Bulk Segregant Research Articles

RAPD markers for a sunflower rust resistance gene

An F2 population of sunflower (Helianthus annuus L.) was tested for segregation of a gene conferring resistance to sunflower rust (Puccznia helzanthi) Australian Race 0 (North American Race 1). The resistant parent, RHA279, of this cross was thought to possess a single dominant resistance gene to this race. Genetic analysis confirmed that this population was segregating for a single dominant gene, the R1 gene, for resistance to this race of the pathogen. Using bulked segregant and RAPD analyses, two markers were identified which co-segregated with the rust resistance gene in the F2 population. These markers, designated OT06959 and 01\/112850, are linked to the rust resistance gene at a distance of 4.5 cM and 26 cM, respectively, with the markers situated one either side of the gene. The availability of markers closely linked to this gene will greatly enhance selection for the gene in future breeding programs, and especially assist efforts to pyramid the gene with other rust resistance genes to produce sunflower varieties with more durable resistance to rust.

Korngrenzensegregation des Phosphors im Austenit und Einfluß von Kohlenstoff

Equilibrium segregation of phosphorus at the grain boundaries of austenite has been studied in Fe-P-, Fe-0.16%C-P- and Fe-0.35% C-P-alloys. The samples were equilibrated at temperatures of 850–1200 ° C and analysed after rapid quenching using Auger-Electron Spectroscopy. The results in Fe-P-alloys may be evaluated according to the Langmuir-McLean equation. The following expression for the free energy of P-segregation in austenite was obtained: -gDGpo= −21300 −25.8* T (J/mole). For the Fe-P-C-alloys the carbon concentration increases at the grain boundaries with increasing carbon concentration in the bulk and phosphorus segregation decreases. The observed carbon segregation does not show any dependence on austenitising temperature and the temperature dependence on P-segregation is also insignificant. Reasons for this behaviour are discussed.