Diagnosis of Mal Secco Disease in Lemon by Enzyme-Linked Immunosorbent Assay

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Abstract
An antiserum was prepared against an acetone precipitate of a culture fluid of Phoma tracheiphila. The antiserum reacted positively by either the double diffusion technique or the double sandwich enzyme-linked immunosorbent assay (ELISA). The latter test was extremely sensitive and yielded a positive reaction up to an antigen dilution of 10-7. The MW of the antigens as determined by fractionation on Sepharose 6B were 0.5-1.5 .times. 106. The ELISA values (A405 nm) obtained with infected lemon tissues were considerably higher than those obtained with healthy tissue, wounded leaves and chlorotic leaves (nonpathogenic cause) or with leaves colonized by saprophytic fungi. Field surveys of lemon trees indicated that ELISA values of extracts from mal secco-infected organs were higher than 0.42, whereas extracts from noninfected organs were lower.