Effect of Biofertilizers on the Phenolic Content in a Hybrid Family of Cacao After Leaf Infection with <i>Phytophthora megakarya</i> and Exogenous Application of Salicylic Acid

Abstract

In order to protect cacao against Phytophthora megakarya, the most aggressive pathogen of this plant in Cameroon, a study was carried out on hybrid genotypes of the family F79SA of cacao (Theobroma cacao L.) to investigate the effect of inoculation of the biofertilizers Gigaspora margarita and Acaulospora tuberculata on the phenolic compound content in hybrid genotypes after leaf infection with Phytophthora megakarya and treatment of salicylic acid (SA). Thus, the phenolic compound content of hybrid genotypes of the family F79SA of T. cacao was evaluated after artificial infection of leaves with P. megakarya and treatment of salicylic acid without control and under control of biofertilizers. The artificial infection of P. megakarya and exogenous application of salicylic acid resulted in an increase in the accumulation of phenolic compounds (PC) in all genotypes. This increase was more important under the control of Gigaspora margarita and Acaulospora tuberculata and varied from one genotype to another. The PC content analysis map of these genotypes at different treatment conditions under the control of biofertilizers showed a gradual evolution of black coloration, a sign of the increase in phenolic compound content related to concentrations of salicylic acid and infected leaves in all hybrid genotypes thus expressing high tolerance. This map allowed to classify hybrid genotypes according to their level of tolerance. A negative and significant correlation (P = 0.05) was observed between the development of necrosis and the accumulation of phenolic compounds on one hand and between salicylic acid and the accumulation of phenolic compounds on the other hand. Salicylic acid can therefore be used in the cacao selection program in the absence of the pathogen for the identification of hybrid cacao genotypes as well as in other similar breeding programs.