THE DOSAGE EFFECT OF THE WILDTYPE GBSS ALLELE IS LINEAR FOR GBSS ACTIVITY BUT NOT FOR AMYLOSE CONTENT - ABSENCE OF AMYLOSE HAS A DISTINCT INFLUENCE ON THE PHYSICOCHEMICAL PROPERTIES OF STARCH

A gene-dosage population was obtained by crossing two genotypes that w ere duplex for the GBSS allele. Nulliplex, simplex, duplex or triplex/ quadruplex plants could be identified by monitoring the segregation of red and blue microspores after staining with iodine. GBSS activity wa s significantly different for all groups and showed an almost linear d osage effect for the wildtype GBSS gene. A dosage effect was found for amylose content that was not linear. The amylose content was similar for both the duplex and triplex/quadruplex group. Within the simplex g roup, differences in amylose content were found, which might be due to a different genetic background. There was no linear correlation betwe en GBSS activity and amylose content. A certain level of GBSS activity led to a maximum amount of amylose, and further increase in GBSS acti vity did not result in a further increase in amylose content. The pres ence of one or more wildtype GBSS allele(s), and therefore the presenc e of amylose in the starch granules, had a great influence on the phys ico-chemical properties of the starch suspensions.