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.
Analysis of Degradation Kinetics and Migration Pattern of Chlorfenapyr in Celery (Apium graveliens L.) and Soil Under Greenhouse Conditions at Different Elevations
The degradation kinetics and migration pattern of chlorfenapyr in celery and soil at Lhasa and Pengzhou were investigated. A simple, rapid analytical method for the quantification of chlorfenapyr in celery and soil was developed using gas chromatography-tandem mass spectrometer. The results indicated that the half-lives of chlorfenapyr in celeries and soils at Lhasa were 6.3 days and 12.8 days. While the half-lives of chlorfenapyr in celeries and soils at Pengzhou were 6.9 days and 20.4 days. The half-lives of chlorfenapyr in celeries and soils at Lhasa were shorter than that at Pengzhou, while the half-lives of chlorfenapyr in soils at Lhasa and Pengzhou were longer than that in celeries at Lhasa and Pengzhou. The final residues of chlorfenapyr in celeries at Lhasa and Pengzhou were 5.074 ± 0.144 mg/kg and 5.981 ± 0.234 mg/kg after 7 days of spraying, respectively. When chlofenapyr was sprayed to soils only, the average root concentration factor of chlorfenapyr were 3.57–4.02, while the average translocation factor of chlorfenapyr in leaves and stems were 0.28–0.38 and 0.20–0.25, respectively. Chlorfenapyr was easy to migrate from soil to the roots of celery, followed by leaves and stems. The limit value of chlorfenapyr in celery has not been specified in China’s National MRL standard (GB 2763 in National food safety standard-maximum residue limits for pesticides in food. Standard, Beijing, 2021), this study was useful to draw up the limit values of chlorfenapyr residues in celery at different elevations.
First report on anthracnose of Sanguisorba officinalis caused by Colletotrichum acutatum
Colletotrichum gloeosporioides(完 全 世 代:Glomerella cingulata MAFF305974)を 取 り寄 せ た. 3.分 離菌株 の病原性 単 胞子 分離 菌株FAO6-48お よびFAO6-50を シ ョ糖加 用 ジャガイモ煎 汁寒天(PSA)平 板培地 で培養 し,1× 106個/mι の分生子懸濁液 と して直径17cmの プラスチ ッ ク製 ポ ッ トに植えた ワレモ コウ実生苗 に全体 が濡 れ るよ うに噴霧接 種 した.接 種 苗はポ リエチ レン袋 で覆 い,昼 温20°C,夜 温15°C,12時 間照 明の人工気象器 に収容 した. 3日 後にポ リエチ レン袋を除去 し,20°C,12時 間照 明 と して発病の有無を経時的に観察 した. 4.病 原菌の同定 ワ レモ コウか ら分離 されたFAO6-48菌 株 を用 い,ブ ドウ糖加用 ジャガイモ煎 汁寒天(PDA)平 板培地25°C, BLBラ ンプ12時 間照射下 で形成 され た分生子 の大 き さ お よび ジャガイ モ ・ニ ンジ ン寒天(PCA)平 板培地25 °C,BLBラ ンプ12時 間照射下 で形成 され た付 着器 の人