(C-A) AND (G-A) ANCHORED SIMPLE SEQUENCE REPEATS (ASSRS) GENERATED POLYMORPHISM IN SOYBEAN, GLYCINE-MAX (L) MERR

We used thirty simple sequence repeats (SSRs) with a variable 2-4 base 'anchor' at their 5' ends (ASSRs) independently or with arbitrary pri mers in analysis of soybean germplasm and the intercross of 'Essex' an d PI 437654. (AG)(6), (GA)(6) or (CT)(6) and (GT)(6), (TG)(6) or (CA)( 6) were efficient in the detection of (G-A) and (C-A) ASSR-generated p olymorphisms, respectively. DNA sequence analysis of the ASSR-amplifie d fragments confirmed the presence of SSR sequences. (A-T) ASSRs faile d to give amplification or generated fewer number of fragments. Only o ne of the four tested decamer primers altered ASSR banding patterns in the soybean. All the six long primers (18-20 mer) tested changed ASSR banding profiles. On average, seven polymorphic fragments per ASSR pr imer were produced in soybean germplasm and four in the intraspecific cross of 'Essex' and PI 437654. The grouping of 48 genotypes in UPGMA analysis using four (C-A) and four (G-A) ASSR primers was consistent w ith the classification obtained with RFLP markers. Seventy-seven (91%) ASSR markers were dominant, while the remaining 8 (9%) showed codomin ant segregation. Fifty-eight ASSR markers were mapped onto IS RAPD/RFL P linkage groups, which covered approximately 50% of the soybean genom e. Of the (G-A) ASSR-derived markers 49% remained unlinked compared wi th 17% of (C-A) ASSR markers at LOD 3.0. Map linkage information showe d that the assigned (C-A) polymorphisms had a biased distribution, whe reas (G-A) polymorphisms were randomly dispersed.