Evaluation of the antagonistic effect of pineapple endophytic bacteria on the biocontrol of Phytophthora nicotianae B. de Haan var. parasitica

Heart rot of pineapple caused by Phytophthora nicotianae is one of the most impactful diseases, and its control has mainly relied on the use of fungicides. The aim of this study was to explore more ecological alternatives to control Phytophthora in pineapple, by evaluating the in vitro antagonistic capacity of 11 native strains of endophytic bacteria against two Phytophthora isolates (CUBA and PHY 9). Evaluating different culture conditions, a higher production of zoospores was observed with an incubation at 28°C during the first 72 h after plate seeding. Then, molecular characterization of the pathogen isolates was performed, evaluating the vegetative compatibility of the two Phytophthora isolates, CUBA and PHY9. Their molecular characterization revealed that they belong to P. nicotianae with 99% similarity (BLAST), and belong to the vegetative compatibility group A1. Finally, with the inoculation of the plantlets, the effectiveness of the pathogen's zoospores to induce heart rot in pineapple was confirmed. All evaluated bacterial strains showed inhibitory effects above 50% on the CUBA isolate, and only four strains did so for PHY9. These results suggest that the evaluated bacteria are good candidates to develop an ecological alternative for the control of heart rot in pineapple cultivation, through the use of native endophytic bacteria. Additionally, important details are provided on the biology, molecular characterization of the pathogen, and effective production of zoospores as a means of infection.