Identification of fungal pathogens and analysis of genetic diversity of Fusarium tricinctum causing root rots of alfalfa in north‐east China

Abstract

AbstractAlfalfa root rot is a devastating disease complex found worldwide. Population structure and genetic diversity of fungal pathogens causing alfalfa root rot in north‐east China are not well understood. In this study, 480 fungal isolates were collected from six major alfalfa‐growing regions in Heilongjiang province, China. They were identified as Fusarium tricinctum, F. oxysporum, F. acuminatum, F. solani, F. equiseti, Phoma medicaginis, Plectosphaerella cucumerina, Alternaria alternata, and Chaetomium globosum and caused root rot on alfalfa in greenhouse studies. F. tricinctum was the predominant species among the isolates, and P. medicaginis and C. globosum had not previously been reported causing alfalfa root rot in north‐east China. Of the 73 F. tricinctum isolates identified, the majority were moderately or highly aggressive on alfalfa. No isolate of F. tricinctum was sensitive to carbendazim (1 and 10 μg/ml), indicating that, although commonly used, it is not suitable for management of the disease in this area. F. tricinctum isolates were analysed using AFLP markers and divided into eight genetic groups with 28 pairs of primers. Analysis of molecular variance indicated significant correlation between genetic groups of F. tricinctum isolates and their geographical locations or aggressiveness. Pairwise comparison and STRUCTURE analysis also indicated that geographical locations and aggressiveness of isolates had a significant effect on population differentiation. This study provides insight into the genetic diversity and reproductive biology of F. tricinctum, enhances understanding of the population diversity of alfalfa root rot pathogens in north‐east China, and facilitates development of effective strategies for managing this destructive disease complex.