DNA markers for genes conditioning resistance to soybean [Glycine max (L.) Merr.] root infection by [Fusarium solani (Mart.) Sacc. f. sp. gfycine (Burk.)] (Rfsl), sudden death syndrome (SDS), and soybean cyst nematode (SCN; Heterodera glycines Ichinohe; Rhg4 and rhgl) were previously identified in 'Essex' X 'Forrest'. This study tests the effectiveness of those markers in selecting for disease resistance among recombinant inbred lines from 'Flyer' X 'Hartwig'. A total of 535 among 739 lines were scored by two markers, providing four genotypes. A stratified random sample of 50 lines was evaluated for SDS by F. solani root infection severity at two locations and SCN race 3 index of parasitism in the greenhouse. Selection with BLT65 identified 281 among 671 lines with the genomic region that underlies Rhg4-derived SCN resistance. Selection with Satt038 identified 230 among 613 lines containing the genomic region that underlies resistance to SDS (rfsl) and rhgl-derived SCN resistance. A total of 93 out of 535 lines had genomic regions that underlie resistance to both SDS and SCN in Essex X Forrest. Segregation of both markers was not random (P =£ 0.05). Infection severity means for genotypes with the Hartwig allele at Satt038 (28-29%) were lower (P = 0.0001, R* = 28%) than with the Flyer allele (31-42%); irrespective of maturity group. BLT65 was not associated with infection severity. Mean SCN index of parasitism was lower (P s 0.05) only for genotypes carrying the Hartwig allele at both Satt038 and BLT65. Therefore, alleles conferring resistance to SDS and SCN in Essex X Forrest are transferable to other populations.

Coinheritance of field resistance of soybean [Glycine max (L.) Merr.] to sudden death syndrome (SDS) [caused by the fungus Fusarium solani (Mart.) Sacc. f. sp. phaseoli (Burk.) Snyd. & Hans.] and soybean cyst nematode (SCN) race 3 (caused by Heterodera glycines Ichinohe) sometimes occurs in crosses among adapted cultivars. Our objective was to characterize the loci underlying this coinheritance. One hundred thirty DNA markers were compared with SDS disease response and SCN score among 100 recombinant inbred lines (RILs) derived from a cross between SDS and SCN resistant ‘Forrest’ and SDS and SCN susceptible ‘Essex’. SDS disease incidence (DI) was determined in replicated sites during 4 yr encompassing five locations. The SCN score was determined in the greenhouse from naturally infested field soil samples. Two separate genomic regions identified by random amplified polymorphic DNA (RAPD) markers OI03450 and OW15400 were associated with mean SCN score (P = 0.0001) and jointly accounted for about 47% of variability in SCN score. OI03450 identified a QTL for resistance to SCN (R2 = 14%) within a genomic region that was strongly associated with SDS DI (R2 = 20%), partly explaining the coinheritance of the two traits. This locus could be assigned to the region of linkage group G already known to encompass the major SCN resistance locus.

A newly designed high-sensitivity isothermal reaction calorimetry system has been used to investigate the thermodynamics of the association between myelin basic protein and phosphatidylserine vesicles. This instrument has allowed us to measure directly the energetics of the protein-lipid interaction under various conditions. Above the phospholipid phase transition temperature the enthalpy of association is highly exothermic amounting to -160 kcal/mol of protein. Below the phospholipid phase transition temperature the enthalpy of association is exothermic at protein/lipid ratios smaller than 1/50 and endothermic at higher protein/lipid ratios. These studies indicate that the association of myelin basic protein to phosphatidylserine vesicles consists of at least two stages involving different types of binding. The first stage, at low protein/lipid ratios, involves a strong exothermic association of the protein to the membrane and the second, at high protein/lipid ratios, a weaker association probably involving attachment of the protein to the membrane surface only. In the gel phase the second binding stage is endothermic and appears to be correlated with the formation of large vesicle aggregates. This vesicle aggregation is a reversible process dependent upon the physical state of the membrane. The isothermal titration studies have been complemented with high-sensitivity differential scanning calorimetry experiments. It is shown that the dependence of the phospholipid transition enthalpy on the protein/lipid molar ratio can be expressed in terms of the different protein-membrane association enthalpies in the gel and fluid phases of the membrane.

DNA amplification fingerprinting (DAF) using a high primer-to-template ratio and single, very short arbitrary primers, was used to generate amplified fragment length polymorphic markers (AFLP) in soybean (Glycine max (L.) Merr.). The inheritance of AFLPs was studied using a cross between the ancestral Glycine soja PI468.397 and Glycine max (L.) Merr. line nts382, F1 and F2 progeny. The amplification reaction was carried out with soybean genomic DNA and 8 base long oligonucleotide primers. Silver-stained 5% polyacrylamide gels containing 7 M urea detected from 11 to 28 DAF products with primers of varying GC content (ranging from 50 to 100% GC). Depending on their intensity, AFLPs were classified into three classes. DAF profiles were reproducible for different DNA extractions and gels. Forty AFLPs were detected by 26 primers when comparing G. soja and G. max. Most AFLPs were inherited as dominant Mendelian markers in F1 and F2 populations. However, abnormal inheritance occurred with about 25% of polymorphisms. One marker was inherited as a maternal marker, presumably originating from organelle DNA while another showed apparent paternal inheritance. To confirm the nuclear origin and utility of dominant Mendelian markers, three DAF polymorphisms were mapped using a F11 mapping population of recombinant inbred lines from soybean cultivars Minsoy x Noir 1. The study showed that DAF-generated polymorphic markers occur frequently and reliably, that they are inherited as Mendelian dominant loci and that they can be used in genome mapping.

Numerous methods now exist for plant breeders and others to estimate genetic relationships among different germplasm. Two of the most commonly used methods have been restriction fragment length polymorphism (RFLP) and pedigrees. The objective of this study was to compare a relatively new method, DNA amplification fingerprinting (DAF), which is a short, arbitrary‐primer, polymerase chain reaction (PCR)‐amplification method, to RFLP and pedigree methods for genetic distance estimation among soybean [Glycine max (L.) Merr.] genotypes. The genotypes consisted of agronomically important soybean lines Archer, BSR101, Forrest, Hartwig, 9171, 9341, 9392, 9593, S8330 and the plant introduction, PI437.654. The 10 genotypes were evaluated by means of 53 RFLP clones, a subset of 12 RFLP clones, seven DAF primers, and available pedigrees. The DAF data set and the subset of 12 RFLP clones each consisted of 18 markers. For each method, the data were used to calculate the 45 pairwise genetic‐distance estimates among the varieties using the average linkage algorithm in SAS. The genetic‐distance estimates were correlated from 0.63 to 0.89 among the four methods. Dendrograms based on each method were therefore considered similarly reliable. For varietal identification, the DAF and RFLP markers distinguished the varieties with similar efficiency. We conclude that both DAF and RFLP marker technologies and pedigrees are useful tools for estimating genetic distances in soybean.