Quantitative resistance to witches’ broom disease in progenies of different sources of resistance

Genetic control using distinct resistant sources stands out as the best approach to control witches' broom disease (WBD) of cacao. Under a scenario of continuous and high inoculum pressure, in Bahia, Brazil, Moniliophthora perniciosa has evolved towards the Scavina's sources (the primary source of resistance used in cacao breeding programs). Therefore, the objectives of the present study were to measure the quantitative resistance of a cacao population with 21 full-sib crosses under high natural pressure of Moniliophthora perniciosa and to what extent this response is organ-specific. The progenies used were crosses of different resistant sources with the resistant source Scavina6 and the susceptible control SIC23. According to results, the adaptation of Moniliophthora perniciosa towards Scavina's sources is organ-specific, i.e., to flower cushions. The effect of this on quantitative pathogen traits was also observed. The Amazonian materials, such as the CSul3 and GU171, which showed resistance to both vegetative and flower cushion brooms, can reduce pathogen evolutionary potential. •The evolution process of M. perniciosa towards Scavinas sources was confirmed.•Amazonian materials, such as CSul and GU17, showed resistance to VB and FCB.•Organ specificity is an important component of resistance to Witches' broom disease.•Adaptation of M. perniciosa to Scavina's sources is specific to flower cushions.•The sporulation potential of FCB is of epidemiology importance.