Quantification of Infection by Alternaria cassiae Using Leaf Immuno‐Autoradiography and Radioimmunosorbent Assays

Amir Sharon, Ziva Amsellem, Jonathan Gressel

Research output: Contribution to journalArticlepeer-review

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.

Original languageEnglish
Pages (from-to)233-243
Number of pages11
JournalJournal of Phytopathology
Volume138
Issue number3
DOIs
StatePublished - Jul 1993
Externally publishedYes

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