Characterization, virulence, epidemiology, and management of Colletotrichum spp. causing anthracnose in onion and celery

Anthracnose symptoms in onions (Allium cepa L.) and celery (Apium graveolens) were observed for the first time in Michigan during the 2010 growing season. Disease symptoms were found in 37 onion and 50 celery fields during the period of 2010 through 2012. Based on colony morphology, conidial characteristics, internal transcriber spacer (ITS) and glutamine synthetase (GS) sequences and species-specific molecular markers, the causal agents were identified as Colletotrichum coccodes (on onions) and Colletotrichum acutatum (on celery). These new diseases were named onion leaf and neck anthracnose and celery leaf curl and petiole anthracnose. A total of 901 C. coccodes and 549 C. acutatum isolates were recovered from symptomatic onion and celery tissue respectively. A subsample isolates of C. coccodes (N=110) and C. acutatum (N=113) were included in population genetics studies. Four Inter-Simple Sequence Repeat (ISSR) markers banding patterns differed by Colletotrichum spp. isolated from onion and celery, and controls (C. gloeosporoides and C. dematium). Within the C. coccodes isolates the banding patterns were identical, while 4% polymorphism was observed among C. acutatum isolates. A total of 2,300 and 2,423 transcripts contained Simple Sequence Repeat (SSR) motif suitable for primer design for C. coccodes and C. acutatum respectively. Out of the primers tested, 64 and 89% amplified the expected fragment size on C. coccodes and C. acutatum DNA, respectively. No polymorphisms were observed in the SSR primers tested on C. coccodes isolates, while 12% of the primers tested in C. acutatum showed polymorphic loci.;Isolates of C. coccodes and C. acutatum from onion and celery were tested for their pathogenicity and virulence. When ripe cherry tomato (Solanum lycopersicum L.) fruit were inoculated with 824 C. coccodes isolates from onion, differences in virulence were identified based on the field where they originated. When 81 C. acutatum isolates were used to inoculate &...