Restriction fragment length polymorphism mapping of quantitative and qualitative traits in soybean
The purpose of this thesis was to map traits of interest to soybean (Glycine max (L.) Merr.) breeders and geneticists with RFLP markers. The thesis consists of three separate studies;In the first study, quantitative trait loci (QTL) for seed size, protein and oil content and for the content of the fatty acids palmitate, stearate, oleate, linoleate and linolenate were mapped. The traits were measured on seed harvested from a replicated trial of 60 F[subscript]2-derived lines from a cross between the G. max experimental line A81-356022 and the G. soja Plant Introduction 468916. Each F[subscript]2 was genotyped with 252 marker loci. Markers that explained significant (Pr < 0.01) variation were found for all traits. Many of the markers significantly associated with variation for the seed traits were clustered on a few major groups;Five Rps genes that confer resistance in soybean to phytophthora root rot caused by Phytophthora megasperma Drechs. f. sp. glycinea Kuan and Erwin were mapped with RFLP markers in the second study. The mapping was conducted by first screening, with RFLP markers, a series of near isogenic lines (NILs). The NILs contained all six of the Rps resistance genes that have been reported. Each NIL had one or two resistance alleles. The RFLP markers that were polymorphic between the NILs and the recurrent parent were tested for linkage with Rps loci. Linkage was found between RFLP markers and Rps1, Rps2, Rps3, Rps4 and Rps5;A variant for the A[subscript]4 polypeptide of the glycinin storage protein was mapped and genetically analyzed in the third study. The variant was identified in PI 468916, the G. soja parent of the population being used to form a public RFLP map. Using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), the A[subscript]4 polypeptide in PI 468916 had a slower mobility than the A[subscript]4 polypeptide in A81-356022, the other parent of the population, or any other genotype reported. The individuals in the population used to form the RFLP map were evaluated for the segregation of the A[subscript]4 polypeptide. This segregation data was integrated with the RFLP segregation data set and was used to genetically map Gy4, the gene that encodes A[subscript]4. A germplasm survey of 24 G soja plant introductions also was conducted which revealed two accessions with A[subscript]4 variants similar to what was observed in PI 468916. Two additional accessions with faster mobilities of A[subscript]4 than any other genotypes we have tested also were found.