Insights into the infection dynamics and interactions between high-virulence and low-virulence isolates of <i>Phytophthora palmivora</i> and durian seedlings

Durian (Durio zibethinus L.) is susceptible to Phytophthora palmivora, which causes rot disease, leading to significant yield loss. This study aimed to investigate local defense responses of durian to P. palmivora and compare the infection dynamics of high virulence (HV) and low virulence (LV) isolates. Durian leaves on 1-year-old seedlings were inoculated with mycelial plugs. Symptoms were observed within 24 h. The HV-isolate was more aggressive, leading to larger lesions, earlier and denser colonization, and higher sporulation. P. palmivora lifestyle related gene (PpEF1α, PpHmp1, PpCdc14, and PpOPEL) were expressed at a higher level in HV compared to LV. Local defense response showed intense accumulation of H2O2, with a stronger response to the HV. Callose deposition increased initially but declined after inoculation, with different diameters between isolates, but no significantly different intensity patterns. These findings provide insights into the P. palmivora-durian interaction, with potential applications in improving disease management strategies.