Some Structural Characteristics of Starches of Maize Having a Specific Genetic Background

Distribution of starch components of maize (Zea mays L.) and their properties were investigated by gel filtration after debranching and by exhaustive hydrolysis of starch-granules with glucoamylase. Based on the results, relationship between genotypes and properties of starch components were discussed. The sugary-1 (su₁), sugary-2 (su₂), and dull (du) mutants produced high amylose maize, while amylopectin of su₂ was normal type and those of su₁ and du were novel type. In the double-mutant combinations, the waxy (wx) gene decreased amylose content. Starches of du su₁ or du su₂ possessed greatest amount of amylose among starches examined. Contents of amylose, intermediate fraction (Fr.) and longer branches of amylopectin increased in most cases when the amylose-extender (ae) gene was introduced. Starches of ae possessed longer average chain-lengths of amylopectin than that of normal. In ae du starches, however, elongation of the amylopectin chain and increase of the intermediate Fr. did not occur. Exhaustive degradation of starch-granules by glucoamylase showed that ae starches were more resistant to amylase.