Quantification of Infection by Alternaria cassiae Using Leaf Immuno-Autoradiography and Radioimmunosorbent Assays |
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Authors: | Amir Sharon Ziva Amsellem Jonathan Gressel |
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Institution: | Department of Plant Genetics, The Weizmann Institute of Science, Rehovot, Israel |
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Abstract: | The severity of fungal infection is usually estimated visually as a rating of injury. A more quantitative method was needed to ascertain the effect of additives used to enhance the virulence of mycoherbicidal preparations. A sensitive and accurate serological method is presented for quantitative measurement of Alternaria cassiae infection of Cassia obtusifolia. An antiserum was prepared against a homogenate of mycelium of A. cassiae. A fast and simple procedure of leaf immuno-autoradiography was developed for the visualization of A. cassiae mycelium on inoculated leaves. A radioimmunosorbent assay (RISA) was developed for quantification of the extent of fungal infection. As little as 1. 6 ng/ ml dry weight equivalent of mycelium could be detected by RISA. There was a linear relationship between the logarithm of the RISA values and the logarithm of fungus concentration up to 300 ng/ml. Reduced sensitivity of the assay was pronounced in extracts containing 400 μ g/ml or more fresh weight of leaves. There was 30–40 % cross-reactivity of the antiserum with two other species of Alternaria, as well as with Monilinia fructicola, and almost no reactivity was found with three other fungi tested. |
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