Cacao Rootstock Selection Resistant to Ceratocystis cacaofunesta at the INIAP Germplasm Collection, Ecuador

ABSTRACT

Ceratocystis wilt, caused by the ascomycete fungus Ceratocystis cacaofunesta , is a plant disease that threatens cacao cultivation in Ecuador. Seeds from resistant, self‐pollinated selections of Amazonian Forastero cacao identified in the 1950s continue to be recommended for rootstock production. Given the limited availability of genetic material, 52 cacao genotypes of diverse origins from INIAP's germplasm bank were screened to identify C. cacaofunesta ‐resistant genotypes suitable for use as rootstocks. Branches were inoculated both in the laboratory and in‐field with a suspension of 30,000 infective units mL ⁻¹ to evaluate mycelial and perithecial development, as well as the lesion index, to subsequently determine resistance levels. The inoculation and evaluation method employed enabled the identification of specific accession groups based on the homogeneity of their linear predictors and the rate of progression of the lesion index across the two evaluation periods. Furthermore, non‐linear regression determined disease progression in resistant versus susceptible genotypes. These results will enable the recommendation of new genotypes for use as rootstocks in the mass propagation of cacao plants.