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.
Life cycle and control of Colletotrichum nymphaeae, the causal agent of celery stunt anthracnose
Colletotrichum nymphaeae, causal agent of celery stunt anthracnose, has caused severe damage to celery production in Nagano Prefecture, Japan. For elucidating the infection cycle, celery seeds in the prefecture were screened on a selective medium and found to harbor C. nymphaeae as did seeds harvested from plants with diseased leaves. When seed samples with 1 and 10 % of the seeds infested were sown and grown, stunt anthracnose developed on seedlings, then finally spread extensively to other plants, suggesting that primary transmission occurred from seeds to seedlings, followed by secondary infection to other plants. These results strongly suggest that the disease cycle of the celery stunt anthracnose is completed through seed transmission in Nagano Prefecture. To disrupt the infection cycle, seed sterilization with hot water was tested. Conidia of C. nymphaeae in suspensions were killed by treatment at 50 °C for 40 min or at >55 °C for 10 min. Seedlings grown from seeds treated at 50 °C for 30 min did not develop any symptoms, and germination was not affected. Thus, hot water treatment at 50 °C for 30 min was the best method to eradicate the stunt anthracnose of celery.
A study of the species of Colletotrichum causing ripe fruit rots in Queensland.
The 7 spp. studied [cf. 43, 2976] include a new var. of C. gloeosporioides [Glomerella cingulata] on mango, papaw, apple, etc. designated C. g. var. minor sp., C. acutatum Simmonds, on papaw, strawberry [cf. 38: 21], and tomato, characterized by small conidia (8.3-14.4 X 2.5-4 μ) with pointed ends. Other CABI sites 