Mapping QTLs for Black pod (Phytophthora palmivora) resistance in three hybrid progenies of cocoa (Theobroma cacao L.) using SSR markers

To identify QTLs for cacao resistance to Phytopthorapalmivora., a study was conducted in three hybrid progenies of CNRA in Cote d'Ivoire obtained from crosses (SCA6 x H) x C1, (P7 x ICS100) x C1 and (P7 x ICS95 x) x C1. SCA6 (Scavina 6) and P7 (Pound 7) are resistant Forastero clones, while ICS100, ICS95 and H are moderately susceptible Trinitario clones and C1 (IFC1), a susceptible Forastero clone. Resistance to P. palmivorawas assessed by means of pod rot rate (PRR) in field and leaf discs inoculation with zoospores (Folres) in both half-sib progenies, while only PRR was investigated in the progeny derived from (SCA6 x H) x C1. For each progeny, a SSR-based linkage map was constructed and Kruskal-Wallis test and interval mapping were applied, associating phenotypic data. Over the three progenies, 8 QTLs of PRR and 3 QTLs of Folres were detected on different chromosomes. One QTL of Folres (R2 = 17.3 %) has been identified on chromosome 10, for the first time. The chromosome 1, carrying QTLs of PRR and Folres, is an interesting support of cacao resistance to Phytophthora. Chromosomes 4 and 6, each, of of two different parents carry QTLs of PRR In addition, the association mTcCIR291-PRR, on the chromosome 6 was noted in the family derived from (SCA6 x H) x C1, as well as in one of the two half-sib families. Markers linked to QTLs are valuable potential candidates for a future exploiting of these QTLs as selection tools. (Resume d'auteur)