GENETIC-ANALYSIS OF RESISTANCE TO CLUBROOT (PLASMODIOPHORA-BRASSICAE WORON) IN 2 BRASSICA-OLERACEA GROUPS (SSP ACEPHALA AND SSP BOTRYTIS) THROUGH DIALLEL ANALYSIS

Clubroot, caused by Plasmodiophora brassicae Woron, is a major disease of cruciferous crops and few sources of resistance have been detected and genetically studied in the Brassica oleracea species, In this stu dy, two diallel mating systems using resistant kale lines and suscepti ble cauliflower lines were performed. Resistance was assessed from a d isease index evaluated on young plants artificially inoculated with lo cal isolates of the parasite. Both general and specific combining abil ity effects (GCA and SCA) and partly reciprocal effects were demonstra ted. Resistance inheritance was, however, characterized by a predomina nce of additive genetic effects (GCA). Three groups of parent lines co uld be separated; kale lines with very high resistance, kale lines wit h intermediate resistance and susceptible cauliflower lines. In the tw o kale groups, two genetically different resistance types were suggest ed and various recurrent selection procedures are proposed following t he dialler results.