Resistance to witches’ broom in adult plants and progeny of local varieties of cacao in Southern Bahia

Abstract

Plants of local cacao variety from Southern Bahia were evaluated in order to verify if there are different levels of resistance to witches' broom disease in the study population and if the evaluation of adult plants in the field is a good predictor of these resistance levels. The seedlings were maintained under greenhouse conditions and inoculated with the fungus Moniliophthora perniciosa. Evaluations of symptoms occurred 60 days after inoculation. In the field, the same genotypes were evaluated by counting the number of dry brooms per plant, per year, and assessing trunk diameter size. The data were subjected to analysis of variance and averages grouped by the Scott-Knott test, differentiated by Tukey's test and compared by Student's T test. The Scavina-6 and CCN51 clones as well as the Catongo variety were used as resistance, moderate resistance and susceptibility patterns, respectively. Twenty-eight percent of the genotypes were among the most resistant and the genotypes 4119 and 4033 were considered the most susceptible to the disease in both field and greenhouse evaluations. Field evaluation was promising as a predictor of resistance level. The selected materials presented good characteristics for witches' broom resistance, with different levels deserving special attention in the context of reducing the vulnerability of Brazilian cacao cultivation to the effects of the disease, especially in the cacao region of Bahia.

Early selection for resistance to cacao witches’ broom in new parental combinations

“…In Brazil, the most adopted resistant pattern is SCA 6 and the susceptible Catongo (a mutation of 'Comum' variety with white seeds) and/or SIC 23 (a 'Comum' selection at the Cacao Institute). In previous inoculation studies, all three patterns performed as expected (2, 5, 13,18,21,23,5,21,13).…”

History, dissemination, and field control strategies of cocoa witches’ broom

“…Research shows that genetic enhancement of the cocoa tree has managed to progress in the selection of cultivars resistant to witches’ broom (Ahnert et al, 2018; Marssaro et al, 2020). In the state of Bahia, Brazil, the first cultivars with specificity of resistance to witches’ broom were launched in 1997 by CEPLAC; however, they lost resistance to witches’ broom in a short space of time, were incapable of self‐fertilization, and there were problems with low productivity.…”