotic maize germplasm. These included several hundred plant introductions and 70 breeding crosses from GEM. Our results revealed that two plant introductions Zia Pueblo NRC 5357 (PI 218188) and Cochiti Pueblo NRC 5298 (PI 218131) and one GEM breeding cross (GUAT209:S13) contributed high amylose modifiers raising amylose levels to at least 70% in the F₃ kernels as described previously by Campbell et al. (2003). Only lines from GUAT209:S13 x (H99ae x OH43ae) were found to survive inbreeding and therefore used in subsequent breeding studies while the others were dropped.

GUAT209:S13 is a 50% tropical exotic breeding cross, classified by GEM as stiff-stalk. It was derived from crossing Guatemala 209 (PI 498583), a yellow flint population of the tropical race, Tusón, to a proprietary stiff-stalk inbred from a private GEM cooperator designated as company 13. Fifty kernels of the original GUAT209:S13 x (H99ae x OH43ae) F₁ seed (from the bulk of approximately five ears using GUAT209:S13 as a female) was planted in a winter nursery in Puerto Rico. Resulting plants were self-pollinated and ears with segregating kernels (3 normal:1 ae-type) were harvested from ten of these plants. Mutant ae F2 kernels were visually selected from each ear, bulked, and planted to establish 50 F₂ plants which, on selfing, produced ears having only ae-type kernels (F₃ seed) in the summer of 1998 near Kirksville, MO. For each (H99ae x OH43ae) x exotic cross, grain samples from at least three F₂ ears were analyzed for starch amylose using a colorimetric iodine affinity (IA) procedure (Williams et al., 1958) following starch extraction and purification. Remnant grain samples were used for inbreeding ear-to-row to the F₅ generation and selections made to fix modifiers based on laboratory IA data obtained following each generation.

GEMS-0067 is currently maintained by sib-mating within the F₅ derived line from the pedigree GUAT209:S13 x (H99ae x OH43ae). Evaluations made in Kirksville from 2002 to 2005 indicate that GEMS-0067 is a vigorous line with pollen shed occurring approximately four days before B73. Its average plant height is approximately 20 cm less than B73, with an upright leaf structure, yellow kernels and a red cob. Since the ae donor was from the non-stiff stalk source H99ae x OH43ae, GEMS-0067 is of mixed heterotic derivation, composed of 50% non-stiff stalk (NS) and 50% stiff stalk (SS). Subsequent crosses made with GEMS-0067 to both NS and SS testers have shown good yield in preliminary data over two years. Data regarding amylose content, plant characteristics, and yield are available on the GEM web site (www.public.iastate.edu/usda-gem; verified 27 March 2007), under Public Cooperator Reports-Campbell, for 2004 and 2005.

Selection for high amylose was initially made solely on the colorimetric IA method which measures only "apparent amylose." Additional analytical techniques used to characterize the starch are shown in Table 1 . GEMS-0067, having modifiers from GUAT209:S13, was compared to several public inbreds possessing the ae gene but without high amylose modifier genes. Starch was isolated from duplicate 100-gram bulk samples obtained from each genotype. Samples 1 and 2 were starches purified from independent single-row plots derived from two GEMS-0067 S4 ears produced in 2004. Similarly, bulk grain from the converted lines H99ae, OH43ae, B89ae, and B84ae (Samples 3, 4, 5, and 6 respectively) grown in the same year were used for starch isolation. All laboratory data represents the average of duplicate analyses. The IA method confirmed the presence of modifiers in two samples obtained from GEMS-0067. Gel permeation chromatography (GPC) was also used to examine the starch. This method separates amylopectin from amylose and the intermediate components which will, therefore, result in higher amylose values in comparison to the IA method. GEMS-0067 displayed a relatively higher amylose value on the basis of analysis of the GPC amylose peaks, which, again, confirmed the presence of high amylose modifying genes. Resistant starch (RS) was also measured by using the Association of Official Analytical Chemists method (AOAC, 1955) for total dietary fiber content for all samples. The RS content of GEMS-0067 starch samples was approximately two times higher than that of the converted public lines. The RS content of the starch samples was positively correlated with the amylose content of the starch, with a correlation coefficient (r) of 0.89. Thermal properties of the native high-amylose maize starch:water mixtures (3:1 ratio) were determined by Differential Scanning Calorimetery. All of the starch samples displayed similar onset gelatinization temperature (63.8–65.0°C) while broader gelatinization temperature ranges were observed for GEMS-0067 starches. The conclusion temperatures of these also varied from 104.8 to 106.7°C, and were substantially higher for GEMS-0067 starch than for the other starch samples (92.8–94.2°C). The results indicated that starch granules of GEMS-0067 samples were not completely gelatinized after cooking at boiling temperature; this is probably due to the increased amylose and intermediate component content.

Footnotes

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Received for publication October 6, 2006.

References

• AOAC. 1955. Method 991.43. Total, Insoluble and Soluble Dietary Fiber in Food-Enzymatic-Gravimetric Method, MES-TRIS Buffer. Official Methods of Analysis, 16th ed AOAC International, Gaithersburg, MD.
• Campbell, M.R., H. Yeager, N. Abdubeck, L.M. Pollak, and D.V. Glover. 2003. Comparison of Methods for Amylose Screening Among Amylose-Extender (ae) Maize Starches from Exotic Backgrounds. Cereal Chem. 79:317–321.[CrossRef]
• Fergason, V. 1994. p. 55–78. High amylose and waxy corns. In Specialty Corns. Arnel Hallauer, ed. CRC Press, Boca Raton, FL.
• Pollak, L.M. 2003. The history and success of the public-private project on Germplasm enhancement of maize (GEM). Adv. Agron. 78:45–87.
• Williams, V.R., W.T. Wu, H.Y. Tsai, and H.G. Bates. 1958. Varietal differences in amylose content of rice starch. J. Agric. Food Chem. 6:47–48.[CrossRef]

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