Studies on disease cycle and control of celery stunt anthracnose caused by Colletotrichum nymphaeae
Celery seedlings are grown in greenhouse nurseries. Celery producers work to keep pathogen-free conditions to grow healthy seedlings in nurseries by thoroughly removing debris of diseased plants, sterilizing soils and cultivating materials, etc. Although there seems to be a very low possibility that the pathogen remains in the nurseries, seedlings were attacked by the fungus in nursery greenhouses kept warmer than usual. This finding led us to assume that celery seeds may be contaminated with the pathogen. Additional lines of circumstantial evidence suggest that this disease may have spread through seed transmission of the pathogen. Almost all celery producers in the major area in Nagano Prefecture had used celery seeds that were harvested by several farmers producing seeds in the area and storing them for more than 1 year. Around 2006, however, farmers began to use seeds collected in the previous year due to the shortage of stored seeds. Concomitantly, an outbreak of celery stunt anthracnose occurred. In addition, this disease is most prevalent in an area where so-called “home-raised” seeds are used. We therefore hypothesized that C. nymphaeae has spread through seed transmission. To test this hypothesis, we divided the possible infection cycle into the following three steps, and tested each one: (1) primary infection from conidia produced on infected seeds to plant leaves, (2) secondary infection from conidia dispersed from infected leaves to leaves of other plants, and (3) infection of seeds from conidia produced on infected leaves. All results strongly suggested that infested seeds provide the source of the primary Celery [Apium graveolens var. dulce (Mill.) Pers.] is native to high-altitude marshlands of Europe and the Middle East and is also widely cultivated as a vegetable. Cultivars improved and grown in the United States originated from a cultivar grown in Japan in Nagano Prefecture, a major area for celery production in Japan. A new disease causing severe chlorotic spots on leaves, stunting, and dwarfing with leaf curl was found on celery in the prefecture. We found the disease in Nagano, Japan and identified its causal agent. We also elucidated its infection cycle to establish a practical method for controlling the disease.
First report of celery stunt anthracnose caused by Colletotrichum simmondsii in Japan
A new disease was found in Japan, on celery (Apium graveolens var. dulce) having severe chlorotic leaf spot, stunt, and dwarf with leaf curl. A spore suspension from the fungus isolated from affected plants induced identical symptoms 14 days after plants were sprayed. Identification and molecular characterization showed that the causal agent is Colletotrichum simmondsii. This report is the first of stunt anthracnose on celery caused by C. simmondsii. We propose the name “stunt anthracnose” for the new disease. Colletotrichum acutatum sensu lato, as reference pathogen of celery anthracnose, should be changed to C. fioriniae based on morphological and molecular characteristics.
A taxonomic re-assessment of Colletotrichum acutatum , introducing C . fioriniae comb . et stat . nov . and C . simmondsii sp . nov
A comparative morphological and molecular analysis of the ITS and β-tubulin regions of 48 Australian isolates identified as Colletotrichum acutatum, with published descriptions and DNA sequence data from Australia and overseas, revealed three distinct groups. One group contained the holotype and two paratypes of C. acutatum, whereas a recently designated epitype was found to be non-conspecific with the holotype. Two new species, C. fioriniae comb. et stat. nov. and C. simmondsii sp. nov., are described and illustrated with the latter having as holotype the non-conspecific epitype of C. acutatum. These three taxa corresponded with phylogenetic groupings of C. acutatum previously reported by other authors.