Sources of resistance to witches' broom disease in cacao (Theobroma cacao L.): Progress update and perspectives

Sources of resistance are an important control measure for witches' broom disease in cacao. Their identification through quantitative trait loci (QTLs) and genetic diversity analysis would assist breeding programs to develop new cultivars with improved resistance traits. We conducted a systematic review that compiles the main advances in the search for resistance to witches' broom disease. The systematic review on Scopus, Springer Link, PubMed, SciELO, and Web of Science databases followed the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines using the State of the Art through Systematic Review (StArt) software. We identified genotypes exhibiting the most significant resistance in phenotypic analysis, along with combinations of crosses that are promising for future studies and cultivar development. Data on genetic diversity indicate a wide possibility of benefits from heterozygosis. Genetic mapping and association studies revealed eight QTLs associated with resistance and several candidate genes with known and unknown biological functions. More comprehensive research of the various sources of resistance to witches' broom disease is crucial for the advance of cacao breeding programs.