2011 Annual Report
1a.Objectives (from AD-416)
Develop maize germplasm for low-input and organic farming systems.
1b.Approach (from AD-416)
Organic farmers need germplasm that is not receptive to transgenic pollen from their neighbors as out-crossing risk is causing them to plant late, leading to reduced yields and profitability. Simple Sequence Repeat (SSR) markers will be applied in the context of an existing traditional breeding project using backcrossing to develop breeding materials homozygous for the genes Ga1-s (a gene that makes the lines non-recipient to foreign pollen), and Tcb1 and its positive modifier genes (another gene that makes the lines non-recipient to foreign pollen). We will determine the effect of combining different genetic mechanisms for producing corn with high levels of the essential amino acid methionine. Methionine is very important for organic poultry production in light of impending bans on the use of synthetic methionine for organic poultry farmers. A breeding project is conducted to provide farmers practicing organic and other low-input agricultural farming systems with high yielding corn, incorporating the traits described above among others, to meet their specialty markets.
Progress was made on all three sub-objectives. Gametic incompatibility genes may be useful for controlling pollen dispersal among market classes of maize. We initiated research with a collaborator at Iowa State University to characterize gametic incompatibility genes of maize at the molecular level. The Ga1S gene was backcrossed into several different inbreds. This will facilitate identification of modifier genes that improve the pollen exclusion of Ga1S. To facilitate development of high methionine inbreds, we are combining inbreds that have high methionine content controlled by different mechanisms. We produced grain from this experiment for evaluation. We continued to advance germplasm toward development of improved varieties for sustainable production systems. We obtained a grant from USDA National Institute of Food and Agriculture (NIFA) Organic Agriculture Research and Extension Initiative (OREI) that allowed us to expand the scope of this work significantly.
A corn trait that will lower the glycemic index of processed foods. Corn starch is the major raw material used in many processed foods. Breeding corn for resistance to digestion will make corn a healthier food since this type of starch functions as a dietary fiber. Foods that are made with higher levels of resistant starch have especially low glycemic indexes. ARS scientists in Ames, Iowa, have found significant genetic variation for this trait and predict that selection for higher levels of resistant starch in corn is likely. The environment has an effect on resistant starch content which will be an important consideration when breeding corn for this trait and during its eventual commercial production.
Pollak, L.M., Scott, M.P., Duvick, S.A. 2011. Resistant starch and starch thermal characteristics in exotic corn lines grown in temperate and tropical environments. Cereal Chemistry. DOI: 10.1094/CCHEM-09-10-0140.