RAPD analysis of two pairs of su1se/su1Se near-isogenic lines for the identification of chromosomal regions affecting the sugary enhancer phenotype

Sweet corn with the sugary enhancer (se) phenotype is traditionally charact erized by elevated sugar content, slow dry down of kernels, more wrinkled p ericarp of mature dried seeds and lighter kernel color. The objective of ou r study Nas to identify chromosomal regions which affect these characterist ics using RAPD analysis of near isogenic lines (NILs). Two independent pair s of near isogenic lines (IL678a and IL451b) were compared. The original su 1se line IL677a was used as a reference. Three hundred and forty arbitrary, 10-mer primers were used to amplify genomic DNA extracted from the differe nt geno-types. Three of the 340 primers generated amplification products wh ich differed between the su1se genotypes and their su1Se isolines. The asso ciation between the RAPD discrete bands and the sugary enhancer phenotype w as confirmed by analyzing 16 additional su1se and su1Se sweet corn inbreds. We mapped mio of these markers to chromosome 6 and one of them to chromoso me 3 by the analysis of their segregation in an se x Se F-2:3 population. T he marked chromosome 3 region had been previously reported as being associa ted with kernel sugar content and taste, while the chromosome G region was associated with both maltose concentration and kernel color. The results in dicate that more than one locus may affect the sugary enhancer phenotype. T he complications in phenotypic selection and the advantage of marker assist ed breeding (MAB) for the se phenotype are demonstrated.