STRUCTURE AND PHYSICOCHEMICAL PROPERTIES OF ENDOSPERM STARCHES OF A WAXY ALLELIC SERIES AND THEIR RESPECTIVE NORMAL COUNTERPARTS IN THE INBRED OH43 MAIZE BACKGROUND

Research over the past three decades has greatly increased our underst anding of the biochemical genetics of varoius waxy (wx) alleles of mai ze, but our knowledge about the structure and physicochemical properti es of endosperm starches obtained from the wx alleles is still incompl ete. We further investigated the structure and physicochemical propert ies of endosperm starches from a wx allelic series and their normal co unterparts in the Oh43 inbred background. Starch granules were prepare d from mature kernels of wx mutant alleles; wx-C31, wx-R, wx-90, wx-a, wx-B3, wx-m-1, wx-m-8, and wx-S5, and their respective normal counter parts in the inbred Oh43 maize background. Measurements of absorption spectra of starch-iodine complexes and by gel permeation chromatograph y of Pseudomonas-isoamylase-debranched starches showed that all of the starches from the wx allelic series were uniquely waxy type in charac teristics, and their normal counterparts were characteristically norma l type. Pasting characteristics of starch granules and retrograded sta rches of the wx allelic series and their respective normal counterpart s were investigated by differential scanning calorimetry (DSC). The pe ak temperature (Tp) and conclusion temperature (Tc) values from starch es of the wx allelic series were slightly higher than those of their r espective normal counterparts and the Delta Hs of starches of the wx a llelic series were greater than those of their respective normal count erparts. The onset temperature (To), Tp, and Tc of all retrograded sta rches were very similar, however, the Delta Hs of the retrograded star ches of the wx allelic series were greater than those of their respect ive normal counterpart. Starch granules of the wx allelic series were hydrolyzed more rapidly than those of their respective normal counterp arts.