Comparative genome mapping of Sorghum bicolor (L.) Moench using an RFLP map constructed in a population of recombinant inbred lines

A restriction fragment length polymorphism (RFLP) linkage map of Sorghum bi color (L.) Moench was constructed in a population of 137 F6-8 recombinant i nbred lines using sorghum, maize, oat, barley and rice DNA clones. The map consists of 10 linkage groups (LGs) and 323 markers. 247 of which (76.5%) w ere ordered at a LOD score greater than or equal to 3.0. The LGs comprise f rom 61 (LG A) to 13 markers (J), which range in length from 205 (A) to 55 c M (J) and have a combined total length of 1347 cM. Highly significant disto rted segregation was detected at all of the 38 loci in a 103-cM segment of LG A, the allelic ratios in the segment ranging from approximately 3 : 1 (o ne end) to 19 : 1 (middle) to 2 : 1 (other end). Duplicated loci located in different LGs have been mapped with 55 of the 295 DNA probes used in the s tudy (18.6%). The distribution of these loci does not provide support for t he hypothesis that Sorghum bicolor (L.) Moench is of tetraploid origin. Com parison of the map with RFLP maps of maize, rice, and oat produced evidence for sorghum-maize LG rearrangements and homoeologies not reported previous ly, including evidence that: (1) a segment of maize 5L and a segment of 5S may be homoeologous to sorghum LG A; (2) maize LGs 4 and 6 are partly homoe ologous to sorghum LG E; (3) the short ann of maize LG 2 is partly homoeolo gous to sorghum LG F; (4) maize LG 4 may be partly homoeologous to sorghum LG G; (5) maize LG 5 and sorghum LG G contain a larger amount of homoeologo us genetic material than previously indicated; and (6) a short segment of m aize LG 1 may be homoeologous to a short segment of sorghum LG I.