Black pod rot is one of the most widespread diseases in the species Theobroma cacao L. In Côte d'Ivoire, it causes significant yield losses, estimated at about 10 to 60% depending on the ecological zones. This study was conducted in order to identify Phytophthora spp isolates in the cocoa orchard by the analysis of their molecular features and assess their pathogenicity on cocoa tree leaf disks having different sensitivity. Thirty-six isolates of Phytophthora spp., from 06 producing regions (Divo, Soubré, Daloa, Duékoué, Abengourou and Aboisso) were taken from immature pods naturally affected by black pod rot. Methods of molecular analysis based on PCR-RFLP techniques, sequencing the ITS1 region of ribosomal DNA and artificial inoculation tests on cocoa tree leaf disks were used to identify Phytophthora isolates and assess their aggressiveness. The results obtained enabled to identify Phytophthora palmivora and showed a difference of aggressiveness between isolates of this species with average grades of foliar sensitivity ranging from 0.90 to 3.93.
Cocoa is one of the major cash crop of Cote d'Ivoire. With 1 964 000 tons in 2018, Côte d'Ivoire is leading the world cocoa beans supply. Unfortunately, this important source of income for the country is under a severe pressure of the Cocoa Swollen Shoot Disease. This disease had been reported for the first time in 1943 in the eastern part of the country. In 2003, important infection areas were reported in the departments of Sinfra and Bouaflé in the Central-West with more than 77.000 ha destroyed. Since that period the disease is reported in several places. But we didn't have a clear idea of all the infected areas. This study aims to study somehow the spread of the disease. The main parameters studied are the incidence and prevalence. The methodological approach consisted in surveys implemented in two steps: 2008-2012 and 2013-2016 on farmer's farms. The study carried out between 2008 and 2012, shows that the CSSD prevalence was 16.37% with 19 regions infected out of 24. The disease reaches 83 departments and 40.680 farms. The second phase of the survey held from 2013 to 2016 shows that the prevalence was 19.51%. It help to highlight a strong progression of the disease in the orchard with 7.734 new farms infected in 111 localities divided into 24 regions. Globally the study shows that the incidence of the CSSD in the orchard ranked from 0% to 76.67 % and the national average is 4.06 %. The areas with low incidence cover 85 localities. The areas with moderate incidence are 25. Doba in San Pedro were the area of highest incidence (76.67%).
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