Fig. 1. Distribution of su1 alleles. Alleles are color coded based on (C). (A) The geographic distribution of su1 mutant alleles. Mixed accessions are indicated by split circles. Exact geographic locations for the majority of the northeastern U.S. accessions are unknown. (B) The three su1 amino acid changes projected on Pseudomonas isoamylase crystal structure (Katsuya et al., 1998). (C) Structure of the Su1 gene and position of mutations. A fifth allele, from the Peruvian accessions, is not depicted in this figure.