Submitted to: Cereal Chemistry
Publication Type: Peer reviewed journal
Publication Acceptance Date: 9/1/2001
Publication Date: N/A
Citation: Interpretive Summary: Corn starch molecules can have many branches (amylopectin) or be linear (amylose). Corn with high levels of amylose has many valuable uses for food and industry, but breeding and selection for amylose requires rapid analytical methods for measuring amylose. Two rapid methods for determining amylose levels were compared to a more time-consuming but accurate method. Each of the rapid methods was found to have uses in special circumstances, which may speed the breeding of high-amylose corn. The corn materials used in the study were exotic by adapted types that had the gene causing high amylose levels incorporated into them. The study showed that exotic germplasm may be a very important source of modifying genes to the high amylose gene, causing the amylose levels to go even higher. In recent years many novel food and industrial uses have been found for starch isolated from high-amylose corn benefiting farmers, processors, and consumers. Corn lines with even higher levels of starch and that are even more efficient to develop could be the catalyst for producing many more novel uses.
Technical Abstract: Breeding for high-amylose corn requires a rapid analytical methods for determining starch amylose so that generating wet chemistry values does not pose a major limitation in the volume of materials that can be screened. Two methods for determining apparent amylose (AA) were examined and compared to an iodine-binding method involving the solubilization of isolated starch in NaOH (method 1). These methods included one based on near-infrared transmittance spectroscopy (NITS) (method 2) and another iodine-binding method involving the solubilizing of starch from ground whole corn with a DMSO-iodine solution (method 3). The materials evaluated consisted of 155 exotic plant introductions and experimental materials generated from the Germplasm Enhancement of Maize (GEM) project. Crosses were made between these materials and a Corn Belt hybrid (Oh43 x H99) converted with the amylose-extender (ae) allele. Grain from 155 F2 ears (from a total of 1006), presumed to be homozygous for the ae allele based on visual selection of mutant kernels on F1 ears from which they were planted, were then subjected to the three methods in order to identify possible modifiers of ae conditioning high starch AA. Method 2 was poorly correlated to method 1 (r=0.88) but NITS appeared to discriminate between samples having been converted to ae versus those having a normal or possibly segregating endosperm type. Method 3 had a better correlation with method 1 (r=0.92) and appeared to more fully discriminate among samples having AA values greater than 65% from those at or near 55%. Results from this study suggest that NITS may be useful for quick screening mutant genotypes when visual identification is difficult.