Anin vitroinvestigation of MalaysianPhytophthora palmivoraisolates and pathogenicity study on oil palm

Abstract

AbstractBud rot disease affecting oil palm in South American countries is reported to be caused byPhytophthora palmivora.P. palmivorais a local pathogen affecting various crops in Malaysia, and this finding caused an alarm, which prompted an investigation of pathogenicity using MalaysianP. palmivorato assess the potentials of this Oomycete to infect oil palm in Malaysia. A total of 11P. palmivoraisolates were obtained from cocoa and durian for the study. Leaf bioassays via artificial inoculation using 50,000 zoospores/ml and mycelial agar disc showed severe necrotic lesions on the infection spot of oil palm (DxP) spear leaves. Mild infection was observed in oil palm spear leaves of OxG hybrids indicating lower susceptibility againstP. palmivorainfection. Phylogenetic analysis using internal transcribed spacer (ITS) data revealed that Malaysian isolates were genetically similar to Colombian isolates supported by significant bootstrap values. The leaf bioassay results revealed that Malaysian oil palm materials are susceptible towards localP. palmivorainfection. The ColombianP. palmivoraisolates causing bud rot incidence may have evolved over a long period of time, undergone sequential genetic shift to become more virulent towards Colombian oil palm planting materials.