Pattern of pairwise LD in ZmGW2-CHR4. All polymorphisms with minor allelic frequency exceeding 0.05 were used. In the gene diagram, filled black boxes represent exons, and open boxes indicate the untranslated regions (UTRs). Grey dash-dot boxes mark the regions sequenced in this study. Polymorphisms 1 to 22 are from the 5' end, 23 and 24 from the middle region, and 25 to 30 from the 3' end. The polymorphisms and their locations on the gene diagram are connected by lines.