GENETIC DIVERSITY AMONG ELITE SORGHUM INBRED LINES ASSESSED WITH DNA MARKERS AND PEDIGREE INFORMATION

The amount of genetic diversity in parental lines of commercial sorghu m [Sorghum bicolor (L.) Moench] hybrids is unknown, yet such comprehen sive knowledge could improve the effectiveness of future hybrid develo pment programs. Restriction fragment length polymorphisms (RFLPs) and pedigree data were used to investigate the genetic relationships in a group of 58 fertility restorer (R) and 47 sterility maintainer (B) eli te sorghum inbred lines. The objectives of this study were to (i) asse ss the level of genetic variation for RFLPs in these Lines, (ii) estim ate genetic similarity (GS) based on RFLPs and pedigree information fo r R- and B-Lines, and (iii) examine the agreement between RFLP-based G S and coancestry coefficient (f) for related (f > 0) pairs of inbreds. R-lines, derived mainly from Feterita and Zera-zera, and B-lines, mos tly from kafir germplasm, were analyzed for RFLPs with 104 DNA probes. A total of 326 patterns of RFLP bands was observed, with 276 being co mmon to both R- and B-lines, 32 unique to R-Lines, and 18 unique to B- lines. On average, 3.6 patterns per clone-enzyme combination were foun d for R-lines and 3.0 for B-lines. Average GS based on RFLPs was 0.67 for R-lines and 0.76 for B-lines, indicating more diversity within the R-group. The average for R-lines was 0.08 and for B-lines 0.07. Clust er analysis of GS estimates from the entire set (105) of inbreds revea led separate groups for R- and B-lines in agreement with parental type s, pedigree information, and the classification system used by breeder s. R-lines clustered into two main groups, one derived mainly from Fet erita and the other from Zera-zera. B-lines were grouped into differen t sub-clusters. GS and f were positively correlated for R-lines (r = 0 .46) and for B-lines (r = 0.43), suggesting that RFLP data may help qu antify the degree of relatedness in elite sorghum germplasm.