Cross-infectivity and genetic variation of Phytophthora capsici isolates from chilli and black pepper in Vietnam

Abstract

Phytophthora capsici is an economically significant pathogen of various important annual and perennial crops in temperate and tropical regions. Not much is known about the genetic diversity of this pathogen worldwide. In Vietnam it is the causal agent of devastating diseases on several hosts, including chilli and black pepper. Crossinfectivity of P. capsici isolates obtained from the two hosts was demonstrated. Analysis of forty-six P. capsici isolates based on Random Amplified Microsatellites (RAMS) and Repetitive Extragenic Palindromic (REP) fingerprinting revealed that isolates from black pepper were genetically distinct from isolates recovered from chilli. Twenty-two isolates from chilli clustered into two clonal groups at a DICE similarity level of >85%, whereas twenty-four isolates from black pepper were separated from these chilli isolates at a similarity level of <50%. In general the genetic diversity among isolates of P. capsici from black pepper was greater than that of the chilli isolates. The current study indicated that the P. capsici population infecting chilli and black pepper in Vietnam consists of two separate genetic strains, adapted to chilli and black pepper, despite their morphological similarity and host cross-infectivity. The implications of these findings are discussed.