Abstract
In Ehime Prefecture, Japan, lettuce leaf spot (Septoria lactucae) caused huge losses in marketable lettuce yields. To explore potential measures to control disease outbreaks, the effects of inoculum density, leaf wetness duration and nitrate concentration on the development of leaf spot on lettuce (Lactuca sativa) were evaluated. Conidia were collected from diseased plants in an infested field by single-spore isolation and were used to inoculate potted lettuce plants with different conidial concentrations. Lesions developed on inoculated lettuce plants at inoculum concentrations from 100 to 106 conidia/ml. The disease was more severe when the inoculum exceeded 102 conidia/ml, and severity increased with increasing concentrations. Assessment of the relationship between disease development and the duration of postinoculation leaf wetness revealed that symptoms appeared when the inoculated plants remained wet for 12 h or longer. The number of lesions and total nitrogen content in the lettuce leaves both increased when nitrate was applied.
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Acknowledgments
I am grateful to Dr. T. Sato (National Institute of Agrobiological Sciences) for his valuable suggestion on a technique to identify the S. lactucae isolate. I thank Drs. F. Fukumoto, T. Kimura (National Agricultural Research Center) and K. Abiko (formerly National Research Institute of Vegetables, Ornamental Plants and Tea) for their valuable advice. I deeply thank Drs. T. Shiraishi (Okayama University) and T. Kobayashi (formerly Tokyo University of Agriculture) for revising the manuscript. The use of facilities at the National Research Institute of Vegetables, Ornamental Plants and Tea in 1996 is also acknowledged.
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Nao, M. Effects of inoculum density, leaf wetness duration and nitrate concentration on the occurrence of lettuce leaf spot. J Gen Plant Pathol 74, 208–212 (2008). https://doi.org/10.1007/s10327-008-0086-4
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DOI: https://doi.org/10.1007/s10327-008-0086-4