MAP ORDER AND LINKAGE DISTANCES OF MOLECULAR MARKERS CLOSE TO THE SUPERNODULATION (NTS-1) LOCUS OF SOYBEAN

The molecular characteristics of markers in the chromosome region surr ounding the supernodulation gene (nts-1) of soybean (Glycine max L. Me rr.) were investigated in 187 F-2 plants from a cross of G. max cv. Br agg (nts) and G. soja PI468.397 (wild-type nodulation). RFLP marker pU TG-132a, linked tightly (0.7+/-0.5 cM) to nts-1, was converted to a PC R marker. The polymorphism resides within a 1.72 kb PstI fragment and consists of an 832 bp insertion in G. max relative to the wild progeni tor G. soja. The insertion is flanked by a 35 bp direct duplication th at was found only once in G. soja. Data suggest that the pUTG-132a seq uence exists only once in the genome, which is compatible with the rec essive nature of nts-1. Accordingly, pUTG-132a is a valuable marker fo r map-based cloning. Another RFLP marker, pA-381, was mapped 4.8 cM di stal to nts-1. Marker order, established by Maximum Likelihood Analysi s, placed nts-1 between pUTG-132a and pA-381. To generate additional m olecular markers, a segregating F-2 population was analysed using bulk ed segregant analysis (BSA) and single oligonucleotide primer-based PC R (DNA amplification fingerprinting; DAF). PCR marker pcr5-4L was mapp ed to soybean linkage group H and sequenced. The data revealed (i) rec ombination events and marker order in the nts-1 region; (ii) the molec ular nature and cause of polymorphisms in linked molecular markers; (i ii) a low density of polymorphisms around nts-1, and (iv) diploidy of the distal region of linkage group H of soybean.