Study of the Pathogenicity of Moniliophthora spp. Isolates from Branches of Kola Trees (Cola nitida (Vent) Scott and Endl.) Infected with witches Broom Disease

The main objective was to study in the greenhouse the pathogenicity of six isolates of Moniliophthora spp. on kola trees. To achieve this objective, branches of kola trees bearing the symptoms of the disease were collected in the main kola nut production areas (Danane, Meagui, Daloa, Agboville, Abengourou and Aboisso) and at the CNRA research station in Divo. The necrotic (dry brooms) and non-necrotic (green brooms) parts were disinfected and then placed on agar water (1.5% gelatin). Six isolates of Moniliophthara spp. were obtained after one week of incubation. The morphological characteristics of these isolates were studied on PDA medium and carrot medium. Thus, all the Moniliophthora spp. isolates studied were able to grow on both culture media. However, the carrot organic medium allowed good mycelial growth. For the identification of the causal agent of the disease, a pathogenicity test was set up and a fully randomised experimental design with seven treatments repeated three times was used. The factor studied was the Moniliophthora spp. isolate with six modalities. The experimental unit consisted of 10 plants, all six months old. The variables measured were the latency period of the isolates, their virulence and their aggressiveness. Results showed that all isolates caused disease symptoms in inoculated plants while uninoculated plants were apparently healthy. The first symptoms appeared after one week for isolates KOCIV 1-1, KOCIV 1-2, KOCIV 1-3 and KOCIV 1-4. Isolates KOCIV 1-5 and KOCIV1-6 showed symptoms after two weeks. The KOCIV 1-4 isolate was the most virulent with a virulence rate of 59% and the KOCIV 1-6 isolate was the least virulent with a virulence rate of 33%. In the future, a molecular identification of the isolates is necessary to better understand the pathogen in order to select resistant plant material