Characterization of the infection cycle of Phytophthora betacearum on tree tomato (Solanum betacearum)
N. GUAYAZAN PALACIOS (1), M. Mideros Bastidas (1), G. Danies Turano (1), S. Restrepo Restrepo (2) (1) Universidad de Los Andes, Colombia; (2) Universidad de Los Andes, Colombia

Phytophthora betacearum is a recently described oomycete plant pathogen closely related to Phytophthora infestans sensu stricto. This newly described plant pathogen, infects tree tomato (Solanum betacueum) crops, but is not able to infect potatoes or tomatoes, the main hosts of P. infestans. The aim of this study was to characterize the infection cycle of P. betacearum, using microscopy and molecular approaches. Eight to 10 week old tree tomato plants belonging to the susceptible Amarillo cultivar were inoculated with a solution of 5x105 sporangia/mL and the progression of the disease was monitored during nine days based on several aggressiveness and virulence measurements. Samples were collected from the inoculated plants 0, 6, 48, 120, and 168 hpi and visualized using Scanning Electron Microscopy (SEM) and trypan blue staining. Timing and progression of the disease was further studied with qRT-PCR by assessing the expression levels of infection-stage specific markers such as haustorium-specific membrane protein Pihmp1, hyphal growth PiipiO1, and the cell cycle regulator Cdc14 along the infection cycle (0, 6, 48, 120, and 168 hours post inoculation (hpi)). Results indicated that the infection cycle of P. betacearum differs from the closely related P. infestans in that the infection cycle of the former is characterized by a longer biotrophic stage, greater lesions and lower sporulation capacity compared to P. infestans when evaluated on the same cultivar. Varying levels of expression were detected for all genes along the infection cycle, and their profile was consistent with the results observed on the whole plant inoculations. This study provides new insights into the interaction between P. betacearum and S. betacearum. Future studies will require the examination of molecular changes along the infection cycle to better understand the mechanisms that cause P. betacearum to be tree tomato specialized.

Abstract Number: P7-171
Session Type: Poster