Physicochemical properties of maize starches expressing dull and sugary-2 mutants in different genetic backgrounds.

Isogenic lines carrying the du or su(2) genes in five different maize inbred lines were developed, and the effect of the starch-modifying genes on general, thermal, pasting, and gel textural properties of starch was studied. Swelling power of du and su(2) starches was significantly lower than that of normal starch. The peak viscosity of du starches was reduced, peaks were sharper, and the setback was lower than in normal starches. The hardness of du starch gels increased and the adhesiveness decreased severalfold during 7 days of storage, indicating unstable gel texture. The su(2)/su(2) starches had flatter viscosity peaks than normal starches, with extremely low viscosity and almost zero breakdown and setback. In the su(2) starch gels hardness and adhesiveness did not change significantly during 7 days of storage. For most measured properties, there was considerable variation among different inbred backgrounds carrying the same mutant genotypes. Genetic background and starch-modifying genes can both be manipulated to select specific desired starch properties.