SUMMARY Artificial onion oil was evaluated as a soil treatment for control of white rot in onions caused by Sclerotium cepivorum. The treatment was tested at Werribee South in a red brown earth with a sclerotial population of c. 40–100/kg soil; and at Colac in a black clay loam with c. 180/kg soil. Treatments were applied before sowing and their effect on numbers of sclerotia, disease incidence and yield of dry bulb onions determined. At Werribee South onion oil reduced numbers of sclerotia at the 0–10 and 10–20 cm depths in soil, reduced disease incidence and increased yield in comparison with the controls. Onion oil at a concentration of 5% in water and injected (440 litredha) at 10 cm was most effective. The treatment reduced sclerotial numbers at 0–10 and 10–20 cm by 77 and 91% respectively, reduced disease from 57 to 13% and increased yield by 103%. Onion oil at 25% in water had no significant effect on populations of sclerotia or on incidence of disease. In an experiment at Colac, the application of onion oil at 5% in water reduced sclerotial numbers from 187 to 87/kg, but not incidence of white rot.

RAPD marker was used to evaluate genetic relationships in a set of 16 inbred lines of sunflower representing the genetic stock, including restorers and maintainer lines, of the classical cytoplasmic male sterility. The genotypes were grouped into eight cluster at 0.83 coefficient level. A total of 164 bands were detected, of which 69.51% were polymorphic among the genotypes tested. The similarity coefficient was maximum between TNAU7 6/8 and EC 68414/1 (0.90) indicating less divergence between them. Lower similarity indices were observed between 62B and GP324 (0.67) and between 852B and GP 324 (0.68), indicating more divergence. Crossing between the genotypes with low similarity coefficient will manifest high heterosis.

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Fertility restoration ability of the restorer was controlled by a single dominant gene. Bulked segregant analysis (BSA) was applied to identify molecular markers linked to a major restorer gene (Rf) using the F 2 population of cms 234 A × RHA 272. A total of 144 random oligo nucleotide primers were surveyed. The primer OPAM 06 1800 was found to produce putative markers, which differentiate parent and bulk from sterile parent and sterile bulk. The co-segregation analysis of the putative marker on the F 2 population confirmed the association of OPAM 06 1800 produced by the primer OPAM 06 with the fertility restoration gene. This will help in transfering the fertility restorer gene to the inbreds lacking restoration genes.