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.
Soil organic matter and microbiological development of technosols in the South Wales Coalfield
Abstract Degraded land (formerly ‘reclaimed’) after surface-coal-mining is a serious problem in South Wales. This project uses forestation to foster soil development on opencast coal-mine spoil technosols. It compares records of humification and the soil microbiological system (microcoenosis) using paired data from the same plantings in 1998 and 2018. Statistical analysis finds no significant difference between samples collected under trees planted by the pit-planting versus trench planting method or trees planted using organic or mineral fertilizer. However, there are strong significant differences in both soil organic matter and microflora components and significant correlations with time since tree planting. Most components of the soil organic carbon (TOC) and the microflora increase, often significantly. However, compared to 2018, 1998 samples contain significantly greater maximum levels of Insoluble Carbon while the microflora had significantly more Ammonifying bacteria. Decreases in Insoluble Carbon explain the relatively small increase in TOC between 1998 and 2018. The % extracted with 0.1 N H2SO4 is significantly larger in 2018, suggesting active weathering. Similarly, both the maxima and minima of total Humic and Fulvic acids content, extracted with 0.1 M Na4P2O7 + 0.1 M NaOH, are significantly greater in 2018. Total microflora shows significant positive correlations with time-since-tree-planting as do the proportions of bacilli and actinomycetes but the correlation with ammonifying bacteria is negative. In 1998, the microflora was dominated by non-spore-forming bacteria while, in 2018, bacilli and actinomycetes prevail; both are involved in the transformation of complex organic compounds and humification. This indicates active transformation of more complex organic compounds and advancing humification. In sum, forestation of these degraded, formerly reclaimed, opencast coal-mine spoils has resulted in a massive increase in both the size and functioning of the soil organic system.