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Poster Presentations


Poster Presentations


Frequency distribution of soybean rust urediospore clumps collected from naturally infected kudzu leaves in Nanning, China

Presenter: X. Li

All authors and affiliations: X. LI (1), J. Y. Mo (2), and X. B. Yang (1). (1) Iowa State University, Ames, IA; and (2) Guangxi Academy of Agricultural Sciences, Nanning, Guangxi, China

Information on spore clump is critical to modeling long-distance dispersal of soybean rust. Kudzu leaf samples were collected from a wild kudzu patch naturally infected by the soybean rust pathogen Phakopsora pachyrhizi in Nanning, China, in spring 2006. Disease severity of the sampled leaves ranged from 10 to 50%. The fungus sporulated well either in the field or after leaves were put in a dark moisture chamber for 1 day. By shaking leaves gently, urediospores falling from the leaf surface were collected on blue wax paper in the field or in the room. The collected spores were examined under a dissecting microscope with magnifications 50-200. The number of spores in each spore clump was counted, or it was estimated if there were too many spores in one clump to count. A total of 3,300, including spore clumps and single ones from 29 leaflets, was examined. The sum of all the spores was 29,160, in which less than 3% were single, though frequency of single spores was the highest. Five thousand spores from 12 leaflets were collected in the field, with 6% of the spores being single. Only 2% of the spores were single in those collected in the room. About 30% of the spores were in clumps with 2-10 spores; among them, clumps with 3-4 spores were of the highest frequency. Although there were a lot of large clumps, some of them were loose, which may break up finally into small groups.

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