2010 Annual Report
1a.Objectives (from AD-416)
Characterize the molecular structure of starch granule formation, and develop analytical methods to identify germplasm for high digestibility and resistant starch. Secondly, characterize GEM germplasm for starch nutritional value (for humans and livestock), biofuel potential, and ethanol yield.
1b.Approach (from AD-416)
Ethanol fermentation tests, and starch digestibility analysis will be conducted on GEM germplasm previously identified with high starch content and/or ethanol content. In addition, other sources of germplasm will be analyzed for resistant starch content. Analytical methods including differential scanning calorimetry (DSC) will be studied to determine applicability for identifying GEM germplasm with desirable starch attributes. The identified germplasm will be recombined for future trials as hybrids, and new breeding crosses made and evaluated.
This project relates to the primary objectives of the parent project which include the development, evaluation, and methodology to release germplasm with resistant starch, high digestibility, and ethanol potential. Further resistant starch (high amylose) research studies were conducted using germplasm with various dosages of high amylose modifier (HAM) genes. The GEM line, GEMS-0067, is a double mutant having the amylose extender gene (ae), and HAM genes in homozygous condition. Therefore, GEMS-0067 has three dosages of HAM, and is designated G/G. Other sources of germplasm were studied which included inbreds with two dosages of HAM (G/H), a single dosage (H/G), and no HAM (H/H). The percent amylose found was 63.7, 54.2, 55.8, and 42.1for G/G, G/H, H/G, and H/H respectively. Although there were differences in amylose content, all of the starch from these sources had similar molecular size distribution with degree of polymerization (DP) ranging from 731-817. To evaluate germplasm with high ethanol potential, four normal and nine waxy GEM sources were studied using a cold fermentation process. The ethanol yield ranged from 16.5% to 18.6%. Starch derived from waxy inbreds was generally higher in ethanol content than starch obtained from normal inbreds. The highest ethanol yield was from the waxy GEM line 08GEM05036 (18.6%), followed by two other waxy inbreds, 08GEM05037 (18.3%), 08GEM05038 (18.3%); and a normal inbred 08GEM04702 (18.2%). It is of interest that the lowest ethanol content was from the waxy inbred, 08GEM05041 (16.5%). Further research is in progress to characterize waxy and normal starch and the attributes which contribute to high ethanol potential. The methods for monitoring activities include progress reports submitted by the Cooperator in July and December for the Annual GEM Cooperator Meeting. E-mail and telephone communication were initiated regularly by the ADODR or the Cooperator to discuss status of nursery in Ames for germplasm used for joint experiments. Germplasm resources and technical information were provided to the Cooperator for selecting genotypes to be used for starch research. A site visit by the Cooperator to the GEM Field Day is made each year.