PUBLIC COOPERATOR REPORTS (Specific Cooperative Agreements, or SCAs):
The GEM Project funded two SCA’s in 2015, Dr. Jay-lin Jane, Iowa State University, and Dr. Mark Campbell, Truman State University; Dr. Jane’s report is attached. Dr. Campbell’s will be posted when available.
Final Progress Report Dr. Jay-lin Jane, Iowa State University
This report serves to document research conducted under a cooperative agreement between USDA-ARS and Iowa State University. Specific objectives of this research project were to (1) Develop and characterize hybrids using normal and waxy GEM lines to produce hybrids with improved yield and starch-ethanol conversion efficiency to increase ethanol yield; and (2) Develop healthy foods and healthy food ingredients using GEM lines.
For objective 1, normal/waxy hybrids were developed by self- and inter-crossing the isogenic normal and waxy inbred corn. Starch physicochemical properties were characterized to understand the dosage effects of waxy gene on starch structures and properties. Two sets of isogenic normal and waxy corn were used as parental lines in this study to eliminate interference from differences in the genetic background. Intercrossing between the isogenic normal and waxy corn was conducted to produce corn lines with various dosages of waxy gene in the endosperm: 0 (normal inbred), 1 (normal × waxy), 2 (waxy × normal), and 3 (waxy inbred). Amylose contents of the starch (1.6-27.9% for set 1 and 0.0-26.6% for set 2, respectively) negatively correlated with the waxy gene dosage. The branch-chain length distribution of amylopectin showed that the percentages of A (DP<12) and B3 (DP>37) chains increased with the increase in waxy gene dosage, whereas the percentage of B1 (DP 13-24) and B2 (DP 25-36) and extra-long branch chains (DP>100) decreased with the increase in waxy gene dosage. The molecular sizes of amylopectin (9.5-11.8×108 for set 1 and 10.5-12.4×108 g/mol for set 2, respectively) and amylose (DP 630-651 for set 1 and DP 638-646 for set 2, respectively) were not affected by the waxy gene dosage. The conclusion gelatinization-temperature, gelatinization temperature-range, and gelatinization enthalpy-change were positively correlated with the waxy gene dosage and inversely proportional to the amylose content. Peak viscosities of the starches were not correlated with the waxy gene dosage, although the waxy corn starch showed substantially higher viscosity than the isogenic normal and hybrid corn. The setback viscosities, however, were negatively correlated with the waxy gene dosage. These results indicated that the waxy gene in the endosperm had dosage effects on the amylose content and amylopectin branch-chain length distribution, which in turn affected the thermal and pasting properties of the starch. The findings contributed to the fundamental understanding of the role of the waxy gene in biosynthesis of both the amylose and the amylopectin.
For objective 2, a high-amylose popcorn (GEM-07048*) was produced by crossing a normal popcorn (Sg1533) with a high-amylose corn (GEMS-0067). The corn kernels of GEM-07048 were separated visually to two groups, normal popcorn with an amylose content of 36.3% and high-amylose popcorn with an amylose content of 61.4%. The high-amylose popcorn displayed a small expansion volume (11.8 cm/g). The popped kernels of high-amylose popcorn showed a large resistant-starch content (46.3%) and slowly-digestible starch content (19.3%), indicating its potential as a healthy snack food.
Summary of progress made between 2014 and 2015
During the period of study, GEM corn lines were developed and characterized to understand the dosage effects of waxy gene on starch structures and properties and to produce resistant starch for human health. The results showed that waxy gene had dosage effects on amylose content and amylopectin branch-chain length distribution of the starch, which in turn affected starch properties. The knowledge could be used to improve the ethanol production from corn. The high-amylose popcorn showed high resistant-starch and slowly-digestible starch contents, although the kernels had a low popping value.
*Note: The GEM-07048 name used in Dr. Jane’s report refers to the identifier for the stock used with the Jane Laboratory. It does not refer to a released line, only the experimental material.