Specifying the introgressed regions from H. argophyllus in cultivated sunflower (Helianthus annuus L.) to mark Phomopsis resistance genes.

A method based upon targetting of introgressed markers in a Phomopsis-resistant line (R) of cultivated sunflower, issuing from a H. argophyllus cross was used to mark the Phomopsis resistance regions. Our study was based upon 203 F(3) families derived from a cross between an inbred line susceptible to Phomopsis (S1) and the introgressed resistant line (R). Families were checked for Phomopsis resistance level in a design with replicated plots and natural infection was re-inforced by pieces of contaminated stems. Thirty four primers were employed for RAPD analysis. Out of 102 polymorphic fragments between (S1) and H. argophyllus, seven were still present in (R) suggesting that they marked introgressions of H. argophyllus into (R). The F(2) plants were scored for the presence or absence of 19 fragments obtained from five primers, and the relationships between the presence/absence of fragments in F(2) plants and Phomopsis resistance/susceptiblity in the F(3) progenies was determined by using an analysis of variance. We found that at least two introgressed regions, as well as favourable factors from sunflower, contributed to the level of Phomopsis resistance in cultivated sunflower.